CN115433871B - High-strength steel resistant to hydrogen embrittlement delayed fracture and manufacturing method thereof - Google Patents
High-strength steel resistant to hydrogen embrittlement delayed fracture and manufacturing method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/32—Soft annealing, e.g. spheroidising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
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- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Abstract
The invention provides hydrogen embrittlement-resistant delayed fracture high-strength steel, which comprises the following chemical components in percentage by mass: c:0.38-0.48%, si:0.03-0.12%, mn:0.23-0.43%, cr:1.00-1.40%, mo:0.30-0.50%, ni:0.15-0.40%, V:0.18-0.35%, nb:0.02-0.12%, al:0.025-0.045%, N: less than or equal to 0.0050 percent, and the balance of Fe and unavoidable impurities. Through the control of alloy components, structure and steel purity, the hydrogen embrittlement resistance delayed fracture performance is improved, the sensitivity to hydrogen embrittlement is reduced, and the hydrogen embrittlement resistance delayed fracture performance is excellent. The invention also provides a manufacturing method of the steel, which comprises smelting, casting, rough rolling, high-speed wire rod rolling, stelmor controlled cooling, spheroidizing or tempering heat treatment, drawing or straightening, cold heading and tempering heat treatment or turning. Can process high-strength steel of high-strength fasteners and other parts with the pressure of more than 1200MPa, and ensures safe and long-time use.
Description
Technical Field
The invention belongs to the field of metal materials, and particularly relates to high-strength steel with hydrogen embrittlement resistance and delayed fracture resistance and a manufacturing method thereof.
Background
The fastener is a general term of mechanical parts adopted when two or more parts (or components) are fastened and connected into a whole, is a mechanical base part with the widest application range and the largest use quantity in various departments of national economy, has the name of industrial meters, has the advantages of simplicity, convenience, multiple disassembly and reassembly, high standardization degree, low cost and the like, and uses various and considerable fasteners on various mechanical equipment, vehicles and ships, aircraft satellites, railway bridges, building structures, tool instruments, articles for daily use and the like. Currently global fasteners are mainly used in the automotive industry, the electronics industry, and the construction and maintenance industry. Of these, the automotive industry is the largest consumer, with demand being about 23.2% of the total sales of fasteners; secondly, the maintenance industry market and the construction industry account for about 20% of the total sales of the fastener; the third is the electronics industry, accounting for about 16.6% of the total sales of fasteners. The automobile high-strength fastener has four performance grades, namely 8.8, 9.8, 10.9 and 12.9, and high-strength (more than 8.8) bolts are manufactured by adopting medium carbon or medium carbon alloy steel and subjected to quenching and tempering at high temperature to ensure that the product has enough strength and yield ratio because the bolts need to bear larger load and the stress state is very complex.
The automobile, mechanical and construction industries also use a large number of pin, connecting rod and shaft parts, which are processed by adopting high-strength steel, and the parts also require high strength to reduce the size of parts and improve the connection strength, and the parts are similar to the application environment of fasteners, often need to bear higher load or work under severe alternating stress, are extremely easy to rust and corrode to cause hydrogen permeation when contacted with atmosphere, water and corrosive liquid, and generate unpredictable delayed destructive fracture in the use process of the parts, so that the parts have great potential safety hazard.
The delayed fracture phenomenon is an environmental embrittlement caused by material-environment-stress interactions, and is a form of deterioration of hydrogen-induced materials (hydrogen damage or hydrogen embrittlement). The delayed fracture phenomenon is caused by diffusion and aggregation of hydrogen in the part to a stress concentration part, and the metal defects (dislocation of an atomic lattice, holes and the like) in the stress concentration part are numerous. The diffusion of hydrogen into these defects, the hydrogen atoms become hydrogen molecules, creating a great pressure that, together with the residual stresses inside the material and the external stresses to which the material is subjected, constitute a resultant force that, when exceeded the yield strength of the material, causes the fracture to occur. Hydrogen embrittlement since it is associated with the diffusion of hydrogen atoms, the diffusion is time-consuming, and the rate of diffusion is related to the gradient of concentration, temperature and material type. Thus, hydrogen embrittlement generally manifests itself as delayed fracture. The steel used in practice is mainly tempered martensitic steel which undergoes delayed fracture in natural environment and generally has the following characteristics: when the tensile strength is more than 1200MPa and the hardness HRC is more than or equal to 38, the sensitivity of delayed fracture is obviously increased; delayed fracture usually occurs near room temperature, but from room temperature to around 100 ℃, the sensitivity of delayed fracture increases with increasing temperature; macroscopically, delayed fracture is not accompanied by large plastic deformation; occurs under static load (strain rate zero); occurs at much lower stresses than the yield strength.
The automobile, bridge and machinery industries use a large amount of high-strength fasteners with the level of more than 8.8 and parts such as high-strength connecting rods, pins, shafts and the like, when the use strength of the parts reaches more than 1200MPa, hydrogen embrittlement delay fracture is very easy to generate, the damage of the high-strength steel parts is sudden and unpredictable, the fracture is instantaneous, and the fracture is a very unsafe point for the application of the high-strength steel, so that the hydrogen embrittlement delay fracture resistance of the products is very needed to be improved, and the safety use requirements of various industries are met.
Patent publication 202010604975.0 discloses a round steel for bolts excellent in corrosion resistance and delayed fracture resistance, which has a carbon content of 0.55-0.60%, and is added with a large amount of Si element to 1.80-2.00%, and also with Cu element to 0.20-0.35%, and is difficult in decarburization control and cracking control during alloy hot rolling and heat treatment, and is poor in formability of processed bolts.
Patent publication 201810357699.5 discloses a high-strength bolt steel with excellent atmospheric corrosion resistance and delayed fracture resistance, which is added with 0.30-1.20% of Ni and 0.20-0.60% of Cu, and simultaneously added with 0.005-0.030 of Re rare earth element, and has high alloy cost and great smelting control difficulty.
Patent publication 201911230974.8 discloses a steel for a high-strength bolt with high atmospheric corrosion resistance and 14.9 grade containing niobium and titanium, wherein the Mo content is 0.80-1.00%, and a large amount of V, nb, ti, cr, cu elements are added, so that the production difficulty of the alloy is high, the cost is high, and the performance stability of a processed part is poor.
Disclosure of Invention
In order to solve the problems, the invention relates to high-strength steel resistant to hydrogen embrittlement delayed fracture, which obviously improves the hydrogen embrittlement delayed fracture resistance through alloy composition, optimal design and tissue and steel purity control, reduces the sensitivity of processed parts to hydrogen embrittlement in the use process and has excellent hydrogen embrittlement delayed fracture resistance. The high-strength steel can be used for processing high-strength fasteners with the pressure of more than 1200MPa and other parts such as connecting rods, pins, shafts and the like, can ensure the safety and long-time use of the processed parts, can be safely and effectively used in hydrogen environment, and can meet the use requirements of automobile, machinery and building industries.
The invention provides hydrogen embrittlement-resistant delayed fracture high-strength steel, which comprises the following chemical components in percentage by mass:
c:0.38-0.48%, si:0.03-0.12%, mn:0.23-0.43%, cr:1.00-1.40%, mo:0.30-0.50%, ni:0.15-0.40%, V:0.18-0.35%, nb:0.02-0.12%, al:0.025-0.045%, N: less than or equal to 0.0050 percent, and the balance of Fe and unavoidable impurities.
According to another embodiment of the invention, the embodiment of the invention discloses the high-strength steel with hydrogen embrittlement resistance and delayed fracture, wherein the size of carbon and nitrogen precipitates of V, nb of the high-strength steel with hydrogen embrittlement resistance and delayed fracture is less than 70nm, and the austenite grain size of the material is less than 60um.
According to another specific embodiment of the invention, the high-strength steel with hydrogen embrittlement resistance and delayed fracture disclosed by the embodiment of the invention further comprises the following chemical components in percentage by mass: 2.ltoreq.V/Nb, and (V+Nb), (C+N). Ltoreq.0.16; al/(O+N) > 5.
According to another embodiment of the present invention, a high strength steel resistant to hydrogen embrittlement delayed fracture disclosed in the embodiment of the present invention, unavoidable impurities include: cu: less than or equal to 0.02 percent, P: less than or equal to 0.010 percent, S: less than or equal to 0.010 percent, O: less than or equal to 0.0008 percent.
According to another specific embodiment of the invention, the high-strength steel with hydrogen embrittlement resistance and delayed fracture disclosed by the embodiment of the invention further comprises the following chemical components in percentage by mass: mn/S > 35.
According to another specific embodiment of the invention, the high-strength steel resistant to the hydrogen embrittlement delayed fracture disclosed by the embodiment of the invention has a microstructure of refined tempered sorbite structure, and the strength of the high-strength steel resistant to the hydrogen embrittlement delayed fracture is more than or equal to 1200MPa.
The invention also provides a manufacturing method of the hydrogen embrittlement resistant delayed fracture high-strength steel, which comprises the following steps of: smelting, namely smelting the components of the high-strength steel with hydrogen embrittlement resistance and delayed fracture; casting; rough rolling; high-speed wire rod rolling; controlling cooling by stelmor, and controlling the tissue transformation of the wire rod by adjusting the components of a stelmor wire fan after the wire rod is rolled; spheroidizing or tempering heat treatment; drawing or straightening; cold heading and tempering heat treatment or turning.
According to another embodiment of the invention, the method for manufacturing the high-strength steel resistant to hydrogen embrittlement delayed fracture disclosed by the embodiment of the invention comprises the steps of carrying out external refining after smelting by an electric furnace or a converter in an alloy smelting step, and carrying out high-vacuum degassing for more than 18 minutes.
According to another specific embodiment of the invention, the embodiment of the invention discloses a manufacturing method of high-strength steel with hydrogen embrittlement resistance and delayed fracture, wherein argon protection is adopted in the casting step; the parameters of pulling speed, cooling and tail end soft reduction in the casting process are adjusted to control the carbon segregation of the core part of the blank to be lower than 1.09; after eddy current flaw detection, magnetic powder flaw detection, grinding wheel die repair, magnetic powder flaw detection and die repair are carried out on the blank, the blank is placed into a heating furnace for heating, the heating is controlled to 960-1200 ℃, and the heat preservation time is 1.0-3.0 hours.
According to another specific embodiment of the invention, the method for manufacturing the high-strength steel resistant to hydrogen embrittlement delayed fracture disclosed by the embodiment of the invention is characterized in that in the high-speed wire rod rolling step, the rolling speed is controlled to be 8-120m/s, the inlet temperature of a finishing mill group is 750-980 ℃, the inlet temperature of a reducing sizing mill group is 750-980 ℃, and the spinning temperature is 700-900 ℃.
Further, in the step of stelmor cooling control, the stelmor line comprises fans F1-F14, wherein the air quantity of the fans F1-F5 is 0-70%, the air quantity of the fans F6-F12 is 0-60%, and the air quantity of the fans F13-F14 is 0-50%.
Further, in the spheroidizing or tempering heat treatment step, the wire rod spheroidizing heat treatment heat preservation temperature is 750-800 ℃, the heat preservation time is 4-15 hours, the wire rod spheroidizing heat treatment heat preservation time is slowly cooled after heat preservation, the speed is lower than 20 ℃/h, the wire rod drawing reduction rate is 5-30%, the tempering heat treatment heating temperature is 850-1000 ℃, and the tempering temperature is 425-600 ℃.
The beneficial effects of the invention are as follows:
the invention aims to provide high-strength steel capable of processing parts such as high-strength fasteners, connecting rods, pins and shafts with the pressure of more than 1200MPa, the steel is controlled by alloy components, tissues and steel purity design, the hydrogen embrittlement resistance and delayed fracture performance are obviously improved, the compound addition of V, nb and carbide precipitation thereof are adopted, the grain structure is refined, the hydrogen diffusion rate in the high-strength parts is obviously reduced, the endurance time is improved by more than 5 times in a hydrogen corrosion environment, and the service life and the safety of the processed parts are greatly improved.
Detailed Description
Further advantages and effects of the present invention will become apparent to those skilled in the art from the disclosure of the present specification, by describing the embodiments of the present invention with specific examples. While the description of the invention will be described in connection with the preferred embodiments, it is not intended to limit the inventive features to the implementation. Rather, the purpose of the invention described in connection with the embodiments is to cover other alternatives or modifications, which may be extended by the claims based on the invention. The following description contains many specific details for the purpose of providing a thorough understanding of the present invention. The invention may be practiced without these specific details. Furthermore, some specific details are omitted from the description in order to avoid obscuring the invention. It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
In the description of the present invention, unless otherwise defined, terms in the specification have the same meaning as commonly understood by one skilled in the art, but are defined differently in the specification; unless otherwise specified, the test methods are all conventional; unless otherwise specified, all materials and test materials used in the present specification are commercially available; unless otherwise specified, the percentages (%) in this specification are mass percentages (mass%).
The high-strength steel resistant to hydrogen embrittlement delayed fracture in the embodiment comprises the following chemical components in percentage by mass:
C：0.38-0.48％、Si：0.03-0.12％、Mn：0.23-0.43％、Cr：1.00-1.40％、Mo：0.30-0.50％、Ni：0.15-0.40％、V：0.18-0.35％、Nb：0.02-0.12％、Al：0.025-0.045％、Cu：≤0.02％、P：≤0.010％、S：≤0.010％、O：≤0.0008％、N：≤0.0050％。
in the material, V/Nb is less than or equal to 2, V+Nb is less than or equal to 0.16, the size of carbon and nitrogen precipitates of V and Nb is less than 70nm, al/(O+N) is controlled to be more than 5, mn/S is controlled to be more than 35, the number of inclusions in steel is reduced, and the austenite grain size of the material is less than 60 microns.
The reason why the alloy steel of the present embodiment selects the chemical composition range is as follows:
the C element is a chemical component necessary for ensuring the steel for the high-strength parts, the content of the C element determines the quantity of precipitated carbide in the wire rod and finished parts after quenching and tempering heat treatment, and the hardness and strength of the alloy are greatly influenced, so that the carbon content in the alloy needs to be higher than 0.38%, but the excessive carbon content design leads to excessive quantity of precipitated carbide in the material, the size grows up, the plasticity and toughness of the material are reduced, the delayed fracture resistance performance is deteriorated, and the carbon content needs to be controlled to be lower than 48%.
Si element is often added into steel as a deoxidizer in the smelting process, meanwhile, si dissolved in an alloy ferrite phase obviously improves the strength of the material, but too high Si content reduces the plasticity of the material, and is unfavorable for the hydrogen embrittlement resistance and delayed fracture resistance of the material. Therefore, the Si content in the alloy is controlled to be 0.03-0.12%.
Mn element is also often added as deoxidizer in steelmaking process, and Mn is easy to combine with harmful element S in steel to form MnS, so that the harm is reduced, and Mn/S is controlled to be more than 35.Mn is also a common strengthening element in steel, and mainly plays a role of solid solution strengthening, and the formed alloy cementite has higher strength, so that the Mn content in the alloy needs to be controlled to be higher than 0.23%. However, when the Mn content is too high, the tendency of coarsening of crystal grains during heating of the material is increased, and in addition, mn element tends to promote segregation of residual elements, so that the addition amount of Mn element should be controlled to be less than 0.43%.
The addition of Cr element is beneficial to improving the hardenability of alloy, refining the structure in the bolt hardening and tempering process, improving the cementite strength, improving the material strength and plasticity, and improving the corrosion resistance of the material, and reducing the hydrogen embrittlement sensitivity, so that the Cr content is higher than 1.0 percent, and the Cr content is lower than 1.40 percent in order to prevent the occurrence of martensite abnormal structure and reduce the control difficulty of wire rod structure.
The addition of Mo element is favorable for refining the structure, improving the tempering stability of the material, improving the strength and hardness of the material under high-temperature tempering and improving the delayed fracture resistance of the material, but excessive addition of Mo element can cause the difficulty of controlling the structure of the material to be increased, and meanwhile, the alloy cost is increased, so that the addition range of the Mo element is 0.30-0.50%.
The Ni element is an austenite forming element, is dissolved in a ferrite phase in a solid manner, is favorable for improving the strength of the material, can effectively improve the hardenability of the material, improves the structure uniformity and the refined structure in the bolt quenching and tempering process, but the excessive Ni content can cause martensite abnormal structure in the material production process and also can influence the alloy cost, so that the control range of the Ni element is 0.15-0.40%.
V, nb element is easy to react with C, N element in high-strength steel to separate out carbonitride, nano-sized precipitate is effective in improving the strong plasticity of the material, and at the same time, the carbonitride of V, nb can be used as a hydrogen trap, especially when the nano-sized precipitate and the nano-sized precipitate are added in a compounding way, the lattice mismatch degree of the precipitate and ferrite in the steel is increased, the lattice distortion energy is larger, the fixing effect on hydrogen atoms is stronger, the hazard is reduced, the V content is controlled to be 0.18-0.35%, the Nb addition amount is 0.02-0.12%, V/Nb is more than or equal to 2, and the (V+Nb) is less than or equal to 0.16, and the carbon-nitrogen precipitate size of V and Nb is less than 70nm, so that the improvement of the delayed fracture resistance of the material can be realized.
Al element is the most effective deoxidizing element in the steelmaking process, but Al2O3 particles are easy to produce in the Al deoxidizing process, sharp edges and corners are provided, particularly when the oxygen content in steel is too high, the fatigue life, durability and delayed fracture resistance of finished parts are greatly influenced, the oxygen content in the material is required to be controlled below 0.0008 percent for ensuring the performance of the high-strength parts, and the purity of the steel is improved. The content of Al is controlled to be 0.025-0.045%, meanwhile Al/(O+N) is more than 5, the oxygen content in steel and the quantity of inclusions in steel are reduced, and carbon nitrogen precipitates of small particles Al2O3 and Nb are reduced, so that grains of the refined material are beneficial to improving the toughness, the grain size of the material is less than 60 mu m, and the increase of the quantity of grain boundaries is beneficial to capturing hydrogen elements and improving the hydrogen containing capacity of the material.
N element can also cause the increase of the material, and the excessively high content of N, C element can cause the increase of the size of micro-alloy precipitates in the steel for the high-strength bolt, and reduce the delayed fracture resistance of the material, so that N in the material is less than or equal to 0.0050 percent.
The Cu element is easy to cause the hot brittleness of the high-strength steel, and meanwhile, the uneven distribution of the too high Cu element in the material can cause the increase of the residual austenite content in the material and the reduction of the performance stability, so that the Cu content is controlled to be less than or equal to 0.02 percent.
Too high a content of P, S element will increase the brittleness of the material, especially when segregation occurs, so that in the design composition range of the material, P needs to be controlled to be lower than 0.010% and S needs to be controlled to be lower than 0.010%.
By adopting the scheme, the material has refined tempered sorbite structure after tempering heat treatment, the size of V, nb composite carbon-nitrogen precipitates is smaller than 70nm, the austenite grain size of the material is smaller than 60 mu m, the strength of processed parts can reach more than 1200MPa, the fatigue life and hydrogen embrittlement resistance delayed fracture performance are obviously improved compared with those of conventional high-strength parts, and the requirements of long service life, safety and reliability in use in the industries of automobiles, machinery, buildings and the like can be met.
In this embodiment, the method for manufacturing the high-strength steel resistant to hydrogen embrittlement delayed fracture includes the key steps of smelting, casting, rough rolling, high-speed wire rod rolling, stelmor controlled cooling, spheroidizing or tempering heat treatment, drawing or straightening, cold heading and tempering heat treatment or turning, and the specific preparation method is as follows:
1) The alloy is smelted by an electric furnace or a converter and then subjected to external refining, the external refining adopts an LF furnace and VD or RH degassing treatment process, the composition and the addition amount of synthetic slag are adjusted in the smelting process, the content of P, S elements in steel is controlled to be lower than 0.010 percent and 0.010 percent respectively, the high vacuum degassing time is controlled to be longer than 18 minutes, the content of O at the end point is controlled to be lower than 0.0008 percent, the content of N is controlled to be lower than 0.0050 percent, and the content of Al/(O+N) is controlled to be higher than 5,H and lower than 2ppm.
2) In the casting step, argon protection is adopted; the parameters of pulling speed, cooling and tail end soft reduction in the casting process are adjusted to control the carbon segregation of the core part of the blank to be lower than 1.09; after eddy current flaw detection, magnetic powder flaw detection, grinding wheel die repair, magnetic powder flaw detection and die repair are carried out on the blank, the blank is placed into a heating furnace for heating, the heating is controlled to 960-1200 ℃, and the heat preservation time is 1.0-3.0 hours.
In particular, the casting may be bloom continuous casting, billet continuous casting, or die casting. More specifically, when the bloom continuous casting method is used for casting, the bloom continuous casting machine is used for casting the bloom, argon is used for protection in the casting process, the size of the bloom is 250-500mm, and the carbon segregation of the core part of the bloom is controlled to be lower than 1.09 by adjusting parameters of drawing speed, cooling and light end pressing in the continuous casting process. And (3) adopting a two-hot forming process, and blooming the continuous casting blank into a square blank with the diameter of 135-240mm at the temperature of 1000-1350 ℃. Fang Piliao is heated in a heating furnace after eddy current flaw detection, magnetic powder flaw detection, grinding wheel die repair and magnetic powder flaw supplement and die repair, the heating is controlled at 960-1200 ℃, and the heat preservation time is 1.0-3.0 hours.
3) In the high-speed wire rod rolling process, the rolling speed is controlled to be 8-120m/s. The on-line temperature control preferred scheme is as follows: the inlet temperature of the finishing mill is 750-980 ℃, the inlet temperature of the reducing sizing mill is 750-980 ℃, and the spinning temperature is 700-900 ℃.
4) The size specification of the rolled wire rod is phi 5.5-28mm, the wire rod structure transformation is controlled by adjusting the component of the stelmor wire fan after the wire rod is rolled, and the wire rod structure is optimized. In the step of controlling cooling by using the Steyr, the Steyr line comprises fans F1-F14, and the adjustment range of the components of the fans of the 14 Steyr line is as follows: the air quantity of the F1-F5 blower is 0-70%, the air quantity of the F6-F12 blower is 0-60%, and the air quantity of the F13-F14 blower is 0-50%. The wire rod after being cooled by the Steyr has good plasticity and toughness.
5) The heat preservation temperature of the wire rod spheroidizing heat treatment is 750-800 ℃, the heat preservation time is 4-15 hours, and the wire rod spheroidizing heat treatment is slowly cooled after heat preservation, wherein the speed is lower than 20 ℃/h. The draw reduction rate of the wire rod is 5-30%. The tempering heat treatment heating temperature is 850-1000 ℃ and the tempering temperature is 425-600 ℃.
Examples
The high strength steel resistant to hydrogen embrittlement delayed fracture of the present invention and the method of manufacturing the same will be further described below with reference to specific examples. However, the present invention is not limited to the following embodiments, and various technical solutions thereof should be included in the scope of the present invention.
The chemical composition of the high strength steel products of examples A1-a10 of the present invention resistant to hydrogen embrittlement delayed fracture is shown in table 1 below. The wire rods and parts of examples A1-A10 were prepared as follows:
1) The alloy is smelted by an electric furnace or a converter and then subjected to LF refining and VD treatment, the P, S element content in steel is controlled to be lower than 0.010%, meanwhile, the high vacuum degassing time is required to be longer than 18 minutes, the O content in the steel is controlled to be lower than 0.0008%, the N content is controlled to be lower than 0.0050%, and the H content is controlled to be lower than 2ppm.
2) Adopting a bloom continuous casting machine to cast 250 square billets A1-A4, 400 square billets A5-A8 and 500mm square billets A9-A10 under the protection of argon, and adjusting parameters of drawing speed, cooling and light end reduction in the continuous casting process to control the carbon segregation in the core part of the blank. The A1-A4 continuous casting billets were then bloomed to 135, 160 and 240mm square billets at 1000 ℃, A5-A8 at 1200 ℃, and A9-A10 at 1350 ℃, respectively. Fang Piliao after eddy current flaw detection, magnetic powder flaw detection, grinding wheel die repair, magnetic powder flaw detection and die repair supplement, heating in a heating furnace, wherein the heating temperature of A1-A4 is 960 ℃, the heating temperature of A5-A8 is 1100 ℃, the heating temperature of A9-A10 is 1200 ℃, and the heat preservation time is 1.0-3.0h.
3) In the process of rolling the wire rod high-speed wire rod, the rolling speed of the wire rod with the length of 5.5mm is 110m/s, the rolling speed of the wire rod with the length of 10mm is 45m/s, the rolling speed of the wire rod with the length of 15mm is controlled to be 23m/s, and the rolling speed of the wire rod with the length of 25mm is controlled to be 15m/s. The on-line temperature control is as follows: the inlet temperature of the A1-A3 finishing mill group is 750 ℃, and the inlet temperature of the A4-A10 finishing mill group is 980 ℃; the inlet temperature of the A1-A5 reducing sizing mill is 800 ℃, the inlet temperature of the A6-A8 reducing sizing mill is 980 ℃, and the inlet temperature of the A9-A10 reducing sizing mill is 950 ℃; the spinning temperature of the A1-A7 alloy is 700 ℃, and the spinning temperature of the A8-A10 alloy is 900 ℃.
4) The dimension specification of the rolled wire rod A1-A3 is phi 5.5 and 10mm, and the adjustment range of the component of the 14 stelmor wire fans after the rolling of the wire rod is as follows: the air quantity of the F1-F5 fans is 0-40%, and the air quantity of the F10-F14 fans is 0%. The dimension specification of the rolled wire rod A4-A6 is phi 15mm, and the component adjustment range of the 14-station fan of the stelmor wire after the rolling of the wire rod is as follows: the air quantity of the F1-F5 fans is 5-65%, and the air quantity of the F10-F14 fans is 0%. The dimension specification of the rolled wire rod A7-A10 is phi 25mm, and the component adjustment range of the 14-station fan of the Steyr wire after the rolling of the wire rod is as follows: the air quantity of the F1-F5 fans is 10-90%, the air quantity of the F6-F10 fans is 0-25%, and the air quantity of the F11-F14 fans is 0%.
5) And (3) performing spheroidizing heat treatment on the wire rod, wherein the spheroidizing heat treatment temperature of the A1-A5 alloy is 750 ℃, the heat preservation time is 6 hours, the wire rod is slowly cooled at 40 ℃/h after heat preservation, the wire rod drawing reduction rate is 10%, the quenching and tempering heat treatment heating temperature is 850-1000 ℃, and the tempering temperature is 425-580 ℃. The spheroidizing heat treatment temperature of the A6-A10 alloy is 790 ℃, the heat preservation time is 12 hours, the wire rod is slowly cooled at 35 ℃/h after heat preservation, the wire rod drawing reduction rate is 20%, the tempering heat treatment heating temperature is 890-950 ℃, and the tempering temperature is 550-600 ℃.
TABLE 1 inventive alloy Steel examples A1-A10 and comparative Steel grade chemical composition (wt%)
| Steel grade | C | Si | Mn | Cr | Mo | Ni | V | Nb | Al | Cu | P | S | O | N |
| A1 | 0.38 | 0.03 | 0.4 | 1.1 | 0.35 | 0.4 | 0.18 | 0.08 | 0.045 | 0.01 | 0.007 | 0.002 | 0.0008 | 0.0045 |
| A2 | 0.4 | 0.12 | 0.4 | 1 | 0.4 | 0.2 | 0.2 | 0.08 | 0.03 | 0.02 | 0.001 | 0.008 | 0.0005 | 0.0019 |
| A3 | 0.39 | 0.05 | 0.42 | 1.1 | 0.3 | 0.25 | 0.25 | 0.12 | 0.025 | 0.015 | 0.01 | 0.009 | 0.0008 | 0.0015 |
| A4 | 0.48 | 0.05 | 0.4 | 1.2 | 0.5 | 0.2 | 0.2 | 0.02 | 0.035 | 0.015 | 0.008 | 0.005 | 0.0005 | 0.005 |
| A5 | 0.4 | 0.07 | 0.23 | 1.2 | 0.4 | 0.3 | 0.3 | 0.04 | 0.025 | 0.016 | 0.008 | 0.003 | 0.0001 | 0.004 |
| A6 | 0.41 | 0.1 | 0.3 | 1 | 0.42 | 0.15 | 0.3 | 0.02 | 0.04 | 0.008 | 0.008 | 0.007 | 0.0006 | 0.003 |
| A7 | 0.4 | 0.05 | 0.3 | 1 | 0.45 | 0.15 | 0.35 | 0.03 | 0.03 | 0.007 | 0.008 | 0.005 | 0.0008 | 0.002 |
| A8 | 0.39 | 0.05 | 0.43 | 1.4 | 0.3 | 0.24 | 0.25 | 0.04 | 0.029 | 0.011 | 0.006 | 0.010 | 0.0002 | 0.005 |
| A9 | 0.44 | 0.03 | 0.39 | 1.3 | 0.44 | 0.4 | 0.3 | 0.05 | 0.03 | 0.018 | 0.006 | 0.003 | 0.0004 | 0.0035 |
| A10 | 0.45 | 0.1 | 0.4 | 1.05 | 0.4 | 0.4 | 0.25 | 0.05 | 0.04 | 0.009 | 0.005 | 0.004 | 0.0007 | 0.0043 |
| Comparative example 1 | 0.4 | 0.25 | 0.75 | 1.1 | 0.2 | 0 | 0 | 0 | 0.035 | 0.09 | 0.008 | 0.01 | 0.0025 | 0.006 |
| Comparative example 2 | 0.45 | 1.7 | 1.2 | 1.5 | 0.4 | 0 | 0.5 | 0.08 | 0.02 | 0.21 | 0.006 | 0.008 | 0.0015 | 0.005 |
| Comparative example 3 | 0.4 | 0.02 | 0.8 | 1.05 | 0.2 | 0.05 | 0.1 | 0 | 0.005 | 0.004 | 0.01 | 0.016 | 0.0008 | 0.0065 |
| Comparative example 4 | 0.35 | 0.2 | 0.78 | 1.05 | 0.65 | 0 | 0.25 | 0 | 0.04 | 0 | 0.009 | 0.006 | 0.0022 | 0.0035 |
The comparative steel grade structure and mechanical properties of examples A1-A10 of the present invention are shown in Table 2 below.
TABLE 2 comparative mechanical Properties of the inventive alloy Steel examples A1-A10 and comparative Steel grade
The hydrogen embrittlement resistance delay performance of the parts with the processing of 1200MPa or more in the examples A1-A10 and the comparative steel grade of the invention is shown in the following table 3, and the results show that the hydrogen diffusion rate of the high-strength parts processed by the steel grade of the novel invention is remarkably reduced, the hydrogen embrittlement resistance delay fracture performance of the novel alloy of the high-strength steel is greatly improved in the environment of hydrogen generation corrosion, and the endurance time is improved by more than 5 times.
TABLE 3 comparison of Hydrogen embrittlement resistance delayed fracture properties of inventive alloy steels examples A1-A10 and comparative grades
| Steel grade | Hydrogen diffusion rate (mm) 2 /s) | Sample duration (hours) of loading in 0.1mol/L dilute hydrochloric acid |
| A1 | 1.69×10 -5 | 403 |
| A2 | 1.80×10 -5 | 390 |
| A3 | 1.92×10 -5 | 500 |
| A4 | 1.89×10 -5 | 450 |
| A5 | 1.99×10 -5 | 564 |
| A6 | 1.87×10 -5 | 498 |
| A7 | 1.50×10 -5 | 650 |
| A8 | 2.02×10 -5 | 561 |
| A9 | 1.78×10 -5 | 660 |
| A10 | 1.84×10 -5 | 532 |
| Comparative example 1 | 3.15×10 -5 | 51 |
| Comparative example 2 | 2.78×10 -5 | 60 |
| Comparative example 3 | 2.95×10 -5 | 68 |
| Comparative example 4 | 3.07×10 -5 | 46 |
The feasibility and prospect of popularization and application of the invention are predicted:
the automobile, machinery and construction fields have a large number of parts such as fasteners, pins, shafts, connecting rods and the like which are processed by high-strength steel, when the strength of the parts is higher than 1200MPa, unexpected delay fracture problems are very easy to occur in the use process, and serious potential safety hazards exist. The invention provides the hydrogen embrittlement-resistant delayed fracture high-strength steel, which realizes the great improvement of the durability of the material in a hydrogen environment through alloy component design and structure regulation, has very wide application prospect in the fields of automobiles, machinery, buildings and the like in the future, and brings good economic benefit and social benefit.
While the invention has been described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing is a further detailed description of the invention in connection with specific embodiments, and it is not intended to limit the invention to the specific embodiments described. Various changes in form and detail may be made therein by those skilled in the art, including a few simple inferences or alternatives, without departing from the spirit and scope of the present invention.
Claims (9)
1. The high-strength steel resistant to hydrogen embrittlement delayed fracture is characterized by comprising the following chemical components in percentage by mass:
c:0.38-0.48%, si:0.03-0.12%, mn:0.23-0.43%, cr:1.00-1.40%, mo:0.30-0.50%, ni:0.15-0.40%, V:0.18-0.35%, nb:0.02-0.12%, al:0.025-0.045%, N: less than or equal to 0.0050 percent, and the balance of Fe and unavoidable impurities;
the mass percentage of the chemical components is as follows:
2.ltoreq.V/Nb, and (V+Nb), (C+N). Ltoreq.0.16;
Al/(O+N)﹥5。
2. the high strength steel resistant to hydrogen embrittlement delayed fracture according to claim 1, wherein the V, nb carbon nitrogen precipitates of the high strength steel resistant to hydrogen embrittlement delayed fracture are less than 70nm in size and the austenite grain size of the material is less than 60um.
3. The high strength steel resistant to hydrogen embrittlement delayed fracture according to claim 2, wherein the unavoidable impurities include: cu: less than or equal to 0.02 percent, P: less than or equal to 0.010 percent, S: less than or equal to 0.010 percent, O: less than or equal to 0.0008 percent.
4. The hydrogen embrittlement resistant delayed fracture high strength steel according to claim 1, further comprising the following chemical components in percentage by mass: mn/S > 35.
5. The high-strength steel resistant to hydrogen embrittlement delayed fracture according to claim 3, wherein the microstructure of the high-strength steel resistant to hydrogen embrittlement delayed fracture has a refined tempered sorbite structure, and the strength of the high-strength steel resistant to hydrogen embrittlement delayed fracture is not less than 1200MPa.
6. A method for manufacturing a high strength steel resistant to hydrogen embrittlement delayed fracture, comprising the steps of:
smelting using the composition of the hydrogen embrittlement resistant delayed fracture high strength steel according to any one of claims 1 to 5;
casting;
rough rolling;
high-speed wire rod rolling;
controlling cooling by stelmor, and controlling the tissue transformation of the wire rod by adjusting the components of a stelmor wire fan after the wire rod is rolled;
spheroidizing or tempering heat treatment;
drawing or straightening;
cold heading and tempering heat treatment or turning.
7. The method for producing a high-strength steel resistant to hydrogen embrittlement delayed fracture according to claim 6, wherein in the alloy-smelting step, external refining is performed after smelting by an electric furnace or a converter while high vacuum degassing time is more than 18 minutes.
8. The method for producing a high-strength steel resistant to hydrogen embrittlement delayed fracture according to claim 6, wherein in the casting step:
argon is adopted for protection;
the parameters of pulling speed, cooling and tail end soft reduction in the casting process are adjusted to control the carbon segregation of the core part of the blank to be lower than 1.09;
the blank is heated in a heating furnace after eddy current flaw detection, magnetic powder flaw detection, grinding wheel die repair, magnetic powder flaw detection and die repair, the heating is controlled at 960-1200 ℃, and the heat preservation time is 1.0-3.0 hours.
9. The method for producing a high-strength steel resistant to hydrogen embrittlement delayed fracture according to claim 6, wherein in the high-speed wire rod rolling step, the rolling speed is controlled to be 8-120m/s, and the finishing mill group inlet temperature is 750-980 ℃, the reducing sizing mill group inlet temperature is 750-980 ℃, and the laying temperature is 700-900 ℃;
in the step of stelmor cooling, the stelmor line comprises fans F1-F14, wherein the air quantity of the fans F1-F5 is 0-70%, the air quantity of the fans F6-F12 is 0-60%, and the air quantity of the fans F13-F14 is 0-50%; and
in the spheroidizing or tempering heat treatment step, the wire rod spheroidizing heat treatment heat preservation temperature is 750-800 ℃, the heat preservation time is 4-15 hours, the wire rod spheroidizing heat treatment heat preservation time is slowly cooled after heat preservation, the speed is lower than 20 ℃/h, the wire rod drawing reduction rate is 5-30%, the tempering heat treatment heating temperature is 850-1000 ℃, and the tempering temperature is 425-600 ℃.
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