Things You'll Need:
- Argon shielding gas
- Shielding gas
- Tungsten electrode
- Welding machine
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Step 1
Identify 4140 steel. This number indicates the alloying agents in the steel. The first digit indicates the primary alloying agent, with a "4" referring to molybdenum. The second digit indicates the second alloying agent, with a "1" referring to chromium. The third and fourth digits indicate the carbon content in hundredths of a percent. Therefore, 4140 steel is a chromium-molybdenum alloy with a carbon content of 0.4 percent.
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Step 2
Select the electrode. The electrode may be pure tungsten for lighter metals, but the harder steels require an electrode with a tungsten alloy. An electrode that contains about 2 percent cerium oxide is a common choice for 4140 steel.
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Step 3
Choose the settings on the welding machine. A TIG welder has several current settings, such as AC, DCEP and DCEN. Steels are generally welded with the DCEN setting, which stands for "direct current electrode negative."
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Step 4
Use the correct shielding gas. Most TIG welding of 4140 steel will be done with virtually pure argon. The pressure is typically in the range of 15 to 20 pounds per square inch.
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Step 5
Preheat the steel. High-carbon steels are more brittle and therefore need to be heated to soften the steel so the welds don't crack; 4140 steel should be preheated to about 700 degrees F.
