CN111590192A - Thermite welding method for seamless steel rail - Google Patents
Thermite welding method for seamless steel rail Download PDFInfo
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- CN111590192A CN111590192A CN201911170674.5A CN201911170674A CN111590192A CN 111590192 A CN111590192 A CN 111590192A CN 201911170674 A CN201911170674 A CN 201911170674A CN 111590192 A CN111590192 A CN 111590192A
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- steel rail
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K23/00—Alumino-thermic welding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2101/00—Articles made by soldering, welding or cutting
- B23K2101/26—Railway- or like rails
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Arc Welding In General (AREA)
- Butt Welding And Welding Of Specific Article (AREA)
- Machines For Laying And Maintaining Railways (AREA)
Abstract
The invention relates to a thermit welding method of a seamless steel rail, wherein the welding flux comprises C, Si, Mn, Cr, Ni, Mo, V, aluminum powder, oxide and iron powder; the process is as follows: polishing, derusting and dehumidifying the steel rail; aligning and assembling; preheating the steel rail until the rail head turns red; igniting thermite flux, preheating, reacting and pouring; heating the steel rail to 250-300 ℃ within 500mm from the sand mold frame at two sides after casting; pushing the edge, and simultaneously keeping the temperature of the steel rail at 250-300 ℃ in the sand mold distance frame of 500m at two sides; cooling the welded junction to 500 ℃, performing hot grinding, cooling the welded part after the hot grinding, keeping the temperature of the steel rail at the inner part 500m away from the sand mold frame at 250-300 ℃ on both sides, and covering and insulating the welded junction for 20 minutes until the welded part reaches 300 ℃ at 250-300 ℃; removing the cover, and naturally cooling to room temperature. The method ensures the welding quality.
Description
Technical Field
The invention relates to a thermite welding method of a seamless steel rail.
Background
The jointless track is a long steel rail track formed by welding steel rails with standard lengths, and is also called a welding long steel rail track. The rail gap is eliminated, so that the impact of wheels on the rail head is eliminated, the train runs stably, and the service lives of the line equipment and the locomotive are prolonged.
Thermite welding is a rail welding technique used for jointless tracks, and is a method of completing welding by melting a metal base material and filling a joint using heat generated by an oxidation-reduction reaction between a metal oxide and aluminum. The welding difficulty is the welding between heterogeneous steel rails, for example, the welding between a bainite steel rail and a pearlite steel rail, which is mainly reflected in that white spots and stress micro-crack sources are easily generated in a heat affected zone.
Through years of research and tests, BTF bainite steel and steel rails are developed by Beijing Temetallurgical industry and trade Co Ltd, and thermite welding flux related to CN105921881A is developed, so that the BTF bainite steel and steel rails can be used for welding homogeneous and heterogeneous steel rails, good hardness transition at welding seams is realized, and the welding seam performance completely meets the TBT1632.3-2005 and TBT1632.1-2005 standards. The hardness difference of the welding seam relative to the base metal is small, and good transitivity is realized.
However, thermite welding of jointless tracks is carried out in railway laying sites, and with the development of railway industry, railways span different areas, and the change of climate, particularly temperature and humidity, in different areas has a great influence on welding quality, which shows that welding defects such as cracks, bubbles and the like are generated in a welding seam transition area. In addition, due to the difference of alloy components of different welding fluxes, each welding flux needs to develop a corresponding welding process, and the existing process is difficult to apply, which also causes certain difficulty for construction. Therefore, it is necessary to develop a new thermite welding process for seamless rails to ensure the welding quality. In view of the above, on the basis of the development of the thermite welding agent, through a great amount of investigation and tests, the new thermite welding process for the seamless steel rail is developed and perfected by Beijing Temetallurgical industry and trade company Limited.
Disclosure of Invention
The invention aims to provide a thermite welding method of a seamless steel rail, which is based on CN105921881A thermite developed by special metallurgy and is suitable for welding steel rails in different environments.
A thermite welding method for seamless steel rail features that the flux contains C, Si, Mn, Cr, Ni, Mo, V, aluminium powder, iron powder and oxide;
the welding process comprises the following steps:
(1) polishing, derusting and dehumidifying the steel rail, wherein the dehumidifying and heating temperature is 300-350 ℃;
(2) aligning and assembling the rails, and wiping the welded junctions again after assembling;
(3) preheating the steel rail for more than 5 minutes until the rail head turns red;
(4) igniting thermite flux, preheating, reacting and pouring;
(5) heating the steel rail to 250-300 ℃ within 500mm from the sand mold frame at two sides after casting;
(6) pushing the knurls, keeping the temperature of the steel rails at 250-300 ℃ in the position of 500m away from the outside of the sand pot mold frame on two sides;
(7) cooling the welded junction to 500 ℃, and performing hot grinding while keeping two sides outside the sand mold frame
Keeping the temperature of the steel rail within 500m at 250-300 ℃;
(8) cooling the welding meat part after hot polishing, keeping the temperature of the steel rail at the two sides within 500m away from the sand mold frame at 250-300 ℃ until the temperature of the welding meat part reaches 250-300 ℃, and covering and insulating the welding opening for 10-20 minutes;
(9) removing the cover, and naturally cooling to room temperature. Further, the meat welding part is blown in step (8).
And further, when the temperature is lower than 15 ℃, a heat-insulating cover is used for heat insulation for 10 minutes after the burl is pushed in the step (6), so that the phenomenon that the temperature is too fast reduced to refine the crystal grains can be avoided, and the hot grinding can be carried out.
When the temperature is lower than 15 ℃, before preheating in the step (3), heating the two sides of the steel rail within the range of 1000mm to 37 ℃.
Further, after the hot polishing in the step (8), the welding meat can be cooled to 250-300 ℃ by wind, so that the tissue transformation is facilitated, the field work efficiency is improved, and the maintenance time is reduced.
Similarly, air cooling may be used to cool the solder meat to 500 ℃ in step (7).
In the step (1), the weld craters are not heated during dehumidification, so that carbon deposition and oxide scale are generated, and the weld craters are wiped or polished clean after heating.
When the rails are assembled in the step (2), the width of the rail gap is preferably 27-30mm, and the difference between the widest and narrowest parts is not large.
And the mold stripping is started 4.5 minutes after the pouring is finished, and the mold stripping cannot be carried out in advance.
The push button should be performed 7 minutes and 40 seconds after the end of the casting, and not ahead of time. .
The thermite welding process of the invention is to perform dehumidification and heating before assembling the rail, so as to avoid the defect of air holes generated by the moisture on the surface of the rail, and to prevent the transition zone from being cooled too fast by heating and heat preservation at 250-.
Drawings
FIG. 1 is a surface photograph of a weld zone of example 1;
fig. 2 is a surface photograph of a land of example 2.
Detailed Description
The present invention will be further described with reference to specific examples to assist understanding of the invention.
Example 1
Rails, U20Mn bainite rail and U75V rail.
Thermite flux, CN105921881A thermite flux.
Time, 12 months in 2018, place, Hebeijing county, air temperature 5 ℃ below zero.
The welding process comprises the following steps:
(1) polishing the steel rail to remove rust, removing rust at the welding part of the rail end, and then preheating the rail end by using propane and oxygen at the temperature of 300 ℃ and 350 ℃, but not heating a welding opening to avoid oxidation and carbon deposition;
(2) aligning the ends of the steel rails by aligning the rails, wherein the rail gap is 28mm, assembling, wiping the welded junction again after assembling, and ensuring cleanness;
(3) installing a sand mold, heating the two sides of the steel rail within the range of 1000mm to 37 ℃ by using a preheating gun, and then preheating the steel rail by using the preheating gun for more than 5 minutes until the color of the rail head becomes red; the temperature difference between the surface to be welded of the steel rail and an aluminum hot-welded steel molten pool is reduced, the fusion of a joint surface is facilitated to form fine grains, the stress distribution of a welding joint is improved, the comprehensive mechanical performance of welding is improved, residual moisture in a sand mold is removed, and the temperature of the steel rail and the mold is increased;
(4) the thermite is poured into the crucible in a rotating mode, the top surface of the crucible is a conical surface, a high-temperature match is inserted with the depth of 25mm, and the crucible is ignited, preheated and subjected to reaction pouring;
(5) heating the steel rail to 250-300 ℃ within 500mm from the sand mold frame at two sides after casting;
(6) the mold is removed after 4.5 minutes after the pouring is finished, the knurls are pushed after 7 minutes and 40 seconds after the pouring is finished, the temperature of the inner steel rail at the position 500m away from the outside of the frame is kept at 250-plus-300 ℃ after the knurls are pushed, and the heat of the welded junctions is preserved for 10 minutes by using a heat preservation cover (the inner layer is rock wool and the outer layer is a metal cover);
(7) removing the heat-insulating cover, naturally cooling to 500 ℃, and performing hot grinding, wherein the temperature of the steel rails at the two sides within 500m away from the sand mold frame is kept at 250-300 ℃ during the hot grinding;
(8) after hot polishing, the temperature of the welded part is continuously reduced, the temperature of the steel rail at the two sides is still kept at 250-300 ℃ within 500m away from the sand mold frame, and when the temperature of the welded part reaches 250-300 ℃, the welded part is covered and the temperature is kept for 10-20 minutes;
(9) removing the cover, and naturally cooling to room temperature.
The weld quality was checked and, as shown in FIG. 1, there were no air holes and no cracks.
Four groups are welded, and the number is 2 #.
Example 2
Rails, U20Mn bainite rail and U75V rail.
Thermite flux, CN105921881A thermite flux.
Time, 7 months in 2019, place, river north view county.
The welding process comprises the following steps:
(1) polishing the steel rail to remove rust, removing rust at the welding part of the rail end, and then preheating the rail end by using propane and oxygen at the temperature of 300-350 ℃;
(2) aligning the ends of the steel rails by aligning the rails, wherein the rail gap is 28mm, assembling, wiping the welded junction again after assembling, and ensuring cleanness;
(3) installing a sand mold, and then preheating the steel rail for more than 5 minutes by using a preheating gun until the color of the rail head turns red; the temperature difference between the surface to be welded of the steel rail and an aluminum hot-welded steel molten pool is reduced, the fusion of a joint surface is facilitated to form fine grains, the stress distribution of a welding joint is improved, the comprehensive mechanical performance of welding is improved, residual moisture in a sand mold is removed, and the temperature of the steel rail and the mold is increased;
(4) the thermite is poured into the crucible in a rotating mode, the top surface of the crucible is a conical surface, a high-temperature match is inserted with the depth of 25mm, and the crucible is ignited, preheated and subjected to reaction pouring;
(5) heating the steel rail to 250-300 ℃ within 500mm from the sand mold frame at two sides after casting;
(6) the mold is removed after 4.5 minutes after the pouring is finished, the knurls are pushed 7 minutes and 40 seconds after the pouring is finished, and the temperature of the steel rail at two sides within 500m away from the outside of the frame is kept at 250-;
(7) blowing air by a fan at the meat welding part, cooling the air to 500 ℃, and performing hot grinding, wherein the temperature of steel rails at the two sides within 500m from the outside of a sand mold frame is kept at 250-300 ℃ during the hot grinding;
(8) after hot polishing, the welding part is continuously cooled by air, the temperature of the two sides of the welding part is kept at 250-300 ℃ within 500m away from the frame, and the temperature is kept for 20 minutes by covering when the welding part reaches 250-300 ℃;
(9) removing the cover, and naturally cooling to room temperature.
The weld quality was checked and, as shown in FIG. 2, there were no air holes and cracks.
Four groups are welded, and the number is 1 #.
And (3) hardness detection:
the weld hardness of No. 1 and No. 2 are respectively detected by taking three longitudinal points at the base metal, the weld position and the center of the weld, detecting the hardness in the period, and expressing the hard bottom of the part by using the arithmetic mean value of the three points, wherein the results are as follows:
hardness test of welded joint (HRC)
The hardness of the welding part forms good transition between the two base metals.
Claims (9)
1. A thermite welding method for seamless steel rail features that the flux contains C, Si, Mn, Cr, Ni, Mo, V, aluminium powder, iron powder and oxide;
the welding process comprises the following steps:
(1) polishing, derusting and dehumidifying the steel rail, wherein the dehumidifying and heating temperature is 300-350 ℃;
(2) aligning and assembling the rails, and wiping the welded junctions again after assembling;
(3) preheating the steel rail for more than 5 minutes until the rail head turns red;
(4) igniting thermite flux, preheating, reacting and pouring;
(5) heating the steel rail to 250-300 ℃ within 500mm from the sand mold frame at two sides after casting;
(6) pushing the edge, and simultaneously keeping the temperature of the steel rail at 250-300 ℃ in the sand mold distance frame of 500m at two sides;
(7) cooling the welded junction to 490-510 ℃, and performing hot grinding, wherein the steel rails at the two sides within 500m away from the sand mold frame are kept at 250-300 ℃ during the hot grinding;
(8) cooling the welding meat part after hot polishing, keeping the temperature of the steel rail at the two sides within 500m away from the sand mold frame at 250-300 ℃ until the temperature of the welding meat part reaches 250-300 ℃, and covering and insulating the welding opening for 10-20 minutes;
(9) removing the cover, and naturally cooling to room temperature.
2. The method of claim 1, wherein: and (4) when the temperature is lower than 15 ℃, performing heat preservation for 10 minutes by using a heat preservation cover after the tumor is pushed in the step (6), and performing heat polishing.
3. The method of claim 1, wherein: when the temperature is lower than 15 ℃, heating the two sides of the steel rail to be within the range of 1000mm to 37 ℃ respectively before preheating in the step (3).
4. The method of claim 1, wherein: after the hot polishing in the step (8), cooling the welding meat to 250-300 ℃ by wind.
5. The method of claim 1, wherein the meat is cooled to 500 ℃ in step (7) by air cooling.
6. The method of claim 1, wherein in step (1), the craters are not heated for de-wetting and are wiped or ground clean after heating.
7. The method of claim 1, wherein the rail gap width is 27-30mm when assembling the rails in step (2).
8. A method according to claim 1, characterised in that the mould removal is started 4.5 minutes after the end of the casting, and cannot be performed prematurely.
9. The method according to claim 1, wherein the knob work should be performed 7 minutes and 40 seconds after the end of the casting without being advanced.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911170674.5A CN111590192A (en) | 2019-11-26 | 2019-11-26 | Thermite welding method for seamless steel rail |
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| CN201911170674.5A CN111590192A (en) | 2019-11-26 | 2019-11-26 | Thermite welding method for seamless steel rail |
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| CN111590192A true CN111590192A (en) | 2020-08-28 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113305417A (en) * | 2021-06-10 | 2021-08-27 | 中国二十二冶集团有限公司 | Thermite welding method for crane track |
| CN115255607A (en) * | 2022-08-04 | 2022-11-01 | 包头钢铁（集团）有限责任公司 | Method for improving quality of U76CrRE heat treatment steel rail aluminum hot welding joint |
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| GB450643A (en) * | 1935-01-05 | 1936-07-22 | Elektro Thermit Gmbh | Improvements in or relating to the aluminothermic welding of metals |
| RU2551751C2 (en) * | 2013-04-19 | 2015-05-27 | Общество с ограниченной ответственностью "ГТ-Алюминотермитная сварка" | Aluminium thermal welding of rails at negative ambient temperatures |
| CN105414797A (en) * | 2015-12-15 | 2016-03-23 | 中国铁道科学研究院金属及化学研究所 | Bainitic steel and pearlitic steel thermit welding material and welding technology |
| CN105921881A (en) * | 2016-05-20 | 2016-09-07 | 张绵胜 | Exothermic welding flux and application thereof |
| CN108581181A (en) * | 2018-04-17 | 2018-09-28 | 中国铁道科学研究院金属及化学研究所 | A kind of processing method of Thermit Welds in Rails hurt |
| CN110363403A (en) * | 2019-06-27 | 2019-10-22 | 中国铁道科学研究院集团有限公司 | Railway track damage forecast method and device |
-
2019
- 2019-11-26 CN CN201911170674.5A patent/CN111590192A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB450643A (en) * | 1935-01-05 | 1936-07-22 | Elektro Thermit Gmbh | Improvements in or relating to the aluminothermic welding of metals |
| RU2551751C2 (en) * | 2013-04-19 | 2015-05-27 | Общество с ограниченной ответственностью "ГТ-Алюминотермитная сварка" | Aluminium thermal welding of rails at negative ambient temperatures |
| CN105414797A (en) * | 2015-12-15 | 2016-03-23 | 中国铁道科学研究院金属及化学研究所 | Bainitic steel and pearlitic steel thermit welding material and welding technology |
| CN105921881A (en) * | 2016-05-20 | 2016-09-07 | 张绵胜 | Exothermic welding flux and application thereof |
| CN108581181A (en) * | 2018-04-17 | 2018-09-28 | 中国铁道科学研究院金属及化学研究所 | A kind of processing method of Thermit Welds in Rails hurt |
| CN110363403A (en) * | 2019-06-27 | 2019-10-22 | 中国铁道科学研究院集团有限公司 | Railway track damage forecast method and device |
Non-Patent Citations (1)
| Title |
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| 周明亮: "《低温条件下钢轨接头铝热焊焊接质量分析及对策研究》", 《中国优秀硕士学位论文全文数据库 工程科学Ⅱ辑》 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113305417A (en) * | 2021-06-10 | 2021-08-27 | 中国二十二冶集团有限公司 | Thermite welding method for crane track |
| CN115255607A (en) * | 2022-08-04 | 2022-11-01 | 包头钢铁（集团）有限责任公司 | Method for improving quality of U76CrRE heat treatment steel rail aluminum hot welding joint |
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