RU2483852C1 - Method of reconditioning thread on shafts - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to metallurgy, particularly, to reconditioning of shaft thread without changing the initial thread dimension and may be used for recovery of stripped or worn-out thread or that with nicks. Shaft thread is reconditioned by turning worn-out and repair threaded surface and cutting the thread for helical insert. Helical insert is made from rhombic-section wire from age-hardening chromium-nickel alloy and screwed on newly-cut thread with artificial ageing.

EFFECT: higher reliability, longer life.

Description

The invention relates to the field of repair of threaded surfaces of shafts without changing the original size and can be used for torn, worn threads and nicks on it.

A known method of restoring the external thread on the shafts, in which the torn thread (less than 3 threads) and nicks are eliminated by sweeping using a thread-cutting tool [1, p.141]. The method is not applicable if there is a large wear of the thread in diameter.

There is a method of repairing threaded holes by installing threaded spiral inserts that are made of rhombic cross-section wire [1, p.142-143, Fig.5.1]. Using this method to repair the external thread on the shafts leads to the movement of the spiral threaded insert during screwing onto the shaft of the mating part along the axis of the shaft.

Closest to the technical nature of the claimed is a method of thread restoration without changing the original size, in which the worn thread is removed by turning it by 1 mm, a metal layer is welded with an allowance of 1.5 ... 2 mm to the side, the weld section of the shaft is machined and a thread of nominal size is cut [ 1, p. 141]. The method has a high complexity. In addition, the method leads to the appearance of an extensive zone of thermal damage to the main material of the shaft, which in many cases is unacceptable.

The objective of the invention is to increase the reliability and durability of the threaded connection after repair of the threaded part of the shaft.

Thread restoration occurs without changing the original size. It is necessary to cut the worn threaded surface, cut the thread under the spiral insert. The spiral insert is made of rhombic cross-section wire.

The claimed technical result in the proposed method is achieved by manufacturing a spiral threaded insert from dispersion hardening chromium-nickel alloy, screwing it onto a newly cut thread, then annealing at 730 ... 750 ° C for 4 hours. If the threaded insert wears out, it is removed after it is heated to 930 ... 950 ° C, held for 1 hour at this temperature and cooled in water, after which the threaded insert is installed and the heat treatment operation is repeated.

The method is as follows. The connection of the newly threaded thread on the shaft under the threaded insert is carried out by shrinkage of the material of the threaded insert made of dispersion hardening chromium-nickel alloys, after its aging (for example, for 36NHTYu alloy, after aging with slow cooling, the shrinkage is 0.3 ... 0.33% ), and the threaded insert is removed as a result of expansion of the alloy by the same amount after quenching (for 36НХТУ alloy, water cooling [2]), the threaded insert for thread repair should be in a soft state. After screwing the threaded insert onto the shaft and aging, the material of this insert shrinks and is firmly fixed to the shaft.

To disassemble a threaded connection in order to remove a worn or broken threaded insert, it is quenched (for example, for 36НХТЮ alloy, it is heated to 930 ... 950 ° C for 1 hour and quickly cooled in water). In this case, the initial clearance reappears between the shaft and the threaded insert and the threaded insert can be screwed from the shaft.

This method of restoring the external thread makes it possible to increase the durability of the threaded part of the shaft with frequent unscrewing and screwing due to the reduction of microroughnesses on the surface of the threaded insert after drawing the rhombic cross-section wire in comparison with the initial thread obtained by metal cutting methods. It also allows you to repeatedly restore threads on the outer surface of the shafts. It is possible to restore external threads on thin-walled bushings. At the same time, the corrosion resistance of the threaded part of the restored shaft is increased both due to the properties of the alloy itself and due to a decrease in the surface roughness.

Information sources

1. Baranov L.F. Maintenance and repair of machinery. - Rostov-on-Don: Phoenix, 2001 .-- 412 p.

2. USSR author's certificate No. 1331614, cl. B23B 27/18, 1987.

Claims (1)

The method of restoring the external thread on the shafts without changing the initial size, including turning the worn and to be repaired threaded surface, threading, characterized in that the thread is cut into a spiral, made of rhombic cross-section from a dispersion-hardening chromium-nickel alloy insert and its installation by screwing onto a newly threaded thread followed by artificial aging.