Some Investigations for the Effect of Working Processes on High Tensile Steels Commercially Produced

Abstract

This paper includes, as its object, the study on the effect of various fabrication operations such as both cold and hot forming, water-quenching and various cutting processes on the notch sensitivity of structural high tensile steels. Tests were made as follows ;
V-notch charpy impact specimens were taken parallel to rolling direction from the strained parts of both cold and hot bending of various radii, and heating centre or embrittled zone of water-quenched parts, then tested over a range of temperature from-65°C to +90°C. To investigate the effect of cutting operations to the notch toughness of the steel, U-notch tear specimens were used. The U-notch of the specimen was prepared by machining, flame-cutting or shearing and tests were made over a range of temperature from -100°C to +70°C The same tests as above-mentioned also were made of mild steel plate and its results were compared with those of high tensile steels.
As a result it has been cocluded that
(1) Cold forming is unfavourable as it reduces ductility of steel when proportion of bending radius vs plate thickness below 3.5 is obtained.
(2) It is easy to intinate crack at embrittled zone of periphery of water-quenched part for HTS steel because of its hardenability
(3) Shearing process reduces ductility of steel remarkably while flame-cut edges show sufficient ductile behaviour.