1welder59 wrote at 2011-01-08 22:25:18
Another way to reduce thermal cracking is to run a temper- bead or half bead process in which you do like the first answer said by putting your first layer down with a 50% overlap using a cold setting on amps. Than grind (flat top) the first layer and proceed with sequential beads at 50% overlap
RichR wrote at 2014-07-29 12:48:05
Hardfacing is nothing like regular welding, the rules for preheating are totally different. When hardfacing 304 with stellite the joint design is critical in the determination of the correct preheat temperature to employ. The more constrained the joint the higher the preheat temperature. 304 stainless, other than internal bores, do require minimal preheats of 500 - 800F for larger parts, but virtually no preheat at all for small parts with external welds (welding does the heating). An internal weld like on a valve seat is where the preheat gets critical, and must be between 800 - 1250F depending on part size/mass and the ability to maintain the preheat by welding or with external heating torches. Never drop the preheat once welding starts and repairs must be at a higher temperature than the initial weld was at. Slow cooling is most essential to all hardfacing. I use mica dust but vermiculite works well. Parts must be completely immersed or covered and cool at no faster than 100F per hour (50F/hr on large parts). Remember, 800 - 1600F is the sensitization range for 304 and corrosion resistance falls drastically after 48 hours above 800F.
Using the oxy-acetylene process preheats range from 1200 - 1600F and must be maintained with auxiliary heating torches.
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.
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.
Blacksmith's Gazzette - Anvil Making
Education/Credentials BA Theatre Technology - Purdue University.