Forged 6"thick 4340 steel bars

[Jap1]

I have seen forged approx. 6"thick x 3feet width x 10 feet long forged 4340 steel bars at work The bar has been quenched, tempered, and stress relief to surface hardness HRC 40 bases on the MTR. Massive amount of bars, probably 80% of the bar is machined to make a semi circular shape. My question is why we don't get annealed condition for rough machining and send it for final heat treatment prior to final machining. I'm not a machinist, but it appears that we waste so many time for this work.

 

[MintJulep]

Forging improves a bunch of material properties.

They may or may not be important to the parts you describe.


From Gemini

The grain structure of a forged metal component is directional and aligned with the part's shape, which is known as grain flow. This grain structure is created by heating and cooling the metal while applying pressure to manipulate the grains into a desired orientation.
Forging is a metalworking process that produces components with several advantages, including:
Strength
Forged components are stronger than machined bars and plates because the grain structure is oriented to the part's shape.
Durability
Forged components are more durable than other types of metal components.
Fatigue and impact resistance
Forged components have better resistance to fatigue and impact than other types of metal components.
Ductility
Forged components have better ductility than other types of metal components.
Reduced cracking
Forged components are less likely to crack or fracture than other types of metal components.

 

[mfgenggear]

OP
40 HRc is perfect for machining
Machining in the annealed condition is to soft and gummy. And material smears and tear. And difficult to obtain a good finish.

 

[Jap1]

OP
40 HRc is perfect for machining
Machining in the annealed condition is to soft and gummy. And material smears and tear. And difficult to obtain a good finish.

Thank you for your insight. Perhaps normalized condition may be better for rough maching.? I was thinking about alternative options for bulk machining, since the final machined surface is likely to have lower hardness values due to the amount of machining. Perhaps we should get a forged ring that is close to the final dimension.

 

[mfgenggear]

OP
down load a copy of timkens
practical data for metalurgist
review the surface depth that 4340 hardens from the surface.

https://www.timken.com/wp-content/uploads/2016/10/Timken-Engineering-Manual_10424.pdf

 

[mfgenggear]

I will if needed is to rough machine before heat treating . to obtain hardness through the core.

 

[Jap1]

I will if needed is to rough machine before heat treating . to obtain hardness through the core.

I need to look into hardenability data of 4340 steel. One bar is about 4000 lbs, and at least 3000lbs of steel is removed.

 

[mfgenggear]

Op
The Timken data supplied has not let me down. Review the jominy data

 

[MintJulep]

One bar is about 4000 lbs, and at least 3000lbs of steel is removed.

That does seem wasteful.

Is your company the designer, or just a machining contractor?