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CN-122007715-A - U71Mn steel rail welding flux under low-temperature weather and welding method

CN122007715ACN 122007715 ACN122007715 ACN 122007715ACN-122007715-A

Abstract

The invention discloses a U71Mn steel rail welding flux which is suitable for a 880 MPa-level 50kg/m U Mn hot rolled steel rail and comprises aluminum powder, ferric oxide, si iron powder, mn iron powder and cast iron balls, and the balance of pure iron powder, wherein the total is 100 percent. A method for welding the steel rail flux is also disclosed. The purpose of the invention is to adapt the flux in low temperature environment.

Inventors

  • ZHENG RUI
  • LIANG ZHENGWEI
  • BIAN YING
  • XUE HUDONG
  • DONG JIE
  • WANG HUIJUN
  • YAN LEI

Assignees

  • 内蒙古包钢钢联股份有限公司

Dates

Publication Date
20260512
Application Date
20260324

Claims (7)

  1. 1. A U71Mn steel rail welding flux under low-temperature weather is characterized by being adaptive to 880 MPa-level 50kg/m U Mn hot rolled steel rails, and comprising aluminum powder, ferric oxide, si iron powder, mn iron powder, cast iron balls and pure iron powder, wherein: aluminum powder accounting for 17.8 to 18 percent of the total weight, and the aluminum content is not less than 99 percent; Iron oxide accounting for 61.5 to 62.5 percent of the total weight and mainly comprising a mixture of FeO, fe 2 O 3 and Fe 3 O 4 ; Si iron powder accounting for 0.4 to 0.6 percent of the total weight, wherein the content of Si is not less than 70 percent, the content of Fe is not less than 29 percent and the content of carbon is less than 1 percent; mn iron powder accounting for 0.88 percent to 1.08 percent of the total weight, carbon content of 0.15 percent to 0.7 percent and manganese content of 65 percent to 75 percent; 7-8% of cast iron balls, and 4-4.5% of carbon; The rest is pure iron powder, which is 100 percent in total; The welding flux is used for U71Mn thermit welding construction, the tensile strength of a welding joint is still not lower than 730MPa even in a low-temperature climatic environment, the fatigue performance reaches more than 3X 10 6 times, and the quality requirement of long-term service of the steel rail in a low-temperature area can be met.
  2. 2. The U71Mn steel rail welding flux under low temperature weather according to claim 1, wherein the total weight of the welding flux is 10kg.
  3. 3. The U71Mn steel rail welding flux under low-temperature weather according to claim 1, wherein the aluminum powder is screened by a screen with a screen mesh size of 0.50mm, and particles are controlled to be less than or equal to 35 meshes, so that moderate thermite reaction intensity is ensured, and insufficient heat or reaction runaway is avoided.
  4. 4. The U71Mn steel rail welding flux under low-temperature weather according to claim 1, wherein the ferric oxide is screened by adopting a screen with a screen mesh size of 1.00mm, the particle mesh number is controlled to be less than or equal to 18 meshes, the reduced iron is facilitated to quickly form molten steel under a low-temperature environment, and the molten iron supply amount and fluidity are ensured.
  5. 5. The U71Mn steel rail flux under low temperature weather according to claim 1, wherein the Si iron powder is sieved using a sieve having a mesh size of 1.00mm, and the Mn iron powder is sieved using a sieve having a mesh size of 2.00 mm.
  6. 6. The U71Mn steel rail welding flux under low-temperature weather according to claim 1, wherein the cast iron balls and the pure iron powder are screened by using a screen with a screen mesh size of 2.00mm, and the content of other elements in the pure iron powder is less than 0.1 percent, so as to supplement the metal content of a welding seam.
  7. 7. The welding method of U71Mn steel rail welding flux under low temperature weather according to any one of claims 1 to 6, characterized by comprising the following steps: The method comprises the steps of rail cutting and rail alignment, namely accurately cutting a U71Mn rail to be welded by using an internal combustion rail sawing machine, removing impurities and burrs on the end surface of the rail, adjusting the butt joint clearance and smoothness of the rail by means of a rail alignment ruler and a wedge, ensuring that the joint alignment error meets the welding standard, and simultaneously fixing the rail by using a sand mold fixture to prevent displacement in the welding process; The special preheating at low temperature comprises the steps of assembling a preheater, matching an oxygen decompression meter, a propane decompression meter and an oxygen propane gas belt to adjust the gas source pressure, and uniformly preheating the rail joints, prolonging the preheating time in a low-temperature environment, ensuring the temperature gradient of the joints to be stable, and avoiding cracks caused by overlarge local temperature difference; Filling the prepared low-temperature adaptive flux into a crucible, igniting the flux to initiate aluminothermic reaction, and separating redundant risers by using riser separators in the reaction process to ensure the formation of welding seams; The process of pushing the burrs, namely, when the weld metal is solidified to a proper temperature, removing redundant burrs at the joint by using a burr pushing machine, ensuring the surface of the steel rail to be preliminary flat, and avoiding the weld from being damaged by excessive force in the process of pushing the burrs; Grading polishing and finishing, namely adopting multistage polishing equipment to carry out refining treatment, firstly using a high-power angle grinder to coarsely grind the allowance of the welding seam, and then using an electric profiling grinder to profile polish according to the profile of the steel rail; And (3) detecting the quality of the welding line, namely checking whether the appearance of the welding line has cracks or not and has no penetration defect after finishing polishing, sampling according to a TB/T1632 welding standard, and detecting the tensile strength and fatigue performance of the joint to ensure that the joint meets the low-temperature service requirement.

Description

U71Mn steel rail welding flux under low-temperature weather and welding method Technical Field The invention belongs to the technical field of steel rail welding, and particularly relates to an aluminum heat welding agent suitable for 50kg/m U Mn hot rolled steel rails in a low-temperature weather environment and a manufacturing method thereof, which are suitable for the operations of steel rail laying, rush repair and the like in a low-temperature area, and can ensure the quality of steel rail welded joints and the railway transportation safety in the low-temperature environment. Background Thermite welding of steel rails is a core technology for realizing seamless connection of the steel rails, is indispensable in construction and maintenance of passenger railways, and can remarkably improve the stability of a seamless line and riding comfort of passengers. The U71Mn steel rail is widely applied as a main stream steel rail variety of passenger railway, but the existing thermite welding agent is mostly suitable for normal temperature environment, and the influence of low temperature climate is not fully considered. Under the low-temperature environment, the conventional thermite welding agent has the defects of insufficient molten iron melting, poor fluidity and the like caused by quick dissipation of heat released by thermite reaction, reduced fusion degree of welding flux and parent metal, greatly reduced tensile strength and fatigue performance of the joint and serious influence on service quality of the steel rail. Meanwhile, the technical scheme of the prior published patent still has obvious defects that the welding requirement of U71Mn steel rails in a low-temperature environment is difficult to adapt, firstly, the corrosion-resistant thermite welding agent disclosed in the patent CN113894463B and suitable for U68CuCr steel rails is reinforced in corrosion resistance, but is not suitable for a U71Mn steel rail component system, and the welding joint is extremely poor in toughness in the low-temperature environment and is easy to have brittle fracture risk in a high-altitude low-temperature area, secondly, the thermite welding agent disclosed in the patent CN118321786A and suitable for 50kg/m U Mn hot rolled steel rails is designed only aiming at normal-temperature working conditions, and is lack of low-temperature adapting components and technology, and the welding joint is easy to have performance attenuation in the low-temperature environment and cannot meet the low-temperature construction quality requirement, thirdly, the alloy welding agent scheme (such as low-temperature welding agent containing bismuth alloy) in the related low-temperature welding field has the problems of poor mechanical property and thermal fatigue property, and the alloy brittleness is high, so that the service life of the welding joint is short and is difficult to be applied to such high-load scenes. At present, a perfect scheme is not formed by a formula and a manufacturing method of the special aluminum heat welding agent for the U71Mn steel rail aiming at low-temperature climate, so that development of a welding flux suitable for low-temperature environment is needed. Disclosure of Invention The invention aims to provide a U71Mn steel rail welding flux and a welding method under low-temperature weather, and U71Mn thermite welding construction is carried out by using the welding flux, so that the tensile strength of a welding joint is not lower than 730MPa even under the low-temperature weather environment, the fatigue performance reaches more than 3X 10 6 times, and the quality requirement of long-term service of the steel rail in the low-temperature area can be met. In order to solve the technical problems, the invention adopts the following technical scheme: The invention discloses a U71Mn steel rail welding flux under low-temperature weather, which is adapted to 880 MPa-level 50kg/m U Mn hot rolled steel rail, and comprises aluminum powder, ferric oxide, si iron powder, mn iron powder, cast iron balls and pure iron powder, wherein: aluminum powder accounting for 17.8 to 18 percent of the total weight, and the aluminum content is not less than 99 percent; Iron oxide accounting for 61.5 to 62.5 percent of the total weight and mainly comprising a mixture of FeO, fe 2O3 and Fe 3O4; Si iron powder accounting for 0.4 to 0.6 percent of the total weight, wherein the content of Si is not less than 70 percent, the content of Fe is not less than 29 percent and the content of carbon is less than 1 percent; mn iron powder accounting for 0.88 percent to 1.08 percent of the total weight, carbon content of 0.15 percent to 0.7 percent and manganese content of 65 percent to 75 percent; 7-8% of cast iron balls, and 4-4.5% of carbon; The rest is pure iron powder, which is 100 percent in total; The welding flux is used for U71Mn thermit welding construction, the tensile strength of a welding joint is still not lower than 730MPa even in