Accession Number : ADA116307

Title :   Individual and Combined Effects of Sulfur and Phosphorus on the Toughness of High Strength Steels.

Descriptive Note : Final rept. Nov 79-Nov 81,


Personal Author(s) : Chang,Edward ; Wallace,John F

PDF Url : ADA116307

Report Date : May 1982

Pagination or Media Count : 177

Abstract : This study sought to determine the feasibility of specifying a maximum sum of phosphorus plus sulfur contents rather than a maximum for each element as related to the effects that these elements exert on the toughness of steel. A computer analysis of the literature was conducted on the influence of phosphorus and sulfur in the toughness of steel. Then, an experimental program was undertaken to produce a series of 4340 cast steels with a matrix of phosphorus and sulfur contents including low, medium and high values of each. These steels were heat treated by oil quenching to martensite and tempering at 1100 F to a 150 ksi yield strength and at 400 F to a 220 ksi yield strength. The steels were then tested to determine the tensile properties, Charpy V-notch transition curves for regular and precracked specimens and the static fracture toughness properties. The behavior of phosphorus and sulfur on the toughness of these steels is sufficiently different that it does not appear feasible to substitute the sum of the elements for maxima for each in specifications for steels requiring specific toughness properties. Phosphorus raises the transition temperature and embrittles the steel significantly, particularly at high strengths and in the presence of sharp notches. Phosphorus is in supersaturated solid solution in the steel and embrittles the steel because of the higher friction stress of the lattice for dislocation motion. Sulfur increases the number of sulfide inclusions and lowers the toughness by the decohesion of sulfide inclusions during the early stages of plastic deformation of the matrix.

Descriptors :   *Steel, *Low alloy steels, *Sulfur, *Phosphorus, *Charpy impact tests, *Mechanical properties, Crack propagation, Notch toughness, Heat treatment, Yield strength, Transition temperature, Plastic deformation, Tensile properties, High strength alloys, Matrix materials, Fatigue(Mechanics), Fracture(Mechanics), Strain rate, Fractography, Regression analysis, Computer programs

Subject Categories : Metallurgy and Metallography
      Test Facilities, Equipment and Methods

Distribution Statement : APPROVED FOR PUBLIC RELEASE