How to Weld High Carbon Steels
High carbon steels are considered "hard to weld" because they are crack sensitive. They are also more vulnerable to significant post-weld changes in both physical and mechanical properties. So, when you're welding high-carbon steel, keep the following in mind.
#1: Avoid excessive penetration.
The goal should be to ensure fusion to the root and side walls but not more than that. Work to ensure your amperage, voltage, and travel speed ranges are tight. This will help to avoid excessive penetration that may lead to cracking issues.
#2: Use the right filler metal.
If welding the same two materials together, you should match the filler metal to the base material properties. In some cases, you can use a slightly lower filler metal strength since there will always be dilution from the base material that will increase the strength of the weld metal. If welding two different base materials, always match to the lower strength base material since this is the weakest link of the weldment.
#3: Focus on high input heat and large weld beads.
When welding high carbon steel, use the highest input heat possible. This slows the cooling rate, so the potential for cracking is minimized. Also, weave or deposit large weld beads rather than using stringers when you're welding.
#4: Use adequate preheat and slow cooling.
When welding high carbon steels, use adequate preheat for the corresponding carbon equivalency and thickness of weld joint sections. Make sure to use a thorough, soaking preheat and when welding is completed, ensure slow cooling by covering the weldment with an insulating layer such as fire blankets or ceramic insulation fiber (Kaowool).
#5: Create a WPS.
Extreme care must be taken with high carbon steels. It's why, once you have the process down, create a WPS to define your procedures. This will ensure future success with your welds.
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