RU2254968C1 - Method for restoring rubber mixer semichambers - Google Patents

Abstract

FIELD: restoration of worn surfaces, namely semichambers of rubber mixers.

SUBSTANCE: method comprises steps of placing on restored part metallic cover plate compensating wear; fusing cover plate along its whole thickness by annular or lengthwise seams at predetermined pitch with use of plasma arc and additional arc. The last burns between melt metal and alloy powder wire that is fed behind plasma arc. Spacing between said arcs is selected in range consisting of (0.4 - 0.6) of length of melt metal bath.

EFFECT: possibility for providing seam root minimally alloyed with powder wire components at keeping wear resistance of remaining metal of seam.

2 dwg

Description

The invention relates to the field of restoration of worn surfaces, namely, half-chambers of rubber mixers.

The rubber mixer used for the manufacture of rubber mixtures for plasticizing natural rubber is a closed chamber with rolls rotating towards each other with curved profiles (rotors). In a loading funnel of the chamber in a certain sequence the components of the rubber mixture, for example,%:

SKMS-8 13%; slaked lime 3.15%; regenerate 31%; ebonite dust 4.95%; sulfur 18.8%; rubrax 2.77% sulfates 0.1%.

A closed chamber consists of two half-chambers, the inner cylindrical surface of which wears out intensively due to the action of the components of the mixture during its mixing. At the final stage of operation, the wear reaches 15 mm. Further operation requires the restoration of worn-out surfaces of half-chambers.

A known method of restoring worn parts [1], in which an overlay is installed on the surface to compensate for wear. The overlay is fixed with fasteners included in the holes previously made in the details, or with a steel bracket installed in the groove cut out between the holes. The main disadvantage of this method is the low wear resistance of metal plates and the complexity of their fastening.

Fixing the lining on the base metal is possible by welding with penetration of the lining to the entire thickness with ring or longitudinal seams with a given step. When the lining thickness is more than 15 mm, its full penetration is feasible by applying the method of arc surfacing [2], while simultaneously solving the problem of obtaining alloyed wear-resistant joints. To improve the quality of hardening to a depth of more than 15 mm by achieving uniformity in the assimilation of alloying elements and eliminating defects in the formation of the roller, surfacing is carried out using two welding arcs forming a common bath of molten metal. A plasma arc is used as a heating source and to achieve the required penetration depth, and an arc burning behind a plasma arc between the molten metal and the alloyed flux-cored wire is used as an alloying source. The distance between the arcs is set in the range from 0.15 to 0.3 of the length of the molten metal bath, which ensures complete mixing of the base and alloy metal in the bath. The main disadvantage of the method [2] in relation to the welding of the lining is the formation of brittle alloyed metal at the root of the seam, which reduces the reliability of welding the lining to the half-chamber.

The technical problem to which the invention is directed is to obtain a weld root minimally doped with flux-cored wire components, while maintaining the wear resistance of the remaining weld metal, which helps to prevent brittle fracture in the weld root. The result is achieved by the fact that after the installation of the metal plate, it is melted to the entire thickness δ with a plasma arc with circular or longitudinal seams with a given step t. To alloy the molten metal behind the plasma arc, an additional arc is introduced, burning between the molten metal and the alloyed cored wire. To obtain an undoped weld root, the distance between the arcs is selected in the range 0.4-0.6 of the length of the molten metal bath. In this case, the weld root metal, which is close in composition to the lining metal, manages to crystallize to the approach of the additional arc and there is practically no alloying with flux-cored wire components, which helps to maintain satisfactory metal ductility in the weld zone of the lining.

The scheme of the proposed method for the restoration of half chambers of rubber mixers with respect to longitudinal seams is shown in figure 1. Section AA in figure 1, together with a diagram of the process of welding the lining depicted in figure 2.

A method of restoring half-chambers of rubber mixers is as follows.

In the worn hole in the housing of the half-chamber 1, a metal plate 2 is installed, curved along the profile of the surface being restored. Then it is melted to the entire thickness S with a plasma arc with longitudinal seams 3 in increments of t, and an alloyed flux-cored wire is fed into the molten metal bath behind the plasma arc at a distance of 0.4-0.6 from the length of the bath. An additional arc burns between the wire and the molten metal. After crystallization of the molten metal, a so-called combined deposited hard layer is formed, consisting of wear-resistant joints alternating with step t. Due to the crystallization of the root of the weld 4 before the approach of the additional arc, it is practically not alloyed by the components of the cored wire and has satisfactory ductility, which ensures the reliability of welding of the lining.

Tests for wear resistance were carried out on the installation described in [3]. The components of the rubber mixture with the addition of 5% silica sand were used as an abrasive. We tested the wear resistance of samples made of steel St.3 (lining material) and hardened by melting by a plasma arc with a flux-cored wire of PP AN-122 fed into the weld pool. The test results showed hardening by the proposed method allows to increase the wear resistance of the restored half-cameras by 5.7 times.

List of references

1. Mikryukov L.A. A method of restoring a worn surface of parts. - RU 2020047, B 23 P 6/00, 09/30/1994

2. The method of arc surfacing / V.Ya. Vorotnikov, Yu.A. Artemenko, O.I. Stelov, etc. - SU 1297349, 23 K 9/04, 9/16, 03/11/85.

3. Grinberg N.A., Petrov I.V., Nikanorov M.I. Methodology for studying the resistance of deposited metal against shock-abrasive wear // Welding production. - 1977. - No. 7. - S.24-27.

Claims (1)

A method of restoring half-chambers of rubber mixers, comprising installing a metal lining that compensates for wear, characterized in that for hardening when restoring half chambers of rubber mixers, the metal lining is fused to its entire thickness with circular or longitudinal seams with a given step by a plasma arc and an additional arc burning between the molten metal and the alloying cored wire, which is fed behind the plasma arc, while the distance between the arcs is selected in the range of 0.4 ÷ 0.6 from dl us molten metal bath.

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