What's a Better Material than D2?

I am not sure of a different material, but you might try a TDC coating over the D2. You may still have to recoat and regrind to size every so often.

In the rollforming business D2 is a very popular choice for wear resistance and toughness. It is possible to achieve hardness values in excess of 62 HRc on D2 by cryogenically heat treating the D2. This approach makes theoretical sense, but success is limited. When marking of the material surface becomes an issue, there are typically three approaches to correct the problem:

1) Make the tooling so that part of the assembly is driven by the input shaft and part of it finds its own velocity. This prevents marking due to large velocity differences across the contact surface of the tooling.

2) Select an aluminum bronze material. This will decrease the likelihood of marking, but shortens the time between tooling rework. A material such as Ampco 25 bronze can be a very good solution for nonmarking applications.

3) The other option that I am referring to is to apply carbide as the tooling material. Carbide has superior wear resistance and has a low coefficient of friction making it great for nonmarking requirements. Carbide does not do so well if the loading is impact in nature. Impact may be in the form of applying a load and removing it again at high speeds as opposed to striking the tool. Carbide is also very expensive to make and to rework.

In applications that I have used carbide, the wear life can be increased up to 10X that of D2; however, replacement of a shattered piece can be as expensive as replacing the entire tooling set made of D2.

Todd

can u increase hardness of the roller???

You can try HSS instead of D2 with 62 HRc. Less costlier than carbide rolls but better than D2.

carbide is the best option, i would suggest to use MG30 carbide

If you feel carbide, which is a good option to retain the life of the tool is costlier, you can think of overlay / surfacing of the rollers using Chromium Carbide Filler wire or Electrode. They give a hardness of 62-65 HRC and above. There are electrodes available with good resistance to abrasion, metal to metal wear, friction or scratching abrasion, wear and moderate impact etc. The properties could be enhanced with proper heat treatment.

Alternatively you can do plasma spray, where many combinations are available and the advantage being the spray thickness can be controlled in micron level and the base metal need not be expensive like in other cases. All are metallurgically balanced and finished by grinding only.

Hardface with suitable *** weldmetal and grind it. No more Heat Treatment .

*** Ask ESAB for the best they have.

I can get the hardfacing done at my site in Guwahati-using China --Beijing Advanced Material BAM 's wire. In Jan08.

See BAM Website

Do you always feed the wire into the rollers at the same spot? try to to use a guide which moves backwards & forwards across the rollers this will distribute the wear evenly and give you a longer life before a regrind is needed. This must be done with new surfaces as once grooving starts it will defeat the feed.

Dont know if this will fly but it might help.

No shortage of suggestions. I would look at some of the hard coatings like TiN. That should help and be reasonably priced. If that doesn't solve the problem, tungsten carbide has been suggested. If that doesn't work, I would look at a ceramic, maybe aluminum oxide.

You might want to perform a hardness test of the D-2 to be sure you are getting the full benefit (hardness) out of the tooling.

If it is at the high hardness limit, try CPM M4 or CPM T15 from Crucible - that should solve your problem for a long time to come.

CPM 10V is less expensive, and will perform better than the D-2, but T15 and M4 are harder yet, and may provide longer intervals between grinding.

We have to send our M4 and T45 to outside heat-treat, because the heat range of our ovens are usually set for CPM 10V or A-2, and these will need a higher range of heat.

Plenty of great suggestions here.

However, not much established in problem description understanding. Could this be contact fatigue,abrasive wear, asperities in rolls, pressure weld from the work strand, brinelling? We have n't identified a root cause, we've just described what failure looks like.

We have not qualified if the tool marking is a result of out of control conditions, or if it normally expected as a result of the amount of material processed, or as one poster suggested, the feed contacting the same point each time.

We are not aware of thetime between repolishes, nor the method of maintaining/finishing the roller surfaces. certainly the expectation isn't the roller remains pristine forever...

I suspect that brinelling is also a possibility as to the cause of marking. This timken link will give us a way to think of your process as going beyond "harder is better." (often its not).

http://www.timken.com/products/bearings/services/valueadd/prevent.asp

Rather than reengineer the rolls, why not try to understand the problem?

That goes beyond saying it failed. Where is data for analysis?

Hours in use, feet/meters between regrinds, geometry pattern of "bit makrs on roller", method of feeding,surface feet per minute, etc.

milo

milo

I have to fully agree with Milo. The basics of an analysis and following suggestions is the understanding of the problem. It was accepted that a better material was needed but it was not analysed why the material was realy or apparently not good enough.

Only Milo suggested the engineering true approach.

This may sound strange, but it is a fact that ultrasonic vibration can temporarily lower the yield strength of metals. After ultrasonic radiation, they return to their original hardness. An ultrasonically vibrated roller may lower the yield stength of your SS wire and lengthen the life of the roller.

Interesting! So how does the ultrasonic motion soften the wire without softening the roller?

Good question. I don't have a precise answer. There may be some softening of the roller however, the combination of normal force (the roller) and shear force (the ultrasonics) causes deformation of the wire at a small fraction of the normal force that would be required without the ultrasonics.

I'm betting it is abrasion due to slippage of the wire against the rolls.