DEVELOPMENT OF FREE CUTTING DENTAL TITANIUM ALLOYS

本研究的目的是评估实验钛合金的可磨削性，以期开发出比CP Ti具有更好可加工性的钛合金用于牙科CAD/CAM。在氩弧熔炼炉中，将海绵钛和银、铜、铌片熔炼成实验用Ti-Ag合金（质量% Ag 5,10,20）、Ti-Cu合金（质量%Cu 2,5,10）和Ti-Nb合金（质量%Nb 2,5,10,15,20,25,30）。使用牙科气压钛铸造机将合金铸造到镁砂模具中。铸造合金试样（3.5 mm x 8.5 mm x 30.5 mm），去除硬化的表面层（250 um），使用SiC砂轮在电动机头上以100 gf的五种周向速度（500,750,1000,1250或1500 m/mm）进行磨削。可磨削性是通过测量磨削后一分钟内去除的金属体积量来评估的。在最低磨削速度（500m/min）下，Ti- cu合金、Ti- ag合金和CP Ti的可磨削性无统计学差异。随着磨削速度的增加，合金的可磨削性提高。在1000和1250 m/min下，20% Ag和10% Cu合金的可磨削性高于CP Ti合金。在最高磨削速度（1500 m/min）下，20%Ag、5%Cu和10%Cu合金的可磨削性均高于CP Ti合金。10%Cu在1500m/min下的可磨性是CPTi的2.9倍。以Ti- nb合金为例，在较低的磨削速度（500和750m/min）下，Ti-30% nb合金的可磨削性约为CP Ti的2倍。结果表明，与银、铜、铌合金化可提高钛的可磨性。在较低合金元素含量下，Ti-Cu合金比Ti-Ag合金具有更高的可磨削性。

The purpose of this study was to evaluate the grindability of experimental titanium alloys with the hope of developing titanium alloys with better machinability than CP Ti for dental CAD/CAM applications. Experimental Ti-Ag alloys (5,10,20 mass% Ag), Ti-Cu alloys (2,5,10 mass%Cu) and Ti-Nb alloys (2,5,10,15,20,25,30 mass%Nb) were made by melting sponge titanium and pieces of silver, copper or niobium in an argon-arc melting furnace. The alloys were cast into a magnesia mold using a dental gas-pressure titanium casting machine. Cast alloy specimens (3.5 mm x 8.5 mm x 30.5 mm), from which the hardened surface layers (250 um) were removed, were ground using a SiC abrasive wheel on an electric handpiece at five circumferential speeds (500,750,1000,1250, or 1500 m/mm) with 100 gf. Grindability was evaluated by measuring the amount of metal volume removed after grinding during one minute.At the lowest grinding speed (500m/min), there was no statistical difference among the grindability of the Ti-Cu alloys, Ti-Ag alloys and CP Ti. The grindability of the alloys increased as the grinding speed increased. At 1000 and 1250 m/min, the grindability of the 20% Ag and 10% Cu alloys were higher than that of CP Ti. At the highest grinding speed (1500 m/min), the grindability of the 20%Ag, 5%Cu and 10%Cu alloys were higher than that of CP Ti. The grindability at 1500m/min for the 10%Cu was about 2.9 times as large as that for CPTi. In the case of Ti-Nb alloys, the grindability of Ti-30%Nb alloy was about 2 times as large as that of CP Ti at the lower grinding speed (500 and 750m/min).It was found that the grindability of the titanium was improved by alloying with silver, copper and niobium. The Ti-Cu alloys showed higher grindability at lower content of an alloying element than the Ti-Ag alloys.