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Factors determining the reversed bending fatigue limit of laser hardened smooth specimens from C70W2 steel
Thermal treatment Factors d e t e r m i n i n g t h e reversed bending f a t i g u e l i m i t o f laser hardened smooth s p e c i m e n s f r o m C70W2 steel. Winderlich, B. and Brenner, B. Hart.-Tech. Mitt. M a y - J u n e 1989 44, (3), 166-173 (in German) Using smooth specimens from pearlitic C7OW2 steel the influence of the depth of laser hardening on the reversed fatigue limit was investigated. A hyperbolic relation between the fatigue limit and the case depth as the critical factor for the fatigue behaviour was found. Starting from the conception of local fatigue strength the results are discussed with regard to the effect of residual stresses and the application to components. 24 refs.
Strength and wear properties of inductive surface hardened components. Kloos, K.H. Hart.-Tech. Mitt. M a y - J u n e 1989 44, (3), 157-166 (in German) The induction hardening of components is an important surface strengthening process to increase the fatigue limit and wear resistance especially on rolling contact fatigue. With regulation and controlling of the process parameters during heating and cooling it is possible to influence the depth of the hardened zone and the residual stress distribution, so that optimal fatigue strength behaviour can be attained. 22 refs.
The application o f t h e drop-lead cerbonitriding process w i t h addition of rare-earth elements. Yao, X.-X. Heat Treat. Met. (China) OCt. 1988 (10), 49-51 (in Chinese) The drop-feed carbonitriding process with addition of a certain amount of rare-earth elements in carbonitriding media was applied to treat various 20CrMnTi gears (total number approx 35 000). Two preferential technologies were introduced. Compared to the regular carbonitriding process, the following benefits were obtained: Carbonitriding temperature was reduced by 50-60°C. Rate of carbonitriding increased by 28-50%. Lives of bending fatigue and contact fatigue were enhanced. Graphs. Tables. Photomicrographs.
Study of t h e p r o p e r t i e s of 2 5 S i M n M o V steel on t h e Grade D link chains used for mining. Xu, Q.-x., Sun, H.-f., Zhao, Y.-z. and Kong, F.-x. Heat Treat. Met. (China) Oct. 1988 (10), 17-23 (in Chinese) Grade D link chains made of 25SiMnMoV steel were studied. A comparison of various strengthening and toughening processes is carried out, and temper brittleness, quenching temperature, intercritical hardening and differential temperature treatment are also discussed. The results of production tests show that the grade D link chains made of 25SiMnMoV steel can fully meet the requirements of MT36-80 standard, and the Mn-Cr-Ni-Mo series steels can be substituted by this steel. Considerable economic benefit is expected. Photomicrographs. Tables. Graphs. 10 refs.
Rolling contact fatigue of rolling elements made of 52100 steal after short t i m e austenitizing. Schlicht, H. Hart.-Tech. Mitt. M a y - J u n e 1989 44, (3), 143-148 (in German)
S t u d y on improving t h e t h e r m o - f a t i g u e resistance o f H M 3 steal. Wang,
investigations into the austenitizing kinetics in 100Cr6 steel showed why a change in the heat treatment parameters has different effects on the material properties, such as hardness, limit of elasticity, bending strength, plastic deformation capability, retained austenite, etc. An appraisal of heat treatments with material properties as criteria is therefore not possible. Rolling contact fatigue is a part property, ie apart from the material properties, it is influenced by residual stresses and the shape and size of the part. A longer rolling contact fatigue life can be achieved with surface layer hardened parts if their residual compressive stress is advantageous. This has been proven with many bearings in rolling contact. 13 refs.
The influence of quenching rate and tempering temperature on the thermo-fatigue resistance of HM3 hot work die steel is presented. The result shows that thermofatigue resistance can be improved when quenching rate is increased and tempering temperature is selected properly. Finally, the optimum heat treatment process for this steel is suggested. Photomicrographs. Tables. Graph. 7 refs.
Induction hardening in the fabrication of engines for commercial vehicles. Velten, E. and Rauh, L. Hart.-Tech. Mitt. M a y - J u n e 1989 44, (3), 138-142 (in German) High loaded engine parts are surface hardened in order to optimize their properties. In this way the fatigue strength and the wear resistance can be improved considerably. The induction hardening system is a cost effective technology appropriate for serial operation. For induction hardening it is important to adjust many of the process parameters and to keep their reproducibility constant over longer production periods. This leads to an enormous control effort mostly in application of destructive testing. The possibilities of induction hardening are not fully utilized. Some examples show that parts with unfavourable geometrical conditions can be hardened with an optimized technology. With an exact adjustment of surface hardness and residual stress, the fatigue strength can be increased. 4 refs.
Fracture mechanics investigations into t h e f a t i g u e behaviour of caseh a r d e n e d steals. Romvari, P., Toth, L., Blumenauer, H., Krempe, M. and
Dehne, G. Wiss, Z. Tech. Univ. Otto yon Guericke Magdeburg 1988 32, (4), 59-64 (in German) Both the blank-hardened and the case-hardened stage must be known for experimental determination of the fatigue failure mechanics. Crack propagation, fracture work and computer-aided materials selection based on the Jominy curve permit economic determination. The effects of the tempering temperature on the residual stress distribution, and thus on the material damage under cyclic mechanical loading, are critical as regards continuous strength and structure change and the residual stress gradients in the boundary zone. Steels 23NiCrMo2, 20MoCr5 and 16MnCr5 were studied. 23 refs.
456
L. and Li, P.-a. Heat Treat. Met. (China) Oct. 1988 (10), 13-17 (in Chinese)
Practical development of direct quenching from forging t e m p e r a t u r e w i t h p o l y m e r quenchants. Yamamoto, H., Otagiri, Y., Miyashita, M. and
Nishiyama, F. Netsu Shori (J. Jpn. Soc. Heat Treat.) 1989 29, (1), 14-18 (in Japanese) $45C and SCM435 steels were directly quenched from the forging temperature into polymer quenchants. This method increases hardenability of the steels in comparison with conventional oil quenching. Loss of hardness was not observed even at the centre of an $45C crankshaft with 28 mm diameter, where homogeneous sorbite structure was observed. Accordingly, the yield point, impact value, and fatigue strength of the crankshaft were excellent. Because the heat for forging is used for quenching, the energy cost is lowered significantly (-85%). For practical application of this method, prevention of quenching crack is necessary. The agitation method of a quenchant and the operation conditions were improved for this purpose. 9 refs.
The influence of tempering temperature on small fatigue crack behaviour monitored with surface acoustic waves in quenched and tempered 4140 steal. London, B., Nelson, D.V. and Shyne, J.C. Metal/. Trans. A July 1989 20A, (7), 1257-1265 Small surface fatigue crack growth in specially designed cantilevered bending samples of high-purity 4140 steel quenched and tempered to various strength levels was investigated. Tempering temperatures of 200, 400, 550, and 700 °C were used to produce a range of yield strengths and microstructures. Crack propagation and crack closure were monitored with a surface acoustic wave uitrasonic technique. The small crack results were compared to those of long cracks in compact tension samples. Small cracks in the 200 and 400 °C tempers grew at &K levels above their long crack thresholds. Small cracks in the 550 °C tempers grew at &K levels slightly below the long crack threshold. The surface cracks in the 700 °C temper grew well below the long crack threshold showing the 'small crack effect'. Small crack growth occurred in a very narrow da/dN-~,K scatter band showing much less variation with microstructure than the long crack data. The differences between the long and small crack data were due to the high, relatively similar closure values for the small cracks and the variation of tong crack growth with microstructure. Graphs, Photomicrographs. 53 refs.
Int J Fatigue November 1989
Strength and wear properties of inductive surface hardened components. Kloos, K.H. Hart.-Tech. Mitt. M a y - J u n e 1989 44, (3), 157-166 (in German) The induction hardening of components is an important surface strengthening process to increase the fatigue limit and wear resistance especially on rolling contact fatigue. With regulation and controlling of the process parameters during heating and cooling it is possible to influence the depth of the hardened zone and the residual stress distribution, so that optimal fatigue strength behaviour can be attained. 22 refs.
The application o f t h e drop-lead cerbonitriding process w i t h addition of rare-earth elements. Yao, X.-X. Heat Treat. Met. (China) OCt. 1988 (10), 49-51 (in Chinese) The drop-feed carbonitriding process with addition of a certain amount of rare-earth elements in carbonitriding media was applied to treat various 20CrMnTi gears (total number approx 35 000). Two preferential technologies were introduced. Compared to the regular carbonitriding process, the following benefits were obtained: Carbonitriding temperature was reduced by 50-60°C. Rate of carbonitriding increased by 28-50%. Lives of bending fatigue and contact fatigue were enhanced. Graphs. Tables. Photomicrographs.
Study of t h e p r o p e r t i e s of 2 5 S i M n M o V steel on t h e Grade D link chains used for mining. Xu, Q.-x., Sun, H.-f., Zhao, Y.-z. and Kong, F.-x. Heat Treat. Met. (China) Oct. 1988 (10), 17-23 (in Chinese) Grade D link chains made of 25SiMnMoV steel were studied. A comparison of various strengthening and toughening processes is carried out, and temper brittleness, quenching temperature, intercritical hardening and differential temperature treatment are also discussed. The results of production tests show that the grade D link chains made of 25SiMnMoV steel can fully meet the requirements of MT36-80 standard, and the Mn-Cr-Ni-Mo series steels can be substituted by this steel. Considerable economic benefit is expected. Photomicrographs. Tables. Graphs. 10 refs.
Rolling contact fatigue of rolling elements made of 52100 steal after short t i m e austenitizing. Schlicht, H. Hart.-Tech. Mitt. M a y - J u n e 1989 44, (3), 143-148 (in German)
S t u d y on improving t h e t h e r m o - f a t i g u e resistance o f H M 3 steal. Wang,
investigations into the austenitizing kinetics in 100Cr6 steel showed why a change in the heat treatment parameters has different effects on the material properties, such as hardness, limit of elasticity, bending strength, plastic deformation capability, retained austenite, etc. An appraisal of heat treatments with material properties as criteria is therefore not possible. Rolling contact fatigue is a part property, ie apart from the material properties, it is influenced by residual stresses and the shape and size of the part. A longer rolling contact fatigue life can be achieved with surface layer hardened parts if their residual compressive stress is advantageous. This has been proven with many bearings in rolling contact. 13 refs.
The influence of quenching rate and tempering temperature on the thermo-fatigue resistance of HM3 hot work die steel is presented. The result shows that thermofatigue resistance can be improved when quenching rate is increased and tempering temperature is selected properly. Finally, the optimum heat treatment process for this steel is suggested. Photomicrographs. Tables. Graph. 7 refs.
Induction hardening in the fabrication of engines for commercial vehicles. Velten, E. and Rauh, L. Hart.-Tech. Mitt. M a y - J u n e 1989 44, (3), 138-142 (in German) High loaded engine parts are surface hardened in order to optimize their properties. In this way the fatigue strength and the wear resistance can be improved considerably. The induction hardening system is a cost effective technology appropriate for serial operation. For induction hardening it is important to adjust many of the process parameters and to keep their reproducibility constant over longer production periods. This leads to an enormous control effort mostly in application of destructive testing. The possibilities of induction hardening are not fully utilized. Some examples show that parts with unfavourable geometrical conditions can be hardened with an optimized technology. With an exact adjustment of surface hardness and residual stress, the fatigue strength can be increased. 4 refs.
Fracture mechanics investigations into t h e f a t i g u e behaviour of caseh a r d e n e d steals. Romvari, P., Toth, L., Blumenauer, H., Krempe, M. and
Dehne, G. Wiss, Z. Tech. Univ. Otto yon Guericke Magdeburg 1988 32, (4), 59-64 (in German) Both the blank-hardened and the case-hardened stage must be known for experimental determination of the fatigue failure mechanics. Crack propagation, fracture work and computer-aided materials selection based on the Jominy curve permit economic determination. The effects of the tempering temperature on the residual stress distribution, and thus on the material damage under cyclic mechanical loading, are critical as regards continuous strength and structure change and the residual stress gradients in the boundary zone. Steels 23NiCrMo2, 20MoCr5 and 16MnCr5 were studied. 23 refs.
456
L. and Li, P.-a. Heat Treat. Met. (China) Oct. 1988 (10), 13-17 (in Chinese)
Practical development of direct quenching from forging t e m p e r a t u r e w i t h p o l y m e r quenchants. Yamamoto, H., Otagiri, Y., Miyashita, M. and
Nishiyama, F. Netsu Shori (J. Jpn. Soc. Heat Treat.) 1989 29, (1), 14-18 (in Japanese) $45C and SCM435 steels were directly quenched from the forging temperature into polymer quenchants. This method increases hardenability of the steels in comparison with conventional oil quenching. Loss of hardness was not observed even at the centre of an $45C crankshaft with 28 mm diameter, where homogeneous sorbite structure was observed. Accordingly, the yield point, impact value, and fatigue strength of the crankshaft were excellent. Because the heat for forging is used for quenching, the energy cost is lowered significantly (-85%). For practical application of this method, prevention of quenching crack is necessary. The agitation method of a quenchant and the operation conditions were improved for this purpose. 9 refs.
The influence of tempering temperature on small fatigue crack behaviour monitored with surface acoustic waves in quenched and tempered 4140 steal. London, B., Nelson, D.V. and Shyne, J.C. Metal/. Trans. A July 1989 20A, (7), 1257-1265 Small surface fatigue crack growth in specially designed cantilevered bending samples of high-purity 4140 steel quenched and tempered to various strength levels was investigated. Tempering temperatures of 200, 400, 550, and 700 °C were used to produce a range of yield strengths and microstructures. Crack propagation and crack closure were monitored with a surface acoustic wave uitrasonic technique. The small crack results were compared to those of long cracks in compact tension samples. Small cracks in the 200 and 400 °C tempers grew at &K levels above their long crack thresholds. Small cracks in the 550 °C tempers grew at &K levels slightly below the long crack threshold. The surface cracks in the 700 °C temper grew well below the long crack threshold showing the 'small crack effect'. Small crack growth occurred in a very narrow da/dN-~,K scatter band showing much less variation with microstructure than the long crack data. The differences between the long and small crack data were due to the high, relatively similar closure values for the small cracks and the variation of tong crack growth with microstructure. Graphs, Photomicrographs. 53 refs.
Int J Fatigue November 1989