Austenitizing temperatures

When a component at an austenitizing temperature is placed in a quenchant, eg, water or oil, the surface cools faster than the center. The formation of martensite is more favored for the surface. A main function of alloying elements, eg, Ni, Cr, and Mo, in steels is to retard the rate of decomposition of austenite to the relatively soft products. Whereas use of less expensive plain carbon steels is preferred, alloy steels may be requited for deep hardening. 

Fig. 19. Effect of cooling rate on structure of a eutectoid steel. = austenitizing temperature > = austenite phase.

Vacuum 830°C, 20 min/oil/air 180°C, 2 h. Even austenitizing temperatures above the CVD temperatures cause almost no changes in the chemical compositions of the D2 substrate and TiN coating as measured by GDOS (glow discharge optical spectroscopy), if the post CVD... 

Hold at austenitizing temperature, e g. one hour per inch of section. 

Martensite is formed when steel with a carbon content above 0.2 % is rapidly cooled from the austenite temperature range to a temperature below the martensite starting temperature. Due to the prompt cooling, the carbon dissolved in austenite is forced to remain dissolved in the mixed crystal. Martensite has a fine-acicular, very hard, and brittle microstmcture which causes increased abrasive wear and high mechanical and thermal stresses during machining. 

Steel parts because the deposition temperatures lies beyond the austenitizing temperature of steel. PVD-appliedTiN is also used for a variety ofrelatively higher melting point materials, such as stainless steels, titanium, and titanium alloys [197]. TiN coatings can also be deposited by thermal spraying, whereas TiN powders are produced by the nitridation of titanium with nitrogen or ammonia at 1200 °C [198]. 

AISI No.=> Treatment Austenitizing temperature (°C) Tensile strength (MPa) Yield strength (MPa) Elongation (%) Reduction in area (%) Hardness (HB)... 

FIGURE 4.84 Interrelationship between the tempering temperature and the austenitizing temperatures of the example steel 1.2379 (XI 53CrMoV12)... 

FIGURE 4.86 Soaking time at austenitizing temperature as a function of wall thickness for different material groups... 

Austenitizing Heating a steel into the austenitic temperature range so that its structure becomes austenitic. Carbide A compound of iron and carbon FesC (cementite) is a hard and brittle substance. Concentration ceU A corrosion cell formed by a difference in the concentration of some constituents in the electrolyte. 

The compression tests were conducted on the thermo-mechanical simulator Gleeble 1500D in a protective atmosphere, with strain rates ranging from 0.001 s" to 5 s and temperatures between 850 °C and 1130 °C or 1150 °C, for cast and wrought state, respectively. The samples were first heated to austenitization temperature with 4 K/s, where they were held for 10 minutes prior to cooling to deformation temperature with 6 K/s where they were held for 10 min prior to deformation. Right after deformation the samples were submerged in water. 

Austenitization temperature was selected on a basis of series of compression test, where it was selected as the highest temperature at which after deforming the samples to strain of 0.9 with a strain rate of 1 s" no macro cracks were present on the surface of the specimens [11-15]. 

The austenitization temperature was selected using an array of special compression tests, which have shown, that the best austenitization temperature was 40-50 X under the melting temperature of the carbides with the lowest melting temperature. 

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