First let me thank you all for your help in previous situations. The task at hand today is to weld a 4140 tube, 3" OD x 1/2" wall x 2 1/2" long to a 4140 plate 1" x 6" x 6". The plate is bored through and the tube inserted 3/4". Is a preheat required for this material, if so what temp. range? What filler/electrode is recommended? Welding processes available are smaw, gmaw and gtaw. Thanks.
Dave
Dave-
What are the service/application requirements of this weldment?
Is hardness, tensile strength, etc a factor? Has the mat'l been quenched and tempered, annealed, stress relieved from the "as received" condition?From your posting it appears you will insert the tube into the plate and make a 1/4" fillet weld inside? Any feed back will help.
John
This weldment is a receptacle for a locator pin. I don't know the loads imposed but it is attached with four 10mm shcs. The material is in the "as received" condition and will be hardened to 58-62 R.C., 0.5 mm deep after welding.
AISI 4140 to 58 ~ 62 Rockwell c?
I didn't know 4140 could get that hard.
Ron,
All I can tell you is what I see on the print, "ION Nitride Harden, R.C. 58-62" Unfortunately, the print doesn't convey any weld information, which is all I'm concerned with.
Nitride makes more sense.
Well one things is for sure, you will need a Preheat & Interpass no less than 400 F.
If you need that kind of hardness with strength to match, I would suggest you use GTAW with RACO 4130. (Techalloy)
But if you don't need 145 KSI Tensile strength I suggest some more user friendly like ER120 S-1.
In additon to the preheat and interpass maintenance (400-600 F), try stick electrode Atom Arc (ESAB, Alloy Rods) 4140, no AWS class.
Dave,
4140 welds have an aggravating tendency to crack if they are allowed to cool down too fast after welding.
You will need to preheat the entire 1" plate and a good foot or so of the tubing, and keep it hot until you are finished welding.
Immediately after you finish welding, wrap the material with insulation in order to force it to cool slowly. We used to use a product called K-wool for insulation as it is fire/melt proof, however, you can use ordinary household insulation if you wrap the metal first with fire blanket (rafrasil).
Check the weld for cracks 72 hours after welding completion.
Let us know how it works out for you.
Tim
Tim,
Sources for insulation for both Dave and you:
Locally a furnace refractory insulation sheet known as Kao-Wool is available through Sid-Harvey chain of HVAC supply houses, as well as any other well stocked supply house.
If the use of a bucket of pearlite is more convenient, as in the size of this roughly 3"x6"x6" weldment, it can be gotten through a well stocked masonary supply house; it's used as an aggregate for light weight concrete as it has very little mass. It can be [re]used as if you were packing the part in foam peanuts except it's pearlite beads about the size of a BB.
IMO the pearlite is a superior method of insulation; much faster and more even where practical.
Hope it's of some value.
Regards,
D
Normally, when an alloy such as this one is used and then given a surface hardening treatment, it would be a requirement that the base material is tough. (or else they would just harden the whole assembly by oil quenching. - this can give you 57HRC)
This means that the weld and HAZ should be tempered following the welding operation. Here is some info:
To Obtain (HRC)--------Temper at (°C)
57----------------------205
53----------------------260
50----------------------315
47----------------------370
45----------------------425
41----------------------480
36----------------------540
33----------------------595
29----------------------650
(Info obtained from ASM Metals Reference book (3rd ed)
You should therefore establish the hardness you require, and PWHT accordingly.
Something else that was not mentioned, that is very important with this material is to keep the hydrogen input as low as possible. So, make sure your electrodes have been baked well, as per manufacturer's instructions, and that the base material is properly clean.
Regards
Niekie Jooste
This is all great reference material for welding 4140.
Does anyone know what the post weld treatment would be for welding 1018 to 4140?
The print does not currently call out a heat treatment, therefore it is used in the annealed state.
Your guidance is appreciated.
Joe
The 1018 is a plain carbon steel, so it will generally not require a PWHT unless you have it working under impact conditions. In addition, most PWHT's will not greatly reduce the properties. As such, the PWHT for your 4140 will generally rule. Therefore use the same as given in my previous post.
Regards
Niekie Jooste
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