RU2119854C1 - Method for aluminothermic welding of rails - Google Patents

Abstract

FIELD: rail repairing in field condition. SUBSTANCE: method comprises steps of arranging end portions of rails in the same level with welding gap between their end surfaces; placing buildup form around rail ends in zone of welding gap and sealing contact of buildup form with rail ends; placing over form reaction crucible with dose of aluminothermic composition; before pouring melt welding metal into buildup form, heating rail ends and form up to 100-1500 C; then curing melt metal until its solidification and formation of welding joint. At pouring process filling welding gap with melt welding metal from downwards to upstairs and feeding part of melt welding metal to mean portion of welding gap after filling lower portion of buildup form. At final stage of pouring additionally heating heads of rail ends and melt metal in welding gap at least until 800 C due to feeding last dozes of melt metal to space over heads of rail ends. After crystallization of welding metal removing top portion of welding joint from head of welded rail. EFFECT: enhanced quality of joints welded in field condition. 2 dwg

Description

 The invention relates to the field of welding, in particular, to methods for aluminothermic welding of rails.

A known method of aluminothermic welding of rails, including setting the ends of the rails at the same level with the formation of a welding gap between their ends, arranging a detachable shape around the ends of the rails of the rails, sealing the contact of the detachable form with the ends of the rails, installing a reaction crucible filled with a dose of aluminothermic composition over the form , heating the ends of the rails and the demountable form, igniting a dose of the aluminothermic composition and heating it to form molten metal, feeding from the reaction crucible the deposited metal into the middle part of the demountable form after filling in its lower part, holding the molten metal to solidify and form a weld and then removing from the head of the welded rail the profitable part of the weld, and the heating of the ends of the rails and the demountable mold is carried out to a temperature of 800-1000 ^o C, and at the end of the supply of molten metal into a demountable form, additional heating of the heads of the ends of the rails and molten metal poured into the welding gap to a temperature of at least 800 ^° C. is carried out by feeding after days of portions of molten metal in the space above the heads of the ends of the rails (RF patent N 2088390, cl. B 23 K 23/00, published. August 27, 1997)
The disadvantage of this method is the insufficient quality of the resulting weld when working in the field, especially in winter, when the cooling rate reaches 50 ^o C / s, because there is a quick and uneven cooling of the molten metal due to the large temperature difference between the molten metal and the ends of the rails and detachable form, as a result of which slags and gases in the molten metal do not have time to stand out in the profitable part of the weld and remain in the weld metal, worsening it with rukturu and mechanical properties.

 The objective of the patented invention is to improve the quality of the resulting weld by reducing the temperature difference between the molten metal, the ends of the rails and the split mold, and thereby prevent rapid and uneven cooling of the molten metal and create favorable conditions for the release of slag and gases.

This problem is achieved by the fact that in the method of aluminothermic welding of rails, including installing the ends of the rails at the same level with the formation of a welding gap between their ends, placing around the ends of the rails in the zone of the welding gap of a detachable form, sealing the contact of the detachable form with the ends of the rails, installing over the reaction form a crucible filled with a dose of aluminothermic composition, heating the ends of the rails and demountable form, igniting a dose of aluminothermic composition and heating it to the formation of molten metal, supply of molten metal from the reaction crucible to the middle part of the split mold after filling in its lower part, additional heating of the rail ends and molten metal poured into the welding gap to a temperature of at least 800 ^° C at the end of the supply of molten metal into the split mold by feeding the last portions of molten metal in the space above the heads of the ends of the rails, the exposure of the molten metal to solidify and the formation of a weld and the subsequent removal from the head of the welded rail of a profitable h STI weld, in contrast to the method according to the prior art, the heating rail ends, and the split mold before applying it produces a molten metal to a temperature above 1000 ^o C to 1500 ^o C.

 In FIG. 1 shows a detachable form; in FIG. 2 is a cross-section along line AA of FIG. one.

 When implementing the patented method, the split mold shown in FIG. 1. The demountable form 1 consists of two half-forms 2.

 The half-molds 2 have a lateral channel 3 communicating its upper space 4 with the lower space 5. An additional channel 6 departs from the lateral channel 3, communicating the lateral channel 3 with the middle part 7 of the half-mold 2 in the region of the heads 8 of the rail 9 and an additional channel 10 communicating the lateral channel 3 with the space 11 of the half-mold 2 located above the heads 8 of the rail 9. On top of the half-mold 2 are closed by an injection bridge 12, which is placed in the cavity 13 of the half-mold 2. On the side of one of the half-molds 2 there is a bucket 14 for collecting slag from the casting groove 15 of the half-mold 2.

 The patented method is as follows.

 Before welding, the rails 9 are installed at the same level with a height difference of not more than 1 mm over a length of 1 meter. In the place of contact of the rails between their ends set a welded gap of 24-26 mm

 In place of the weld gap, a split mold 1 is placed so that the half-molds 2 are directed along the axis of the weld gap. Previously, on one half-mold 2, the casting trough 15 is filled with mastic, and on the other, the weakened wall of the casting trough 15 is removed to remove slag and the ladle 14 is attached to collect slag.

 The contact point of mold 1 with rail 9 is sealed with molding material, for example, material based on kaolin and asbestos wool can be used.

 The heating of the ends of the rails and the split mold is carried out using a gas burner.

A burner with a normally adjusted flame is installed in the welding zone for preheating the ends of the rails 9, the casting bridge 12 and the mold 1. The heating time, for example, for the R-65 rail at a propane pressure of 3.5 bar and oxygen 1 bar is 7-10 minutes. During this time, the ends of the rails are heated to a temperature of 1000-1500 ^o C.

As experiments showed when performing work in the field, especially in winter, to obtain a high-quality weld and maintain an optimum temperature of at least 800 ^o C along with pouring molten metal into a split mold in three stages - the lower, middle and then the upper part detachable form above the rail heads - it is also necessary to heat the ends of the rails and detachable form to a temperature above 1000 ^o C to 1500 ^o C.

The heating of the rail ends to a temperature above 1500 ^o C is impractical, since a partial melting of the metal of the rails and the loss of their original mechanical properties that it possesses after the manufacture of the rails can occur and, thus, the weld joint is not equally equal.

The heating of the rail ends and the demountable mold to a temperature below 1000 ^° C does not prevent the rapid cooling of the molten metal poured into the demountable mold and, thereby, ensure the release of slag and gases from it.

One minute before the end of heating of the ends of 2 rails 9 and form 1, the casting bridge 12 of form 2 is also heated to a temperature of 1000-1500 ^o C, after which it is installed in the cavity 13 of form 1 and the thermite match is ignited from the burner flame, from which the aluminothermic dose is ignited composition in a crucible (not shown) mounted above the mold. After ignition of a dose of aluminothermic composition, alloying, refining and deoxidizing reactions occur, as a result of which it is heated to the formation of molten welded metal and, after 20-28 s, the molten welded metal is automatically released from the crucible into a split mold 1.

The molten welded metal pouring out of the crucible enters the casting bridge 12 of the split mold 1 and then flows along the side channel 3 into the lower space 5 of the half-mold 2 of the split mold 1 and rises up along the split mold 1 and the weld gap, with the resulting slag falling along with the molten welded metal to the casting bridge 12, are discharged through the casting groove 15 into the ladle 14 for collecting slag. After filling the lower part of the demountable mold 1 with molten welded metal to the outlet level of channel 6 therein, the molten metal begins to fill the demountable mold 1, circulating from the side duct 3 already through the duct 6 and then up. T.O. the middle part of the detachable mold 1 is filled with molten welded metal below the heads 8 of the ends of the rails 9, and until the channel 10 exits into the detachable mold 1. Then, the last portions of the molten welded metal from the side channel 3 pass through the channel 10 into the detachable mold 1 into the space above the heads 8 ends of rails 9. Since Since the last portions of molten welded metal leaving the crucible are the warmest (have the highest temperature), then after they are poured into the space above the heads of the 8 ends of the rails 9, the heads of the 8 ends of the rails 9 and the molten welded metal located in the weld gap are additionally heated. This allows you to maintain the temperature not lower than 800 ^o C.

When the physical state of the molten weld metal filling the weld gap changes, its additional heating from the heated heads of the 8 ends of the rails 9 and from the most heated last portions of the molten welded metal facilitates the evolution of gases and the smelting (removal) of slags from it. This is facilitated by the preliminary heating of the ends of the rails and the demountable form to temperatures above 1000 ^o C to 1500 ^o C, because it allows a long time to maintain the molten metal in an unstructured state, especially in winter.

 Due to this, gases and slags float from the molten welded metal filling the weld gap and pass into the profitable (weld) part of the weld formed above the heads of 8 ends of rails 9, i.e. outside the weld gap. T.O. in the profitable part of the weld above the heads of the ends of the rails, contaminants and bubbles from the exhaust gases are concentrated, and the weld metal remains without any defects - there are no inclusions of slags and gas bubbles in it.

So, pouring a demountable mold is carried out in three stages, starting from the bottom, then the middle and at the end - the upper part. Such filling of the demountable mold and the weld gap with metal in combination with the preheating of the rail ends and the mold to 1000-1500 ^o C does not allow the molten welded metal and rail ends to cool below the optimum temperatures for the welding process, which should not fall below 800 ^o C. In addition Moreover, the circulation of molten weld metal from the bottom up and additional heating to maintain the temperature at the optimum level allows slag and gases to freely stand out and carry out to the upper part of the weld Azora continue beyond the mold channel 10 and the casting trough 15 to the ladle 14 and not released outside the mold 1 slags and gases accumulate in the space 11 under the casting bridge 12 and profitable part of the weld, but not in the welded seam.

 The crystallization time of the weld metal, depending on the dose of the aluminothermic composition of the temperature of the preheating of the rail ends and the mold, as well as the ambient temperature, lasts 4.5-7 minutes.

 After the weld metal has solidified, its profitable part is removed from the head of the welded rail with a trimmer (not shown), and then the surface of the weld on the rail head is ground to a height of about 1 mm above the top of the rail head, and after the weld has completely cooled down (to ambient temperature ) grind the entire weld on the rail head to the size of the rail head with a tolerance of 0.3 mm.

 After stripping the weld seam of the rail head, the rest of the weld is cleaned of the remnants of the mold material.

 It turns out a high-quality, welded joint of rails in the field, especially in winter, which is confirmed by the results of experimental welding. Welding of rails on railways showed that we obtain more durable and durable welded joints of rails that can withstand significantly higher loads and for a longer period of operation.

Claims (1)

A method of aluminothermic welding of rails, including setting the ends of the rails at the same level with the formation of a welding gap between their ends, arranging a detachable shape around the ends of the rails of the rails, sealing the contact of the detachable form with the ends of the rails, installing a reaction crucible filled with a dose of aluminothermic composition over the form, heating the ends of the rails and the demountable form, igniting a dose of aluminothermic composition and heating it to form molten metal, feeding from the reaction crucible is molten th metal in the middle portion of the split mold after filling in its lower part, an additional heating of the head rail ends and poured into the welding molten metal gap to a temperature not lower than 800 ^o C at the end of the molten metal flow in the split mold by feeding the last of the molten metal portions in the space above the heads the ends of the rails, the exposure of the molten metal to solidify and the formation of a weld and the subsequent removal from the head of the welded rail of the profitable part of the weld, characterized in that the heating of the ends of the rails and the demountable mold before supplying molten metal to it is carried out to a temperature above 1000 ^o C to 1500 ^o C.

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