Vendor Supplied Wrong Material- Where does the responsibility end?

Hi, I have a quick question- I make brake rotors for off-road motorcycles and have used 410 stainless for 10+ years with excellent performance. The steel vendor we normally use was out of stock for several months, so we found another local vendor. We ordered 410, however, the vendor supplied 410-S. 410-S is a special alloy that does not harden when welded- We heat treat our rotors and unfortunately did not discover the mistake until the first step of heat treat. The 410-S won’t harden beyond RHC 8. We need RHC 32. The vendor has agreed to replace the material, however, they do not feel any responsibility for the $7200 in process cost (laser, de-burring and heat treat). I proposed that we split the cost and take it as a credit towards future material purchases and they are still pushing back. What is the general opinion of where the responsibility lies? If we are totally at fault for not checking certs, then we’ve learned an expensive lesson.

Please help.

Thanks!

I didn’t find the right solution from the Internet.

References:http://www.engineersedge.com/engineering-forum/showthread.php/4882-Vendor-Supplied-Wrong-Material-Where-does-the-responsibility-end?s=8de2168305849c0a316b8b227b21d0e4

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