Resistance Welding
Frequently Asked Questions

Q - We are a tooling manufacturer and we are currently quoting on making a rotary electrode for a tube mill.  The drawing states R.W.M.A Group ‘A’ Class 3 H.T. & C. W. Alloy Cooper.  My question is as follows:  Is Copper C17510 the same material?  If so I would appreciate if you could tell me what H.T. & C.W. are acronyms for.

A - Yes alloy 17510 is Class 3.  You should use the material in the fully heat treated and aged condition.  Cold working is advised in all forged seam welding wheels.  This is normally performed between the solution anneal and aging steps.  Most reputable forged wheel manufacturers will have no problem supplying your needs.  

Q.  I recently received a part that was designed as RWMA Class 2. What specifications are associated with RWMA Class 2?

A - The Resistance Welding Manual, chapter 18, and Bulletin 18, section 18, should provide you with the info you need. You can see more detail in bulletin

Q. We are trying to change the method of welding an .036” CRS piano hinge to either a .024” or .030” CSR door.  We currently weld a 16” hinge to the doors using (6) welds on 3” centers using a single point welder.  We are trying to change this to an 18” hinge using a 6-point, multi-tip welder with welds on 3.4” centers. We are incurring a puckering of the hinge material between the welds.  Is this due to the additional distance between the welds or could it be something else?  Is there some criteria that would tell us the optimum distance between welds?

A.    I have seen this before. I resolved it on a multi-spot welder by bringing 1 head down at a time starting from the center and working back and forth outwards.

Q.  I am looking for information on welding .8MM Galv- 1.0MM Galv steel through sealer.

A. Welding through conductive sealants, our recommendation to our customers is to first weld coupons without sealant.  Then weld coupons with the sealant.  Check to see nugget size to determine if the sealants presence degrades the weld quality. If it does, then make more coupon welds with the sealant present with an adjusted weld schedule.  Higher currents or longer weld times.  We usually favor the longer weld times.  Then we suggest that actual parts be welded with sealant present to determine

Q. I am looking for information on welding .8MM Galvanized steel  1.0MM Galvanized steel through sealer.

A.    Welding through conductive sealants, our recommendation to our customers is to first weld coupons without sealant.  Then weld coupons with the sealant.  Check to see nugget size to determine if the sealants presence degrades the weld quality. If it does, then make more coupon welds with the sealant present with an adjusted weld schedule.  Higher currents or longer weld times.  We usually favor the longer weld times.  Then we suggest that actual parts be welded with sealant present to determine

Q. I am looking for copper to use as electrodes for a resistance welding operation.  I have found suppliers who use RWMA class 100, 200, 300 to define material.  Could you please give me a cross reference to either a UNS or ASTM equivalent. I need to determine the machinability properties of this material.

A. Contact the RWMA and obtain document Bulletin #16.  Refer to section 1-8. Starting on page 2 of section 8 we refer to a RWMA #. If you remove the 1., 2., 3 from these numbers you will get the CABRA numbers.

Q. I am looking for a formula or any comparative information on the economics of a spot weld to that of any equal size mig (are weld). I have the Resistance Welding manual and have found nothing I can use.  Do you know of any such formulas or studies done? Can you steer me on where I can look?

A. In volume I of the AWS handbook (available from AWS) covers the costs of MIG welding in chapter 8.  A meaningful comparison will have to examine a specific test case.  Generally, there is no question that RW is less expensive and considerably easier to work with, but there may be other cost drivers that make MIG a desirable way to go (although this is pretty rare). Answer provided by David Beneteau

Q. I am looking for some good fundamental information on resistance welding.  To be more specific, Spot, Seam, and Projection welding.  I want to use this in my Bosch Series 6000 Welding course.

A.   The Resistance Welding Manual would be a good resource.  We use the Manual in our RWMA school, it is a very fundamental manual that covers the items you are inquiring about.  See the RWMA web page or contact RWMA at 215-564-3484.

Q.    We are a tooling manufacturer and we are currently quoting on making a rotary electrode for a tube mill.  The drawing states RWMA Group ‘A’ Class 3 H.T. & C.W. Alloy Copper. My question is as follows: is Copper C17510 the same material?  If so I would appreciate if you could tell me what H.T. & C.W. are acronyms for.  

A.    Yes alloy 17510 is Class 3. You should use the material in the fully heat treated and aged condition.  Cold working is advised in all forged seam welding wheels.  This is normally performed between the solution anneal and aging steps.  Most reputable forged wheel manufacturers will have no problem supplying what you need.  Two member companies manufacture wheels Non Ferrous and Cadi.  Either can supply the product you would need.  There are several other member companies that can supply the wheels.  You can contact the RWMA to obtain a free RWMA Membership Directory. This will have further contact information you are looking for.

Q. I am looking for RWMA material standards for Class 2 bar stock.  I am interested in the mechanical and chemical requirements as well as dimensional tolerances of the bars stock.

A. The RWMA publishes 2 documents that can assist you in these areas.  See our website www.rwma.org for literature ordering information.  The two I would recommend are the Resistance Welding Manual and Bulletin #16.  In Bulletin #16, refer to section 1-8.  Starting on page 2 of section 8 we refer to an RWMA #.  If you remove the 1., 2., 3. from these numbers you will get the CABRA numbers.  RWMA offers no dimensional specifications on the bar or rod dimensions.

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