Accession Number:

ADA164312

Title:

The Influence of Microstructure on the Strength and Toughness and the Fatigue Crack Propagation in CrWMn Steels,

Descriptive Note:

Corporate Author:

FOREIGN TECHNOLOGY DIV WRIGHT-PATTERSON AFB OH

Personal Author(s):

Report Date:

1986-01-24

Pagination or Media Count:

23.0

Abstract:

In this paper, we describe the interrelation between the microstructures of CrWMn high carbon steels of cold punch dies and strength, fracture resistance at static bending state, deflection and fracture toughness after various heat treatments. The influence of microstructures on the pregnant period of the fatigue crack No and the fatigue crack growth rate dadN is also studied. Our experimental results show that after carbides refining pretreatment, the quenching and tempering structures have maximum strength, the No increases remarkably and the dadN decreases at the low stress intensity factore Delta K range. After carbides refining pretreatment, the isothermal quenching structures have the best combination of strength and toughness of a mixed martensite structure with 50 bainite is obtained. It also can prolong the pregnant period of nucleation of fatigue cracks and reduce dadN at the midstream intensity factor Delta K range. According to the examination of fatigue fractures by a scattering electron microscope, the fracture of a conventional quenching and tempering structure with coarse carbides is mainly intergranular.

Subject Categories:

  • Properties of Metals and Alloys
  • Fabrication Metallurgy

Distribution Statement:

APPROVED FOR PUBLIC RELEASE