Abstract: A lead-free steel for machine structural use with excellent machinability and low strength anisotropy, which does not contain Pb and is equal to or higher than a conventional Pb-containing free cutting steel in properties, is provided. This steel includes, on the weight basis, C: 0.10 to 0.65%; Si: 0.03 to 1.00%; Mn: 0.30 to 2.50%; S: 0.03 to 0.35%; Cr: 0.1 to 2.0%; Al: less than 0.010%; Ca: 0.0005 to 0.020%; Mg: 0.0003 to 0.020%; O: less than 20 ppm; and the balance being Fe and inevitable impurities.

Abstract: Disclosed is a production process of a steel product for induction hardening and a steel product for carburizing, having improved grain size properties and machinability. This production process comprises the steps of: providing an ingot or bloom comprising a steel comprising, by weight, carbon (C): 0.10 to 0.45% or 0.25 to 0.70%, silicon (Si): 0.03 to 1.0%, manganese (Mn): 0.2 to 2.0%, titanium (Ti): 0.05 to 0.2%, aluminum (Al): 0.005 to 0.05%, and nitrogen (N): not more than 0.01% with the balance consisting of iron (Fe) and unavoidable impurities; and subjecting the steel ingot or bloom to a series of hot working steps including the step of rolling the steel ingot or bloom into a semi-finished steel product, the step of rolling the semi-finished steel product into a steel bar or wire rod, and the step of forging the steel bar or wire rod into a product. In the above series of hot working steps, the steel is given a thermal history in which said steel is at least once heated to 1,250 ° C.

Abstract: Disclosed is a production process of a steel product for induction hardening and a steel product for carburizing, having improved grain size properties and machinability. This production process comprises the steps of: providing an ingot or bloom comprising a steel comprising, by weight, carbon (C): 0.10 to 0.45% or 0.25 to 0.70%, silicon (Si): 0.03 to 1.0%, manganese (Mn): 0.2 to 2.0%, titanium (Ti): 0.05 to 0.2%, aluminum (Al): 0.005 to 0.05%, and nitrogen (N): not more than 0.01% with the balance consisting of iron (Fe) and unavoidable impurities; and subjecting the steel ingot or bloom to a series of hot working steps including the step of rolling the steel ingot or bloom into a semi-finished steel product, the step of rolling the semi-finished steel product into a steel bar or wire rod, and the step of forging the steel bar or wire rod into a product. In the above series of hot working steps, the steel is given a thermal history in which said steel is at least once heated to 1,250° C.

Abstract: The first invention provides a steel product which, while minimizing an increase in hardness after forging to ensure machinability and cold workability, is improved, for example, in fatigue strength in its non-hardened part and is improved, in its hardened part, in rolling contact fatigue life, antipitting level, abrasion resistance, and fatigue strength. The highly machinable and high strength steel for induction hardening comprises, by mass, carbon (C): not less than 0.40% and less than 0.50%, silicon (Si): 0.5 to 0.9%, manganese (Mn): 0.5 to 1.0%, chromium (Cr): not more than 0.4%, sulfur (S): not more than 0.035%, and vanadium (V): 0.01 to 0.15% with the balance consisting of iron (Fe) and unavoidable impurities, said steel being forged into a component a part of which is then inductively hardened before use, the steel satisfying a carbon equivalent (Ceq) requirement represented by 0.75?Ceq?0.90, and a machinability index (a value) requirement represented by a value ?0.62.

Abstract: Disclosed is a steel for machine structural use which is usable instead of Pb (lead) free-machining steel, has no adverse effect on environment, and can be stably machined. This steel for machine structural use comprises by mass carbon (C): 0.10 to 0.60%, silicon (Si): 0.05 to 1.0%, manganese (Mn): 0.3 to 2.0%, sulfur (S): 0.02 to 0.25%, aluminum (Al): 0.002 to 0.030%, and calcium (Ca): 0.0005 to 0.01%, with the balance consisting of iron (Fe) and unavoidable impurities, the steel satisfying Ca/Al ratio=0.1 to 1.0 in terms of % by mass ratio.

Abstract: A lead-free steel for machine structural use with excellent machinability and low strength an isotropy, which does not contain Pb and is equal to or higher than a conventional D Pb-containing free cutting steel in properties, is provided. This steel includes, on the weight basis, C: 0.10 to 0.65%; Si: 0.03 to 1.00%; Mn: 0.30 to 2.50%; S: 0.03 to 0.35%; Cr: 0.1 to 2.0%; Al: less than 0.010%; Ca: 0.0005 to 0.020%; Mg: 0.0003 to 0.020%; 0: less than 20 ppm; and the balance being Fe and inevitable impurities.

Abstract: Disclosed is a free machining steel for machine structural use, which can realize very good chip disposability without incorporation of any harmful material such as lead (Pb). This free machining steel is a hot rolled or hot forged free machining steel having improved chip disposability. The free machining steel comprises, by mass, carbon (C): 0.01 to 0.70%, silicon (Si): 0.05 to 2.00%, manganese (Mn): 0.20 to 3.50%, calcium (Ca): 0.0003 to 0.01%, sulfur (S): 0.020 to 0.300%, aluminum (Al): 0.002 to 0.300%, nitrogen (N): 0.003 to 0.035%, and oxygen (O): 0.0010 to 0.0080% with the balance consisting of iron (Fe) and unavoidable impurities. The steel comprises sulfides having the major axis of from 0.5 &mgr;m to 20 &mgr;m, exclusive, and comprising MnS as the main component, in a number of not less than 30% of the total number of sulfides. The steel also comprises oxide inclusions having the major axis of from 0.

Abstract: Disclosed is a process for producing a retainer for a constant velocity joint for automobiles or the like, which has improved flexural strength properties without sacrificing the machinability, using a steel corresponding to SCr 415 (JIS) or SCM 415 (JIS). This production process comprises the steps of: providing a steel comprising by weight carbon (C): 0.10 to 0.25%, silicon (Si): 0.03 to 0.15%, manganese (Mn): 0.20 to 0.60%, sulfur (S): 0.003 to 0.030%, chromium (Cr): 1.00 to 1.50%, titanium (Ti): 0.05 to 0.20%, boron (B): 0.0005 to 0.0050%, and nitrogen (N): not more than 0.01% with the balance consisting of iron (Fe) and inevitable impurities; hot forging the steel at a heating temperature of 1000 to 1100° C. to prepare a forged product having a Rockwell hardness of not more than 88 HRB; machining and optionally piercing the forged product; carburizing and quenching and tempering the machined steel to attain an effective case depth of 0.4 to 0.

Abstract: The present invention provides a steel product which, while minimizing an increase in hardness after forging to ensure machinability and cold workability, is improved, for example, in fatigue strength in its non-hardened portion and is improved, in its hardened portion, in rolling resistance level, antipitting level, abrasion resistance, and fatigue strength. The high strength steel for induction hardening comprises, by mass, carbon (C): 0.5 to 0.7%, silicon (Si): 0.5 to 1.0%, manganese (Mn): 0.5 to 1.0%, chromium (Cr): not more than 0.4%, and sulfur (S): not more than 0.035% with the balance consisting of iron (Fe) and unavoidable impurities, the steel being forged to produce a component at least a part of which is then inductively hardened before use.

Abstract: Disclosed is a titanium(Ti)-added steel wherein the formation of TiN or nitrogen-rich TiCN, which is found in a conventional titanium-added steel for machine construction and adversely affects the properties of the titanium-added steel for machine construction, has been suppressed, particularly a titanium-added, high strength steel wherein various properties can be stably exhibited and Ti(C)N has been regulated.

Abstract: Disclosed is a production process of a steel product for induction hardening and a steel product for carburizing, having improved grain size properties and machinability. This production process comprises the steps of: providing an ingot or bloom comprising a steel comprising, by weight, carbon (C): 0.10 to 0.45% or 0.25 to 0.70%, silicon (Si): 0.03 to 1.0%, manganese (Mn): 0.2 to 2.0%, titanium (Ti): 0.05 to 0.2%, aluminum (Al): 0.005 to 0.05%, and nitrogen (N): not more than 0.01% with the balance consisting of iron (Fe) and unavoidable impurities; and subjecting the steel ingot or bloom to a series of hot working steps including the step of rolling the steel ingot or bloom into a semi-finished steel product, the step of rolling the semi-finished steel product into a steel bar or wire rod, and the step of forging the steel bar or wire rod into a product. In the above series of hot working steps, the steel is given a thermal history in which said steel is at least once heated to 1,250° C.

Abstract: Disclosed is a process for producing an inner race for a constant velocity joint comprising the steps of: providing a steel comprising by weight carbon 0.10 to 0.25%, silicon 0.03 to 0.15%, manganese 0.20 to 0.60%, sulfur 0.003 to 0.030%, chromium 1.00 to 1.50%, titanium 0.05 to 0.20%, boron 0.0005 to 0.0050%, and nitrogen not more than 0.01% with the balance consisting of iron and impurities; hot rolling or hot forging the steel, to prepare a rolled/forged product; cold forging and machining the rolled/forged product; and carburizing, quenching, and tempering the machined rolled/forged product so that the treated steel satisfies an effective case depth of 0.4 to 0.9 mm, a thickness of abnormal-carburizing layer of not more than 15 &mgr;m, and an austenite grain size number as specified in JIS G 0551 of not less than 7.

Abstract: Disclosed is a process for producing an inner race for a constant velocity joint for automobiles or the like, which has improved rolling fatigue life and flexural strength properties without sacrificing cold forgeability and machinability, using SCM 420 (JIS) or a steel corresponding to SCM 420. This production process comprises the steps of: providing a steel comprising by weight carbon (C): 0.10 to 0.25%, silicon (Si): 0.03 to 0.15%, manganese (Mn): 0.20 to 0.60%, sulfur (S): 0.003 to 0.030%, chromium (Cr): 1.00 to 1.50%, titanium (Ti): 0.05 to 0.20%, boron (B): 0.0005 to 0.0050%, and nitrogen (N): not more than 0.

Abstract: Disclosed is a process for producing a retainer for a constant velocity joint for automobiles or the like, which has improved flexural strength properties without sacrificing the machinability, using a steel corresponding to SCr 415 (JIS) or SCM 415 (JIS). This production process comprises the steps of: providing a steel comprising by weight carbon (C): 0.10 to 0.25%, silicon (Si): 0.03 to 0.15%, manganese (Mn): 0.20 to 0.60%, sulfur (S): 0.003 to 0.030%, chromium (Cr): 1.00 to 1.50%, titanium (Ti): 0.05 to 0.20%, boron (B): 0.0005 to 0.0050%, and nitrogen (N): not more than 0.01% with the balance consisting of iron (Fe) and inevitable impurities; hot forging the steel at a heating temperature of 1000 to 1100° C. to prepare a forged product having a Rockwell hardness of not more than 88 HRB; machining and optionally piercing the forged product; carburizing and quenching and tempering the machined steel to attain an effective case depth of 0.4 to 0.

Abstract: The present invention provides a steel product which, while minimizing an increase in hardness after forging to ensure machinability and cold workability, is improved, for example, in fatigue strength in its non-hardened portion and is improved, in its hardened portion, in rolling resistance level, antipitting level, abrasion resistance, and fatigue strength. The high strength steel for induction hardening comprises, by mass, carbon (C): 0.5 to 0.7%, silicon (Si): 0.5 to 1.0%, manganese (Mn): 0.5 to 1.0%, chromium (Cr): not more than 0.4%, and sulfur (S): not more than 0.035% with the balance consisting of iron (Fe) and unavoidable impurities, the steel being forged to produce a component at least a part of which is then inductively hardened before use.

Abstract: An induction-hardened rolling bearing device used by disposing rolling elements in a raceway track member, with excellent cold drawability and improved wear resistance and extended service life, in which ingredients of an alloy for the raceway track member contain, from 0.40 to 0.90% of C, from 0.05 to 0.80% of Si, from 0.10 to 2.0% of Mn, from 0.05 to 0.50% of Ti and 0.03% or less of N, on the weight basis, induction hardening is applied at least to the raceway surface of the raceway track member, and Ti carbide and Ti carbonitride each having an average particle diameter of from 5 to 100 nm are dispersed on the surface and in the steels of the raceway track member to make the hardness of the raceway surface to HRC 59 or more.

Abstract: Cleanliness of a metallic material to be tested is provided. The method includes the steps of setting n inspection fields in predetermined portions of the metallic material to be tested, scanning each inspection field by ultrasonic flaw detection method for non-metallic inclusions in the metal thereby to determine the maximum non-metallic inclusion diameter aj (j=1,n), and calculating the estimated maximum non-metallic inclusion diameter amax in the metallic material to be tested from the maximum non-metallic inclusion diameter aj (j=1,n) determined for each inspection field, thereby evaluating the cleanliness of metallic materials quickly with high accuracy and high reliability.

Abstract: At least one of input/output disks, a power roller and a cam disk of a toroidal type continuously variable transmission is formed of a high-cleanness steel in which a size of a maximum inclusion is estimated by the following extremum statistical process. In step S1, a plane including a central line of the high-cleanness steel is cut out in a direction of rolling of the high-cleanness steel. In step S2, a portion d of the cut-out cross-section, which is defined by 40% of a diameter D in the vicinity of the central line, is used as a to-be-tested surface. In step S3, a test reference area S.sub.0 is set at an area not less than 300 mm.sup.2 within the to-be-tested surface, and a root of an area of the maximum inclusion is measured five times or more. In step S4, a maximum inclusion distribution straight line is obtained. In step S5, the root, that is, the size of the area of the maximum inclusion within an estimation area S is estimated.

Abstract: The method for analyzing a metal for oxygen, using inert gas carrying fusion/infrared absorption analysis, having the steps of: placing a metal analyte in a graphite crucible; heat-melting the metal analyte; extracting a gas from the melt bath; and analyzing the gas to determine the total oxygen content of the metal in the form of a plurality of separated waves, wherein the metal analyte is heated at a temperature rise rate of not more than 20.degree. C./sec in a period from a starting point A of a first wave to a peak point B of the first wave, held at a constant temperature in a period from the peak point B of the first wave to an end point C of the first wave, and, after the completion of the appearance of the first wave, is heated to melt the metal analyte for further analysis.

Abstract: The process for producing a constant velocity joint having improved cold workability, rolling fatigue life, and torsional strength comprises the steps of: rolling or forging an alloy at a heating temperature of Ac.sub.3 to 1000.degree. C. with a reduction in area of not less than 30%, said alloy comprising by weight carbon: 0.52 to 0.60%, silicon: 0.03 to 0.15%, manganese: 0.10 to 0.40%, chromium: 0.05 to 0.30%, molybdenum: 0.10 to 0.30%, sulfur: 0.003 to 0.020%, boron: 0.0005 to 0.005%, titanium: 0.02 to 0.05%, nitrogen: not more than 0.01%, aluminum: 0.005 to 0.05%, and manganese+chromium+molybdenum: 0.35 to 0.80% with the balance consisting of iron and unavoidable impurities; spheroidizing the rolled or forged alloy in such a manner that, after heating to Ac.sub.1 to 770.degree. C., slow cooling is performed from 730.degree. C. to 700.degree. C. at a rate of not more than 15.degree. C.