UK low alloy steel stress relief - effect on props?
UK low alloy steel stress relief - effect on props?
(OP)
We have a supplier who wants to stress relieve a machined component made of UK low alloy steel 817M40 (see BS 970-3).
They want to do so at 570 deg C (1060 deg F) for 5 hours. (This is to keep dimensional control tight, as they feel it will move a bit when they machine it.)
The material's minimum tempering temperature is 600 deg C (1110 deg F) and it's not supposed to be tempered above 660 deg C (1220 deg F).
a) would this change the mechanical properties much?
b) what sort of time is 817M40 (and/or similar alloys) usually tempered for?
Alloy composition (from the mill assay):
C: 0.38.
Mn: 0.55.
Cr: 1.03.
Ni: 1.4.
Mo: 0.26.
Si: 0.28.
S: 0.008.
P: 0.009.
Cu: 0.08.
Here's the nominal (if it helps):
C: 0.36 to 0.44.
Mn: 0.45 to 0.70.
Cr: 1.00 to 1.40.
Ni: 1.30 to 1.70.
Mo: 0.20 to 0.35.
Si: 0.10 to 0.40.
S: 0.040 max.
P: 0.035 max.
They want to do so at 570 deg C (1060 deg F) for 5 hours. (This is to keep dimensional control tight, as they feel it will move a bit when they machine it.)
The material's minimum tempering temperature is 600 deg C (1110 deg F) and it's not supposed to be tempered above 660 deg C (1220 deg F).
a) would this change the mechanical properties much?
b) what sort of time is 817M40 (and/or similar alloys) usually tempered for?
Alloy composition (from the mill assay):
C: 0.38.
Mn: 0.55.
Cr: 1.03.
Ni: 1.4.
Mo: 0.26.
Si: 0.28.
S: 0.008.
P: 0.009.
Cu: 0.08.
Here's the nominal (if it helps):
C: 0.36 to 0.44.
Mn: 0.45 to 0.70.
Cr: 1.00 to 1.40.
Ni: 1.30 to 1.70.
Mo: 0.20 to 0.35.
Si: 0.10 to 0.40.
S: 0.040 max.
P: 0.035 max.





RE: UK low alloy steel stress relief - effect on props?
Unless this component has a very thick cross section your time seems to be a little long as something like 90% of the stress relief for a specific temperature is accomplished in the first few minutes when the part is at that temperature.
One approach to a problem like yours is to double or triple temper, rough machine, stress relieve and finish machine.
RE: UK low alloy steel stress relief - effect on props?
Alloy steels like these typically are temepered for around 1 to 2 hours.
Regards,
Cory
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RE: UK low alloy steel stress relief - effect on props?
Unclesyd: these are quite thick parts, at least by my standards; the original billet could be up to 8" thick and the part to be stress relieved could have a maximum effective thickness of about 4".