[Andy]

Hi all.

When reading these lines please keep in mind I am from Germany. Some things that may appear to be obvious to you are not on this side of the pond.

I have had some parts machined that need welding and apparently the machine shop used “quenched and tempered”(!?) 4140 (tensile strength 900-1100N/mm2). After searching the web and talking to official institutions here in Germany it is very hard to find the correct translation/american term so I don’t know if the correct description/term is quenched and tempered 4140 or prehard 4140.

As I understand 4140 should be annealed to ensure best weldability so I was searching for the correct info to give to the hardening shop on “annealing”. A term not known here. I searched many US websites and got a lot of confusing information:

Some sources call for heating to 800-850°C and cooling in a furnace other sources call for heating to 600°C-650°C and cooling in a furnace and if heated to 850-900°C and cooled in still air it is called “normalization”.

The procedure offered at the hardening shops here in Germany which includes “cooling in a furnace” is heating to 680°C-720°C and cooling in a furnace. The shops also offer what is described above as normalization with cooling in still air after heating to 850-900°C.

So what should I go for? Is heating to 800-850°C and especially the cooling in a furnace decisive? If so I have a major problem because this process is not offered here. I probably won’t be able to convince the hardening shop to heat to 800-850°C and cool in the furnace as my parts are only a tiny bit of a large batch processed at once.
What would the disadvantages of only heating to 680°C-720°C be?

Most of the welded parts will be hardend/tempered after welding.

Thanks in advance for any support, advice and assistance offered. Please be assured that I have been searching for answers for weeks.

Best regards
Andy

[Coldman]

Hi Andy,
my information for 4140 is:
-usually supplied in the tempered and quenched condition.
-Annealing is required prior to welding. Heat to 800*C-850*C, hold till uniform, cool in furnace.
-Normalising happens above 870*C and involves cooling in still air
-Stress relieving happens between 600*C and 700*c and also involves cooling in still air. Tempering can be done in this range as well.

I think that the above annealing process is important prior to welding.

I know that the German word "temper" can mean a number of things including annealing depending on context which may be the point of confusion.

If you continue to have disagreement in your various departments, the best thing would be to get the formal welding advice in writing from the supplier/manufacturer of your 4140, then there can be no arguments.

Good luck!

[Andy]

Hi Coldman,
thanks for your reply. Much appreciated. Actually 4140 is classified as not or at least as hardly weldable in Germany. I have talked to many renown institutions and welding schools. All suggest not to weld 4140. Most of the teachers can't weld it themselves.

We have totally different materials here. I import my 1018 square stock and my 4140 square stock from the USA because it is not obtainable here. Neither is anything similar. Shipping is always more expensive than the material itself!

I have learned about welding 4140 from weldingtipsandtricks.com and I am aware that annealing is needed. But it is definitely a problem finding a shop that will anneal it as you (and others) have described (heating to 800-850*C and cooling in a furnace). The only thing close to this process is apparently called (weich Glühen in German or) "soft annealing" in the states. But only involves heating to a much lower temp. I have found the process described on US supplier/manufacturer pages but not sure if it makes 4140 weldable and if so involves any major disadvantages.

Cheers
Andy

[Coldman]

Andy,
I'm a little surprised 4140 isn't more common in Germany.
Definitely weldable with the correct heat treatment. I think only the manufacturer will tell you if the " soft annealing" will do the job for you. I can't find anything about this lower temperature treatment.
Also my information for locally manufactured product (Aussie) is that stress relieving is required immediately after welding and then tempering afterwards.
Can you have the 4140 annealed in the USA prior to shipping to you? Then all you have to organise is the post welding heat treatment. Too late for this job but maybe for next time?
Cheers,
Vic.

[Andy]

Hi Vic.

Sorry, I probably didn't express myself correctly. 4140 is popular in Germany but classified as not/or hardly weldable - so resellers don't have much info on the matter.

I import small amounts of 4140 cold rolled annealed square stock as it is not obtainable here. It comes in handy that I need it in 3/4" as well. 1018 isn't available at all.

4140 is offered normalized or quenched and tempered. The machine shop used quenched and tempered 4140 because I usually just harden and temper my parts. They didn't understand it was to be welded this time. I could have it normalized again at the hardening shop though. Importing all 4140 as annealed from the US is not an option as it is way to heavy and shipping costs are outrageous. I am just starting off with some projects where I'd like to weld 4140 so I am trying to find how to get best results for weldability with techniques offered at hardening shops here. I am not sure but it may be just a translation deal.

What exactly is the difference in material structure if you compare what is called annealing to normalization (which is an annealing method also, isn't it?)? The heating temp seems to be nearly the same just the cooling method differs:
annealing: cooling in the furnace vs.
normalization: cooling in still air.

Cheers
Andy

[RamboBaby]

"Thin work pieces cool faster and hence are harder after normalizing than the thicker work pieces. This is different than in the case of annealing where the hardness of thin and thicker work pieces is same after furnace cooling."

"The main difference between full annealing and normalizing is that fully annealed work pieces are uniform in softness (and machinability) throughout the entire part, since the entire part is exposed to the controlled furnace cooling. In the case of the normalized part, depending on the part geometry, the cooling is non-uniform resulting in non-uniform material properties across the part."

----- http://ispatguru.com/normalizing-process-for-steels/

[Arno]

May want to use the german DIN or international ISO notations on this side of the pond

If you look for AISI/ANSI 4140 in the USA it's classed as 3 distinct alloys in germany:

- 41CrMo4 -> werkstoff nr. 1.7223 / DIN 17212
- 42CrMo4 -> werkstoff nr. 1.7225 / DIN 17200-1654
- 42CrMoS4 -> werkstoff nr. 1.7227 / DIN 1.7227

When ordered as quenched and tempered alloy steel ('Legierte Vergütungs-stähle') the 'werkstoff' types get a 'TK' prefix, so 42CrMo4 in it's quenched and tempered form becomes known to german vendors as 'TK 1.7225'

A bit of info on the base material from Thyssen-Krupp:

http://www.thyssenkrupp-stahlkontor.de/ ... CrMoS4.pdf

Perhaps checking with steel vendors in Germany using the steel types/identifiers they know helps to find out their preferred methods of tempering ('Vergütung' or 'glowed') or heat treating/hardening afterwards and that might help in communicating with machine shops or heat-treating shops?

Bye, Arno.

[Andy]

@Raymond
thanks for the reply and the very informative link. Lots of insights! Really appreciate that!

@Arno
Thanks, but I know what 4140 is. I am trying to understand the key facts of the "US-annealing procedure".

As I wrote I have been searching down info on the process of annealing as described in US sources to improve weldability for weeks. It is not practiced in Germany! I have spoken with many experts of the trade at DVS (Deutscher Verband für Schweißen), SLV (Staatliche Lehr- und Versuchsanstalt), GSI (Gesellschaft für Schweißtechnik International), Thyssen Krupp, Saarstahl, Böhler, at least 5 hardening shops and others. All say don't weld 4140 (42CrMo4, 1.7225). Böhler even told me if I try to weld it to use stick welding, because if I tried to TIG or MIG weld 4140 the shielding gas may not shield the weld correctly because of the required high preheating temps. Please mind they told me this although they produce and sell MIG wire and TIG rod (DCMS-IG) for 4140.

Standard annealing procedures in Germany are as mentioned above (Normal-Glühen und Weich-Glühen). If the process of annealing as described in US sources is standard in NL please let me know and I will gladly drive over the border to have my stuff annealed.

Cheers
Andy

[kiwi2wheels]

I understand what you are going through Call Barry at Tennant Metals, as they may be able to give you the name of a HT company who know what is required.

http://www.tennant-metall.de/en/start

But confirm the DIN # of the material that the machine shop used. Also, do you have access to a copy of

http://www.keytosteel.com/en/

From memory, it has details of heat treatment / annealing for some steels.

[Arno]

Standard annealing procedures in Germany are as mentioned above (Normal Glühen und Weich Glühen). If the process of annealing as described in US sources is standard in NL please let me know and I will gladly drive over the border to have my stuff annealed.

Gotcha!

Didn't mean to teach you to suck eggs. Apologies.

Unfortunately I suspect you'd run into similar issues on this side of the border as most 'industrial' work like steel-work has been moved into bigger and bigger conglomerates of companies who like to use certain 'industry standard procedures' and there's little small-time shops left that can work with customers on specific (aka. 'non standard') processes or requests

I guess your problem is two-fold.. Finding the correct procedure description for the heat-treating process you want to get the desired result (perhaps in the end this is even the 'easy' step.. ) and then locating a heat treatment facility that's small/flexible enough to go outside their normal parameters for your job (and do it at decent cost )

If the parts are small enough and the amount of them not too crazy you might even consider getting your own (small) oven for the second part?

Bye, Arno.

[Andy]

@ kiwi2wheels (sorry didn’t get your real name)

Thanks for the tip, I’ll give Barri a buzz and ask if he can help by recommending a heat- treater.

@ Arno, no hard feelings here!

I realize that many people on forums are lazy a*#es, cough up a problem without doing any research themselves at all and leave it up to others to do the work. That’s not me …

In fact I have did some further research and understand what is happening on the thermal and micro structural level now and why it needs to happen. Soft annealing or non critical annealing at temperatures ranging from 680-720°C will not improve weldability.

Now I’ll need to talk to some heat-treaters and maybe do some thinking outside the box.

Cheers
Andy

EDIT : P.S. Just to get an idea, what does one pay in the US to get a small amount of 4140 annealed? Does it go by the pound? If so, how much is it for a few small tool pieces weighing like 1/2 pound each? Thanks in advance for any input.

[jethro]

I used to see my dad anneal high carbon tool steels by heating them to a dull red and then quickly burying the part
in the center of a bucket of powdered lime. The lime forms a heat proof insulating material which is a make shift
substitute for being in a heat treating oven set to slowly ramp down.
I have used this for annealing small hardened parts before machining. Not an exact method but it works.

Don't know if that helps your situation any though.....

Tim