Abstract: This paper represents a summary of experimental results dealing with the time dependence of microstructure and mechanical properties during austempering, and with the austempering temperature dependence of microstructure and mechanical properties.

Abstract: An austempered ductile iron alloy with a mixed austenitic-bainitic structure is made by a method which enables the iron to withstand high cyclical stresses while having a high resistance to abrasion. Articles such as automobile roller-follower camshafts that are made from the iron alloy may have portions thereof selectively austempered to reduce the overall cost and time required to manufacture the article.

Abstract: Spheroidal graphite cast iron whose matrix is composed of a mixture of bainite and retained austenite, containing 250 to 800 graphite grains/mm 2 , and its production method comprising the steps of forming the casting, annealing the casting so as to change the matrix to ferrite, machining the casting and subjecting the casting to austempering so as to subject the casting to austenitizing and isothermal transformation.

Abstract: A low carbon Cr-Ni steel has been used to investigate the formation of upper bainite. Experimental results indicate that the start temperatures of the three morphologies of upper bainite in this steel,i.e., carbide-free bainite, bainite with carbide between and within ferrite laths, are about 600°, 500δ, and 425 °C, respectively; the habit plane of bainitic ferrite in this steel is close to (1 7 11)α, which is 13.3 deg away from (0 ll)α; and the orientation relationship between cementite and ferrite is consistent with Bagaryatskii’s. By means of the superelement approach, a thermodynamic treatment which applies to Fe-C alloys is extended into that suitable for low alloy steels, and calculation shows that the driving force for bainite formation at BS temperatures is insufficient to compensate for shear strain energy.

Abstract: Austempered ductile iron (ADI) exhibits a favourable combination of strength and toughness, and has been used as a substitute for quench-tempered or carburise-quenched steel. A characteristic featu...

Abstract: PURPOSE: To manufacture the title cast iron member in which matrix structure is regulated to the mixed one of bainite and residual austenite by subjecting the manufactures made of low alloy ductile cast iron having specific compsn. to austempering heat treatment. CONSTITUTION: Low alloy ductile cast iron contg., by weight, 3.0 to 3.8% C, 2.4 to 3.0% Si, 0.2 to 0.4% Mn, <0.04% P, 0.2 to 0.4% Ni, 0.4 to 0.6% Cu, 0.05 to 0.10% Nb and 0.03 to 0.06% Mg is subjected to the following austempering heat treatment. namely, a cast member by ductile cast iron is heated to the austenitizing temp. of 880 to 950°C and is held for about 1hr to convert the structure into austenite. The member is then poured into a salt bath of 225 to 275°C and is rapidly cooled to convert the structure into the mixed one of bainite and residual austenite, where NbC is deposited to manufacture the member made of ductile cast iron having excellent strength and wear resistance. COPYRIGHT: (C)1990,JPO&Japio

Abstract: PURPOSE:To produce machine parts provided with high strength, high toughness and wear resistance by subjecting the parts consisting of a steel material contg. specific ratios of C, Si, Mn, Cu and Mo to an austempering treatment. CONSTITUTION:The parts are produced by the steel material contg., by weight, 0.40-0.80% C, 2.00-3.50% Si, 0.20-1.00% Mn, 0.50-2.00% Cu, 0.20-0.40% Mo and the balance consisting of Fe with ordinary inevitable impurities. Said parts material is quenched to about 200-400 deg.C over the Ms point from an austenite field over the A, transformation point by using a salt bath, mist or the similar cooling medium and is retained at the a temp. for the prescribed hr. By this method, various machine parts having about 150-190kgf/mm , about 10-30% elongation and about 3-5kgf/mm impact toughness value are obtd. at a low cost.

Abstract: PURPOSE:To provide magnetic characteristics, high strength, high ductility and toughness with the titled material by subjecting the alloy contg. specific ratios of C, Si and the balance consisting substantially of Fe to an austempering treatment. CONSTITUTION:The alloy contg., by weight, 0.30-0.80% C, 1.70-3.70% Si and the balance Fe with inevitable impurities is subjected to the austempering treatment. The working such as rolling and forging is preferably executed as well to the alloy at the temp. lower than the A3 transformation point during the austempering treatment or after the austempering treatment. One or more kinds among 0.15-1.10% Mn, 0.20-2.30% Cu, 0.15-1.10% Mo and 0.30-5.50% Ni are furthermore incorporated into the above-mentioned compsn. at need. The semi-hard magnetic material unites the magnetic characteristics, tensile strength and impact toughness and these characteristics can be furthermore changed at need, by the above-mentioned constitution.

Abstract: PURPOSE:To improve the mechanical properties and to extend the service life of a die by austempering the die for casting molding made of spheroidal graphite cast iron at the specific condition to make the matrix the mixing structure of bainite and austenite CONSTITUTION:After finishing-working the die for casting molding having chemical composition of spheroidal graphite cast iron, it is held as heating at 830-950 degC for 05-3hr to austenitize After that, it is dipped into a salt bath or fluid bath at 200-430 degC and rapidly cooled and after transforming to bainite by holding for >=05hr, and cooled to the room temp By this austemper treatment, the matrix structure forms a mixed structure of bainite and austenite This mold has excellent mechanical properties and wear resistance and corrosion resistance Therefore, increase of the service life and lightening of the die weight are contrived

Abstract: PURPOSE:To improve the machinability of the titled casting after an austempering treatment by regulating the matrix of the casting to the mingled structure of bainite and residual austenite and increasing the number of graphite grains CONSTITUTION:The titled casting is subjected to the austempering treatment and the matrix is regulated to the mingled structure of the bainite and residual austenite At the same time, the graphite having 250-800pieces/mm graphite grains is incorporated into the casting In this conditions, the machinability of the casting after the austempering treatment is improved The hard-enability and mechanical characteristics are furthermore improved at the time of incorporating about 03-10wt% Mn into the titled casting

Abstract: PURPOSE:To obtain a wheel for industrial machinery reduced in manufacturing costs and increased in service life, by subjecting spheroidal graphite cast iron, in its state of stock or after rough processing, to austempering treatment under specific conditions so as to form a matrix into mixed structure and then by working the above into accurate dimensions. CONSTITUTION:The spheroidal graphite cast iron is used in its state of stock or is subjected to rough processing into the shape of an industrial wheel, which is heated and held to and at 830-900 deg.C for 0.5-3hr, cooled rapidly down to 200-400 deg.C, and held for >=0.5hr. Owing to the above austempering treatment, the matrix structure is formed into a mixed structure of bainite and austenite. After that, the above material is worked into accurate dimensions so as to be formed into the desired wheel shape. In this way, manufacturing process can be shortened and the wheel for industrial machinery having superior wear resistance can be manufactured while obviating the necessity of induction hardening.

Abstract: An improvement of the austempering process, which in the prior art has included a transfer of castings from the austenitizing furnace to a bath containing a liquid medium. Castings in the improved process are instead cooled in situ by the application of fluids such as air and water jets, and the same furnace is used for both austenitizing and austempering.

Abstract: PURPOSE:To produce the titled part having high strength and high ductility by finding CCT curve from alloy composition of steel and spheroidal graphite cast iron parts, deciding the optimum isothermal transformation temp. by heat analysis and executing feed-back to the furnace temp. control. CONSTITUTION:The shape of the steel and the spheroidal graphite cast iron parts as an objective parts for the austenite heat treatment is inputted to CPU 2 from a drawing reader 1 and mesh division for mathematical process (difference calculus) is executed. Further, the material quality (alloy composition) is indicated, and data base of the CCT curve stored in the CPU 2 is called and the aimed hardness and the position (depth from surface of the parts) are inputted. Next, the CPU 2 executes unsteady heat conductive analysis and displays cooling curve diagram, temp. distribution diagram and structure prediction diagram on a displaying device 2 and also indicates the setting value of the furnace temp. By inputting these data, the temp. control in a heating chamber 4 of an isothermal furnace 7 is executed and the steel and the spheroidal graphite cast iron having the aimed bainite matrix and high strength and high ductility is easily produced.

Abstract: PURPOSE: To prevent the structure decomposition of a ferrous member by the heat at cast-in time and to improve the combining power of the both by forming a porous heat insulating material layer between the both in case of cast-in the ferrous member subjected to an austempering treatment for a base metal. CONSTITUTION: The bearing metal (ferrous member) 5, 6 of the crank shaft of a cylinder block (casting member) 1, for instance, is subjected to cast-in in the block base metal 7, 8 of an Al alloy. The bearing metals 5, 6 are subjected to austempering treatment to set to the coefft. of thermal expansion with the base metal 7, 8 and to increase the fatigue strength as well. In the metal 6, for instance, the surface of its internal chilled part is subjected to shot blasting after its cleaning and degreasing and the mixed powder of Ni, Cr and Al is plasma thermal sprayed on the surface thereof as an undercoating. A heat insulating layer 14 is then formed by thermal-spraying the mixed powder of ZrO 2 and Y 2 O 3 on this surface similarly, this metal 6 is held on a die 12, an Al molten metal is poured into a cavity 13 and the base metal 8 subjecting the metal 6 to cast in is formed via the heat insulating layer 14. COPYRIGHT: (C)1989,JPO&Japio

Abstract: PURPOSE:To accurately inspect the quality of a structure, by a method wherein the thermal expansion quantity of cast iron after austempering is measured to be compared with a set value and the mixing ratio of the bainite and residual austenite of the structure of the cast iron is detected. CONSTITUTION:A specimen 2 is set on the plate 3 of an inspection apparatus and, thereafter, the length of the specimen 2 is measured at room temp. and this measured data is used in later operation. A heating unit is turned on and controlled to maintain a predetermined temperature by a temperature control device 8. The thermal expansion of the specimen is measured after it is kept at the temperature for a predetermined time. This process is repeated to measure the expansion quantities of the specimen 2 at various temperatures. Coefficient of linear expansion is calculated from the length of the specimen 2 measured at room temp., the difference between heating temp. and room temp. and the expansion quantity at the heating temp. At the same time, the composition of cast iron and the residual austenite quantity for the coefficient of linear expansion under an austempering treatment condition are read from a memory part. Subsequently, both read values are compared with reference values to judge the quality of the structure of the cast iron and, as a result, the composition of the cast iron and the austempering treatment condition are printed.

Abstract: PURPOSE:To manufacture bainitic spheroidal graphite cast iron maintaining characteristics peculiar to cast iron and having toughness by adding a component for reducing the austenitizing temp. of iron to spheroidal graphite cast iron during melting, micro-segregating the component after solidification and carrying out isothermal transformation. CONSTITUTION:A component for reducing the austenitizing temp. of iron, e.g., Ni or Cu is added to spheroidal graphite cast iron during melting. After the cast iron is melted and solidified, the component such as Ni or Cu is micro- segregated on the interface between the graphite and matrix and in the eutectic cells. The resulting structure in which the micro-segregated component remains is subjected to isothermal transformation from a temp. at which the micro- segregated component is not perfectly diffused or homogenized. By the austempering, a bainitic structure is deposited to toughen the spheroidal graphite cast iron.