Blanking / Punching of SS Coil

Well, having lack of metallurgy knowledge, i will not prefer to change my product's material.

But SS420 is best suitable material for my application i.e. cutlery items.

I am facing this issue just after changing two parameters,

1) Press tool manufacturer ( I am not aware if any process/material has been changed)

2) SS coil manufacturing mill ( Both the materials which I was using earlier and currently are matching SS420 chemical composition requirements; but just chromium content of earlier coil was around 11.5 - 12% whereas current coil is having chromium content around 13- 13.5%)

The SS420 coil which I use is of cold rolled, closed annealed conditions.

So, you changed two parameters and now have problems?

You should be able to deduce the next steps.

1. As I said, get a material that has the lower Ni content.

2. Go back to the toolmaker that gave you satisfactory tooling.

You are beyond help, until you return to the material and tooling that gave good results.

It sounds like you are trying to operate above your level of competence. Maybe you should consider hiring someone who knows metals and tooling.

Finally, if you know nothing about metallurgy, how do you know a softer material will not give satisfactory results?

Good luck.

Ok...thanks...i will try/ check feasibility of your suggestion but please let me know just one thing so that my doubt can be cleared..i just want to know whether the claim made by toolmaker is true or he is just trying to save his side ...he is claiming that the higher chromium content in SS coil causes the wear/chip off of punch.

He's probably right about higher Cr and hardness/toughness.

It also depends on the hardness/toughness/brittleness of the tooling steel.

These questions cannot be answered by this forum.

My advice to you, lacking any experience, go back to what was working.

You might also consider 410 as a material. It is lower even in Cr but still suitable for cutlery.

Whilst he's telling you it cannot be done, you can damn bet someone else is doing it - and doing it reliably. If he's playing CYA and you cannot trust him to work with you on this, find someone else. One monkey don't make no show.

It sounds to me like you have clearance issues....your tolerances are set too tight....here are some suggestions that may help you tweak your operation....

http://www.ssina.com/download_a_file/fabricate.pdf

Yes exactly, i am also having the same doubt but the tool maker is not accepting the same and instead diverting the topic to metallurgy...

That's why i just want to know whether the claim made by him about root cause of higher Cr content is true or he just don't want to accept the clearance issue.

Clearance issues are part of tool design and must be suitable to produce the part. You and your tool maker must be partners with the same desire, a satisfactory end product.

Having a good relationship with your tooling supplier is critical.

Get some softer steel and see what the results are.

Well what is the clearance? .025 mm should be minimum...Have you tried any lubricant, that might be an easy fix.... It's hard to figure the problem without specific details about the entire process....You just need to keep trying things until something works...It could be poor alignment in the machine for all I know....

#1 then do they not meet your specification?

#2 does the other user of such equipment pre-heat and water quench to soften the coil?

#3 are you cycling your machine too fast, and heating up your punching dies, as this can soften them, or embrittle depending on how hot.