RU2363738C2 - Manufacturing method of detail with key groove - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: invention relates to mechanical engineering. Method includes implementation of key groove in detail and strengthening electrocontact processing of detail. Key groove in detail is implemented of depth more than nominal for value of half of detail's allowance by treated diametre. It is manufactured technological bushing key. It is installed bushing key into key groove of the detail and it is implemented preliminary mechanical operation of detail with technological bushing key by diametre with keeping of allowance for the following treatment. Then it is implemented strengthening electrocontact processing of detail and its connection to technological bushing key and finishing mechanical operation. After what technological bushing key is removed from key groove.

EFFECT: it is achieved details improvement.

2 ex

Description

The invention relates to mechanical engineering and can be used in the manufacture of keyways on the outer and inner surfaces of machine parts.

Known methods for the manufacture of keyways on parts formed by cutting methods, with subsequent methods of thermal or chemical-thermal treatment [Polyak MS Hardening technology. - M .: Mechanical Engineering, L.V.-SKRIPT, 1995].

However, with volumetric methods of thermal or chemical-thermal treatment, the entire surface of the keyway is exposed to heat exposure, including the stress concentration zone at the base, which leads to the appearance or development of microcracks and reduces the quality of parts in operating conditions.

A known method of electrical contact processing [SU 361207 A, C21D 1/06, 12/07/1972] the surface of the hole parts.

However, this method does not improve the quality of the keyway, which under operating conditions leads to wear of its side surfaces and fatigue damage to the shafts.

The objective of the invention is to improve the quality of the keyways in their manufacture with the hardening of the side surfaces in an electric contact way.

The task is achieved by manufacturing the technological key, pre-machining the part and the technological key in diameter while maintaining the allowance for subsequent processing, performing electrical contact hardening of the surface of the part and the technological key, final machining of the connection, removing the technological key from the keyway moreover, the depth of the keyway on the part is greater than the nominal by half the allowance over part details on the processed diameter.

The invention is illustrated by the following examples.

On shafts and bushings made of steel 45 GOST 1050-94, keyways are made by cutting (milling, chiselling or pulling). The shaft-sleeve coupling operates under alternating loads. The requirements for hardness of parts are set within 42 ... 48 HRC, which provides for hardening and subsequent average tempering.

When a keyway is formed on the parts due to technological factors, microcracks can form in the base zone, especially in the radius part. Hardening and subsequent tempering lead to the appearance of thermal microcracks in dangerous sections of the groove, and also contribute to the development of microcracks obtained at the stage of forming keyways. In addition, during bulk heat treatment, oxidation and decarburization of the surface layer constantly occur. In operating conditions, this leads to emergency destruction of the shaft in the area of the keyway. In addition, due to the insufficient strength of the groove, its wear on the lateral surfaces occurs, especially in the upper part at the interface between the keyway and the diameter of the part. The operating conditions of the connection are violated and the machine must be stopped for repair work.

On a low-speed shaft with a diameter of 75.5 mm of the Ts2-300 power reducer, a keyway is formed by milling with a width of 20 mm and a depth of 8.15 mm. A technological key was made with a width of 20 mm and a height of 8.3 mm. The key is installed in the keyway of the shaft with an interference fit. On a turning screw cutter 16K20, the shaft was turned with the technological key installed in the groove to a diameter of 75.2 mm.

To improve the quality of parts with keyways, they were contact-electrically machined to ensure the effect of hardening of the executive surfaces, without affecting the zone of voltage concentrators at the base. Contact processing is performed on the same screw-cutting lathe, without changing the shaft base. From an electric current source of industrial frequency 50 Hz, current is supplied to the tool rollers through current-carrying buses. Having ensured reliable contact in the tool-surface connection, the electric current source is switched on and the tools are moved and the part is rotated. When processing, the zone of electrical contact extends to the lateral surfaces of the keyway and to the adjacent diametrical sections of the shaft (sleeve), without thermal effects on the base zone. As a result of processing, the hardness of the surfaces of the keyway and the surface layer along the shaft diameter increases to 56 ... 60 (steel 45, 40X) with a hardening depth of 3 mm. The structure of the surface layer is fine martensite in the presence of residual austenite. After completing the electrical contact processing of the shaft with a diameter of 75.2 mm, we perform the final machining (turning, grinding) to a nominal shaft diameter of 75k6. The depth of the keyway on the shaft was 8 mm. Having processed the shaft and keyway, the technological key is removed and replaced with a standard one.

Obtaining a hardened surface layer on the external or internal machined surface while maintaining the original structure and properties of the underlying metal layers will improve the quality of manufacturing parts with keyways and extend the life of the machines.

Claims (1)

A method of manufacturing a part with a keyway, including the execution of a keyway in the part and hardening electrical contact processing of the part, characterized in that the keyway in the part is deeper than the nominal by half the allowance of the part along the diameter to be machined, a technological key is made, it is installed in the keyway of the part and carry out preliminary machining of the part with a technological key in diameter while maintaining the allowance for subsequent processing, then reinforcing Electrocontact machining of the workpiece and its junction with the spline processing and final machining after which process the key removed from the keyway.