Magna

Through intense research, Magna developed a welding process exclusively designed for maintenance. Since 1965, it has repeatedly been proven that Magna Maintenance Welding Alloys and Electrodes are not only based on sound scientific principles, but offer numerous advantages over ordinary welding rods. Along with advanced welding alloys, Magna provides a unique maintenance-oriented service in over 50 countries.

Today there are over one million industries that rely on Magna for their maintenance welding requirements. The savings made each year by industry in using the unique Magna Maintenance Welding Process is inestimable.

Information

How Magna alloys are designed for maintenance

Cast iron maintenance welding

Maintenance welding of steel

Maintenance soldering process

Magna maintenance welding techniques

Maintenance welding safety

How Magna alloys are designed for maintenance

It happens frequently that electrode users analyze the core wire of an electrode to predict or consider the weld metal composition. This procedure falls down completely. The analysis of the core wire of an electrode is by no means the same as the deposit chemistry.

Many people presume that if they are welding a specific base metal, they will have an identical and satisfactory weld if they use an electrode having a core wire of the same composition as the base metal. As an example, they presume that by welding a base metal of Type SAE 4130 (chrome moly steel) with an electrode with a Type SAE 4130 steel core wire, the weld deposit will match exactly the base metal and the weld will perform identically to the base metal.

This is an understandable, but completely illogical conclusion for many reasons. Following are a few examples:

(1) The base metal is usually a hot or cold worked material, having had grain refinement from the working (such as rolling). The weld metal is a cast material and thus cannot exactly resemble the base metal if the analysis is the same, unless the electrode has additional properties to compensate for this vast difference.

(2) Weld metals are prone to pore-formation, which will also make a weld deposit differ from a base metal even if the analysis of the core wire is identical.

(3) Some ingredients of the core wire, such as chromium, are invariably lost in gaseous form into the atmosphere during the arc transfer.

(4) Ordinary welds are prone to contamination from many sources including:

(a) Carbon, phosphorous, and sulphur content of the electrode or the base metal fused into the weld deposit, which often cause interdentric cracking in the weld deposit. These contaminants, and many others, segregate following solidification of the weld metal and follow the primary grain boundaries causing hot-cracks. Phosphorous also causes welds to be brittle at low temperature.

(b) Ordinary weld deposits are quite susceptible to oxygen contamination. Oxygen in solid solution reduces the impact toughness and tensile strength of steel. Welds made with other electrodes than Magna generally contain more oxygen than do ordinary steel base metals.

(c) Nitrogen absorption of welds made with ordinary electrodes is a matter of serious concern. Nitrogen in solid solution absorbed from the atmosphere during welding lowers the impact toughness of welds, lowers the elongation, and is generally responsible for "ageing", which is a precipitate process in welds which causes impact toughness and ductility to deteriorate to very low values. When one considers that 78% of the air is nitrogen and that nitrogen causes welds to be brittle, the need for prevention of nitrogen contamination becomes obvious.

Magna has recognized that a series of problems result from the old idea of presuming that the same type core wire as base metal is adequate and will supply good results for maintenance applications.

Magna research has proven that in virtually any maintenance weldment, the electrodes must have much higher alloy content and much higher physical properties than the base metal.

Magna solutions

An electrode consists of two parts: a core wire and a coating. Magna uses high-purity core wire having generally a much higher content of noble or semi-noble metals (such as nickel, molybdenum, columbium, cobalt, silicon, manganese, vanadium, chromium, and other "super-metals") than ordinary electrodes.

The highly researched super high alloy Magna core wires with extra high alloy content, stabilizing agents, highly deoxidized metals, and high purity metals and other improvements completely change the character of the arc. The core wires of Magna Maintenance Welding Electrodes are carefully controlled so that metals or elements that - in excess - can cause difficulty or possible weld failure, such as carbon, sulphur, or phosphorous, are either refined out or held in exceedingly low amounts. This enables them to be stabilized by special additives which Magna incorporates in the formulation of the electrode. Nothing has been left to chance.

Magna conducts continuous extensive research in electrode coating chemistry and electrode coating technology. Magna employs leading scientists and many highly qualified chemists and technicians who perform studies in electrode coating technology. Among the reasons for Magna Maintenance Welding superiority is the advanced state of Magna' s Maintenance Electrode coating technology. It is believed that the coatings of Magna electrodes are the most advanced in the world with respect to maintenance applications. Magna electrode coatings contribute to maintenance weld quality in many special ways, including:

  • Magna's unique coatings deoxidize the weld metal. Oxygen contamination is a major cause of weld failure. Magna electrodes contain special deoxidizers which completely remove most oxygen and reduce the balance to exceedingly finely dispersed inclusions. The deoxidizer system is of a proprietary and special nature not universally available.
  • Magna coatings actually produce a super shielding gas to protect the molten weld metal. This gas envelope produced by the melting of the coatings is especially designed to prevent the weld from being contaminated by nitrogen, oxygen, hydrogen and other harmful elements that often cause failure in ordinary electrode deposits.
  • Pore-resistant coatings. Magna electrode coatings contain scavengers, cleansers, degreasers, and have an ability to absorb foreign matter, dirt, contamination, and impurities, float them away, and hold them in the slag for easy removal. This special feature enables Magna maintenance welds to be made without the porosity that is common with ordinary electrodes.
  • Magna Maintenance Electrodes provide a slag layer around the molten metal globules during transfer, and then form a protective chemical slag blanket over the complete weld deposit. With most electrodes, the slag is usually little more than a residue of the electric welding process. Magna Maintenance Electrodes have a completely different type coating which forms a protective blanket that not only provides a resistance to oxidation and other contamination but emphatically retards the cooling rate. A "Widmanstatten" structure occurs when ordinary electrodes are used which allow the weld to cool too rapidly. The Widmansttten structure caused by rapid cooling with ordinary production electrodes is harmful. Rapid cooling causes the ferrite to form needle-like plates which are transverse to the pearlite.

The Magna slag blanket holds the heat and retards the cooling to permit the complete precipitation of the ferrite in the grain boundaries in such a way that the ferrite surrounds the pearlite grains. The Magna protective slag blanket effectively retards the cooling rate and promotes a more refined and more desirable grain structure.

  • Hydrogen gas inclusion (commonly referred to as "fish-eyes") is a major problem in maintenance welding. Hydrogen's main threat to welding comes from the chemically combined water which is present in the coatings of many production welding electrodes. This water decomposes into hydrogen and oxygen in the arc transfer process. Iron has a high solubility for hydrogen even at moderate temperatures, so considerable amounts of hydrogen enter weld deposits. The hydrogen which enters the weld when production welding electrodes are used can be completely removed by heating the weld to 482oF (250oC) and holding the part at this heat for 15 hours.

This procedure can be carried out in production factories as another step in manufacture. However, it is totally impractical in maintenance welding. This is why the Magna Research Department has given consideration to the problem of hydrogen inclusion in maintenance welds.

It has repeatedly been demonstrated that hydrogen contamination of welds causes cracking and underbead cracking (this is a type of cracking in the heat affected zone adjacent to or under the weld, caused by the hydrogen contamination during welding). Hydrogenous welds cause a pronounced reduction in ductility and elongation and are crack sensitive.

Magna has built into the special coatings a resistance to hydrogen transfer across the arc. Electrodes such as Magna 305, Magna 303 Gold and many others are based on all mineral coatings with special additives that tend to repel hydrogen. These coatings, in manufacture, are baked at high temperatures to remove even the last traces of hydrogen. These special coatings are another reason Magna electrodes result in more reliable maintenance welds.

Magna coatings are not mere simple cellulose or rutile formulations. They contain many supplements and special features. Some of these are:

(1) Higher purity, higher quality binders.

(2) Higher purity, higher quality chemicals. There are many grades of chemicals available to electrode manufacturers including the lower quality technical grades, U.S. pure, Pharmaceutical grades, etc. Magna quality requires unusually high grades of chemicals.

(3) Magna coatings are produced with special mixing equipment, using a variety of mixers to attain different results with different chemicals. The particle size of chemicals is carefully studied. The mixing of the coatings is carefully monitored so that every batch is identical.

(4) Magna introduces many additional metals such as strontium, sodium, aluminium, graphite, as well as stabilizing compounds and various other additives such as fluorides, carbonates and calcium, through the unique coatings to improve both maintenance weld quality and weldability.

(5) Magna upgrades the quality of the deposit by adding finely ground metal to the coating. Such metals as molybdenum, chromium, cobalt, nickel and many others enrich the weld deposit.

(6) The concentricity of all Magna Maintenance Welding Electrodes is controlled with such surgical preciseness that the maximum core-plus-one-covering dimension by more than 5 per cent of the minimum core-plus-one-covering dimension. This precise concentricity control prevents "finger-nailing", uneven burn-off, erratic performance and spatter which occurs with so many welding electrodes because of poor concentricity.

(7) Magna employs carefully controlled amounts of ferrite formers in the coatings in order to enable the Magna deposits to resist hot-cracking. Magna electrode coatings are highly sophisticated coatings, many containing more than 20 ingredients. They are the result of specific research to design coatings especially engineered for the special problems of maintenance welding. It is believed that they represent the highest state of the art today for the purpose for which they have been designed. They supply weld deposit additions that provide increased physical properties and increased resistance to cracking or costly weld failures. The coatings are so rich in extra metals and supplements that the final alloying process is actually only completely finished at the tip of the electrode.

Cast iron maintenance welding

How to weld cast iron

Cast iron is a common metal in industry because of its simplicity of manufacture. It can be cast with only a gas furnace whereas steel, having a higher melting point, requires an electric furnace for casting. Cast iron can be machined easier and at higher speeds than steel. This metal alloy is readily and economically manufactured into useful machinery because of its low melting point, fluidity, and simplicity of melting.

Cast iron is manufactured from an endless number of formulae. A great deal of scrap iron of unknown analysis is used in manufacturing cast iron. Most cast iron contains in addition to iron and carbon, silicon, manganese, sulphur, and phosphorous.

The main difference between steel and cast iron is its carbon content. Mild steel contains less than 0.30% carbon, and most high carbon steel contain less than 1.0% carbon. The maximum carbon that can be put into steel is 1.7% as this is the maximum carbon that can be absorbed in solution with iron. When larger amounts of carbon are combined with iron, the carbon not absorbed by the iron is present in the form of small flakes of graphite. Grey iron contains up to 4.5% carbon, usually between 3.0% and 4.0%.

When cast iron is heated, at a temperature near its melting point, practically all of the carbon goes into solution with the iron in a combined form of iron carbide. If the cast iron is allowed to cool very slowly nearly all of the carbon will pass out of the combined state and segregate as free flakes of graphite. If the iron is cooled rapidly a large portion of the carbon will remain combined with the iron as iron carbide.

It is this high carbon content that makes cast iron so different from steel. If we could remove the graphite flakes from cast iron and squeeze what is left together, we would have steel.

The factor of the two forms in which the carbon can exist in cast iron requires major attention in welding. If the cast iron (or parts of it) is melted and then cools slowly, the weld and the base metal will be soft and machinable. If cast iron is melted during welding and cooled rapidly, the cast iron, or at least areas of it, will be hard and difficult if not impossible to machine. This is what causes the condition of "hard-spots" in cast iron welds.

Because cast iron has the flake-graphite structure which prevents it from bending and causes it to have no elongation, it breaks readily. It is a common event in factories, construction companies, farms, and all other industries for cast iron machinery to fracture. Often a costly casting breaks simply from vibration. Costly downtime from mishap with cast iron machinery is common in industry. Also, because cast iron is soft, it often wears. For example in threaded holes, the threads wear or strip easily. No one can estimate the loss to industry by breakage of automobile and truck motor blocks, exhaust manifolds, transmission housings, and in factories of such indispensable machines such as pump housings, punch presses, electric motor housings and the myriad of other cast iron machinery components.

When a cast iron part breaks, the cost is enormous to almost any industry. It is impossible for an industry to carry spare castings in their store room. Often the machinery is old and obsolete and the manufacturer cannot provide a spare. To make a new casting usually involves making a pattern first. This can take up to four weeks just to make a pattern and often the pattern can cost thousands of dollars.

It is for these reasons that industry must be well prepared with Magna Maintenance Welding Electrodes and Alloys, to enable quick restoration of the broken machinery to useful service.

Many engineers who have encountered repeated failures in attempts to repair cast iron with ordinary cast iron production welding rods.

Some engineers state that they have been able to weld cast iron, in some cases using brazing rods or gas welding rods, which require a long complicated procedure. Usually brazing or gas welding cast iron involves: Dismantling; building a fireplace around the casting; preheating, often for as much as 24 hours; gas welding; burying the casting in lime or other insulating material; and slow cooling for up to one week.

The answer to successful welding of cast iron is the development of Magna 770 which has brought industry a practical solution.

Maintenance-designed cast iron electrode

There are a number of companies that market production welding cast iron electrodes. They usually offer from 3 to 7 different cast iron electrodes, since they readily admit that each electrode has only a limited range of applications on which it can be used on.

Obviously welding electrode manufacturers that offer several different electrodes for cast iron are not capable of serving the needs of maintenance. Such a variety of cast iron electrodes, each with a limited scope of usage, is generally all right for production welding where only a limited number of applications exist. A production factory manufacturing, for example, pumps and has only one analysis and one thickness of cast iron to weld under perhaps only one condition, can select one of these production cast iron electrodes for the one application.

In maintenance the conditions are completely different. In maintenance they never know what type of cast iron will break, what thickness it will be or whether or not the weld will have to be machined or not. Generally they do not know what the analysis of the casting that may break will be.

Magna has solved this old industrial problem of cast iron failures with Magna 770, which welds all types of cast iron, thick or thin, including grey, malleable, meehanite and nodular iron. It welds in all positions, including overhead or vertical. It makes porosity-free welds without undercut. The welds are fully machinable and crack-free. Magna 770 even welds cast iron to steel.

Magna 770 is the one practical solution that can help you prevent costly downtime and loss of profit due to cast iron failure.

Maintenance welding of steel

In maintenance welding there is more steel welded than any other metal. Surveys show that there are more breakdowns caused by steel weld failures than welds in any other metal.

Many people believe that steel is easy to weld and so they do not give it much attention. Often in industry one hears "Oh, it's only mild steel", and so they weld it with any cheap mild-steel welding rod that is around. This attitude has cost industry more lost production, more downtime, and more injuries and damaged equipment than most people are aware of.

No doubt, simple mild steel structures in a production factory are relatively simple to weld since all or nearly all the variables can be controlled. In maintenance, however, few of the variables can be controlled. Laboratory conditions simply do not exist in maintenance welding. There are almost no simple easy maintenance welds to make on mild steel or any other steel.

There are over 30 different common types of mild steel and semi-mild steel electrodes now in common usage. They were all designed for production welding. The welder welds the one application repeatedly so that he becomes highly efficient on the highly repetitive applications he makes. The ordinary production welding rods are satisfactory where the variables are controlled.

The same electrodes are also sold by many welding supply marketing companies for maintenance welding applications for which they were not designed. In maintenance welding, the conditions are entirely different. The welder does not know the analysis of the steel he is welding. He cannot control the variables, such as joint design and in maintenance the steel is often oily, rusty, painted or dirty.

Production welding steel electrodes have been designed for an exceedingly limited range of applications - usually only one per type.

In a production plant the variety of steel welding is limited. For example, they may weld only one type of structure - hot water tanks. These usually consist of only one type of joint such as a butt joint. They probably use a positioner so the welding is all performed flat (downhand). The analysis of the clean new steel is known and they probably have elaborate jigs and fixtures for perfect alignment so distortion and warpage are not problems either. They have selected an easy-to-weld steel base metal to make the tanks from.

The maintenance welder, however, is faced with a completely different set of circumstances which require a welding electrode designed for the different conditions he is confronted with:

(1) The maintenance mechanic more often than not, does not work full time as a welder. In most industries welding is only one of his important jobs. He attends to mechanical repairs, electrical repairs, machine rebuilding, plumbing, truck repair, etc. Since he doesn't work exclusively as a welder, often he understandably cannot develop maximum welding skill.

(2) The maintenance welder does not do the same welding project repeatedly as the production welder does. Every job is different. In general the maintenance welder does not have a large volume of one type of welding, but has an infinite variety of applications. If he relies on production welding rods he has to have possible as many as 30 different types of steel electrodes.

(3) The maintenance welder often has to weld steel in confined areas of poor access to the fracture awaiting repair.

(4) Maintenance welding of steel is much more difficult than production welding. In production, the engineers and designers select an easy-to-weld steel. The maintenance welder is often called upon to weld "unweldable" steels, eg, a pump shaft or electric motor shaft. When the equipment was manufactured there was no welding performed on the shaft, thus the engineers or designers most likely selected a free-machining steel which could be machined at low cost.

Such a steel is considered unweldable. Nevertheless, the maintenance welder has to weld it. And when he does he should always use Magna Maintenance Welding Electrodes, as these have been specially designed for the wide variety of complex welding the maintenance department has to do.

(5) The maintenance welder often has to weld "poor-fit" applications, thick-to-thin, and difficult metals such as alloy steel, galvanized iron, high carbon steel, crack sensitive steel, and steel of unknown analysis.

Steels that were "simple mild steel" when in a production factory, and thus not difficult to weld, become highly crack sensitive when later maintenance welding has to be done on them. This is because they are painted, have grease crayon marks, carbon smudges from a cutting torch, or oil and grease on them. All of these materials are carbonaceous. When welding a piece of mild steel that has oil or other carbonaceous material on it, the maintenance welder is actually welding high carbon steel.

All of these carbonaceous materials inherent on steel in maintenance conditions, go into the weld as carbon and cause the weld and weld area to become high carbon steels. Every engineer knows that a high carbon steel weld is highly crack sensitive.

(6) Maintenance welding has to be of a higher quality standard than production welding. In production welding, it is customary for an inspector to follow the production welder and locate any weld flaws - usually about 3-6%.

In maintenance, the welder is allowed zero defects. He usually has one broken part to repair and he must weld it right the first time or else a great deal of costly downtime or possibly injury to his fellow workers will occur when the weld fails in service.

(7) The maintenance welder often has to weld equipment which is old and the original design was not intended for today's higher-speed, higher-powered requirements. Thus the welds must be of greater toughness and greater strength in maintenance than in production. Plus the fact that the maintenance industry has to cope with machinery that was poorly designed and needs to be "beefed up" and reinforced with higher strength welds. The higher strength Magna Maintenance Welding Electrodes are often the only solution.

(8) In a production factory they often weld a part and then stress-relieve or heat-treat after welding. However, when this part breaks down and has to be repair welded in the field, it has to be repaired without dismantling and it is impossible for stress relief after welding. When Magna Maintenance Welding Electrodes are used, problems such as these are simplified.

The maintenance welding solution

Magna has reduced the complexity of steel welding in maintenance to where it is no longer a cause of anxiety. In literally hundreds of thousands of industries all over the world they have discontinued using production welding rods for steel maintenance and now use only genuine Magna Maintenance Welding Electrodes and Alloys.

Magna products are believed to be the only welding electrodes and filler metals in the world which are designed, produced, sold, and serviced internationally, solely for maintenance. All the other products are manufactured for production.

Magna Electrodes and Alloy Filler Metals are better for maintenance in several important and completely exclusive ways:

(1) Magna products have greater versatility built into them. Each product gives optimum performance on a wide range of different joint designs, different base-metal types and different conditions.

(2) Magna products have extra-high physical properties including higher tensile strength, higher yield strength, higher elongation and greater holding power. This gives the welder an edge. The greater strength tends to compensate for any flaws in the weld due to inaccessibility, poor position, unknown composition, and conditions that are not ideal, as well as difficult-to-weld metals.

(3) Magna Alloys and Electrodes are easier to apply. Even unskilled welders can accomplish difficult jobs. Even more importantly, highly skilled welders can achieve extraordinary results with a combination of their skill and Magna's ease of application.

Magna supplies five electrodes for steel welding:

  • Magna 303 Gold AC-DC . This one electrode welds all steels and it is the only electrode a small maintenance department needs to stock.
  • Magna 305 AC-DC. This electrode welds all low alloy steels and mild steels. It is widely used for fabricating the new high strength construction steels in the maintenance department.
  • Magna 307 AC-DC. Is an alloy steel electrode for all mild and miscellaneous steels.
  • Magna 393 AC-DC. An electrode for stainless that provides improved corrosion resistance and that runs off even small AC "buzz-box" welding machines satisfactorily.
  • Magna 395 AC-DC. Designed to tackle the repair of duplex stainless steels.
Maintenance soldering process

Magna maintenance soldering

Technically speaking, welding can be divided into three broad categories:

Fusion welding. The joining of two or more metals by melting (fusing) them together, eg, welding steel with an alloy such as Magna 303 Gold.

Brazing. The joining of two or more metals with a welding alloy that has a lower melting than any of the base metals, but has, itself, a melting point over 450oC.

Soldering. The joining of two or more metals using a welding alloy with a melting point below 450oC.

Soldering is probably the most widely used of all methods of joining metals. However, soldering is also probably the least understood of all metal joining methods.

Soldering is used for two main types of application: production joining and maintenance joining. In production, soldering such items as automobile radiators, electronic and electrical equipment, are usually the result of a mass soldering installation machine which is complicated and programmed by a specialist consulting engineer.

Once the initial adjustments have been made, the operation becomes a simple metronome assembly without the need for human assistance. All or most of the variables are controlled. Production soldering is an automated system based on ideal conditions, clean metals, preplanned joint design and no human error factors.

Industrial maintenance soldering is entirely different from production Soldering can play an important part in industrial maintenance such as electrical circuits, plumbing, tubing, vehicles, sheet metal, wiring and a myriad of applications.

There are many different applications where Magna Maintenance Soldering is the ONLY answer and the RIGHT answer. For example, in a milk factory. There are times when dismantling or enjoining parts is essential to the efficiency of the operation. The stainless steel piping can be joined with Magna 88C. The result is a sanitary, leak-proof strong joint. However, the time comes when the cleaning operation must be done and, the only way to do this is to take the piping apart and - clean it. This can be easily achieved by a minimal amount of heat to dismantle the piping. The piping is cleaned and then once again joined back together with Magna 88C.

This could not be done, either by brazing or welding. Nor could the machine be transported back to the manufacturers for dismantling and repair. This, however, is only an isolated example of the thousands of situation-saving applications for the Magna Maintenance Soldering Process.

There are endless numbers of applications where Magna Maintenance Solders salvage equipment that might otherwise have had to be scrapped. Instrumentation components, galvanized sheet metal, plumbing connections, water piping, sheet metal machine guards, electrical apparatus and numerous other applications that occur in every factory, farm, mine or industry can benefit from the use of Magna Maintenance Soldering Alloys.

Magna Solders are better for maintenance applications than ordinary solders for the following reasons:

(1) The Magna vacuum-melted method of solder production

Magna Solder Alloys are made by an exclusive proprietary vacuum- melting process. Ordinary solders are not manufactured with vacuum melting but are melted in the open air. The Magna vacuum melting process provides the following major advantages:

  • Vacuum melting eliminates dross, gas, tin oxides, lead oxides and other contaminants.
  • This unique manufacturing method gives the Solder Alloys fewer centres of nucleation than ordinary solders. Because of this, when the molten Magna solders cool, the grain structure is finer and there is less danger of segregation of the component metals.
  • Magna Solders provide shallower fillets with better contours; they exhibit vastly superior holding power.
  • Magna Solder Alloys are so superior to ordinary solders that solder joint failures are almost unknown.

(2) Magna solders contain higher-purity metals

Ordinary solders are made from low-cost scrap tin and lead. The fact that the results from these solders are limited seems to have little or no distraction to its sale for the simple reason that few industries realize just what goes into a solder.

The impurities in ordinary solders cause serious and repetitive problems in nearly every field of soldering. The impurities include such metals as copper (which lowers the over-all resistivity); zinc (which will not go into solution but remains crystalline and gritty); bismuth (which has the ability to change the microstructure); aluminium (another that will not go into solution) and finally cadmium (which lowers the spread-rate).

Magna uses only virgin metals rated at 99.99% purity. These are melted in a vacuum and homogenized ultrasonically. Resistivity tests are then made on a double-Kelvin bridge using the four-pronged method.

Magna Solders are made from exceptionally high grade tin ore, which is crushed and concentrated by the floatation process. Impurities such as arsenic and sulphur are completely removed by an oxidizing roast and a dilute acid bleach. Other impurities such as lead, bismuth and antimony are removed by choloridizing roast and acid bleaches.

The ore is then purified once again in a reverberatory furnace which has been charged with concentrated tinstone, and mixed with metallurgical grade coal. The tin at this stage is approximately 99.50% pure.

However, in the Magna process, the purity factor does not stop there. The tin is refined by four additional processes to bring it to the highest level of purity available in any commercial solder today.

Sub formulations: The perfect solders are those that can be applied at the lowest temperatures. However, soldering temperature is the combination of 2 factors: Time and degree of heat. For example, a solder that requires 190oC and remains molten or liquid for 3 minutes, requires substantially more heat energy than a solder that requires 210oC to melt but which solidifies in five seconds. Molten solder reacts with metals such as copper - and formed on the copper surface, is a chemically distinct, intermetallic compound phase. And, most important, as long as the solder remains MOLTEN, the reaction forming this intermetallic compound continues. This compound (chemically CN6 SN6) is extremely hard and brittle. It is quite easily broken in shock by tearing forces.

Thick intermetallic alloys are weaker than thin layers. The obvious answer then is to reduce the soldering time. The less time the solder is molten and the faster it solidifies, the stronger and less brittle the bond.

The Magna Solder Alloy range achieves this rapid-solidification process admirably. Thus, the Magna Solders provide the optimum strength. However, let's take a look at production again. The normal solder used is the 40/60 tin and lead solder. Melting point is 237oC and the solidification point is 182oC). A solder of this nature is apt to produce a joint of low physical properties because the solder is liquidated by heat over 55oC (the difference between the melting and solidification points). By contrast, Magna 88C has no plastic range at all!

It is a fact that a properly made Magna solder joint between two pieces of steel has the full tensile strength of the steel itself. The only problem is fear itself - maintenance engineers do not trust soldered joints - because their only experience has been with ordinary production type solders which often do fail. Once they realize that there is a vast difference between Magna Maintenance Solder Alloys and ordinary solders, they will have the confidence to perform repairs at low heat they would never have attempted before.

Magna maintenance welding techniques

Maintenance welding requires a combination of skill, ingenuity, confidence, imagination and determination, all intermingled with scientific principles. Welding, of course, involves the four sciences of chemistry, metallurgy, physics and engineering. One without the others will fail. However, proper proportions of all will result in greater savings through maintenance welding.

(1) One of the great difficulties in maintenance welding is the fact that the know-how steps often have to be carried out by the welder himself. In a production plant, metallurgists and engineers generally supply the informational know-how, while the welder or operator only provides the manipulative skill. This is not the case in maintenance welding.

(2) The maintenance welder must have a great many more talents than a production welder. First of all, in production welding it is usually the case that the base metals being worked on are clean, new metals. This is not so in maintenance. Often the maintenance welder is faced with salvaging equipment which may be many, many years old, having had service in corrosive conditions, may be oily or greasy and so dirty and contaminated that everything in the text book goes wrong when the welder attempts to weld repair it.

(3) In production welding, it is usually possible to position the work so that the welding can be done in a convenient position, usually downhand. This is not so in maintenance welding because as often as not the maintenance welder must repair objects and in awkward positions which he can hardly see or reach, let alone weld.

(4) An additional difficulty in maintenance welding is the wide variety of work that must be accomplished. Often in production welding, an operator will work on a limited number of jobs constantly. In maintenance welding, the operator does not do one type of work constantly; and as a result, he understandably cannot become proficient in every type of work that he does, because certain types of breakdown occur so rarely. It is extremely difficult for a mechanic to learn how to do all the myriad projects required in maintenance welding efficiently. One of the most difficult problems in maintenance welding is that the welder often does not know the analysis of the base metal.

(5) In spite of the fact that maintenance welding is more complex than production welding, it is undoubtedly true that maintenance welding is far more profitable to a plant or industry to do than production welding. Frequently, a maintenance welder does in one day, work which may save his company hundreds, if not thousands of dollars. Such savings are not possible with one man's time in one day in production welding.

(6) The first step in maintenance welding is to determine the base metal. Knowing something about each metal will help identify metals. Spark tests, hardness tests, magnet tests, chemical tests, weight tests and file tests are common methods of identifying base metals. However, there are often cases where it is almost impossible to be certain enough for safety by common shop methods of analysis. In those cases, it is imperative to use a welding filler metal with the highest physical properties to make certain that the weld equals or exceeds the base metal irrespective of what the base metal may be.

The second step in establishing a welding procedure is to calculate the effect of the heat to be applied. All welding requires heat, and heat will cause a certain reaction to the base metal.

The heat generated in a weld is predictable from the formula H=A2RT (Heat equals amperage squared times resistance times welding time).

The undesirable effects of heat can be listed as excessive grain growth, hardening cracks, porosity, thermal cracks, warpage, locked-up stresses, distortion, and hydrogen contamination.

(7) The non-uniform localized heating and cooling during welding and the joining of the heated base metal by means of the molten weld-filler metal creates a hindrance to both expansion and contraction. The stresses arising through heating and cooling of the base metal are called contraction or shrinkage stresses. The stress system left in the object being joined after welding, due to thermal or shrinkage stress, is called the residual stress.

(8) A molten metal usually shrinks when it cools and solidifies. If all metals had a zero co-efficient of expansion, most of the problems that occur in maintenance welding would be non-existent. In a foundry, a molder's rule gives the expected contraction. In welding, however, no such handy tool is available and the amount of stress can only be calculated by the experience of the welder. In welding, the weld filler metal is applied in a liquidus and is actually cast into a mold which is formed by the base metal.

(9) As in any metal casting into a mold, stress in the weld metal resulting from hindered contraction is related in intensity to the dimensions of the weld. Therefore, the maximum stress is in the direction of welding, longitudinally. The transverse stress is next intense and the stress in the thickness direction is least because less hindrance to contraction occurs here.

(10) Welds contract in all three directions - length, breadth and width - and the resulting stress may be called multi-axial stresses. In maintenance, welders are constantly called upon to solve welding problems where multi-axial stresses are a source of anxiety. The thermal stress problem is accelerated when heat is applied locally and is dissipated into the base metal mass. The harmful results of stress are both complex and of serious concern in maintenance welding.

(11) The temperature gradient is the heat-affected zone; that is, the area starting from the centre of the weld to the extremity to which the weld heat travels. Within this heat affected zone most welding problems are created. Some sections of this heat affected zone may be cooling while other parts are still being heated, which contributes to the thermal stress problem. Unless there is an equal amount of residual compressive strength in the metal system to balance the residual tensile strength, cracking will occur.

(12) The problem created by stress and distortion causes several difficulties. First, they restrict normal ductility of the material. Second, they may cause localized stress corrosion cracking that may fail under impact load. Stresses may exceed the yield strength of the base metal and result in cracking. Additionally, a loss of dimensional stability occurs through distortion.

The amount of stress and distortion which occurs in a part being welded depends upon a number of variables such as thickness of plate, degree of restraint, speed of electrode travel, movement of air, preheating, higher heat input and other factors. It is well known that since the welding involves both heating and cooling during welding operation, the weldment is subjected to thermal expansion and contraction. The expansion and contraction rate of metal produces serious internal stresses and only requires a slight excess strain to exceed the yield strength of the metal and produce weld failure.

(13) Another serious problem in maintenance welding is that of a martensitic zone adjacent to a weld. When hardenable steel and cast iron are heated into their critical range and allowed to cool faster than their critical cooling rate, a brittle martensitic zone tends to occur next to the weld. This is due to the limited graphite rejection in the region adjacent to the frontier zone between weld and base metal. Other problems which occur in this region are carbide precipitation, grain growth, porosity and hardening graphites. If a martensitic zone is allowed to occur.

(14) In addition to the problems already mentioned that occur in maintenance welding, an added problem is that of stress raisers. Any factor which produces a localized area of high stress is called a stress raiser. Any engineer is aware that abrupt changes in section design, notches, grooves, screw threads, surface irregularities and discontinuities such as cracks, holes and inclusions, are considered stress raisers. However, in maintenance welding, we are only concerned with those avoidable notches which occur as a result of welding. These notches have very little effect on the tensile strength of ductile materials but are of great importance in fatigue. The notch sensitivity factor depends not only on the material but on the type of notch and level of stress. Those notches which are avoidable are crater cracks, hard spots, undercuts and porosity.

(15) Take, for example, a typical butt weld. There are three starting points for fatigue fracture. These are; internal defects an undercut at that point where the weld makes a junction with the plat or base metal; and poor quality of weld at the root.

(16) The shape of the welding bead has a considerable influence on stress raisers, especially on cast iron and the hardenable steels. For example, if a weld bead is applied to a cold piece of base metal, at the beginning of the weld, the weld will appear to be convex and lap over at the cold start. This makes perfect stress raiser and as such it will be highly efficient in starting a crack. Additionally, when the electrode is abruptly removed from a weldment, there will be a crater at the end of the weld. A crater is often a source of cracks because a crater solidifies from the outside towards the centre. Since the weld crater is a smaller mass than the remainder of the welding bead, it will cool at a faster rate than the heavier section. These conditions usually result in a starter crack and the creation of a severe stress raiser.

(17) Angular distortion is still another problem in maintenance welding. Angular distortion is created when a contracting metal is shorter at the root of the weld than at the face of the weld bead, such as in a single 'V' or 'J' root type joint.

Magna solutions

These are the main problems of maintenance welding. There are without a doubt, others, but these are of utmost concern. Let’s now review the solution to these problems.

When a martensitic zone, residual stress or distortion results after a weld has been made, these conditions can be improved by stress relief or mechanical relief. However, the only practical solution is to anticipate these problems before the welding is accomplished and to apply corrective measures to avoid their occurrence during welding.

Some of the techniques which we have employed to eliminate or minimize stress and distortion follow. None of these techniques are empirical or can be used in every case, nor are any of them absolutely foolproof. In many cases it will require more than one of these corrective measures because in some instances, one alone will not be sufficient.

(1) An important technique we call the 'Buttering' technique. If you have a piece of metal which has failed because of a fracture extending completely through the base metal, the cracks very seldom occur at a convenient 90 degree angle. Sometimes a large piece will fall out when the part is bevelled. The best system is to use a double 'V' or double 'U' joint, but in many cases in maintenance welding this is not practical, since the weld must be made entirely from one side due to the lack of accessibility.

(2) We have already mentioned that the amount of contraction is governed by the amount of cross section of weld metal which exists. If faced with this problem, many inexperienced welders might attempt to use a wide weave bead and fill up the large gap which is exposed in such a joint. However, a preferred solution is to 'butter' or pad the vacant spots and fill those in first, leaving the root opening as small as possible before the root bead. The two sides should also be coated and it is a good idea additionally, to allow the weld padding bead to overlap the face of the plate for a small area. By using the buttering technique, we have greatly reduced the amount of cross section of weld bead being applied at one time. We have now substantially reduced the cross section of the area to be welded.

(3) The next step is to join the two sections together using substantial weld bead to prevent a crack. By reducing the cross section of the weld area substantially, we have greatly reduced the tendency for contraction and thus we will have less stress and less distortion.

(4) It was previously mentioned the problem of angular distortion which occurs from having a shorter weld at the root than at the face of the weld. This can be eliminated by welding from both sides. On heavy sections, as a matter of fact, it is important to use a double 'V' or double 'U' and weld from both sides simultaneously if possible. If only one welder is available, stagger the weld bead application from one side to the other to make the tension balanced on both sides of the joint, thus eliminating angular distortion. The buttering technique is especially advantageous when joining thick to thin sections.

(5) Another solution which is often of indispensable help in welding heavy sections, particularly of alloyed steel or cast iron, where a great deal of operational stress is encountered, is what we call the 'anchoring' technique. This consists of cutting grooves in the bevelled joint of the weldment. These grooves should be approximately 5mm deep and should occur approximately 2.5cm apart.

These grooves are then filled in first of all with weld metal and then the exposed area of the 'V' is buttered or coated with weld bead before the joint is made. The grooves can be machined or cut with a torch. A very good method of making the grooves is with Magna 100 - a chamfering electrode which removes metal with incredible speed with the electric arc without oxygen.

(6) The anchoring technique, when working on dirty, oil saturated cast iron removes contaminated metal and exposes the subsurface sound metal. Secondly, we are anchoring the weld metal into the base metal in much the same way that a snow tread tire gives better traction than a smooth tire when operating in the snow. However, most important of all, we have broken up the continuity of a vulnerable martensitic hardened zone adjacent to the weld. Thus, when stresses are applied, rather than the weld failing adjacent to the weld, the continuity has been broken up so the strain will not be focused at one vulnerable zone. Additionally, the grooves create a mechanical bond and also result in more metal-to-metal contact for greater holding power.

(7) The anchoring technique is of immense value before applying hard facing alloys to heavy equipment and is especially important when welding cast iron. We have seen jobs accomplished successfully in this manner which were attempted time and time again with failure with other methods.

(8) One of the most important ways to control stress and distortion is the practice of peening, which consists of tapping the weld bead while still not with a rounded tool (such as a ball-peen hammer). The reason for peening is that when a warm weld bead is peened the weld metal is stretched and expanded. This stretching of the weld bead compensates, at least to some extent, for the contraction which will occur upon cooling.

(9) There are several important things to know about peening. It is standard practice to peen all but the first and last pass. If you are peening upon and air-hardening tool peened, cracking may occur. Therefore, the first pass should not be peened. Subsequent passes should all be peened up to the last pass, the cover pass. The reason these are not peened is that a peened weld, and this is true even if it is mild steel, is a work-hardened weld bead, and a work-hardened weld is an efficient crack starter.

(10) The internal passes will not be work-hardened because the subsequent weld beads which are applied over them will anneal the work-hardened condition and does not cause cracking.

(11) Incidentally, stress relieving after welding does not always relieve peening damage, but subsequent welding does. Therefore, the rule in peening is to peen all but the first and last passes. it is important to use moderate blows because repeated moderate blows are much better for peening than a few heavy blows. It is imperative that the peening tool be light in weight and blunt rather than sharp in design.

(12) One of the most universally used methods of controlling distortion and stresses is that of preheating. Preheating before welding eliminates or lessens the danger of crack formation, minimized hard zones adjacent to the welds, minimizes shrinkage stresses, lessens distortion and enhances the diffusion of hydrogen from the steel. A rough but realistic rule of thumb is that a 260oC preheat usually equals 800oC of post heat (just as an ounce of prevention is said to equal a pound of cure).

(13) Of course, the question in maintenance welding is: when is preheating necessary? Many welders believe that it is never necessary to preheat on mild steel. This is a great error because mild steel should always be preheated if the sections are over four inches thick, as well as in other special cases. The need for preheating is greatly increased if the piece being welded has - first, a large mass; second, is at a low temperature, or is in an environment of lower temperature; third, if welded with small electrode diameters; fourth, is welded at high linear speed; fifth, has a complicated shape and design; sixth, if the base metal has high carbon or high alloy content; seventh, if it has an air-hardening capacity, or, finally, if it has a large variation in size of adjacent parts. In these cases, preheating is all the more important.

Maintenance welding safety

The maintenance welding of metals involves the generation of temperatures up to thousands of degrees. It also involves working with electricity, with combustible gases and with a wide variety of metals, chemicals, fluxes and other potentially hazardous situations, often in confined spaces. Yet in the 80 or so years that welding has been regularly practiced, it has been proven repeatedly that it is a relatively safe occupation which is not injurious to health. However, as in all trades and all industrial activities, some safety precautions must be taken. Magna recommends the following be included in your safety program:

(1) Welders should never carry or use butane lighters while welding. Several fatal accidents have occurred when welders were carrying butane lighters in their pockets. A spark from a welding arc can penetrate the pocket, land on the lighter, burn through and thus expose the fluid in the lighter, and an explosion occurs. There is the same amount of force in a disposable butane lighter when it explodes as there is in approximately three sticks of dynamite.

(2) Always wear protective clothing suitable for the welding to be done.

(3) Always wear proper eye protection, when welding, grinding or cutting.

(4) Keep your work area clean and free of hazards. Make sure that no flammable, volatile or explosive materials are in or near the work area.

(5) Handle all compressed gas cylinders with extreme care. Keep caps on when not in use.

(6) When it is necessary to arc weld in a damp or wet area, wear rubber boots and stand on a dry insulated platform.

(7) Shield others from the light rays produced by your welding arc.

(8) Do not weld on sealed containers or compartments without providing vents and taking special precautions.

(9) Do not weld on containers that have held combustibles without taking extra special precaution.

(10) If it is necessary to splice lengths of welding cable together, make sure all electrical connections are tight and insulated. Do not use cables with frayed, cracked or bare spots in the insulation.

(11) Do not weld in a confined space without extra special precautions.

(12) When compressed gas cylinders are empty, close the valve and mark the cylinder "MT".

(13) Do not allow flame cut sparks to hit hoses, regulators or cylinders. Remember flame cutting sparks can travel 9-12m.

(14) Never use acetylene at a pressure in excess of 1kg per cm2. Higher pressures can cause an explosion.

(15) Never use oil, grease or any similar material on any apparatus or threaded fittings in the oxyacetylene or oxy-fuel gas system. Oil and grease in contact with oxygen will cause spontaneous combustion.

(16) Always use this correct sequence and technique for lighting a torch:

(a) Open acetylene cylinder valve.
(b) Open acetylene torch valve 1/4 turn.
(c) Screw in acetylene regulator, adjusting valve handle to working pressure.
(d) Turn off acetylene torch valve (you will have purged the acetylene line).
(e) Slowly open oxygen cylinder valve all the way.
(f) Open oxygen torch valve 1/4 turn.
(g) Screw in oxygen regulator screw to working pressure.
(h) Turn off oxygen torch valve you will have purged the oxygen line.
(i) Open acetylene torch valve on 1/4 turn and light with a proper lighter. Do not use matches or cigarette lighters.
(j) Open oxygen torch valve 1/4 turn.
(k) Adjust to proper flame.

(17) Always use this correct sequence and technique of shutting off a torch:

(a) Close acetylene torch valve first, then close oxygen torch valve.
(b) Close cylinder valves, acetylene valve first then close oxygen valve.
(c) Open torch's acetylene and oxygen valves (this will release pressure in the regulator and hose).
(d) Back off regulator adjusting valve handle until no spring tension is felt.
(e) Close torch valves.

(18) Use adequate ventilation at the point of welding when welding lead, cadmium, chromium, manganese, brass, bronze, zinc, galvanized steel or other materials that can produce noxious gases.

(19) Make sure your arc welding equipment is installed properly and grounded and is in good working condition.

(20) Welding may produce fumes and gases hazardous to health. Avoid breathing these fumes. Use adequate ventilation.

(21) Nearly all gas welding fluxes and arc welding fluxes are toxic or at least can cause allergies to certain persons. Do not take welding fluxes internally. Keep out of reach of children.