Abstract: PURPOSE:To manufacture cast steel goods having superior fatigue strength and toughness, by applying composite treatment composed of carburization and austempering treatments to cast steel product, then applying compressive stress to surface part CONSTITUTION:Cast steel goods having compsn contg 02-08% C, 20-45% Si, <08% Mn, <005% P, <005% S, <10% Mo, <20% Ni, <10% Cr is subjected to composite treatment in which it is heated and carburization treated under existence of carburizing material, and austemper treated by lowering temp to 200-450 degC and holding for a fixed time By the treatment, inner part is made to bainite structure while leaving a large quantity of residual austenite structure at surface part Next, compressive stress is applied to surface of cast steel goods by shot peening or roll working, etc, to cause transformation induced by working of residual austenite structure at surface to martensite structure High strength and toughness cast steel goods comparable with forged steel is obtd

Abstract: PURPOSE:To provide high strength and toughness to the stock of spheroidal graphite cast iron in a well-balanced state by austenitizing the stock and austempering it under conditions during multistage isothermal transformation CONSTITUTION:The stock of spheroidal graphite cast iron is austenitized under the conditions of 850-950 degC and >=10min It is then subjected to at least two cycles of isothermal transformation consisting of the 1st isothermal transformation under the conditions of 250-350 degC and several min-1hr and the 2nd isothermal transformation under the conditions of 350-450 degC and several min-1hr

Abstract: Taking the fracture initiation point of a nodular graphite cast iron into consideration, a manufacturing method of bainitic nodular graphite cast iron whose mechanical property is superior by far to the same cast iron obtained by the prior art is provided. The process comprises the steps of segregating elements of a material which are effective in strengthening residual austenite, and applying incomplete oil quenching in short time to the material, then applying incomplete austempering to the material.

Abstract: PURPOSE:To manufacture a coil spring in which the section of an element wire has an arbitrary form by carrying out austempering treatment consisting of subjecting a coil spring made of spheroidal graphite cast iron to heating and holding and then quenching and holding under specific conditions so as to form the matrix into a mixed structure of bainite and austenite. CONSTITUTION:The coil spring which is a casting and made of spheroidal graphite cast iron is subjected to austempering treatment consisting of heating and holding at 820-900 deg.C for 0.5-3hr and the quenching down to 200-400 deg.C and holding for >=0.5hr to form the matrix into the mixed structure of bainite and austenite. In this way, the coil spring excellent in fatigue strength, wear resistance and corrosion resistance, having superior self-lubricity and conformability and increased in service life can be manufactured with high productivity.

Abstract: PURPOSE:To manufacture a spheroidal graphite cast iron with bainite matrix having uniform mechanical properties at a low cost by subjecting a spheroidal graphite cast iron material successively to heating and holding, to rapid cooling and to heating and holding under specific conditions. CONSTITUTION:The spheroidal graphite cast iron material is heated to 820-900 deg.C and held for 0.5-2hr. Subsequently, the above material is subjected to rapid cooling so that pearlite nose may be avoided and that the material may be kept at a temp. higher than the Ms point by means of spraying of oil, fluidized bed or water held at <=250 deg.C, without use of salt as cooling medium. After cooling, the material is thrown into a fluidized layer kept at 250-400 deg.C and is held for 0.5-4hr. In this way, uniform mechanical properties can be obtained when castings dissimilar in thickness or complicated in shape are subjected to austempering treatment and moreover, environmental pollution can be prevented.

Abstract: PURPOSE: To mold an austempering treatment spheroidal graphite cast iron having drastically improved gear precision by executing gear machining to a gear material formed of the spheroidal graphite cast iron in which the matrix structure consists of bainite and residual austenite and having the specific hardness and number of graphite grains CONSTITUTION: The gear material formed of the spheroidal graphite cast iron in which the matrix structure consists of bainite and residual austenite, having ≥350 HB hardness and having ≥300 pieces/mm 2 graphite grains of ≥8μm grain diameter observable by a microscope is subjected to the gear machining to form the austempering treatment graphite cast iron gear The method by strong inoculation, the method by the use of a chiller, etc, are furthermore utilized to increase the number of the graphite grains In this way, the mechanical properties and machinability suitable for the gear material is provided to the same before executing the gear cutting, by which the drastic improvement of the precision of said material is served COPYRIGHT: (C)1988,JPO&Japio

Abstract: PURPOSE:To ensure an extremely easy balancing process for a crankshaft and the like by punching preliminarily small bores on the balancing processing part thereof before the application of austempering treatment and drilling the small bores after the austempering treatment. CONSTITUTION:Before austempering, small bores 4, 4 and so forth are punched on each balance weight part 3. Thereafter, austempering applies and a crankshaft A is heated and retained at a temperature of approximately 900 deg.C for one hour or so, then quenched to approximately 300 deg.C to 400 deg.C in a salt bath and retained for approximately one to two hours. After the austempering treatment applies, the balancing process of the cooled crankshaft A is carried out with the small bores 4, 4 and so forth punched on the balance weight 3, using a drill 5 of diameter larger than the bore 4. As a result, the chisel part 5a of the drill 5 is almost free from cutting resistance, thereby making a drill wear small and ensuring an extremely easy balancing process.

Abstract: PURPOSE:To obtain a high strength and high toughness ductile cast iron product having a high quality zinc layer formed by hot dip galvanizing by properly regulating the chemical composition of ductile cast iron, conditions during austempering, the temp of a hot dip galvanizing bath and the immersion time CONSTITUTION:Cast iron contg, by weight, 3-4% C, 2-3% Si and 01-04% Mn is subjected to isothermal heat treatment by holding at 820-880 degC for 05-5hr, immediate rapid cooling to 350-400 degC and holding at 350-400 degC for >=05hr The cast iron is properly pretreated, immersed in molten zinc at 455-475 degC for 60-120sec, taken out of the bath and water-cooled