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CN-122012858-A - Method for improving maximum tensile resistance stability of extra-high voltage insulator steel feet

CN122012858ACN 122012858 ACN122012858 ACN 122012858ACN-122012858-A

Abstract

The invention belongs to the technical field of steel rolling and forging processing, and discloses a method for improving the maximum tensile resistance stability of an extra-high voltage insulator steel foot, wherein the steel grade is 45Mn2, and the production process comprises converter smelting, LF refining, RH vacuum treatment, continuous casting, rolling, straightening, blanking, forging and cooling. By controlling the steelmaking DiZ value, rolling steel, controlling out-of-roundness and dimensional tolerance, straightening and controlling the bending degree of a material, and controlling the final forging temperature and cooling rate after forging, the stability of the maximum tensile force of the insulator steel feet among different batches can be greatly improved, and the fluctuation range of the maximum tensile force is controlled within +/-4.5 KN compared with a reference value.

Inventors

  • Pang Zhuochun
  • FENG HAIRUI
  • DENG XIANGYANG

Assignees

  • 中天钢铁集团有限公司
  • 常州中天特钢有限公司

Dates

Publication Date
20260512
Application Date
20260213

Claims (5)

  1. 1. A method for improving the maximum tensile resistance stability of a steel foot of an extra-high voltage insulator is characterized in that the steel is 45Mn2, comprises ：C 0.42-0.49％,Si 0.17-0.37％,Mn 1.20-1.80％,Cr ≤0.30％,Ni ≤0.30％,Mo ≤0.10％,Cu ≤0.30％,V ≤0.05％,Zr ≤0.05％, parts by mass of Fe and unavoidable impurities, and comprises the following steps of converter smelting, LF refining, RH vacuum treatment, continuous casting, rolling, straightening, blanking, forging and cooling; The LF previous procedure does not need to specially control residual elements such as Cr, ni, mo and the like, and the DiZ value is controlled to be 53.5-57.5 mm in the final stage of LF refining, wherein the DiZ value =25.4*(0.265*[C]*[C]+0.001*[C]+0.171)*(0.7*[Si]+1)*(5.1*[Mn]-1.12)*(2.16*[Cr]+1)*(0.363*[Ni]+1)*(3*[Mo]+1)*(0.365*[Cu]+1)*(1.73*[V]+1)*(1+2.5*[Zr]),[X] is the mass content of metal elements, and X represents the metal elements; sampling and assaying molten steel components before RH vacuum treatment, and controlling targets to be 55.0-56.0 mm by feeding carbon wires and manganese metals or prolonging vacuum treatment time to finely adjust DiZ values according to the combination of DiZ values of real-time components; control of rolling process finished products the dimensional accuracy is +/-0.1 mm, the non-roundness is less than or equal to 0.15mm; Steel material controlled by straightening process the curvature is less than or equal to 1.5mm/m; the final forging temperature is controlled to be 910-950 ℃; Immediately placing the steel feet into an insulation box with a cover plate for cooling after forging, controlling the cooling rate to be less than or equal to 62 ℃ per hour, and opening the cover plate for cooling when the temperature of the steel feet reaches 300 ℃.
  2. 2. The method for improving the maximum tensile stability of the extra-high voltage insulator steel foot according to claim 1, wherein if the value of the molten steel DiZ before breaking by RH vacuum treatment is lower than 55.0, a carbon wire is fed or metal manganese is added, the value of DiZ is increased to 55.0-56.0, if the value of the molten steel DiZ before breaking by RH vacuum treatment is higher than 56.0, the vacuum treatment time is prolonged, the flow rate of lifting gas is matched and adjusted, the value of DiZ is reduced to 55.0-56.0, and if the value of DiZ is between 55.0-56.0, the adjustment is not needed.
  3. 3. The method for improving the maximum tensile stability of the steel feet of the extra-high voltage insulator according to claim 1, wherein the insulation box comprises a box body and a cover plate, the cover plate covers the opening end of the box body, and a through hole is formed in the cover plate.
  4. 4. The method for improving the maximum tensile stability of the steel feet of the extra-high voltage insulator according to claim 1 or 3, wherein the box body and the cover plate of the insulation box are of a three-layer structure, the outermost layer is made of steel, the middle layer is a heat-insulating layer, and the inner layer is a heat-resisting layer.
  5. 5. The method for improving the maximum tensile strength stability of the extra-high voltage insulator steel leg according to claim 1, wherein the extra-high voltage insulator steel leg is 840 (760) in strength grade.

Description

Method for improving maximum tensile resistance stability of extra-high voltage insulator steel feet Technical Field The invention belongs to the technical field of steel rolling and forging processing, and particularly relates to a method for improving the maximum tensile resistance stability of an extra-high voltage insulator steel foot. Background In order to improve the transmission capacity of the power line and reduce the energy loss, research and development of the extra-high voltage line are performed in various countries, and as the diameter of the extra-high voltage line is larger and larger, the weight is correspondingly increased, and insulators with higher strength grades are required to be adopted to reduce the number of the insulators used in the line, reduce the load of a pole tower, simplify the line connection and improve the safety coefficient of the line. The development of extra-high voltage technology puts higher demands on the insulator industry, and currently, 840 (760) strength grade insulators are the highest grade insulators at home and abroad. The extra-high voltage insulator steel feet are used as core bearing connecting pieces between insulator strings and towers in overhead transmission lines and bear multiple mechanical stresses such as wire tension, wind load, ice and snow load, vibration fatigue and the like for a long time, and the mechanical properties, especially the stability of the maximum tensile resistance, are directly related to the safe operation of the whole line. 840 The (760) strength grade steel foot needs to have good toughness while ensuring enough strength, and the uniformity of the performance is important. The mechanical strength of each part of the insulator is matched with that of a glass piece, an adhesive, an iron cap and a steel foot in sequence from high to low. The mechanical properties of the steel feet are the mechanical properties that the final insulator string can carry. Currently, in production and application, the maximum tensile resistance of the steel feet of the model still has certain fluctuation, and can cause early failure or performance redundancy of individual components in actual service, thereby becoming potential safety hazards and quality control difficulties of the ultra-high voltage electric network. From the current situation at home and abroad, the manufacture of the high-end insulator steel feet is forward to the direction of high strength, high consistency and high durability. The international advanced enterprises realize narrow fluctuation of the mechanical properties of products through refined material design and overall process control. In contrast, domestic production still has room for improvement in terms of the structural uniformity of the base material and the process stability, and particularly, how to systematically control the parameter dispersion degree of each link from smelting, rolling to hot working is a challenge commonly faced by the industry. Disclosure of Invention The invention provides a method for improving the stability of the maximum tensile force of a steel foot of an extra-high voltage insulator with 840 (760) strength grade, which aims to control the out-of-roundness and dimensional tolerance by controlling DiZ values, straighten the bending degree of a control material, control the final forging temperature and cooling rate after forging, and control the performance fluctuation range within +/-4.5 KN so as to meet the severe requirements of an extra-high voltage transmission project on the reliability of key parts. The technical scheme adopted for realizing the purpose of the invention is that the method for improving the maximum tensile resistance stability of the steel foot of the 840 (760) strength grade extra-high voltage insulator comprises the following procedures of converter smelting, LF refining, RH vacuum treatment, continuous casting, rolling, straightening, blanking, forging and cooling; (1) The converter tapping does not need to specially control residual elements such as Cr, ni, mo and the like, the types of scrap steel are not limited, the scrap steel ratio and the molten iron ratio can be freely matched according to the production rhythm, and the DiZ value is controlled to be 53.5-57.5 mm at the end of LF refining; wherein DiZ value =25.4*(0.265*[C]*[C]+0.001*[C]+0.171)*(0.7*[Si]+1)*(5.1*[Mn]-1.12)*(2.16*[Cr]+1)*(0.363*[Ni]+1)*(3*[Mo]+1)*(0.365*[Cu]+1)*(1.73*[V]+1)*(1+2.5*[Zr]),[X] is the mass content of the metal element, and X represents the metal element. LF refining can flexibly fine tune main elements C, mn and Cr according to the content of residual elements of molten steel, so that LF outbound DiZ values hit the required range. The raw material requirements on the converter procedure are released, the production cost can be reduced, and the production efficiency of the converter can be improved. (2) Sampling and assaying molten steel components before RH vacuum treatment