WELDING M-2 TOOL STEEL 1

[duc916]

I am in the process of designing a part made form M-2 tool steel, which will need to be welded. I will have two tubes 0.600" in diameter with 0.050" wall thickness. The tubes will be "butted" together with a small overlap on the I.D. for centering then welded. The welding will be done pre heat treatment.
From what I can find, I will need to pre-heat the parts to above 200F and use a rod that has material properties similar to M-2 when heat treated. I am planning on having the parts TIG welded. Is there a good resource for welding rod type, pre-heat temp, post weld cooling, etc. for dealing with M-2 tool steel? Has anyone had any experience with welding M-2? Thanks for the help.
Dan

 

[metengr]

Welding in the annealed condition will provide maximum protection for crack resistance during welding. According to my source book you have several options for weld filler metal (matching filler metal for M2, carbon or low alloy steel that results in moderate strength and hardness, and the third option is austenitic or nickel base filler metals that have low strenght and hardness).

After reading your post, you probably will need to select a filler metal that matches the M2 base metal for strength and hardness. To locate a source, you can do an internet search or check with some tool steel suppliers concerning a reputable vendor for filler metal. Please note that the filler metal will not be a standard alloy, it will be a custom alloy that closely matches the M2 tool steel.

The welding parameters are as follows;
1. Prep the edges of each tube for a vee groove butt weld deposited from the OD side of the weld joint.

2. Locally preheat the M2 between 950 deg F to 1100 deg F. Keep the interpass temperature below 1100 deg F.

3. Use tight stringer beads with the GTAW process - welding grade of Argon gas.

4. After the completion of welding, slow cool to ambient temperature.

5. I would perform a wet fluorescent magnetic particle inspection of the weld prior to heat treatment to make sure the weld is acceptable.

6. Heat treat per the tool steel supplier recommendations. You will probably be required to utilize a double or even triple temper process to assure an acceptable hardness range for M2.

 

[duc916]

metengr,
Thanks for the valuable information. That pretty much sums up all the data I need.

Dan