Koyo Thermo Systems Co., Ltd.

Mitsui High-tec Incorporated

Showa Tachisato

Yusuke Hasuo

Ryosuke Yamamoto

Takeaki Kozono

Shin Matsuda

Tomoyuki Ishibashi

Shohei Tsuji

A heat-treatment apparatus includes a casing, a loader which loads a workpiece to an inner part of the casing in order to apply a heat-treatment to the workpiece, and a canopy surface provided in the casing to cover the workpiece. The canopy surface includes a slope way with a sectional configuration where the canopy surface is cut on a plane vertical to a conveying direction of the workpiece inside the casing. The slope way includes a highest point and a downward inclined surface extending from the highest point to an outside of a zone between a perpendicular line extending from a left end of the workpiece and a perpendicular line extending from a right end of the workpiece.

Heat-treatment apparatus and heat-treatment method

In a first step of a method of gas carburizing, a steel treatment object is heated in a carburizing atmosphere comprising a carburizing gas until the surface carbon concentration of the treatment object reaches the final target value that is not higher than the solid solubility limit at a carburizing temperature that is not higher than the peritectic point, at which steel transforms from &#x3b4; iron and liquid phase to &#x3b3; iron, and is not less than the eutectic point, at which steel transforms from liquid phase to &#x3b3; iron and cementite. In a second step the gas carburizing is advanced after the first step so that the carburizing depth of the treatment object increases while the surface carbon concentration of the treatment object is kept at the final target value by reducing the carbon potential of the carburizing gas with the lapse of time.

Method of gas carburizing

A carburizing apparatus that can reduce cost and shorten the carburizing time is provided. A single coil for raising temperature, a plurality of coils for soaking, and a conveying mechanism that conveys a treatment object from a position of induction heating with the coil for raising temperature to positions of induction heating with the coils for soaking are provided inside a container for carburization treatment. The rated capacity of a power source for raising temperature that is connected to the coil for raising temperature is higher than the rated capacity of a power source for soaking connected to the coil for soaking.

Carburizing apparatus and carburizing method

A method of gas carburizing is carried out at a carburizing temperature which is not higher than a peritectic point temperature at which &#x3b4; iron and liquid phase are transformed into &#x3b3; iron and not less than a eutectic point temperature at which liquid phase is transformed into &#x3b3; iron and cementite. The method comprises the step of predetermining the limiting carburizing conditions at which the surface layer of a sample of a steel treatment object present in a carburizing atmosphere is austenitized without melting and the step of gas carburizing the treatment object under carburizing conditions which are set so as not to contradict the limiting carburizing conditions, at a carburizing temperature which is not higher than the peritectic point temperature and not less than the eutectic point temperature. The limiting carburizing conditions comprise an upper limit value of a partial pressure of carburizing gas at which the surface layer of the sample is austenitized without melting.

In a first process of a method of gas carburizing, a steel treatment object in a carburizing atmosphere containing carburizing gas is heated to an initial set temperature which is not higher than a peritectic point at which &#x3b4; iron and a liquid phase transform into &#x3b3; iron and not less than a eutectic point at which the liquid phase transforms into &#x3b3; iron and cementite, such that the surface carbon concentration thereof does not exceed a solid solubility limit. In a second process following the first process, the carburizing temperature is gradually decreased from the initial set temperature such that the surface carbon concentration of the treatment object increases without exceeding the solid solubility limit, and such that the carburized depth of the treatment object increases.

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Yamatokoriyama, Japan

Showa Tachisato