High-speed steel and applications inengineers' cutting tools

Abstract

The heat-treatment characteristics and unique red-hardness properties of high-speed steels are described in relation to the historical development of modern compositions. Economic factors have hastened the adoption of molybdenum-type high-speed steels in place of the tungsten grades originally favoured. Standardization of grades has been aided by the wide usage of the AISI classification system and the publication of British Standard BS 4659 ‘Tool steels’. The selection of popular standard grades for various cutting tool applications is discussed. Many aspects of quality, including hardening response, carbide segregation, and surface decarburization are covered by BS 4659 and developments in the manufacture of high-speed steels to meet some of the high standards now demanded are also described. The special considerations and practices involved in the annealing, stress-relieving, hardening, and tempering of high-speed steels are reviewed in relation to the manufacture of engineers' cutting tools. Precautions to be taken in rehardening and in tool grinding are emphasized and reference is made to the use of such tool finishing operations as salt-bath nitriding and steam tempering. The consistent attainment of high standards of heat treatment is complementary to good material quality and control of engineering aspects in the manufacture of successful cutting tools.