N. Brian Huegel wrote:
As part of my interest in understanding powder metallurgy, I sent an email to Ronald Long at Carpenter Technology Corporation. He is the Commercial Manager of the Knife Blade Products division. He has graciously allowed me to share it with the forum. Here is a portion of our correspondence.
Q: Per this Spyderco forum thread, in what began as a discussion about their latest Mule made with Böhler M390, I have attempted to compare / contrast with your CTS-204P. As part of the discussion, it has been brought up that your powder metallurgy is 2nd generation whereas Böhlers is 3rd generation.
A: From one of Carpenters R & D managers: The first generation powder product that was originally produced in Sweden by Erasteel and Anval (now CPP AB) consisted of air induction melting in a top pouring furnace followed by pouring the molten metal into a tundish from which the molten metal is bottom poured out of the tundish and is atomized to produce a coarse powder, typically -1000 microns or -500 microns.
The second generation powder product as practiced by Erasteel, CPP AB, and Böhler, consists of the first generation air induction melting process followed by pouring the molten metal into a heated, refining tundish called an ESH tundish (Electro-Slag Heated tundish), where the molten metal is heated with graphite electrodes (Erasteel and Böhler process) or a plasma torch (CPP AB). The refining tundish permits the molten metal to be purified (reduce the amount of inclusions). After refining, the molten metal is poured out of the bottom of the tundish and is atomized to produce a coarse powder, typically -1000 microns or -500 microns (the same powder size as the first generation process).
Böhlers third generation powder product consists of the second generation process followed by a modified atomization process that produces a finer powder, typically 250 microns. Böhler claims the finer powder reduces the presence of coarse carbides compared to the first and second generation, coarser powder.
As noted above, CPP AB uses the second generation powder process. CPP BVL (BVL is our facility in the US and our source for CTS 204P) uses both air induction melting and vacuum induction melting coupled with the use of reticulated refractory filters in its tundish to produce 150 micron powder (finer than Böhlers powder) for P/M tool steel millform products. CPP BVLs powder manufacturing process does not directly compare to the European classification system of first, second and third generation powder processing. BVLs vacuum induction melting + filtration process plus the use of -150 micron powder is cleaner than the third generation process. The air induction melting process + filtration process plus the use of -150 micron powder is equivalent to the second generation process with a finer powder than the second generation process.
From Ron: As you can see it is not exactly an apples to apples comparison when one puts the processes side by side.
Effectively, from dimensional perspective, our 2nd generation process produces a finer, 150 micron powder than their 3rd generation process which is 250 microns. And I dont believe they would argue that their 250 micron material would have finer carbides than our 150 micron material.
The other issue is product cleanliness. I have asked for information on product rejection rates for inclusions and have yet to find an example. I am not saying they do not happen; just that folks are having problems finding the last time it did happen. In my short tenure here I have not dealt with an inclusion. I will look to get you a better definition of cleanliness relative to our product.
Regards,
Ronald Long
Carpenter Technology Corporation
Commercial Manager- Knife Blade Products
His only concern in allowing me to quote him and Carpenter is that he does not want to get into a situation where he might sound like, or be accused of, being critical of Böhler-Uddeholm which was not his intent. I do not believe that this will be the perception and I sincerely appreciate his explanation and knowledge on the subject. I also invited him to participate directly with this forum and also encouraged him and Carpenter to consider establishing a forum or sub-forum of their own. Time will tell if this comes to fruition, however, I do believe that the above is a definitive expression of Carpenter Technologys deep commitment to our industry and the future of cutlery steels.
