Hot/Warm forming of steel
Hot/Warm forming of steel
(OP)
I have developed a product that requires warm forming to produce. How would I go about selecting the best steel chemistry for hot or warm forming (800 to 1400 deg f). This material would be used in high volume and reasonable cost. ie. not exotic. Any and all comments welcome.





RE: Hot/Warm forming of steel
Ease of fabrication is only one consideration in selecting material for use in a specific application. What is the end use of this component? Your final selection of material (steel) depends on strength requirements for service, static or dynamic load conditions in service, environmental conditions, cost and availability and .....
RE: Hot/Warm forming of steel
In my experience that entire range is warm forming, but I digress...anyway, you may need to consider control of certain elements as they can adversely affect the forming operation. Depending on the severity of the forming steps, you may need to limit sulfur or silicon to avoid splitting. You may also require turned and polished stock as well. Of course the more you tighten the range from general mill tolerances the higher the steel price.
Let us know if there is any machining involved or final property requirements. That will influence your forming temperature range.
RE: Hot/Warm forming of steel
Strength is best when alloying elements are in higher concentration.
Microalloy elements like V, and Nb help avoid excessive grain growth during hot forming.
Most of the common alloys would be suitable for the actual process, so your material selection should be based on the final properties required of the part.
Regards,
Cory
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RE: Hot/Warm forming of steel
RE: Hot/Warm forming of steel
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Forging http://mech.e.tripod.com
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Ddraig Breuddwydia....www.tailofthedragon.com
RE: Hot/Warm forming of steel
We are trying to stretch a 2.5"long x 0.25"wide x .018"thk by 15%. Due to the direction of the forces, we are heating the center 2" of the 2.5" leg. The heat is only to reduce the yield strength in the area intended to stretch. If no heat is applied, the material tears at the web (I have pictures to send but this web site seems to be malfunctioning. Help?).
We have tried both HSLA 950 and 1010. The HSLA fractured with minimal elongation around the point of the fracture. The 1010 fractured with significantly more uniform elongation around the fracture.
The strength of the end part is significantly determined by the shape of the part. This being said, the higher the end strength of the material, the less material needed and the lower the cost to manufacture.
Questions:
1) Do you think the difference between the 950 and 1010 was more the result of yield and tensile, chemistry or other?
2) Do you have suggestions in regard to steel chemistry / grades etc.?
3) Can you explain what is meant by "1400 may be above the lower critical temperature"?
4) How can I get the photo's on line?
RE: Hot/Warm forming of steel
RE: Hot/Warm forming of steel
The difference between HSLA and 1010 is due to differences in strain hardening, uniform elongation, and total elongation.
Metallurgically speaking, the lower critical temperature refers to steel's phase change from BCC (ferrite) to FCC (austenite) crystal structures.
Regards,
Cory
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RE: Hot/Warm forming of steel
The reason that we can't do it at room temperature is the tearing action at the end of the strip that occurs. The force to tear is significantly lower than the yield strength of the steel strip in the area we want to stretch. To lower the force we heat it.
Are you saying that 1010 or other plain carbon steels would be more likely to succeed?
Is there a concern with going above the critical temperature for what we are doing? Is heat treating the concern?
Best Regards,
Jeff
RE: Hot/Warm forming of steel
There is no question that low carbon steel like 1010 will be more formable than anything else.
The critical temp consideration was a metallurgical one for us "experts" to help understand the distinction between warm and hot. I don't think you need to reach hot working temperatures.
Regards,
Cory
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RE: Hot/Warm forming of steel
Does the addition of heat make the HSLA elongation look more like that of 1010? In other words, I would think that heating the material will enhance the elongation of both materials?
Regards
Jeff
RE: Hot/Warm forming of steel
Have you done a basic calculation of stress and strain on the legs? Get some data for your incoming material at various temperatures and compare what you have with what you need.
Regards,
Cory
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: Hot/Warm forming of steel
===================================
Forging http://mech.e.tripod.com
-------------------------------------------------
Ddraig Breuddwydia....www.tailofthedragon.com
RE: Hot/Warm forming of steel
We have as close to uniform heat across the entire length of the leg as possible. Per video tape, there is no visible difference in color (ie heat) across the 2" heated area leg.
It wants to fracture at we assume is the hottest spot. More noticeable on the 950 than the 1010.
By "pre-drill", do you mean to create a hole at the ends of the legs?
Regards
RE: Hot/Warm forming of steel
We have done heated pull tests and are showing 25 to 30% elongation at approx 1100 deg f. The part requires 15%.
regards
RE: Hot/Warm forming of steel
Regards,
Cory
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: Hot/Warm forming of steel
Thanks for the advice. This process saves about 40% on material over existing product, I'm hoping that will offset the cost of the final product.
Do you think higher carbon such as 1014 1016 would allow me to keep the formability advantage (and cost?) over 950 and give me added strength on the final product?
Regards
RE: Hot/Warm forming of steel
Or if larger radii is obtainable on the tooling, same place; where the split is occurring.
Otherwise, it seems a wider leg or beam (whatever you call the broke piece) should be tried.
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Forging http://mech.e.tripod.com
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Ddraig Breuddwydia....www.tailofthedragon.com
RE: Hot/Warm forming of steel
I have successfully formed 1010 material as shown in the above pictures.
If I wanted to increase the strength of the material and maintain the uniform elongation under elevated temperatures, am I better to to go with a higher carbon steel (1012,1014, etc.) or an HSLA (035,050, etc)?
Thanks
Jeff