Time at Temperature, Normalizing
Time at Temperature, Normalizing
(OP)
How critical is time at temperature when normalizing carbon steel?
Specifically, if the mill supplies green material with test coupons normalized for 1 hour/ inch, and the fabricator normalizes the part for 1/2 hr / inch, is there reason to be concerned that the test coupons don't properly represent the part?
Specifically, if the mill supplies green material with test coupons normalized for 1 hour/ inch, and the fabricator normalizes the part for 1/2 hr / inch, is there reason to be concerned that the test coupons don't properly represent the part?





RE: Time at Temperature, Normalizing
What is the section thickness for the test coupon supplied by the mill? What section thickness is the fabricator working with for normalizing?
RE: Time at Temperature, Normalizing
However, the mill had normalized the test coupons for that material at 1 hr / inch.
RE: Time at Temperature, Normalizing
Normally, the 1 hour/inch is a conservative value and accepted norm to allow an object to reach a uniform temperature profile and complete through-thickness austenitization.
Did you review the recorded austenitizing temperature of the fabricator and compare to the temperature recorded by the mill? It may be that the fabricator austenitized at a higher temperature.
If the austenitizing temperature of the coupon was within 100 deg F of the fabricators austenitizing temperature, I would be concerned about an inadequate normalization heat treatment. I would perform bulk hardness testing at several locations and compare to the coupon hardness, just to be sure.
RE: Time at Temperature, Normalizing
If you can assure that the whole section of your piece has reached the target temperature, a carbon steel does not need any more time at temperature (esp. for C-contents < 0,30%). Holding on temperature is not necessary, but does not have a negative effect neither.
Rules like 1 hour/inch are often chosen to assure an equalisation of the temperature over the whole section when temperature is measured at the surface. These rules are very approximative as the time for equalization is strongly dependant on the heating rate, heating capacity of the furnace, position of the burners, form of the product (plate, shell, head,..) ...
RE: Time at Temperature, Normalizing
S
Corrosion Prevention & Corrosion Control
RE: Time at Temperature, Normalizing