42CrMo4 Alloy Structural Steel

Description: 42CrMo4 materials have been widely used in automotive driving elements. Although 42CrMo4 is more expensive than 41Cr4, it is more preferable in terms of material properties. In this study, these two materials were heat treated by austenitizing in a continuous furnace at 850 °C and quenched in oil at 90 °C.

After they were tempered at various temperatures, mechanical properties were determined for each tempering temperature. The material properties for both materials were compared with each other. Results indicated that same mechanical properties for 41Cr4 and 42CrMo4 can be achieved by tempering 41Cr4 about 50 °C lower temperature than for 42CrMo4.

In addition to the mechanical tests, fatigue tests were performed for both materials. Weibull distributions were plotted. Results indicated that 42CrMo4 had a longer life than 41Cr4 material.

Chemical Composition Properties Metric Imperial Hardness, Brinell (typical) 300 33 Hardness, Rockwell C (typical) 30 30 Tensile strength, ultimate 965-1030 MPa 140000-150000 psi Yield strength, 827-862 MPa 120000-125000 psi Elongation at break (in 50 mm (2")) 20.0% 20.0% Compressive strength 862 MPa 125000 psi Charpy impact (V-Notch) 27.1-33.9 J 20.0-25.0 ft-lb Poisson's ratio 0.27-0.30 0.27-0.30 Elastic modulus 190-210 GPa 27557-30457 ksi

Hot forming Narmalaizing+N Quenching+Q Quenching+Q Tempering+T Stress-relieving+SR 1100-850C 870 C air 860 C oil or polymer 850 C water 540-680 C 50°C under the temperature Soft annealing+A Isothermal annealing+i Spheroidizing annealing+AC End Quench hardenability test Pre heating welding Stress-relieving after welding 720 C air(HP max 241) 820 C fumace cooling to 670 C, then air (HB max 200) 840 C water 300 C 550 C fumace cooling Ac1 Ac3 Ms Mf 745 C 790 C 335 C 120 C

Mechanical Properties((Hardened and Tempered): Dia Scope(mm) Tensile Strength Rm (Mpa) Yield Strength R2 (Mpa) Elongation (longitudinal direction) Al (%) Reduction of area (%) Impact Energy Joules (-20°C) 16 max 1100-1300 900 min 10 min 40 min 30 min 16-40 1000-1200 750 min 11 min 45 min 35 min 40-100 900-1100 650 min 12 min 50 min 35 min 100-160 800-950 650 min 13 min 50 min 35 min 160-250 750-900 500 min 14 min 55 min 35 min

Heat Treatment: • Forging: Heat to 1150°C Hold until uniform.Minimum forging temperature 850°C. Cool slowly in ashes or sand etc. • Annealing: Heat to 830°C – 850°C. Cool in furnace. • Normalising: Heat to 870°C – 900°C. Cool in still air. Forging Heat to 1150 °C Hold until uniform. Minimum forging temperature 850°C. Cool slowly in ashes or sand etc.

ANNEALING Heat to 830°C – 850°C. Cool in furnace. Normalizing Heat to 870°C – 900°C. Cool in still air.

Stress Relieving: • Annealed: Heat to 600°C – 650°C • Hardened: Heat to 500°C – 550°C. Cool in still air • Hardening:Heat to 830°C – 880°C. Quench in oil or polymer. • Tempering:Heat to 450°C – 700°C cool in still air. NB.

Tempering within the range 200°C–420°C will result in temper brittleness and should be avoided Flame and Induction Hardening: Heat quickly to the required case depth at 860°C – 890°C and quench immediately in water or oil. Tempering at 150°C – 200°C will reduce stresses in the case with minimal effect on its hardness.

All de-carburised surface material must first be removed to ensure best results. • Nitriding: Heat to 500°C – 530°C and hold for sufficient time to develop the depth of case required Parts should be pre-hardened and tempered as required and also premachined leaving a small grinding allowance only.