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CN-117535492-B - SiMn spring steel without full decarburization layer and manufacturing method thereof

CN117535492BCN 117535492 BCN117535492 BCN 117535492BCN-117535492-B

Abstract

The invention provides SiMn spring steel without a full decarburization layer and a manufacturing method thereof, wherein the manufacturing method comprises blank charging, heating, dephosphorization and rolling treatment, the heating treatment comprises a preheating section, a heating section I, a heating section II and a soaking section II, the temperature of the preheating section I is 600-800 ℃, the temperature of the heating section I is 1000-1100 ℃, the temperature of the heating section II is 1050-1200 ℃, and the temperature of the soaking section II is 1150-1250 ℃. The SiMn spring steel prepared by the manufacturing method has the thickness of 0 of the full decarburized layer, the thickness of the total decarburized layer meets the GB standard requirement, and the yield is more than or equal to 95%.

Inventors

  • WU ZHENG
  • SHI XIAOFENG
  • ZHENG WENCHAO
  • LI BOPENG
  • LV JIAHUI
  • WANG YANG
  • ZHONG WENQIANG
  • OU RONG

Assignees

  • 大冶特殊钢有限公司

Dates

Publication Date
20260512
Application Date
20230920

Claims (13)

  1. 1. The manufacturing approach of SiMn spring steel without all decarburization layer, characterized by, including blank charging, heat treatment, dephosphorization treatment and rolling treatment; The heating treatment comprises a preheating section, a heating section II and a soaking section, wherein the temperature of the preheating section is 600-800 ℃, the temperature of the heating section II is 1000-1090 ℃, the temperature of the heating section II is 1050-1200 ℃, and the temperature of the soaking section is 1150-1250 ℃; When the blanks are charged, the total heating time of each blank is shortened by adopting a mode of spacing 1-3 blanks between adjacent blanks; the total heating time of the heating treatment is 120-200 min; The air-coal ratio of the heating section is 0.5-1.5, the air-coal ratio of the heating section is 1.0-2.0, and the air-coal ratio of the soaking section is 2.0-3.0; The blank is a 60Si2Mn blank; The 60Si2Mn blank comprises, by weight, 0.56-0.64% of C, 1.5-2.0% of Si, 0.7-1.0% of Mn, less than or equal to 0.35% of Cr, less than or equal to 0.35% of Ni, less than or equal to 0.25% of Cu, less than or equal to 0.025% of P, less than or equal to 0.020% of S, and the balance of Fe and other irreducible elements.
  2. 2. The method according to claim 1, wherein the soaking period time of the heat treatment is 30 to 90 minutes.
  3. 3. The method according to claim 1, wherein the total residual oxygen concentration in the heating furnace is <3%.
  4. 4. The method of manufacturing according to claim 1, wherein the blank charging mode is cold blank charging; and/or a step-type heating furnace is adopted in the heating treatment.
  5. 5. The method according to claim 4, wherein the cold blank is obtained by cooling a normal-temperature stack.
  6. 6. The method according to claim 1, wherein the dephosphorization pressure is not less than 18MPa.
  7. 7. The method according to claim 1, wherein in the rolling treatment, a start rolling temperature is 1080 to 1180 ℃ and a finish rolling temperature is 850 to 950 ℃.
  8. 8. The method of manufacturing according to claim 1, wherein in the rolling process, the blank is rolled into flat or round steel.
  9. 9. The method according to claim 8, wherein the flat steel has a gauge of (6 to 40) mm× (60 to 150) mm, and the round steel has a gauge of from 16mm to 90mm.
  10. 10. The method according to claim 8, wherein the steel sheet has a total decarburized layer thickness of 0 and a total decarburized layer thickness of 1.5% or less of the thickness thereof, and the round steel sheet has a total decarburized layer thickness of 0 and a total decarburized layer thickness of 0.8% or less of the diameter thereof.
  11. 11. The method according to claim 1, wherein the ingot is a 60Si2Mn continuous cast ingot.
  12. 12. The method of manufacturing according to claim 11, wherein the strand gauge is 240mm x 240mm.
  13. 13. A SiMn spring steel without fully decarburized layer, characterized by being produced by the manufacturing process as claimed in any one of claims 1 to 12.

Description

SiMn spring steel without full decarburization layer and manufacturing method thereof Technical Field The invention relates to the technical field of smelting, in particular to SiMn spring steel without a full decarburization layer and a manufacturing method thereof. Background Spring steel has been widely used in the fields of automobiles, railways, engineering machinery, military industry, etc. In recent years, spring steel has been developed toward high strength, light weight, and long life due to the demand for the development of light weight automobiles. Surface decarburization is an important index affecting the fatigue life of spring steel, whereas total decarburization has a fatal effect on the fatigue life of spring steel. Because the thermal expansion coefficients of the full decarburized layer and the half decarburized layer are different, microcracks are easy to generate at the junction of the full decarburized layer and the half decarburized layer due to residual stress during quenching, and the microcracks can be rapidly expanded under the action of alternating stress in the using process of the spring so as to cause failure and fracture of the spring. The generation of a fully decarburized layer has been reported to result in a 50% reduction in the fatigue limit of the spring. SiMn series spring steels such as 60Si2Mn and 60Si2MnA are easy to decarbonize in the steel rolling production process due to higher C and Si contents, and particularly, full decarbonizing with larger influence on fatigue life is generated. There are many studies on reduction of the thickness of the decarburized layer of the SiMn spring steel, but most of the literature is experimental, and there are many cases where the total decarburized layer is simply reduced, and the total decarburized layer of the SiMn spring steel cannot be completely absent. Patent CN102560046a discloses a control method for decarburizing the surface of a spring steel wire, which achieves the purpose of controlling the whole decarburization layer-free cooling speed by controlling the heating temperature, the heating time, the furnace atmosphere, the toast temperature, but the method is suitable for producing 55SiCr wires and is not suitable for producing 60Si2Mn spring steel flat steel and bars. Patent CN113699335A discloses a method for manufacturing a high quality 60Si2Mn low decarburized layer, which reduces the total decarburized layer, but does not mention the effect of this method on the total decarburized layer. There are reports of reducing the decarburized layer of the SiMn spring steel by using the decarburized preventing coating, but this method is costly, complicated in process, and unsuitable for mass production. In view of this, the present invention has been made. Disclosure of Invention The invention aims to provide SiMn spring steel without a full decarburized layer and a manufacturing method thereof, wherein the manufacturing method is simple and easy to operate, is suitable for large-scale production and is low in cost, the thickness of the full decarburized layer of the obtained SiMn spring steel is 0, and the thickness of the total decarburized layer meets the GB standard requirement. In order to achieve the above purpose, the present invention provides the following technical solutions: The invention provides a manufacturing method of SiMn spring steel without a full decarburization layer, which comprises the steps of blank charging, heating treatment, dephosphorization treatment and rolling treatment; The heating treatment comprises a preheating section, a heating section and a soaking section, wherein the temperature of the preheating section is 600-800 ℃, the temperature of the heating section is 1000-1100 ℃, the temperature of the heating section is 1050-1200 ℃, and the temperature of the soaking section is 1150-1250 ℃. Further, when the blanks are charged, the total heating time of each blank is shortened by adopting a mode of spacing 1-3 blanks between adjacent blanks, and the total heating time of the heating treatment is preferably 120-200 min. Further, the soaking period time of the heating treatment is 30-90min. Further, the air-coal ratio of the heating section is 0.5-1.5, the air-coal ratio of the heating section is 1.0-2.0, and the air-coal ratio of the soaking section is 2.0-3.0; And/or the total residual oxygen concentration in the heating furnace is <3%. Further, the blank charging mode is cold blank charging, preferably, the cold blank is obtained after cold cooling of a normal-temperature stack; and/or a step-type heating furnace is adopted in the heating treatment. Further, in the dephosphorization treatment, the dephosphorization pressure is more than or equal to 18MPa. Further, in the rolling treatment, the initial rolling temperature is 1080-1180 ℃ and the final rolling temperature is 850-950 ℃. Further, in the rolling process, the blank is rolled into a flat or round steel; preferably, the specificati