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Welding/440 stainless tig

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Question
my customer is trying to repair a 440 stainless part. It is 440 stainless material for both pieces. They are tig welding a bracket of approx 1/4" thickness to a 1-3/4" shaft with their 350 syncrowave tig welder. They tried with 410 stainless tig rod but it cracked post weld. Is this rod acceptable for the work and if not what alloy would be recommended. Also, is there a certain procedure to follow? pre or post heat? Temps?  Thank You! Al

Answer
Wow, TIG welding 440 SS is going to be very tricky.

You did not state whether it is 440A, 440B or 440C SS.
440C has much higher carbon content than the others. hence why it is used for knife blades.


The problem with welding 440SS is going to be martensite formation in the Heat Affected Zone.
The only way to prevent this will be a full furnace anneal post weld.

410SS is compatible with 440SS as a filler, but is not as strong.

To put this another way, 440A, 440B and 440C are all used for different kinds of knife blades.
410SS is used for stainless steel rulers and other tools where a SS spring is required.

Find a local heat treater, and they should have a furnace program to anneal 440SS.
It will take a very long slow cool down to prevent martensite from forming.
This process could in theory be done with a torch, but it really should be done in a computer controlled electric furnace, to prevent too much surface oxidation.

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Ernie Leimkuhler

Expertise

Questions about Oxy-Acetylene welding/cutting, MIG, TIG, Flux-core, Stick welding, brazing and soldering, bike frames, air frames, motorcycle frames, structural welding. Also questions about Welding Certifications and Inspections. All questions about fabrication of metals (stainless steel, steel , aluminum, brass, bronze, copper). Basic questions about underwater welding. TIG is my strongest subject.

Experience

Extensive background in most welding fields. 18 years fabrication of metal theatre scenery, 16 years structural steel, 2 years pipe welding, 9 years as a Welding Instructor at South Seattle Community College, and 5.5 years as a Welding Instructor at the Divers Institute of Technology. 16 years Industrial Welding Consultant for fabrication shops in the greater Seattle Area. 11 years Architectural Metal Fabrication. 8 years in Film/TV; SPFX/construction/set-deco/props/. 33 years Blacksmithing and Knifemaking. Currently a Field Welding Inspector for Otto Rosenau and Associates.

Organizations
American Welding Society - Certified Welding Inspector Washington Assoc of Building Officials (WABO) - Special Inspector - Structural and Reinforcing Steel.

Publications
Do a search on google groups for "Ernie Leimkuhler" in the rec.crafts.metalworking and sci.engr.joining.welding groups. http://www.stagesmith.com/ http://www.metalwebnews.com/ Blacksmith's Gazzette - Anvil Making

Education/Credentials
BA Theatre Technology - Purdue University.

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