Chain Sheave Problem

[etdarlak]

My company is having problems with a recent batch of safety chain sheaves. For years, we specified the sheaves be made from 1045 and flame hardened to Rc 55 max.

The vendor who supplied the last batch of sheaves said he was not setup to flame hardened, so he thru-hardened them in an oven to Rc 55.

The sheaves in service are failing. The Rexnord safety chain is digging up the sheaves.

My question is, can 1045 be thru hardened? Is it only supposed to be flame or induction hardened to get a surface hardness of Rc 55?

There is obviously a heat treating problem here, and I need some expertise.

Thanks in advance!

 

[TVP]

1045 can be through hardened if the cross-section is small enough, such as an M6 fastener. However, at 55 HRC the fracture toughness of 1045 will be practically nil. I would not recommend using 1045 through hardened at 55 HRC.

 

[arunmrao]

1045 has a low hardenability,i.e the depth of through hardening is low. In this instance of sheave being through hardened,though the rim outer surface would have required hardness the core would not be tough enough to support.

Flame or induction hardening is the desired method of increasing hardness for sheaves,sprocket wheel etc.

As an aside,did you not observe any distortion in the sheaves after they were through hardened? How was the bore finish machined after hardening?

Chocolates,men,coffee: are somethings liked better rich!!
(noticed in a coffee shop)

 

[redpicker]

Are the sheaves failing by fracturing or by wear. From your comment

The sheaves in service are failing. The Rexnord safety chain is digging up the sheaves.

if the chain is just wearing out the sheave prematurely, then they did not achieve a surface hardenss of 55 HRC (which I doubt they could achieve with through hardening with 1045). If they are fracturing, then the heat treater may have had some success in getting the 1045 to harden, but, as has been noted, 1045 at this hardness level is not going to have much ductility, so if it is through hardened, it would not be surprising to see it fracturing.

Flame hardened is appropiate. Inductin hardening would be an acceptable alternate. If such heat treating options are not available, then another material should be used.

rp

 

[salmon2]

The idea of flame hardening 1045 is to get a hard surface and tough core, while the through hardening, if the cross section is small enough, will give you hard but brittle structure throughout the part.