新第1章课件.pptVIP

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Some other alloying elements such as cobalt, aluminum are added so that their heat stability is higher (can keep hardness HRc60 up to 630~650℃). They are suitable for cutting materials which is difficult to machine and have longer working life. Typical ones include high carbon high-speed steel 9W18Cr4V, high vanadium high-speed steel W6MoCr4V3, cobalt high-speed steel W6MoCr4V2Co8, super-hard high-speed steel W2Mo9Cr4VCo8 etc. （2）Super high-speed steels 1.2.2 Frequently-used cutting tool materials 1. High-speed steels (HSS) （3）High-speed steel made by powder metallurgy In powder metallurgy, the steel fluid is sprayed into powder in inert gas under high pressure and then made into steel ingots through a cold and hot press and sintering process. after that, it becomes steel materials through rolling and forging. In this way the homogeneity for the distribution of carbides and the size of grains are controlled. The materials have good structures and properties. 1. High-speed steels (HSS) 1.2.2 Frequently-used cutting tool materials The carbide alloys are made of metallic carbide powder (WC, TiC etc.) and bonding mediums (Co, Mo, Ni) through powder metallurgy. The higher the carbide content in carbide alloys, the higher the hardness of carbide alloys, better chemical and heat stability. The cutting temperature for carbide alloys reaches up to 800~1000℃. 1.2.2 Frequently-used cutting tool materials 2. Carbide alloys The disadvantages of carbide alloys mainly are their poor bending strength and impact toughness so they are not suitable for heavy cuts or for intermittent cutting. Except for small size tools, generally carbide alloys are inserts welded or clamped in cutter body instead of a integral-type cutting tool. 1.2.2 Frequently-used cutting tool materials 2. Carbide alloys （1） WC-Co (YG, ISO: K) It consists of WC and cobalt, the trade marks are YG6,