Welding 4130 with 309 SS?

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Hi im building a 4x4 chromoly frame. Ill be welding 4130 to 4130. The two sizes are .120-2" and .060-1.5".I will be welding with a tig but am wondering if i can use 309 SS as filler since I have a free supply  Or is some regular mild steel wire ok? Ive heard that 310 ss is ok, so would 309 be about the same?I do plan on tacking with 316 ss stick, before i take it to be tiged. Thanks for your help guysDoug
Reply:Chromoly is best done with 70S-2..309 will work...somewhat.. but it will not pass tech...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:IMO, do not tack with stick and then attempt to TIG weld over it.  You'll lilkely have problems with too large of a tack, irregular tacks, and porosity in the tacks, since stick is much less controllable than TIG.  Also, residual slag could casuse problems with the TIG.316 SS is NOT the proper alloy choice for welding carbon steel.  It will likely result in a hard, brittle, crack prone, martensitic weld.309 SS is the recommended alloy for disimilar joining of austenitic SS (300 series) to carbon steels, and would probably be ok for your application, although in detail it depends on how much 309 and 4130 end up in the weld mix.I've read from others here in previous posts, that E70S-2 is the common choice with TIG.
Reply:RG60 works well for chrome moly.  RG 60 wets out better than ER70 and is more ductile.
Reply:RG60 is intended for oxyacetylene, but you reccomend it for TIG?
Reply:Originally Posted by pulserRG60 is intended for oxyacetylene, but you reccomend it for TIG?
Reply:I have taken the flux off of 7024 (3/32)..rods and polished them with a wirebrush and used them..Works rather well..
Reply:RG60 works extremely well with a TIG torch.  Once you try it, you may never want to go back to ER70.  It wets out so well and produces a very smooth bead appearance.  The added ductility of RG60 is important when welding chrome moly without post weld heat treatment.
Reply:76GMC1500,I was thinking that since RG60 is "designed" for oxyacetylene welding, that it may have different alloying additions, such as additional deoxidizers, to help offset the presumably poorer shielding environment compared to TIG, and that this could have unintended affects on the weld material properties when using RG60 for TIG vs for Oxyacetylene.I compared the specified composition ranges of E70S-2 with RG60, and found that RG60 has higher carbon (.16 vs .07), lower silicon (.10-.35 vs .40-.70), and equal manganese (.90-1.4).  But in addition, the RG60 is specified to contain copper (.30) and tin (.035), where none of the E70S-x fillers include these.  Not sure what effect this could have, but there must be a reason why these are designed differently.Apparently, from your experience, this is not a problem, and as you say actually a benefit in the case of the lower tensile strength (60 ksi) providing a more ductile weld which can help reduce stresses on the less ductile HAZ in the non-post weld treated 4130.
Reply:Well, I don't have much personal experience with RG60 on chrome moly, but I have run it with a TIG torch.  However, in aviation, RG45 and RG60 are the prefered filler when 4130 is involved and post weld heat treatment is not.  RG45 produces a weaker bead, but penetrates better and fillets better.
Reply:Thanks for the info on RG45/60 for aviation 4130.Can you pass on any sources/references on this subject?New subject, just felt the need to harass and nit pic, so I want to comment on your statement, "RG45 produces a weaker bead, but penetrates better and fillets better".I understand "weaker" because it's specified ultimate tensile strength is 45 ksi.Not sure what "fillets better" means, but assume it has to do with ease of wetting, flow, smoothness, bead contour, etc.My main question is, can you explain how TIG with RG45 "penetrates better".As I understand it, TIG penetration is a primarily a function of current (amps), current density, shield gas composition, and travel speed.  Other factors, which probably relate to current density, are electrode diameter and end preparation, torch angle, and arc gap (voltage).  The influence of wire would probably involve things related to chilling the pool, or obstructing the direct action of the arc on the pool, such as wire diameter, wire feed rate, and where it is introduced into the pool.There is however, a more obscure phenomena that could explain how filler wire could affect weld penetration, and this is the "Marangoni" or "themocapillary convection" phenomena.  In brief, certain "surface active" elements such as sulfur, selenium, and oxygen can dramatically affect a very powerful surface tension driven fluid flow within the weld pool, and cause huge changes in the cross sectional depth and width of steel and stainless welds.This is one of a couple hundred papers related to the subject of Marangoni flow.http://files.aws.org/wj/supplement/Pierce/ARTICLE3.pdf
Reply:Have you ever seen the back side of a weld on stainless steel done without proper back-up?  The weld is usually crystalized and has poor penetration.  Mild steel fillers do this same thing to a limited extent.  Maybe the alloying elements reduce this effect?  RG45 is certainly more fluid while molten than ER70x
Reply:Guess so.Could be an interesting comparison, hope to try it some time.
Reply:Hi,I would tend to agree with Zaps comments, For C/M welding that will not be heat treated post weld ER70S2 is the recommended wire for the girls I dance with. I would see no benefit to using the SS wire other then it is free. But as someone stated, in most sactioning bodies you can rest assure it would not pass tech.ric