AISI 4130 alloy steel is a medium carbon, low alloy steel in ASTM A29 standard also referred to as a chromoly steel, or chrome moly steel, containing nominally 0.28-0.33% Carbon, 0.8-1.1% Chromium and 0.15-0.25% Molybdenum. Annealing ASTM 4130 alloy steel offers excellent corrosion resistance, ductility and strength, usually supplied as round bar commonly in the hardened and tempered condition. Here are 10 of the most common questions with 4130 chromium-molybdenum welding.

Q1: Can 4130 chromium molybdenum steel be welded by argon arc?

A: yes, argon arc welding of 4130 chromium-molybdenum material has been widely used in the field of aerospace. Similar to other welding methods, argon arc welding requires reasonable procedures and a skilled process.

Q2: Do you need pre-heating?

A: Thin-walled 4130 steel tubes (thickness less than 0.12 "or 3mm) generally do not require preheating of 300-400F (149-204 ℃) to achieve the desired effect, but the steel tube itself should not be lower than room temperature 70F (about 21 ℃) before welding.

Q3: What wire is used?

A: ER80S-D2 is the most suitable welding wire and its weld strength is basically close to the strength of 4130 material itself. ER70S-2 can also be considered while offers slightly weaker weld strength.

Q4: Did ER70S-2 wire sacrifice its strength for better ductility?

A: Yes, when the welding wire fuse with the base material, the strength of welding wire is generally less than that of 4130. However, reasonable structural design (such as adding stiffeners or support pipes) or multi-point support and longer welds can make up for the insufficient strength of the welding wire itself.

Q5: Why is the 4130 wire not recommended?

A: 4130 wire is generally used in the back of the need for heat treatment of the workpiece. It is not recommended for using in sports equipment such as aircraft, racing car frames and roll frames due to its high hardness and poor ductility. 

Q6: Other welding wire can be available for 4130?

A: Some welders use austenitic stainless steel wires such as 310 and 312 to weld 4130 steel pipes. Stainless steel wire is more expensive and some stainless steel grades will cause cracking.

Q7: Does the 4130 steel tube need heat treatment to destress after welding?

A: Generally speaking, thin wall tube is not required to stress and only the steel tube with wall thickness more than 0.12 "or 3mm be heat treated after welding. The optimum treatment temperature for the 4130 tubes is 1100 F (about 593 ℃). The neutral flame formed by oxygen and acetylene can be used for heating, and is continuously moved during heating to avoid local overheating.

Q8: Does 4130 workpoece need to be cleaned before welding?

A: Clean steel surface for better welding effect. Impurities and oil on the surface of the steel pipe need to be removed with medium size sandpaper and acetone. Burrs and corner tips need to be polished.

Q9: Do you need back side gas protection for 4130 welding?

A: Generally there is no need to weld back gas protection although some welders do this as well. Backside gas protection is not bad for welding and can improve weld quality for some welds.

Q10: Can the welded workpiece be quenched?

A: No, rapid quenching of welding parts can cause cracks or split tears. Natural cooling is feasible.