20CrMnTi vs AISI 4320/8620
20CrMnTi vs AISI 4320/8620
(OP)
Thanks in advance for any help.
So, the company I work for uses big gears PD ~20" Face 8" Thick. Material we current use is AISI 4320 / 8620. I started searching for vendors in China and the usual response I get is they want to replace the material with 20CrMnTi. What is the difference? I am having difficulty finding a direct comparision. I have read the thread thread367-143938 but did not know if their application used gears similar to size as ours.
Thanks.
Steve
So, the company I work for uses big gears PD ~20" Face 8" Thick. Material we current use is AISI 4320 / 8620. I started searching for vendors in China and the usual response I get is they want to replace the material with 20CrMnTi. What is the difference? I am having difficulty finding a direct comparision. I have read the thread thread367-143938 but did not know if their application used gears similar to size as ours.
Thanks.
Steve





RE: 20CrMnTi vs AISI 4320/8620
At a minimum you could ask for Jominy test profiles for the proposed material and compare it with those of the steels you know and trust.
http://www.welding-advisers.com/
RE: 20CrMnTi vs AISI 4320/8620
Mn 1.0 , Si 0.26, Cr 1.19, 'Ti 0.03, Cu 0.95,balance Fe . A google search provided the chemistry of 20CrMnTi.
This chemistry indicates no Mo and the presence of Ti may be more as tramp. Normally there have bben attempts to replace Ni by Cu,hence the nearly 1% Cu presence.
It is advisable to specify 4320 or 8620 alloy.Most of the Chinese companies seem to be popularising 20CrMnTi.
Why did you not explore the possibility of sourcing from India? Cost/availability??
RE: 20CrMnTi vs AISI 4320/8620
These are obviously carburizing grades, so the core properties are not likely to be as important as the surface.
What are your requirements for properties?
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: 20CrMnTi vs AISI 4320/8620
Depending upon core properties desired, and since this is a large gear, you may need to restrict the chemistry/hardenability to the high side somewhat so there is not too much dropoff in performance from the NiCrMo grade.
RE: 20CrMnTi vs AISI 4320/8620
But as is suggested Ni and Mo are absent. But since it is a large gear forging suggest Ni and Mo additions in the alloy selected.
RE: 20CrMnTi vs AISI 4320/8620
Now:
Arunmrao: We have looked into companies from India and in fact have some parts from them. However, we are interested in exploring China because they may be able to outsource other parts as well. However, if you have a reliable source in India and are open to sharing that with me, it would be appreciated.
CoryPad: the gears need to be able to be hardened to 56-62 Rc. They are used for a low speed, high torque application. Torque ~ 280,000 ft-lb.
dbooker630: so, there is indeed a drop off in performance? What about wearability? The important part is the gear tooth life as changing a broken gear is time consuming and costly. I doubt the gear would fail from the core, but rather from the tooth. Am I correct in this assumption?
Again, thanks for all your help everyone.
Steve
RE: 20CrMnTi vs AISI 4320/8620
If you give me some more details perhaps I can suggest a few more Indian companies. My business line is steel castings .
RE: 20CrMnTi vs AISI 4320/8620
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: 20CrMnTi vs AISI 4320/8620
The 20MnCr5 hardenability band extends well below the mins for 4320 and its max is typically 4 points below 8620.
I cannot say for sure that there will be a dropoff but I did not want to take the chance of allowing the use of the full band of material without testing a low side chemistry.
RE: 20CrMnTi vs AISI 4320/8620
dbooker: thanks for the info. I will ask the company if they have this material. Any other suggestions for material substution?
Steve
RE: 20CrMnTi vs AISI 4320/8620
Standard hardenability bands may or may not work for you. You need to pay attention to the core hardness that you have been getting using the current material. Based on the hardenability of the current steel, you can figure out the equivalent J position for the core hardness and make sure that 20CrMnTi has enough hardenability to meet your core hardness requirements. You may have to specify the hardenability band and D.I. that you can live with to obtain the core hardness.
Hope this helps.
Rao Yallapragada