RU2265065C2 - Tool for hardening thread - Google Patents

Abstract

FIELD: modifying physical structure of ferrous metals.

SUBSTANCE: tool is shaped to be mating the contour to be treated. The contact surface of the tool is provided with grooves for supplying coolant to the contact site. The grooves are made so that they are not located in the middle diameter of the thread and boundary of the intersection of sides with the outer diameter of the thread.

EFFECT: prolonged service life.

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Description

The invention relates to mechanical engineering and can be used in the manufacture of threads on parts operating under alternating loads and under abrasive wear.

Known methods of manufacturing a thread with a tool to increase wear resistance and fatigue strength / Yakushev A.I., Mustaev R.Kh., Mavlyutov P.P. Improving the strength and reliability of threaded joints. - M.: Mechanical Engineering, 1979 - 215 p. /.

These methods of manufacturing threads do not allow complex to carry out hardening and finishing-hardening treatment with quenching of the thread profile along the entire perimeter with a simultaneous favorable arrangement of metal fibers.

A known method of hardening helical surfaces by electromechanical processing / Askinazi B.M. Hardening and restoration of machine parts by electromechanical processing. - M.: Mechanical Engineering, 1989-200 p. (p. 111 ... 115) /.

A known method of manufacturing a thread on a part, including finishing and hardening processing of the full profile of the thread with tools moving along a helical line, by applying electric current / GB 798609, B 23 G 1/00, 1958, 4 pages /.

However, with these methods, the tools are executed without interrupting the working surfaces and it is not possible to provide uniform cooling of the contact heating zone along the entire length of the threads, which leads to the top of the threads without surface hardening.

The objective of the invention is to improve the quality of screw surfaces by hardening the surface layer of the thread.

Using the proposed tool for hardening threads can increase the wear resistance and fatigue strength of screw surfaces and increase the tool life due to forced cooling of the contact surfaces.

The problem is achieved in that the contact surface of the tool is made with grooves for supplying a cooling medium through them, while the grooves are made so that during quenching they are not in the zone of the average diameter of the thread and do not fall on the boundary of the intersection of the side surfaces with the outer diameter of the thread .

The drawing shows the proposed design of a tool for hardening a threaded profile with electric heating of the surface layer.

The invention is illustrated by the following example.

On the machine model 1K62 thread processing was performed according to the proposed method. The M18 × 2.5 thread was cut with a cutter. Part material - steel 45 GOST 1050-88, thread length 25 mm. The cut thread had a profile angle of 60 °, the metal fibers were cut, the initial hardness of 18 ... 20 HRC.

Technologically, electrical contact thread processing was performed as follows.

The tool was sharpened at an angle of 60 degrees with a rounded radius at the apex. By setting the tools along the profile of the thread being machined and creating a reliable contact in the connection of the tool with the side surfaces of the thread, the rotation of the part and the source of electric current is successively turned on. A current of high strength and low voltage, concentrated in the “tool-thread” contact zone, leads to instantaneous heating of the surface layer to a temperature of 900 ... 1000 ° C. However, with this treatment scheme, the heat released in the contact zone is evenly distributed over the surfaces of the thread. In order to obtain a quenching structure, in addition to surface heating, it is necessary to provide rapid cooling with phase changes. The amount of heat removed from the base of the thread, the side surfaces and the top of the turns will be different. In the most optimal position are the zone of the cavity and adjacent side surfaces of the thread, since cooling takes place in the body of the cold part and is taken by the tip of the tool. With electrical contact heating, the top of the thread heats up intensively due to its small volume. Heat removal, however, is often below the required cooling rate and hardening structure is not observed.

When hardening the thread along the entire length of the part, the tool heats up, which indicates the need for forced cooling. Through the grooves on the side surfaces of the tool, it is cooled not only along the periphery, but also inside the contact zone.

The use of a tool having a high hardness of HRA 89 ... 91 and red color resistance of 1100 ° C, in comparison with the processed material HRC 18 ... 20 allows to carry out hardening treatment of the base and side surfaces of the thread. Hardening treatment leads to structural changes in the surface layer with quenching to a depth of 0.2 mm while maintaining the structure and properties inside the coil in the initial state.

The test results of threaded surfaces treated in this way showed that the wear resistance increases by 2.3 ... 3 times, the shear strength of the thread increases by 8 ... 12%, the force on the destruction of the rod 3 ... 5%.

Claims (1)

The tool for hardening the thread by the method of electrical contact, made along the profile of the machined circuit, characterized in that the contact surface of the tool is made with grooves for supplying through them to the contact point of the cooling medium, while the grooves are made so that they are not in the zone during hardening the average diameter of the thread and did not fall on the border of the intersection of the side surfaces with the outer diameter of the thread.