JPS6270515A - Manufacture of wear resistant spheroidal graphite cast iron having high toughness - Google Patents

Abstract

PURPOSE:To obtain wear resistant spheroidal graphite cast iron having high toughness by subjecting the surface layer part of spheroidal graphite cast iron to heating and air cooling with a moving heat source and further subjecting it to heating and rapid cooling to form a bainite-martensite mixed layer around spheroidal graphite. CONSTITUTION:For example, in case of a spheroidal graphite cast iron gear 1, the surface layer parts of the gear 1 are heated are air-cooled by moving heat sources 2 such as high frequency heaters from one end A of the gear 1 to the other end B to form normalized layers 3. The heat sources 2 are then returned to the end A and moved again from the end A to the end B. At this time, cooling water or cooled air is spouted from coolers 4 to cool rapidly the heated parts and to form hardened layers 5 on the toothes surfaces of the gear. The layers 5 are bainite-martensite mixed layers.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing high-toughness, wear-resistant spheroidal graphite cast iron.

[Conventional technology]

Conventionally, wear-resistant spheroidal graphite cast iron has been manufactured by the following method.

(1) A method in which pearlite is precipitated in the base structure by adding pearlite-stabilizing alloying elements such as Cl, Mn, and Sn.

(2) Using a heat treatment furnace, perform overall heating and rapid cooling, (1
), as well as a method of turning it into pearlite.

(3) Using a mold, pour the molten spheroidal graphite cast iron into the mold,
A method of chilling the surface layer by rapidly solidifying it.

(4) Adding austenite-stabilizing elements such as Ni and No, reheating to the austenitizing temperature, rapidly cooling to the bainitizing temperature range, and holding the baitonite structure to a so-called so-called so-called structure containing mainly some altenside and residual austenite How to obtain an austempered tissue.

(5) Rapidly heat and cool the surface layer from a moving heat source,
A method of forming a surface hardening layer that is a mixed layer of batonite and martensite.

[Problems to be Solved by the Invention] However, in the methods (1) to (4), the base structure is strengthened as a whole including the surface layer and the inside, so although the wear resistance is improved, the toughness is A decrease in Also,
Regarding (5), in order to obtain an appropriate quenched hardness, it is necessary to previously transform the base structure into pearlite by adding an alloy precursor or by heat treatment. It had the disadvantage of cracking and deformation due to metamorphosis.

The object of the present invention is to improve wear resistance while maintaining good toughness, and to prevent hair cracks and deformation due to uniform transformation of the surface layer.

In addition, spheroidal graphite cast iron that has undergone uniform altenside or bainite transformation on its surface undergoes microscopic deformation due to the transformation accompanied by volumetric expansion. The surrounding area also undergoes deformation simultaneously and uniformly, resulting in a low-toughness structure, which cannot serve as a buffer for this deformation.

The present invention relates to a manufacturing method in which the transformation region by surface hardening is limited to only the periphery of spherical graphite, and a ferrite structure with excellent toughness remains in the periphery. While conventional methods for manufacturing wear-resistant spheroidal graphite cast iron uniformly transform the surface or interior of the member into pearlite, baitonite, or altenside, the method of the present invention can produce only the surface layer or microscopically. is characterized by the formation of a batonite or martensite mixed layer only around the spheroidal graphite.

[Means and effects for solving the problems] In the present invention, the surface layer of spheroidal graphite cast iron is heated and air-cooled and heated and rapidly cooled using a moving heat source to form a mixture of pei-1-night and martensite around the spheroidal graphite. The formation of layers was avoided to obtain high toughness and wear-resistant spheroidal graphite cast iron.

[Example] Next, the method of the present invention will be explained using a specific example in which it is applied to a gear material made of spheroidal graphite cast iron shown in FIG.

In Figures 1 to 3, 1 is a spheroidal graphite cast iron gear whose surface layer is to be hardened, 2 is a heat source placed along the outer periphery of the gear to sandwich it, and 3 is a gear that is heated by the heat source 2. 4 is a cooling device, and 5 is a part that is air-cooled from the austenite temperature formed on the surface layer of the It is an entry layer. The cooling device 4 is directed toward a method of moving the heat source 2 during heat treatment,
It was placed behind the heat source 2. When the heat source 2 and the cooling device 4 are provided in a stacked manner, a heat insulating material (not shown) is placed between the heat source 2 and the cooling device 4.

Note that FIG. 2 is a sectional view of the device shown in FIG. 1.

By moving the heat source 2 from the A end face to the B end face of the spheroidal graphite cast iron gear 1 whose surface layer is to be hardened, the heat source 2
The reference layer 3 formed on the gear tooth surface immediately below moves sequentially from the gear A end face toward the gear B end face. The heat source 2 used here is not particularly limited, but one with high energy density is desirable, and welding devices such as TIG and plasma, heating devices such as flame, medium, and high frequency can be used. By the way, at this time, the cooling device 4 is not activated.

After the heat source 2 reaches the B end surface, the heat source 2 is moved from the A end surface toward the B end surface again. At this time, cooling water or cooling air is jetted out from the cooling device 4. The heated area immediately after passing through the heat source 20 is rapidly cooled by the action of the cooling device 4, and a hardened layer 5 is formed on the gear tooth surface.

The thickness of the hardened layer on the tooth surface of the spheroidal graphite cast iron carrier 1 and the hardened layer around the spheroidal graphite is based on the first standard, the feed rate of the heat source 2 during the second hardening, and the cooling conditions of the cooling device 4. It can be easily made uniform by keeping it constant.

The standards and quenching conditions are as follows.

(1) Temperature of standard heat-treated material 850-900°C Moving speed of heat source 2 2,5-3 m/see Distance between heat source 2 and heat-treated material 2-5 mm (2) Temperature of quenched heat-treated material 850-900 'C Moving speed of heat source 2: 2,5-3mm/See Distance between heat source 2 and the material to be heat treated: 2-5mm Type of coolant: Water (addition of 3% anti-seize agent) Temperature of coolant: Room temperature. , using high-frequency induction heating. When the present invention was carried out using an anchor drum carrier of FCD50, the quenching depth was 3 to 4M, and the hardness after quenching was 1Q of Hs60.

[Effects] Thus, the following effects can be obtained by the method of the present invention.

(1) The wear resistance of ferritic spheroidal graphite cast iron having high toughness can be easily improved.

(2) It can be easily applied to products with large wall thickness.

(3) It is easy to control the hardened layer.

(4) Since it is a mobile heat source, it saves energy.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of an apparatus for carrying out the method of the present invention, and FIGS. 2 and 3 each do not show a sectional view of the apparatus shown in FIG. Illustrated. DESCRIPTION OF SYMBOLS 1... Spheroidal graphite cast iron gear, 2... Heat source, 3... Standard part, 4... Cooling device, 5... Quenched layer patent applicant Ube Industries Co., Ltd. 3 people

Claims (1)

[Claims] A moving heat source heats and air-cools the surface layer of spheroidal graphite cast iron.
A method for producing high-toughness, wear-resistant spheroidal graphite cast iron, which is then heated and rapidly cooled to form a mixed layer of bainite and martensite around the spheroidal graphite.