Abstract: Etude du mecanisme de rupture sur differentes microstructures de fonte bainitique. Correlation entre la tenacite et la surface de rupture

Abstract: PURPOSE:To improve the fatigue strength of an alloy steel contg. a prescribed percentage of C by austempering and shot-peening the steel under prescribed conditions so as to make the mechanically processed layer thick as well as to shorten the time required to heat treat the material. CONSTITUTION:An alloy steel contg. 0.5-1% C is austempered to increase the hardness HRC to 50-60. The steel is subjected to warm shot peening at the austempering temp., and it is cooled once to room temp. The steel is then subjected to secondary shot peening with shot having a smaller diameter than shot used in the primary shot peening.

Abstract: PURPOSE:To obtain high strength spheroidal graphite cast iron with superior machinability by austempering spheroidal graphite cast iron contg prescribed percentages of various elements under prescribed conditions so as to regulte the structure and the Vickers hardness CONSTITUTION:The composition of spheroidal graphite cast iron is composed of, by weight, 3-45% C, 05-3% Si, 02-12% Mn, 002-01% Mg, one or more among <05% Mo, <1% Ni and <15% Cu, and the balance Fe with impurities The cast iron is austempered under conditions during austenitizing by heating at 860-930 degC for 05-1hr and under conditions during isothermal heat treatment by holdin at 370-430 degC for 1-4hr to form a structure consisting of <=70vol% retained austenite, <=3vol% free cementite and the balance bainite The Vickers hardness is regulated to 250-310

Abstract: Amelioration des proprietes de tenacite, resistance a l'usure et stabilite dimensionnelle apportees aux fontes a graphite spheroidal par la trempe etagee bainitique. Competition avec l'acier

Abstract: PURPOSE:To obtain a sufficient depth of hardening and high fatigue strength by specifying the composition of a steel and applying austempering as pretreatment and high frequency treatment as surface hardening treatment. CONSTITUTION:The composition of a steel is composed of, by weight, 0.45-0.65% C, 0.9-1.2% Mn, 0.7-1.2% Ni, 0.5-1.2% Cr, 0.19-0.12% Mo, Si, P, S and Cu by amounts as ordinary impurities and the balance Fe. The steel is heated and held at a conventional hardening temp. such as 800-850 deg.C, and it is isothermally hardened by quenching from the hardening temp. in an isothermal bath at 200-400 deg.C, holding for a fixed time and air cooling. The steel is then subjected to induction hardening.

Abstract: PURPOSE:To obtain a spring holder having a prolonged endurance life by subjecting a spheroidal graphite cast iron blank to rough working, heating and holding at a specified temp., austempering and working to regular dimensions. CONSTITUTION:A spheroidal graphite cast iron blank is rough-worked as required, heated, and held at 830-900 deg.C for 0.5-3hr. It is austempered by quenching in a salt or a fluidized bed at 200-400 deg.C and holding for >=0.5hr to convert the matrix structure into a bainite-austenite mixed structure. The blank is then worked to regular dimensions. By this method a spring holder for a truck suspension, a railway vehicle or the like having superior mechanical properties and fatigue strength can be manufactured at a low cost in a high yield of materials.

Abstract: Pulsating tension fatigue tests (R=0.1) and statical tension tests at room temperature to 500°C were performed on the as-cast and heat-treated materials of spheroidal graphite cast iron. The macro and microscopic observations of the fatigue-fracture surface of the specimens were carried out by SEM to interpret fatigue strength data.The results obtained are summarized as follows:(1) The tensile strength at elevated-temperatures decreased with the elevation of testing temperature. However, the effect of normalizing and austempering heat-treatment was remarkably noticed.(2) The fatigue strength decreased with the elevation of testing temperature, which is the same as the tensile strength, but the effect of heat-treatment was noticed very slightly. The fatigue limit at 500°C for the bainitized material was σu=92MPa and for the annealed material σu=77MPa.(3) Fatigue cracks appeared from internal defects such as small pinholes. Therefore, it is considered that the heat-treatment does not affect the fatigue strength so much.

Abstract: PURPOSE:To obtain a connecting rod having a prolonged endurance life by subjecting a spheroidal graphite cast iron blank to rough working, heating and holding at a specified temp., austempering and working to regular dimensions. CONSTITUTION:A spheroidal graphite cast iron blank is rough-worked as required, heated, and held at 830-900 deg.C for 0.5-3hr. It is austempered by quenching in a salt bath or a fluidized bed at 200-400 deg.C and holding for >=0.5hr to convert the matrix structure into a bainite-austenite mixed structure. The blank is then worked to regular dimensions. By this method a connecting rod for an internal-combustion engine or the like having superior mechanical properties and fatigue strength can be manufactured at a low cost in a high yield of materials.

Abstract: of the Disclosure A method is disclosed for forming a surface hardenable cast iron article by development of metastable retained austenite in the cell boundary of a ductile or semiductile cast iron. The method comprises (a) controlling the solidification of a cast iron melt to extend the eutectic arrest time to 4-12 minutes, the melt having by weight percent a carbon equivalent (carbon plus one-third silicon) equal to 4.3-5.0, manganese .55-1.2, nickel .5-3 0, and the remainder essentially iron, the melt having been treated to form cell boundaries in the solidified iron with a high proportion of the manganese being segregated in the cell boundaries; (b) subjecting the solidified cast iron to an austempering heat treatment to permit the segregated manganese in the cell boundaries to form metastable retained austenite; and (c) terminating the heat treatment prior to the conversion of the metastable austenite to a stable microstructure. To obtain the benefits of wear resistance, the method further comprises using the heat treated cast iron by stressing a surface region thereof and transforming the microstructure of such surface region to martensite.

Abstract: PURPOSE:To improve remarkably the surface pressure resistance of a steel having a specified composition by selecting conditions during austempering for stabilizing retained austenite in the surface layer of the steel. CONSTITUTION:A steel having a composition consisting of, by weight, 0.5-0.7% C, <1.5% Si, 0.4-1.3% Mn, <4% Ni, <1.5% Cr, <0.7% Mo and the balance Fe with inevitable impurities is carbonitrided at 800-900 deg.C and austempered by putting in a hot bath at 230-300 deg.C. The steel is held in the bath for a time long enough to finish transformation into lower bainite in the base part and to produce 5-35vol% lower bainite in the surface layer. The steel is then cooled. The surface layer of the steel has a mixed structure consisting of retained austenite, 5-35vol% lower bainite and martensite, and the base part has a lower bainite structure.

Abstract: An observation under TEM was made of the (M-A) structure and \"bamboo shaped\" bainite in the isothermally quenched ultra high strength steels containing Si after the isothermal transformation The retained austenite in the isothermal structure of bainite region at temperature≥300℃ is often found in the M-A and \"bamboo shaped\" bainite In the bainite formed isothermally at 180, 300, 320 and 420℃, the e-carbide is observed. The type of carbide in decomposition products is related to the distribution and morphology of retained austenite. The e-carbide may precipitate along the austenite side of martensite/austenite boundary.

Abstract: PURPOSE: To facilitate the machining of the title parts and to reduce the thermal deformation and expansion after austempering by relieving the residual stress after machining when the raw material is pearlitized, machined, and then austempered. CONSTITUTION: The raw material is pearlitized, and hence the expansion when austempered can be controlled. The residual stress of the raw material is relieved in the temp. range where the pearlite is not decomposed. The stress relieving is carried out by heating the material, for example, at about 400W650°C for about 0.5W8.0hr, and then cooling the material with air or annealing the material. Namely, the raw material with the carbon content in the material increased by the pearlitization is heat-treated in the temp. range where the carbon in the material is not graphitized, and the stress generated in the pearlitization is relieved. The raw material is then austempered to improve the mechanical properties. COPYRIGHT: (C)1987,JPO&Japio

Abstract: PURPOSE:To obtain a lightweight wheel axle for an automobile or the like with high productivity by subjecting a spheroidal graphite cast iron blank to rough working, heating and holding at a specified temp., austempering and working to regular dimensions. CONSTITUTION:A spheroidal graphite cast iron blank is rough-worked as required, heated, and held at 830-900 deg.C for 0.5-3hr. It is austempered by quenching in a salt bath or a fluidized bed at 200-400 deg.C and holding for >=0.5hr to convert the matrix structure into a bainite-austenite mixed structure. The blank is then worked to regular dimensions. By this method a wheel axle having superior mechanical properties and fatigue strength can be manufactured at a low cost in a high yield of materials.

Abstract: PURPOSE: To increase the service life of a metal die and to reduce the production cost by forming the ground organization in the mixed organization of a bainite and austenite with the execution of the heating and rapid cooling at specific temp. and for specific time on the sheet metal forming die made of a spherical graphite cast iron. CONSTITUTION: The die 1 made of a spherical graphite cast iron (a circular die) is held by heating for 0.5W3hr at 830W900°C after its rough working. An austempering is then executed with the rapid cooling by dipping in the salt bath, etc. of 200W400°C quickly and holding for ≥0.5hr. It is worked in the regular size by cooling upto room temp. after making it in the mixed organization of austenite and bainite. It is more effective for a scuffing causing to perform a phosphate coating treatment on the surface of the is die. In this way the durable life as to the wear resistance and scuffing resistance improvements of the die is increased and the production cost can be reduced. COPYRIGHT: (C)1987,JPO&Japio

Abstract: PURPOSE:To prolong the endurance life of a detachable chain made of spheroidal graphite cast iron by austempering the chain under specified temp. conditions so as to increase the rupture load. CONSTITUTION:A detachable chain made of spheroidal graphite cast iron is heated to 830-900 deg.C, held for 0.5-3hr, rapidly cooled to 200-400 deg.C, and held for >=0.5hr. By this austempering, the matrix structure is transformed into a bainite-austenite mixed structure. By this method, a detachable chain having such characteristics as high average rupture strength and satisfactory wear resistance is obtd.

Abstract: PURPOSE:To prolong the endurance life of a barn cleaner chain having a monolithic structure and to reduce the cost of manufacture by using spheroidal graphite cast iron and forming a bainite-austenite mixed structure as the matrix structure. CONSTITUTION:A barn cleaner chain made of spheroidal graphite cast iron is manufactured. The chain is austempered by heating, holding at 830-900 deg.C for 0.5-3hr, rapid cooling to 200-400 deg.C and holding for >=0.5hr. A bainite- austenite mixed structure is formed as the matrix structure by the austempering.

Abstract: PURPOSE:To make strength and tenacity in a car ball joint improvable, by processing a material of spheroidal graphite cast iron for the ball joint by means of austempering, and also processing a ground composition to a mixed composition making it volumetrical percentage of residual austenite and remnant bainite. CONSTITUTION:As a material of a ball joint installed in front wheels and the like and a cross parts between a lower arm and a suspension of an automobile, at the time of using spheroidal graphite cast iron into bainitization, in regard to austenitizing conditions, temperature is set down to a range of 880-920 deg.C and time to a range of 15-120min, by way of example, and as regard to constant temperature variation conditions, it is within the temperature range of 350-390 deg.C, and the time required is set to a range of 50-120min. With this constitution, a ground composition is made into more than 60% of residual austenite and remnant bainite organization at volumetrical percentage, and in regard to static strength such as fatigue strength, tensile strength, etc., it can be made equal to average steel,while an impact value is 1kgm/cm at actual low temperature as -30 deg.C, and more than 2kgm/cm at normal temperature as room temperature. As above-mentioned, it has high strength and high tenacity and, what is more, specific gravity is reduced whereby the promotion of lightweightiness is thus promoted.

Abstract: A method is disclosed which comprises: (a) forming a ferrous alloy melt consisting essentially of, by weight, 3-4% carbon, 2.0-3.0% silicon, .1-9% manganese, up to .02% phosphorus, up to .002% sulphur, up to 1% contaminants or impurities, 0-.4% molybdenum, 0-3.0% nickel or copper, and the remainder essentially iron, the melt being subjected to a graphite modifying agent in an amount and for a period of time effective to form either ductile or semiductile iron upon solidification; (b) heat treating the solidification of said melt by austempering to form a matrix consisting substantially of high carbon austenite and ferrite and a cell boundary having unreacted low carbon austenite; (c) heating said austempered iron to a pearlite forming temperature (1200-1300°F) and holding (2-5 minutes) at said temperature to permit the unreacted low carbon austenite to form pearlite; and (d) cooling said heat treated iron to room temperature.