Welding Heat treated 4130
Welding Heat treated 4130
(OP)
Russ0448 (Mechanical) May 9, 2003
I'm looking to weld 4130 (4" round bar) to a lower carbon steel (pipe) that is unknown. The required strength of the 4130 will call for it to be heat-treated. The required strength = 100 Ksi Yield. The question is that would it be better to heat treat the 4130 before welding?
The process that I have seen before is of heat-treating the 4130 component then weld and then stress relieve. With this in mind, would the stress reliving (by heating the welded component) have a large impact on the previous heat treatment?
Also What type of preheating of the material would be recommended?
I'm looking to weld 4130 (4" round bar) to a lower carbon steel (pipe) that is unknown. The required strength of the 4130 will call for it to be heat-treated. The required strength = 100 Ksi Yield. The question is that would it be better to heat treat the 4130 before welding?
The process that I have seen before is of heat-treating the 4130 component then weld and then stress relieve. With this in mind, would the stress reliving (by heating the welded component) have a large impact on the previous heat treatment?
Also What type of preheating of the material would be recommended?





RE: Welding Heat treated 4130
Different story if it's a 4" tube!
Whatever, when you weld it the strength in the HAZ will drop way down, so you won't have to be concerned about what stress-relieving will do.
RE: Welding Heat treated 4130
The weld will be located at the 4" section, with the high stress seen just pass the 4" to 2.36" step on the 2.36” dia side. The high stress is due to bending.
Being that the stress, due to bending, drops down after the increase in the dia.(Area of weld), and the area of concern is at a distance 9/16" plus the vertical distance due to the step. Then it may be that the heat will not reach the area of concern. This was just a thought that I will probably not pursue. In any case, would heat-treating the entire piece be the better option?
Would localized heat-treating after be a better option?
Appreciative
Russ
RE: Welding Heat treated 4130
Preheat, for a material of given composition and strength, all depends on the thickness of the component, (which you say is 9/16"), and the heat input of the weld. Those two things control the cooling rate. A conservative preheat for your situation would probably be 250-300F. Depending on the size of your weld, you could probably establish a lower preheat by testing. You also want to establish a maximum interpass temperature also for Q&T steels. 4-500F is a reasonable limit, in order to prohibit too much grain coarsening, or overtempering in the HAZ.
Also, I don't think that it would be impossible to get 100ksi YS in a 4" dia. 4130 bar. We achieve 110 ksi YS no problem in the center of a 7" thick x 14" wide x 20" long block from 8630 after water quench and tempering at 1150F, and I wouldn't think that it is much more hardenable than 4130.
RE: Welding Heat treated 4130
Also T1 Steel is another alternative that would eliminate heat treat.
RE: Welding Heat treated 4130
If you do persue this, simply buy 4130 heat treated to your requirements. You can still easily machine it, and the welding heat won't affect the critical area.
Then do a PWHT as per GRoberts said.
GRoberts,
You probably have heats of 8630 that are near the max. in the hardenability elements. Depending on the heats, 8630 can be somewhat deeper hardening than 4130.
I have some old Bethlehem steel data which shows a YS of 86 ksi on a 4" round, temp. at 900 deg. F. That drops to 72 ksi when temp. at 1100 deg. Both were water quenched-maybe they used hot water? <g>
RE: Welding Heat treated 4130
I would imagine that the YS would depend a lot upon where the particular heat is whithin the chemistry range. Unless Russ0448 is buying a whole heat, it can be hard to controll. We do have good control over out quench tank temperature though.
RE: Welding Heat treated 4130
I'll plan on asking for a preheat of 300 F and a 450 F interpass temperature. (Per GRoberts)
I'll plan to match the filler to the low carbon material strength by using a Low Hydrogen 7018 rod.
And then request stress relieving at a temperature of 100 F below 4130 tempering temperature.
How dose this sound?
Thanks
Russ
RE: Welding Heat treated 4130
RE: Welding Heat treated 4130