Strain Hardenability and Thermal Conductivity

Strain Hardenability

Many metals exhibit a dramatic increase in hardness when they are subjected to strain in the form of cold working. During cold working operations like rolling, forging and bending internal stresses are developed which act to harden the material. The degree to which a material gets hardened due to strain is a typical characteristic of the material.

Since the material gets increasingly hardened as the machining process is proceeding, the cutting force and power required for these strain hardening material are high. The tool life is also very low as the strain hardened particles of the work material cause increased abrasive wear. However for dead soft material strain hardening by cold working improves tool life and surface finish as it helps avoid built up edge formation.

Thermal Conductivity

Thermal conductivity of a material is the ability of the material to conduct heat through it which is expressed as K.Cal/m/hr/^oC. If a work material has very low thermal conductivity then the heat generated in the machining process is not transmitted away from the cutting zone. Thus the tool and work piece become extremely hot. This excess heat accelerates the wear at the cutting edge.