Can hardened 1144 Stressproof or 4140 ASTM A193 B7 be crackless
Can hardened 1144 Stressproof or 4140 ASTM A193 B7 be crackless
(OP)
Hello group,
I am specifying 2" bar 1144 Stressproof to be induction hardended to Rockwell C 45-55 at case depth of 0.060"-0.080". As an alternate material, I specify 4140 ASTM A193 B7 with the same hardness requirements. Can either of these two materials be supplied without visual and microscopic cracks due to quenching? I understand that the Stressproof material can only be plastic quenched to a max of Rockwell C 55 at max depth of 0.120". Our vendor says that they cannot supply the bar without cracks.
Thanks,
kklinger
I am specifying 2" bar 1144 Stressproof to be induction hardended to Rockwell C 45-55 at case depth of 0.060"-0.080". As an alternate material, I specify 4140 ASTM A193 B7 with the same hardness requirements. Can either of these two materials be supplied without visual and microscopic cracks due to quenching? I understand that the Stressproof material can only be plastic quenched to a max of Rockwell C 55 at max depth of 0.120". Our vendor says that they cannot supply the bar without cracks.
Thanks,
kklinger





RE: Can hardened 1144 Stressproof or 4140 ASTM A193 B7 be crackless
RE: Can hardened 1144 Stressproof or 4140 ASTM A193 B7 be crackless
We purchase a completed product from a vendor. But as an engineering company we specify the design of the product including the material specs. Our vendor purchases the parts made from these bars from their vendor. And in turn, their vendor sends these bars out to another vendor to be hardened. We had an issue of the 1144 Stressproof material cracking, most likely due to water quenching. The application of this bar can be critical, in that failure of this bar can be catastrophic (loss of life). Therefore, we would like to have the bars to be crack-free, but the bars need to be hardened for wear. As you can see from above, we do not know much about the hardening process. We are not hardening experts; therfore, specifying the heat treatment procedure could get us in trouble since we unknowingly could specify the wrong procedure. Our vendor is telling us that they cannot supply the bars crack-free. Is this a true statement?
TIA
kklinger
RE: Can hardened 1144 Stressproof or 4140 ASTM A193 B7 be crackless
With this statement:
I am astonished that 1144 steel is speced at all in this case. I would think that the presence of the large sulfides equate to the same as large numbers of cracks, similar to graphite in Grey Iron?
Nick
I love materials science!
RE: Can hardened 1144 Stressproof or 4140 ASTM A193 B7 be crackless
Can you comeback with the end application as there might be different avenues of approach to this problem.
RE: Can hardened 1144 Stressproof or 4140 ASTM A193 B7 be crackless
RE: Can hardened 1144 Stressproof or 4140 ASTM A193 B7 be crackless
RE: Can hardened 1144 Stressproof or 4140 ASTM A193 B7 be crackless
The steel bar needs to be produced to a surface defect limit, and tested by eddy current and/or magnetic particle methods. A typical limit for cold drawn bar that will be subsequently hardened and ground is 0.13 mm maximum. The steel will likely be cold drawn and possibly turned, ground, or ground and polished, depending on the exact needs. All of this will minimize the number & depth of surface defects like cracks, seams, etc. The best cold drawn bars are tested with 2 types of eddy current systems-- one is a comparator method for short defects and one is a rotating probe method for long defects.
Once the high quality steel bar has been suitably manufactured, the induction hardening and quenching processes need to be well controlled. The power should be as low as possible to reach the austenitizing temperature, without overheating. The scan speed should be as low as possible to allow for as much homogenization as possible, and to reduce the possibility for quench cracks. The quenchant needs to be a water + polymer mix, with a controlled concentration of 5-15% (typical) and a temperature > 20 C. Quenching into cold water produces cracks, and if this is the current process, it needs to be changed. The best process would involve grinding/polishing after hardening in order to remove any traces of surface defects.
Based on the above, it is possible to produce millions of induction hardened bars of the requirements you mentioned with exceedingly few cracks. Highly stressed applications should test the fullly processed parts with a non-destructive method such as eddy current, magnetic particle, etc.
RE: Can hardened 1144 Stressproof or 4140 ASTM A193 B7 be crackless
Is this through the same mechanism as Mg additions to a melt of Grey Cast Iron (flake type graphite will result in Ductile Cast Iron (nodular graphite)?
Nick
I love materials science!
RE: Can hardened 1144 Stressproof or 4140 ASTM A193 B7 be crackless
Regards,
Cory
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