Effect of technological factors on the strength of a sulfidized iron-graphite material

Abstract

1. The strength of iron-graphite powder metallurgical materials after sintering is governed not only by the charge composition but also by a number of technological parameters. Varying the degree of alloying of the iron particles with carbon enables the strength properties of a sulfidized iron-graphite material to be changed by a factor of nearly two; decreasing the starting powder particle size by a factor of four produces a 30% increase in strength; lowering the porosity from 30 to 1% increases the strength characteristics of the material four to five times. 2. The strength of a material can be changed appreciably by alloying its interparticle contacts. Adding zinc sulfide to an iron-graphite material causes alloying of its contacts with zinc and raises its integral hardness by almost 30%. 3. The starting porosity determines the character of strengthening and rupture of a material in compression. During the compression of porous materials, densification and increase in the area of contacts per unit sectional area (geometric factor) constitute the main mechanism of strengthening, but with nonporous materials strengthening is due to the work-hardening of particles and interparticle contacts (physical factor). Rupture may take place in both the contacts and particles. 4. Raising the test temperature from 20 to 600°C lowers the strength of ZhGr3Tss4 material by a factor of 2–2.5, but produces a twofold increase in its ductility properties.