Abstract: The invention provides a carburized part which has excellent medium-cycle fatigue strength in particular subjected to surface-hardening treatment by carburization. The invention provides a carburized part including a carburized layer formed by performing carburizing treatment to a steel, the steel including, in terms of % by mass: 0.15% to 0.25% of C, 0.15% or less of Si, 0.4% to 1.1% of Mn, 0.8% to 1.4% of Cr, 0.25% to 0.55% of Mo, 0.015% or less of P, and 0.035% or less of S, with the remainder being Fe and unavoidable impurities, and the steel satisfying the following relation; 0.10?[Mo]/(10[Si]+[Mn]+[Cr])?0.40, in which [M] represents a content of element M in terms of % by mass.

Abstract: A method for producing a steel component by performing the treatments of the following sequentially steps 1 and 2 to a steel material containing, by mass %, C: 0.15 to 0.25%, Si: 0.01 to 0.10%, Mn: 0.50 to 0.80%, S: 0.003 to 0.030%, Cr: 0.80 to 1.20%, Mo: 0.30 to 0.45%, Al: 0.015 to 0.050%, and N: 0.010 to 0.025%, wherein Cr/Mn is 1.3 to 2.4, the balance being Fe and impurities, and contents of P and O among the impurities are P: not more than 0.010%, and O: not more than 0.0020%: step 1: a treatment which holds the steel material at a temperature of 850 to 1000° C. in a carburizing atmosphere or carbonitriding atmosphere, and step 2: a treatment which quenches the carburized or carbonitrided steel material, by using quenching oil having a temperature of 40 to 80° C. and a kinetic viscosity of 20 to 25 mm2/s at 40° C.

Abstract: A method for producing a carbonitrided member comprising the steps of carburizing a steel part having a composition of, by mass percent, C: 0.10 to 0.35%, Si: 0.15 to 1.0%, Mn: 0.30 to 1.0%, Cr: 0.40 to 2.0%, S: 0.05% or less with the balance being Fe and impurities in a carburizing atmosphere of 900 to 950° C. The carburized steel part is carbonitrided in a carbonitriding atmosphere with the temperature of 800 to 900° C. and the nitrogen potential of 0.2 to 0.6%. The carbonitrided steel part is qhenched and then shot peened. The shot peening treatment may be further performed while heating to a temperature not higher than 350° C. or immediately after heating to a temperature not higher than 350° C. After quenching, the shot peening treatment may be further performed after tempering in the temperature range exceeding 250° C. and not higher than 350° C.

Abstract: A process for producing a carbonitrided part comprising the steps of preparing a base steel part, having a composition comprising, in mass percent, C: 0.10 to 0.24%, Si: 0.15 to 1.0%, Mn: 0.30 to 1.0%, Cr: 0.40 to 2.0%, S: 0.05% or less, with the balance being Fe and impurities and performing the following steps 1-4 in sequence. Step 1 is carburizing the base steel part under a carburizing atmosphere at a temperature of 900 to 950° C. Step 2 is carbonitriding the base steel part carburized according to step 1 under a carbonitriding atmosphere at a temperature of 800 to 900° C. with a nitrogen potential of 0.2 to 0.6%. Step 3 is quenching the base steel part carbonitrided according to step 2. Step 4 is tempering the base steel part quenched according to step 3 at a temperature of more than 250° C. to not more than 350° C.

Abstract: The invention provides a carburized part which has excellent medium-cycle fatigue strength in particular subjected to surface-hardening treatment by carburization. The invention provides a carburized part including a carburized layer formed by performing carburizing treatment to a steel, the steel including, in terms of % by mass: 0.15% to 0.25% of C, 0.15% or less of Si, 0.4% to 1.1% of Mn, 0.8% to 1.4% of Cr, 0.25% to 0.55% of Mo, 0.015% or less of P, and 0.035% or less of S, with the remainder being Fe and unavoidable impurities, and the steel satisfying the following relation; 0.10?[Mo]/(10[Si]+[Mn]+[Cr])?0.40, in which [M] represents a content of element M in terms of % by mass.

Abstract: A method for producing a steel component by performing the treatments of the following sequentially steps 1 and 2 to a steel material containing, by mass %, C: 0.15 to 0.25%, Si: 0.01 to 0.10%, Mn: 0.50 to 0.80%, S: 0.003 to 0.030%, Cr: 0.80 to 1.20%, Mo: 0.30 to 0.45%, Al: 0.015 to 0.050%, and N: 0.010 to 0.025%, wherein Cr/Mn is 1.3 to 2.4, the balance being Fe and impurities, and contents of P and O among the impurities are P: not more than 0.010%, and O: not more than 0.0020%: step 1: a treatment which holds the steel material at a temperature of 850 to 1000° C. in a carburizing atmosphere or carbonitriding atmosphere, and step 2: a treatment which quenches the carburized or carbonitrided steel material, by using quenching oil having a temperature of 40 to 80° C. and a kinetic viscosity of 20 to 25 mm2/s at 40° C.

Abstract: A method for producing a carbonitrided member comprising the steps of carburizing a steel part having a composition of, by mass percent, C: 0.10 to 0.35%, Si: 0.15 to 1.0%, Mn: 0.30 to 1.0%, Cr: 0.40 to 2.0%, S: 0.05% or less with the balance being Fe and impurities in a carburizing atmosphere of 900 to 950° C. The carburized steel part is carbonitrided in a carbonitriding atmosphere with the temperature of 800 to 900° C. and the nitrogen potential of 0.2 to 0.6%. The carbonitrided steel part is qhenched and then shot peened. The shot peening treatment may be further performed while heating to a temperature not higher than 350° C. or immediately after heating to a temperature not higher than 350° C. After quenching, the shot peening treatment may be further performed after tempering in the temperature range exceeding 250° C. and not higher than 350° C.

Abstract: A carbonitrided part, where a base steel contains, in mass percent, C: 0.10 to 0.35%, Si: 0.15 to 1.0%, Mn: 0.30 to 1.0%, Cr: 0.40 to 2.0%, S?0.05%, and according to need further Mo?0.50%, with the balance being Fe and impurities, and in the region to a position of effective hardening depth from the surface of a hardened layer of the carbonitrided part, iron nitride particles of ?-Fe3N and/or ?-Fe2N are dispersed, and retained austenite is decomposed into bainitic ferrite, Fe3C, and ??-Fe16N2 has excellent abrasion strength and high pitting strength, although the base steel is a low-cost one with less content of Mo of an expensive alloy element or without addition of Mo. This carbonitrided part can be produced, for example, by subjecting the base steel part to carburizing in which the base steel part is held in a carburizing atmosphere at 900 to 950° C. and successively to carbonitriding in which the base steel part is held in a carbonitriding atmosphere with a nitrogen potential of 0.2 to 0.

Abstract: A method for producing a steel material having a high fatigue strength and given a uniform residual stress by a rapid treatment. A marageing steel is subjected to a cold plastic working to have a predetermined dimension, to a solution treatment for 60 minutes or more at a temperature of 750 to 800° C., and to an aging.

Abstract: A pushing block for the CVT belt has a hyper-eutectoid structure overall and exhibiting a structure in which spheroidal cementite having an area percentage of 0.4% or more are dispersed in a matrix of a martensite.

Abstract: A pushing block for the CVT belt has a hyper-eutectoid structure overall and exhibiting a structure in which spheroidal cementite having an area percentage of 0.4% or more are dispersed in a matrix of a martensite.

Abstract: A method for producing a steel material having a high fatigue strength and given a uniform residual stress by a rapid treatment. A marageing steel is subjected to a cold plastic working to have a predetermined dimension, to a solution treatment for 60 minutes or more at a temperature of 750 to 800° C., and to an aging.

Abstract: A pushing block for the CVT belt has a hyper-eutectoid structure overall and exhibiting a structure in which spheroidal cementite having an area percentage of 0.4% or more are dispersed in a matrix of a martensite.

Abstract: A pushing block for the CVT belt has a hyper-eutectoid structure overall and exhibiting a structure in which spheroidal cementite having an area percentage of 0.4% or more are dispersed in a matrix of a martensite.