Properties for SAE 8640 Castings

This being a quenched and tempered tool steel, I am not familiar with it as a cast product. Given its tensile and yield as wrought, I suspect that 20% elongation would be pushing the upper limit. Whatever you may be trying to cast, I would leave plenty of extra material for removal to attain true form. Also, the rate of cooling will be critical so section thicknesses need to be uniform to maintain physical properties and minimize internal stresses.

Thanks for your answer, i too didn't get much information , please reply if you get a complete spec of sae 8640 in casting form

Hi,

plss find below the chemical and Mechanical properties of theis grade SAE8640.

The mechanical properties given here are not for Quench and tempered material! Look at that HRC hardness-18! That is not heat treated, nor is 123,000psi indicative of the highest heattreatment for this 0.40 carbon steel. Below are actual data from my personal work for grade 8640 1" rounds, oil quenched from1525 degrees F. tested as .505 specimens, taken from the center of the 1" rounds.. temperatures in Fahrenheit, all units US. Thats how I did it. 8640 1" rd quench and tempered at 800 degrees F results in 200,500psi TS, 179,000 YS 10%el in 2"; At 900 degrees 181,000 TS, 162,000 YS, 13% el in 2"; 1000degregees 155,000 ts, 137,000 YS, 17% el; 1100 degrees 148,500 TS, 132,000 psi YS, 16% el; 1200 degrees temper gives 125,500 TS, 110,500YS, 20%el. Regarding cracking and distortion, please see my blog below: http://pmpaspeakingofprecision.com/2009/10/20/8-reasons-steel-parts-can-warp-in-heat-treat/ milo

Thanks for the answer it will satisfy my requirement.

Thanks for your answer . please mention whether the given properties are in As Cast Condition or Heat Treated Condition. If Heat Treated, what was the process cycle which was followed?

The properties given in that table appear to me to be closest to those of unannealled hot roll. 8640 unannealled cold drawn I would expect to be 140,000 TS, 120,000 YS, and 277 BHN; 8640 annealled cold drawn I would expect to be 107,000 TS, 90,000 YS, 217 BHN; 8640 unannealled Hot roll I would expect to be 124,000 TS, 94,000 YS, 255 BHN; Finally 8640 annealled HR would be 99,000TS, 58,000YS, 183 BHN. So you can see that in the original data table, the BHN and the Tensile Yield strengths are somewhat at odds. I'm a bar guy, so I don't have 'as cast' data. It is possible that that data was for as cast properties, I cannot say. milo

cooling rate and tempering practice is going to be critical. it has .4% carbon which is quite a bit. it is going to want to harden on you as it cools and you'll need to temper it as it cools or it is going to crack.

May i ask if you are sure you mean 8640 and not 8620? The most common SAE.40 steels are 1045,4140 and 4340.SAE 8620 are higher quality for pinions and gears than simple 1020.But 8640 seems very uncommon to me.