Selection of Suitable Welding Wire According to the Condition of Steel

Strength Undermatch: When the part design and/or welding limitations are limited, such as pre-hardened workpieces. It is not possible to pre-heat or post-weld. For example, maintenance welding work, in such a case, if it is accepted that the welding line may not need to be as strong as the metal work piece. 

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It is also possible to use welding electrodes of lower strength, such as carbon steel welding electrodes. with a tensile strength of approximately 70 ksi, such as Thermatech TM-76 or Bohler Fox S EV 50 electrodes for manual arc welding. or Thermatech TM-70 welding electrodes for MIG/MAG welding processes; or 309 stainless steel electrodes such as TM-309L or 310, 312; or nickel electrodes such as ENiCrFe-2 and ENiCrFe-3.

This type of electrode has a great advantage in resistance to cracking due to its toughness. This makes it resistant to the stresses generated by the expansion and contraction of welding. The welding seam will be able to bear force in the plastic state without causing damage to the main work piece. Will have a weld that is less strong than the workpiece metal But as long as the part design can handle this undermatch condition, it is not a problem to achieve a weld with lower strength than the part itself. See Figure 2 for a carbon steel electrode. that can be used to weld 4140 steel with lower strength (Undermatch) workpiece metal

Welding wire that gives strength in the annealed condition is the same as the workpiece metal (Matching annealed strength): If 4140 steel is in the annealed condition (This is the recommended condition for welding To avoid cracking) after welding, there is no heat treatment to increase the strength of the material. The use of welding electrodes with comparable strength properties is normal and acceptable. Wires that provide a tensile strength of about 80 – 90 ksi, according to Table 1., are suitable wires for 4140 steel in the annealed condition. These types of electrodes have the advantage of equivalent joint strength with no susceptibility to cracking due to differences in chemical composition.

Chemistry Match : For 4140 steel that must be quenched and tempered after welding. In this case, it is necessary to use a welding wire that can support the improvement of thermal properties in the same way as the workpiece metal. To make it easy to understand, 4140 steel must be paired with a 4140 wire that offers the same mechanical strength and chemical composition.

It is important to note that 4140 steel has a high carbon content. Therefore, it can be heat treated. This results in a greater susceptibility to cracking. Therefore, if the application does not require heat treatment after welding. There is no benefit to selecting electrodes that are chemically compatible with the workpiece metal.

There are other electrodes that can be used to successfully weld 4140 steel such as 309 (Thermtech TM-309L) or 310, 312 stainless steel electrodes, or nickel alloys such as ENiCrFe-2 and ENiCrFe-3 electrodes. This type of welding gives good strength. Toughness therefore provides good resistance to cracking. Can be used to weld different metals however This type of welding wire has a higher price than general welding wire. But making it easy to successfully weld 4140 group steel.

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