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Holding period of normalizing temperature of steel castings

Holding period of normalizing temperature of steel castings

(OP)
Is there any standard or thumb rule to decide the holding/ soaking period of temperature during normalizing heat treatment of carbon steel castings with thickness varying from 4 inch to 8 inch? I believe 1/2 hour per inch of thickness is sufficient for normalizing at 1650F/ 900C.

RE: Holding period of normalizing temperature of steel castings

Typically, from 4 to 8 inches the rule of thumb is 1 hour per inch of thickness up to 5" material thickness. Beyond 5" is 15 minutes for each additional inch of thickness, so...

5 hours + 45 minutes ~ 6 hours. This all depends on the furnace size and survey of the furnace to ensure uniform heating.

RE: Holding period of normalizing temperature of steel castings

Agree with metengr's comment. If your furnace is not uniformly heated, I would add another hour. You may see the castings portion near the door, being dark.
The problem of having uniform temperature in the furnace is important during tempering, where the mode of heat transfer is by convection.

"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

RE: Holding period of normalizing temperature of steel castings

We used to use 1 hr plus 1 hr for the first inch and 30 min for each additional.
So 8" would be 1+1+(7*0.5)=5.5 hr
and 4" would be 1+1+1.5=3.5hr
But even for thin parts we never went below 2hr.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Holding period of normalizing temperature of steel castings

(OP)
Thanks for the responses.It appears that there are different practices in different foundries. Is there any literature or standard to support?

RE: Holding period of normalizing temperature of steel castings

tamal1475 ...

Recommend that You review at AMS-H-6875 [was MIL-H-6875] Heat Treatment of Steel Raw Materials ... Last few pages deal with tempering soak time based on thickness, various types of steels. There is also an illustration showing how configuration [plate, bar, hollow, etc] relates to the concept of 'thickness' for this aspect of HT.

Also suggest You review latest versions of following specs for some insight, this subject...

AMS2750 Pyrometry

AMS2759 Heat Treatment of Steel Parts, General Requirements

AMS2759/1 Heat Treatment of Carbon and Low-Alloy Steel Parts Minimum Tensile Strength Below 220 ksi

AMS2759/9 Hydrogen Embrittlement Relief (Baking) of Steel Parts

AMS2759/11 Stress Relief of Steel Parts

Regards, Wil Taylor

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o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
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