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CN-121977902-A - Method for reducing occurrence frequency of abnormal fracture of ball head during tensile test of insulator steel feet

CN121977902ACN 121977902 ACN121977902 ACN 121977902ACN-121977902-A

Abstract

The invention relates to a method for reducing the occurrence frequency of abnormal fracture of a bulb during tensile test of a steel foot of an insulator, belonging to the technical field of steel milling and forging processing, and aiming at solving the problem of high abnormal fracture frequency caused by insufficient genetic control of a whole-flow structure in the prior art. The technical scheme is characterized in that 45Mn2 steel with specific components is adopted, and the flow line and the structure of a high stress area of the ball head are stabilized through the cooperative control of key processes such as large-section casting blank and electromagnetic stirring in a continuous casting process, cold charging into a furnace and high-temperature heating, initial forging temperature control, twice forming forging of the ball head, dispersing cooling after forging and the like. The invention is mainly used for manufacturing insulator steel feet for high-voltage and ultra-high voltage transmission lines, and reduces the abnormal breaking frequency of the ball head to less than or equal to 2 times per million.

Inventors

  • Pang Zhuochun
  • ZHOU YING
  • DENG XIANGYANG

Assignees

  • 常州中天特钢有限公司
  • 中天钢铁集团有限公司

Dates

Publication Date
20260505
Application Date
20260203

Claims (10)

  1. 1. The method for reducing the occurrence frequency of abnormal fracture of the bulb during tensile test of the insulator steel foot is characterized in that the steel foot is made of 45Mn2 steel, and the 45Mn2 steel comprises the following components in percentage by mass: C 0.42～0.49%,Si 0.17～0.37%,Mn 1.20～1.80%,P ≤0.030%,S ≤0.030%,Cr ≤0.30%,Ni ≤0.30%,Mo ≤0.10%,Cu ≤0.30%,V ≤0.05%,Zr ≤0.05%, The balance of Fe and unavoidable impurities; The method comprises the following working procedures of converter smelting, LF refining, RH vacuum treatment, continuous casting, rolling, blanking, forging and cooling which are sequentially carried out, wherein: (1) In the continuous casting process, adopting continuous casting blank section and rolling ratio capable of obtaining enough deformation, and applying crystallizer electromagnetic stirring to optimize the internal structure uniformity of the casting blank; (2) The continuous casting blank before rolling is loaded into a furnace in a cold way, and the heating temperature and time are controlled in the rolling heating process so as to realize the sufficient homogenization of the structure and the components of the casting blank; (3) When the ball head is forged, the initial forging temperature is controlled to keep the plasticity of the material and prevent uneven deformation; (4) The ball head is forged by twice forming, deformation distribution is controlled, and lubricant is used in the last forming to ensure smooth filling of metal streamline; (5) The forged steel feet are dispersed and cooled to prevent abnormal structures from being precipitated.
  2. 2. The method for reducing the occurrence frequency of abnormal fracture of a ball head in the tensile test of an insulator steel foot according to claim 1, wherein in the step (1), the section of a continuous casting blank is 225mm multiplied by 270mm, the diameter of a rolled finished product is phi 28mm, and the rolling ratio is 98.7.
  3. 3. The method for reducing the occurrence frequency of abnormal ball head fracture during tensile testing of an insulator steel foot according to claim 1, wherein in the step (1), the electromagnetic stirring current of the crystallizer is 340-380A, and the frequency is 7-10 Hz.
  4. 4. The method for reducing the occurrence frequency of abnormal fracture of the ball head in the tensile test of the insulator steel foot according to claim 1, wherein in the step (2), the heating temperature of the two heating sections and the soaking section of rolling heating is 1190-1240 ℃, and the total heating time is 160-260 min.
  5. 5. The method for reducing the occurrence frequency of abnormal fracture of a bulb during tensile testing of an insulator steel foot according to claim 1, wherein in the step (3), the initial forging temperature of bulb forging is 990-1100 ℃.
  6. 6. The method for reducing the occurrence frequency of abnormal fracture of a ball head in the tensile test of an insulator steel foot according to claim 1, wherein in the step (4), the first forging ratio of the two-time forming process is 1.9-2.4, the total forging ratio is more than or equal to 3.5, and the lubricant is a graphite-based lubricant.
  7. 7. The method for reducing the occurrence frequency of abnormal breakage of the bulb during tensile testing of the insulator steel feet, which is disclosed in claim 1, is characterized in that in the step (5), the forged steel feet are scattered and cooled on a cooling roller way in sequence one by one, the head and the tail are not connected, and the bulb falls into a collecting box after the temperature of the bulb is reduced to below 500 ℃.
  8. 8. The method for reducing the occurrence frequency of abnormal ball head fracture during tensile test of the insulator steel feet according to claim 3, wherein the electromagnetic stirring current of the crystallizer is 360A, and the frequency is 8Hz.
  9. 9. The method for reducing the occurrence frequency of abnormal ball fracture in the tensile test of the steel feet of the insulator according to claim 6, wherein the first forging ratio is 2.3, and the total forging ratio is 4.1.
  10. 10. The method for reducing the occurrence frequency of abnormal ball fracture during tensile testing of an insulator steel foot according to claim 5, wherein the initial forging temperature is 1060 ℃.

Description

Method for reducing occurrence frequency of abnormal fracture of ball head during tensile test of insulator steel feet Technical Field The invention relates to the technical field of steel rolling and forging processing, in particular to a method for reducing the occurrence frequency of abnormal breakage of a bulb during tensile testing of an insulator steel foot. Background The insulator steel feet are key bearing components in high-voltage and extra-high voltage transmission lines, and the reliability of the insulator steel feet is directly related to safe and stable operation of a power grid. The failure of the insulator steel foot can be divided from two dimensions of an occurrence stage and a failure mechanism, and mainly comprises failure exposed in a manufacturing stage and a test stage, such as abnormal fracture in a tensile test, unqualified hardness and metallographic structure and the like, failure in a long-term service process, such as fatigue fracture, stress corrosion fracture, overload fracture and the like, and failure related to connection and assembly, such as screw failure, mismatching or abrasion of ball-socket connection and the like. Wherein, the abnormal fracture of the tensile test is closely related to the process control of a steel mill and a forging mill. This defect results in the actual load carrying capacity of the steel foot being far below the design value, and the fracture being abrupt and hidden, constituting a significant safety hazard. The method is characterized in that under extreme climate or uneven load, individual steel feet can be broken suddenly, so that the whole string of insulators falls off and the wires fall down to cause major power grid accidents, the fallen wires and insulator strings can also cause personal injury, equipment damage and secondary disasters, in addition, as a key structural member, frequent quality problems can seriously damage brand reputation of manufacturing enterprises, and the admittance qualification is lost in high-end market competition such as ultra-high voltage. At present, the quality control of high-strength steel feet by most enterprises at home and abroad still mainly stays on the detection of the size and the conventional mechanical properties of the final forging piece, and the knowledge of the tissue genetic control of the whole process is insufficient. The technology aims to break through the technical barriers that the internal quality (especially the streamline and organization in the high stress area) of the product is unstable and the batch difference is large, and reduce the abnormal breaking frequency of the insulator steel foot ball head in the tensile test, thereby providing reliable guarantee for the construction and the safe operation of the power grid. Disclosure of Invention The invention aims to solve the technical problems that: in order to overcome the defects of insufficient genetic control on the whole flow structure of the insulator steel foot and unstable internal quality of products in the prior art and high abnormal breaking frequency of the bulb during the tensile test, the method for reducing the occurrence frequency of abnormal breaking of the bulb during the tensile test of the insulator steel foot is provided, the method optimizes the electromagnetic stirring parameters of a crystallizer by reasonably selecting the rolling ratio, the cold charge and high temperature heating system is adopted, forging start forging temperature, ball head forging deformation distribution and cooling after forging are controlled, so that streamline and organization of a high stress area at the joint of a ball head R angle and a rod part are stabilized, the occurrence frequency of abnormal breakage of the ball head is reduced to less than or equal to 2 times per million parts, and the severe requirement of power transmission engineering on the reliability of the insulator steel foot is met. The technical scheme adopted for solving the technical problems is that the method for reducing the occurrence frequency of abnormal fracture of the bulb during tensile test of the insulator steel foot is characterized in that the steel foot is made of 45Mn2 steel, and the 45Mn2 steel comprises the following components in percentage by mass: C 0.42～0.49%,Si 0.17～0.37%,Mn 1.20～1.80%,P ≤0.030%,S ≤0.030%,Cr ≤0.30%,Ni ≤0.30%,Mo ≤0.10%,Cu ≤0.30%,V ≤0.05%,Zr ≤0.05%, The balance of Fe and unavoidable impurities; The method comprises the following working procedures of converter smelting, LF refining, RH vacuum treatment, continuous casting, rolling, blanking, forging and cooling which are sequentially carried out, wherein: (1) In the continuous casting process, adopting continuous casting blank section and rolling ratio capable of obtaining enough deformation, and applying crystallizer electromagnetic stirring to optimize the internal structure uniformity of the casting blank; (2) The continuous casting blank before rolling adopts a cold