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CN-116904849-B - Non-quenched and tempered cold-forging steel with excellent corrosion resistance and production method thereof

CN116904849BCN 116904849 BCN116904849 BCN 116904849BCN-116904849-B

Abstract

The invention provides a non-quenched and tempered cold-heading steel with excellent corrosion resistance and a production method thereof, wherein the components comprise, by weight, 0.21% -0.30% of C, 0.02% -0.1% of Si, 1.8% -2.5% of Mn, 0.05% -0.20% of V, 0.0005% -0.0030% of B, 0.02% -0.04% of Ti, 0.1% -0.3% of Cr, 0.1% -0.3% of Ni, 0.1% -0.3% of Cu, 0.015% -0.035% of Alt, less than or equal to 0.010% of P, less than or equal to 0.010% of S, less than or equal to 0.0020% of T.O, less than or equal to 0.0065% of N, and the balance of Fe and other unavoidable impurities; compared with the prior art, the invention has the advantages that through component design and process optimization, the austenite grain size of the product is more than or equal to 11.0 level, the product has good strength and plastic toughness, and simultaneously has good atmospheric corrosion resistance, and spheroidizing annealing and tempering can be omitted.

Inventors

  • YIN DEFU
  • MOU ZUMAO
  • HAO JIE
  • WANG KAIZHONG
  • ZHANG XIAORUI
  • DING LEI
  • XIE ZHAOYUAN
  • JIANG TING
  • GUO ZHAN
  • YU LIANGQI
  • TANG PENG

Assignees

  • 马鞍山钢铁股份有限公司

Dates

Publication Date
20260508
Application Date
20230630

Claims (9)

  1. 1. The non-quenched and tempered cold-heading steel with excellent corrosion resistance is characterized by comprising the following components in percentage by mass: C 0.21%～0.30%、Si 0.02%～0.1%、Mn 1.8%～2.5%、V 0.05%～0.20%、B 0.0005%～0.0030%、Ti 0.02～0.04%、Cr 0.1～0.3%、Ni 0.1～0.3%、Cu 0.1～0.3%、Alt 0.015%~0.035%、P ≤0.010%、S ≤0.010%、T.O≤0.0020%、N≤0.0065%, The balance of Fe and other unavoidable impurities; the non-quenched and tempered cold heading steel with excellent corrosion resistance also satisfies that the composition of 4.5 is less than or equal to 15 XCr+10× (Ni+Cu) +20XTi is less than or equal to 10.0; The hot-rolled microstructure of the non-quenched and tempered cold heading steel with excellent corrosion resistance is a granular bainite/ferrite dual-phase structure, and the tensile strength is 860MPa or more and R m MPa or more and 800MPa or more; After the non-quenched and tempered cold heading steel with excellent corrosion resistance is subjected to drawing and stabilizing treatment, the tensile strength R m is more than or equal to 1020MPa, the yield ratio R P0.2 /R m is more than or equal to 0.9, the elongation after fracture A is more than or equal to 15%, the area shrinkage Z is more than or equal to 52%, the room temperature impact energy KV 2 is more than or equal to 52J, and the austenite grain size of the steel is more than or equal to 11.0 levels.
  2. 2. A production method of non-quenched and tempered cold-forging steel with excellent corrosion resistance according to claim 1, which is characterized by comprising the following technological processes of proportioning, electric furnace smelting, LF furnace refining and RH vacuum refining, bloom continuous casting, square bloom rolling, finishing and peeling, heating, large coil wire rod rolling, steyr cooling line controlled cooling, large coil finished product packaging and warehousing according to the component proportion.
  3. 3. The production method of the ladle furnace is characterized in that ladle bottom argon is blown in the whole process of ladle refining, argon flow is based on the condition that molten steel does not splash the ladle, premelted refining slag and lime are added for slag making, the alkalinity is R3-5, and the white slag time is more than or equal to 20 minutes.
  4. 4. The production method according to claim 2, wherein the RH vacuum degassing is performed at the early stage of vacuum, the vacuum holding time is more than or equal to 10 minutes if the vacuum degree is less than or equal to 100 Pa, the vacuum holding time is more than or equal to 15 minutes if the vacuum degree is less than or equal to 100 Pa, the vacuum holding time is more than or equal to 10 minutes at the later stage, and the soft argon blowing treatment is performed before the vacuum degassing is performed at the outlet, wherein the soft argon blowing time is more than or equal to 15 minutes.
  5. 5. The production method according to claim 2, wherein the bloom continuous casting is carried out by adopting a bloom continuous casting with the thickness of 380mm multiplied by 450mm, the whole process is protected and cast, a protective sleeve and an argon seal are adopted between a ladle and a tundish, the tundish is protected by adopting a molten steel covering agent and argon blowing, a submerged nozzle is adopted between the tundish and a crystallizer, the primary cooling water flow is 100-130 m 3 /h, the secondary cooling specific water flow is 1.0-1.4 l/kg, the superheat degree is controlled to be 15-30 ℃, and the pulling speed is 1.9-2.1mm/min.
  6. 6. The production method according to claim 2, wherein the square billets are rolled by adopting 150 square billets, the temperature of the square billets in a soaking section of a heating furnace is controlled to 1250-1350 ℃, the total heating time is controlled to 250-350 min, the initial rolling temperature is controlled to 1100+/-50 ℃, and the stack cooling temperature after rolling is more than or equal to 400 ℃.
  7. 7. The production method according to claim 3, wherein the large coil wire is rolled, the rolling deformation is more than or equal to 50%, the initial rolling temperature is 970-1030 ℃, the final rolling temperature is 760-800 ℃, then the large coil wire enters an LCC roller way to be cooled under control, the cooling rate is 4-7 ℃ per second to 450-500 ℃ and then is slowly cooled, the cooling rate is 0.7-1.0 ℃ per second, the temperature of a heat preservation tunnel is kept to 400-440 ℃, and then the large coil wire is cooled to room temperature.
  8. 8. The method according to any one of claims 2 to 7, wherein the hot-rolled microstructure of the non-quenched and tempered cold-forging steel having excellent corrosion resistance is a granular bainite+ferrite dual-phase structure, and the tensile strength is 860MPa or more R m MPa or more 800MPa or more.
  9. 9. The method according to any one of claims 2 to 7, wherein the non-quenched and tempered cold-forging steel having excellent corrosion resistance is produced, after drawing and stabilizing, to have a tensile strength R m to or higher than 1020MPa, a yield ratio R P0.2 /R m to or higher than 0.9, an elongation after break A to or higher than 15%, a reduction of area Z to or higher than 52%, an impact energy at room temperature KV 2 to or higher than 52J, and an austenite grain size of the steel to or higher than 11.0.

Description

Non-quenched and tempered cold-forging steel with excellent corrosion resistance and production method thereof Technical Field The invention belongs to the technical field of non-quenched and tempered cold-forging steel, and particularly relates to non-quenched and tempered cold-forging steel with excellent corrosion resistance and a production method thereof. Background The fastener is the most common general basic member which is very important and has a large range, is widely applied to the industries of machinery manufacturing, engineering structures, railways, automobiles, tractors, buildings and the like, and about 70 percent of the connected members and combined devices are connected by the fastener. The fastener is mainly formed by cold heading, the total deformation of the material is required to be up to 70-80% in the manufacturing process, and the material is required to have better plasticity and low hardness before cold heading, so that the cold-headed steel wire produced by the traditional process needs to be subjected to two heat treatment procedures of time-consuming and energy-consuming spheroidizing annealing and tempering before cold heading and drawing. In recent years, under the pressure of energy conservation and cost reduction, a fastener manufacturer is urgent to develop a novel energy-saving cold heading steel wire rod capable of omitting quenching and tempering and spheroidizing annealing before drawing in place of quenched and tempered steel, so that energy can be saved, and the highest electric energy per ton of steel can be saved by 2500 kw.h according to statistics. At present, the same quenched and tempered steel level is achieved mainly by adopting microalloying, rolling control and cooling control and cold work hardening at home and abroad. The cold work reinforced non-quenched and tempered steel is researched and developed in the 80 s of the last 20 th century internationally, and the non-quenched and tempered cold heading steel is developed successfully in China, can be used for producing fasteners with small deformation such as screws, tooth bars and the like, and is mainly oriented to the mechanical and building industries. However, with the rapid development of construction and construction industry, the use environment of the fastener is more and more complex, so that the fastener is required to have good mechanical properties, corrosion resistance and meet the use requirement of the complex environment. Patent publication number CN 106480376A published in 3.8 of 2017 discloses a non-quenched and tempered cold heading steel wire rod for a 10.9-grade fastener and a production method. The components and weight percentage of the non-quenched and tempered cold heading steel wire rod for the 10.9-grade fastener are ：C0.10～0.15％;Si 0.50～0.80％;Mn 1.60～2.10％;P≤0.015％;S≤0.010％;Cr0.30～0.50％;B 0.002～0.005％％,Ti 0.03～0.05％,, unavoidable impurities are not higher than 0.1%, the balance is iron, the accurate control of the wire rod structure and performance is realized through the accurate design of alloy components, the cooperation of smelting, continuous casting and rolling and wire rod controlled rolling and controlled cooling process, the produced non-quenched and tempered cold heading steel wire rod for the 10.9-grade fastener has uniform components, the structure is granular bainite, the sufficient strength and better cold drawing property are achieved, and the production of the 10.9-grade high-strength fastener by adopting the non-quenched and tempered process is satisfied. But the fasteners produced by this method do not have good corrosion resistance. The patent with publication number CN112359275A published in 2 months of 2021 discloses a non-quenched and tempered cold-heading steel wire rod for high-strength fasteners and a preparation method thereof, wherein the composition of the non-quenched and tempered cold-heading steel wire rod is C：0.16～0.18％,Si：≤0.20％,Mn：1.40～1.50％,P：≤0.008％,S：≤0.008％,Ti：0.05～0.06％,V：0.10～0.13％,Al：≤0.01％,N：60～90ppm,, and the balance of Fe and unavoidable impurities. The preparation method comprises converter smelting, LF refining, billet continuous casting and wire rod rolling. The method has the advantages that through optimizing the component design of elements in the components and adopting an innovative smelting process and combining an advanced rolling and cooling control technology, the strength and plasticity of steel are effectively improved, the production of a 10.9-level high-strength fastener without annealing and tempering is realized, and the processing cost of downstream industries is remarkably reduced. But the fasteners produced by this method do not have good corrosion resistance. Therefore, it is necessary to provide economical, high strength and corrosion resistant non-quenched and tempered cold-heading steel products. Disclosure of Invention The invention aims to provide non-quenched and tempered cold-heading steel with excelle