High-Strength Steels Welding: Medium-carbon harden steels with low-alloy
Multiprocess welders are trained to operate with different steels and under different conditions and circumstances. In several consecutive articles we will present the welding process when the MIG welders, TIG welders, Arc welders and Stick welders perform welds with high-strength steels. The first situation to be covered here is the welding of medium-carbon harden steels with low-alloy.
The steels that are best known to the commercial welders include AISI 4140 and AISI 4130 steels, as well as the steels of higher strength AISI 4340 and AMS 6434. MIG welders know that by processing these steels with heat, they obtain high strength which improves their toughness and ductility. It should be said, as arc welders confirm, that the temperatures used affect the strength levels in those steels. The carbon used by the Stick welders here is of medium and low range, however the amount is sufficient to secure the desired strength. The impurities in these welds are minimal, as the multiprocess welders use melting and other refining methods.
The steels that are used by the Stick welders, the Arc welders, the TIG welders, and the MIG welders here are bars and sheets, as well as light plates and tubing. The medium-carbon harden steels with low-alloy that belong to this group can be flame cut and mechanically cut. The flame cut here requires preheating to 316°C. Before additional operations to be done, the flame-cut parts should be annealed so that the hardness of the flame-cut edges to be reduced.
All medium-carbon harden steels with low-alloy could be processed by the commercial welders only if they are in normalized or annealed condition. When the welding is done, they have to be treated with heat in order to reach the desired strength.
When welding these steels Stick welders, Arc welders, TIG welders, and MIG welders all use gas metal arc, gas tungsten arc, shielded metal arc, and gas welding processes. The filler wire composition in these situations is designed to make a weld that responds to heat treatment almost like the base metal responds. To avoid cracks and brittleness, the commercial welder here should use interpass temperatures and high preheating.