RU2423212C1 - Method of aluminothermic welding of rails - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention may be used for welding long-welded rails in the field conditions. Rail ends are arranged to have weld gap there between. Split die is arranged in weld gap zone and reaction crucible with a portion of aluminothermic composition is arranged above said die. Rail ends are split die is heated to preset temperature while said composition is heated to produce molten metal. Molten metal is fed from reaction crucible into split die center after its bottom is filled. Last portions of metal are fed into space above rail ends to keep molten metal unless welded seam is formed. Said welded seam is cooled down by air-water mix to temperature of ("Мн"+100)°C - "Мн"°C, and, then, in air. Rag and slag collar removed from welded rail head, it is hardened by oblique impact wave at 90° and 15-28 GPa.

EFFECT: repair in field conditions, higher wear resistance and longer life.

1 tbl, 1 ex

Description

The invention relates to mechanical engineering, to thermite welding of joints, and more particularly to welding rails using aluminothermic welding.

A known method of aluminothermic welding, which consists in bringing to the path a metal funnel, pouring 4-7 kg of a special powdery metallized mixture into it and setting it on fire. In the molten state, it fills the gap closed by peculiar profiles designed to fill it with liquid metal. After “seizing” the junction, the molds are removed and the grata and slag deposits of molten metal from the head of the rails are cut off with special equipment [Journal of Path and Track Management, No. 2, 2005, p.23].

The disadvantage of this method is the decrease in the hardness of the weld compared to the hardness of the base metal and the formation of pores and foreign inclusions in the weld.

A known method of aluminothermic welding of rails, in which the ends of the rails are installed with the formation of a welding gap between their ends, is placed on the ends of the rails in the welding gap zone, a detachable form is sealed, the contact of the detachable form with the ends of the rails is sealed, a reaction crucible filled with a dose of aluminothermic composition is installed on the form, heated the ends of the rails and the demountable form to a temperature in the range of (1000-1500) ° C, ignite the dose of aluminothermic composition and heat it to form molten metal, serves h the reaction crucible the molten metal into the middle part of the split mold after filling its lower part, the ends of the rails and the molten metal cast into the welding gap are heated to a temperature not lower than 800 ° C at the end of the supply of molten metal into the split mold by feeding the last portions of molten metal into the space above rail heads, withstand molten metal until hardening and the formation of a weld, cool with an air-water mixture with a water content of (20-50)% with a cooling rate of (7-11) ° C / s to temperatures (MH + 100) ° C Mn ° C in air and then removed from the head rail welded burr and slag accretions (RF Patent №2349433, IPC: 23/00 V23K, V23K 101/26, C21D 9/50. Method of aluminothermic welding of rails, authors Bondarenko A.A., Mayerova G.R. et al., publ. November 10, 2008).

The disadvantage of this method is the low hardness of the weld, which is inferior to the hardness of the base metal.

This technical solution is taken as a prototype.

The technical result is to increase the hardness in the joint zone due to hardening by a direct shock wave at an angle of 90 ° with a pressure of 15-28 GPa.

The technical result is achieved by the fact that in the method of aluminothermic welding of rails, in which the ends of the rails are installed with the formation of a welding gap between their ends, a detachable form is placed at the ends of the rails in the welding gap region, the contact of the detachable form with the ends of the rails is sealed, a reaction crucible is installed over the form, filled with a dose of aluminothermic composition, the ends of the rails and the split mold are heated to a temperature in the range of (1000-1500) ° С, a dose of aluminothermic composition is ignited and heated to form of molten metal, the molten metal is fed from the reaction crucible into the middle part of the demountable mold after filling its lower part, the ends of the rails and the molten metal cast into the welding gap are heated to a temperature of at least 800 ° C at the end of the molten metal supply to the demountable mold by feeding the last portions molten metal into the space above the rail heads, the molten metal is held until hardening and the formation of a weld, cooled with an air-water mixture with a water content of (20-50)% at a speed cooling (7-11) ° C / s to a temperature of (Mn + 100) ° C-Mn ° C, after which, in the air, the burrs and slag flows are removed from the head of the welded rail and then hardened by a direct shock wave at an angle of 90 ° with a pressure of 15-28 GPa.

All this increases the hardness of the weld by (10-20) units. HB.

The test results are summarized in table.

Hardness of space-hardened rails of type P65 (in the weld zone) with various welding technologies Welding method The hardness of the rails in the weld zone, units HB Method aluminothermic welding (prototype according to patent No. 2349433) 340 Method of aluminothermic welding (according to the proposed technical solution) 350-360

An example implementation of the method

For example, rails of type P65 are welded from steel M 76. Before welding, the ends of the rails are machined. The rails are combined along the perimeter, heated and poured aluminothermic mixture. After the split mold and the reaction crucible are placed, the end ends of the rails and the split mold are heated, the aluminothermic mixture is poured, the exposure is held until hardened, where during the pouring process, the heads of the end ends of the rails and the molten welded metal are additionally heated. Then the joint is first cooled with an air-water mixture with a water content of (20-50)% with a cooling rate of (7-11) ° C / s to a temperature of (Mn + 100) ° C-Mn ° C, and then in air. The burrs and slag deposits are removed from the head of the welded rail. Then hardening is performed by a direct shock wave at an angle of 90 ° with a pressure of 15-28 GPa.

Hardening by a direct shock wave at an angle of 90 ° with a pressure of 15-28 GPa provides the creation of a dislocation structure of a weld with increased hardness.

The proposed technical solution allows to increase the hardness in the weld zone by 10-20 units. HB, to increase the service life of welded rail joints by 10-20%, which corresponds to a reduction in labor costs per 1 km of track maintenance by 10-15%. The proposed method improves the wear resistance and durability of welded joints, the reliability and safety of the operation of the welded jointless path and allows for the repair of rails in the field, which gives significant savings in material costs.

Claims (1)

A method of aluminothermic welding of rails, in which the ends of the rails are installed to form a welding gap between their ends, a detachable form is placed at the ends of the rails in the welding gap zone, the contact of the detachable form with the ends of the rails is sealed, a reaction crucible filled with a dose of aluminothermic composition is installed over the form, the ends are heated rails and demountable form to a temperature in the range (1000-1500) ° C, ignite a dose of aluminothermic composition and heat it to form molten metal, fed from the reaction After the filling of the crucible, the molten metal in the middle part of the demountable mold after filling in its lower part, the ends of the rails are heated and the molten metal cast into the welding gap to a temperature of at least 800 ° C at the end of the molten metal supply to the demountable mold by feeding the last portions of molten metal into the space above the heads rails, withstand the molten metal until hardening and the formation of a weld, cooled with an air-water mixture with a water content of 20-50% with a cooling rate of 7-11 ° C / s to a temperature of (Mn + 100) ° C - Mn ° C, then cooled in air and removed from the head of the welded rail burr and slag flows, characterized in that after removing from the head of the welded rail burrs and slag bursts, the weld is hardened by a direct shock wave at an angle of 90 ° with a pressure of 15-28 GPa.