CN114807738A - High-strength bolt steel and manufacturing method thereof - Google Patents
High-strength bolt steel and manufacturing method thereof Download PDFInfo
- Publication number
- CN114807738A CN114807738A CN202110113145.2A CN202110113145A CN114807738A CN 114807738 A CN114807738 A CN 114807738A CN 202110113145 A CN202110113145 A CN 202110113145A CN 114807738 A CN114807738 A CN 114807738A
- Authority
- CN
- China
- Prior art keywords
- steel
- temperature
- strength
- quenching
- tempering
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
- B21C37/04—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of bars or wire
- B21C37/047—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of bars or wire of fine wires
-
- 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
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
-
- 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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- 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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- 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
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
-
- 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
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
-
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
-
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
-
- 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Heat Treatment Of Articles (AREA)
Abstract
The invention discloses a high-strength bolt steel, which comprises the following components in percentage by mass: c: 0.35 to 0.45 percent; si: 0.15 to 0.24 percent; mn: 0.20 to 0.40 percent; cr: 0.75 to 1.35 percent; mo: 0.55 to 1.00 percent; v: 0.08 to 0.30 percent; al: 0.005% -0.10%; s: 0 to 0.005%. Also disclosed is a method for producing a high-strength bolt steel having excellent delayed fracture resistance.
Description
Technical Field
The invention relates to the field of alloy steel, in particular to high-strength bolt steel and a manufacturing method thereof.
Background
The high-strength bolt belongs to a notch part, has high notch sensitivity, is easy to corrode in different degrees after being exposed in humid air, rainwater and other environments for a long time, and easily causes hydrogen-induced delayed fracture of the high-strength bolt due to diffusion and enrichment of trace hydrogen generated by corrosion reaction at a corrosion pit and trace hydrogen existing in the bolt under the action of stress.
Hydrogen induced delayed fracture is associated with plastic deformation, i.e., hydrogen promotes dislocation emission and movement. When hydrogen promotes the development of localized plastic deformation to critical conditions, the stress concentration in localized areas (e.g., at the front of the dislocation plug mass) is equal to the atomic bonding forces reduced by hydrogen, resulting in the nucleation of hydrogen induced cracks thereat. The grain boundary can block dislocation movement, and dislocation plugging in front of the grain boundary is easily caused, so that the intergranular fracture is the most common mode of delayed fracture of the steel for the high-strength bolt in a hydrogen-containing environment. And as the grains are refined, the number of dislocations accumulated before the grain boundary is reduced, and under the same variable, deformation is dispersed in more grains, so that the stress concentration degree is reduced, and the delayed fracture resistance of the material is further improved.
Disclosure of Invention
The invention aims to solve the problem of low delayed fracture resistance of high-strength bolt steel. The invention provides a high-strength bolt steel having excellent delayed fracture resistance, and a method for manufacturing the same.
In order to solve the technical problems, the embodiment of the invention discloses a high-strength bolt steel, which comprises the following components in percentage by mass: c: 0.35 to 0.45 percent; si: 0.15 to 0.24 percent; mn: 0.20 to 0.40 percent; cr: 0.75 to 1.35 percent; mo: 0.55 to 1.00 percent; v: 0.08 to 0.30 percent; al: 0.005% -0.10%; s: 0 to 0.005%.
By adopting the technical scheme, the steel for the high-strength bolt has excellent delayed fracture resistance.
According to another embodiment of the present invention, there is disclosed a high-strength bolt steel, the balance being Fe and inevitable impurities.
According to another embodiment of the present invention, an embodiment of the present invention discloses a high-strength bolt steel, wherein the mass percentage of V, the mass percentage of C, and the quenching temperature satisfy the following relational expression: log { [ V ] [ C ] } > 6.72-9500/T; wherein [ V ] is the mass percent of V in the high-strength bolt steel, [ C ] is the mass percent of C in the high-strength bolt steel, T is the quenching temperature, and the unit of the quenching temperature T is K.
By adopting the technical scheme, the steel for the high-strength bolt meets the relational expression, so that a certain volume of undissolved VC precipitated phases are still reserved in the microstructure of the steel for the high-strength bolt, and the VC precipitated phases can pin original austenite grain boundaries to prevent the original austenite grain boundaries from growing up, thereby preventing the microstructure from coarsening and achieving the purpose of further improving the delayed fracture resistance.
According to another embodiment of the present invention, an embodiment of the present invention discloses a steel for high strength bolts, the microstructure of which is tempered sorbite, and the grain size of prior austenite in the tempered sorbite is less than or equal to 20 μm.
By adopting the technical scheme, the microstructure of the steel for the high-strength bolt can be prevented from coarsening, and the aim of further improving the delayed fracture resistance is fulfilled.
Here, the prior austenite grain size has an important influence on the mechanical properties of the steel material.
The prior austenite grain size and the uniformity are one of the important indexes influencing the mechanical properties of the steel,
the size of the original austenite grains directly influences the structural change in the controlled rolling and controlled cooling process, so that the mechanical property of the material is greatly influenced, and the accurate display of the original austenite grains of the steel has important significance.
According to another specific embodiment of the invention, the embodiment of the invention discloses high-strength bolt steel, wherein the tensile strength of the high-strength bolt steel is more than or equal to 1400MPa, the yield strength of the high-strength bolt steel is more than or equal to 1260MPa, and the reduction of area of the high-strength bolt steel is more than or equal to 50%.
By adopting the technical scheme, the steel for the bolt has high strength and better plastic toughness.
According to another embodiment, the present invention discloses a high strength steel for bolts having a strength loss rate of < 20% in a hydrogen-charged environment and a plastic loss rate of < 50% in a hydrogen-charged environment.
By adopting the technical scheme, the steel for the bolt has excellent delayed fracture resistance.
The embodiment of the invention also discloses a manufacturing method of the steel for the high-strength bolt, which comprises the following steps:
smelting and casting: smelting and casting the components into a continuous casting billet or a steel ingot, wherein the ratio of the cross sectional area of the continuous casting billet or the steel ingot to the cross sectional area of a wire rod rolling billet is more than 6, and the cross sectional area of the continuous casting billet or the steel ingot is more than or equal to 320 multiplied by 425 mm;
soaking treatment: soaking the continuous casting slab or the steel ingot, wherein the soaking temperature is 1200-1250 ℃, and the heat preservation time is more than or equal to 24 hours;
blooming in the first rolling: cogging the continuous casting billet or the steel ingot to form a steel billet;
rolling the wire rods: heating the steel billet to 1000-1080 ℃, and rolling a wire rod, wherein the finish rolling temperature is 830-900 ℃, and the wire rod spinning temperature is 780-810 ℃, so as to obtain a wire rod;
quenching and tempering: and (3) quenching and tempering the wire rod, carrying out oil quenching after keeping the temperature for 60-80 min at the quenching temperature T, tempering at the temperature of more than or equal to 500 ℃ for the heating time of more than or equal to 90min, and carrying out air cooling to obtain the high-strength bolt steel.
By adopting the technical scheme, the manufactured high-strength bolt steel has excellent delayed fracture resistance.
Detailed Description
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure. While the invention will be described in conjunction with the preferred embodiments, it is not intended that features of the invention be limited to these embodiments. On the contrary, the invention is described in connection with the embodiments for the purpose of covering alternatives or modifications that may be extended based on the claims of the present invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The invention may be practiced without these particulars. Moreover, some of the specific details have been left out of the description in order to avoid obscuring or obscuring the focus of the present invention. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
Hereinafter, the component system of the present invention will be described.
C：0.35％～0.45％
C is added into steel as a cheap element, can improve the hardenability and the hardenability of steel, forms fine dispersion carbides after quenching and tempering, is important for improving the strength of the steel, and can cause Fe in the steel when the content of C is higher than 0.45 percent 3 The amount of C increases, resulting in a decrease in the plasticity of the steel, and therefore, the C content is set at 0.35% to 0.45%.
Si：0.15％～0.24％
Si replaces iron atoms in the steel in a replacement mode, dislocation movement is hindered, the strength of a ferrite phase can be obviously improved, the hardness of the annealed material is improved due to the high silicon content, cold heading forming is not facilitated, the service life of a forming die is shortened, and the low-temperature impact toughness of the steel is reduced, so that the Si content is set to be 0.15% -0.24%.
Mn：0.20％～0.40％
Mn has a strong solid solution strengthening effect, is an important strengthening and toughening element, can effectively improve hardenability and strength, has little influence on the plasticity of steel by adding a certain amount of manganese element, is easy to segregate in the solidification process of ferroalloy, ensures the strength and hardenability of the alloy when the content of Mn is more than 0.20 percent, and avoids the phenomenon of material uniformity deterioration caused by manganese segregation when the content of Mn is less than 0.40 percent, so the content of Mn is set to be 0.20 to 0.40 percent.
Cr：0.75％～1.35％
Cr has the function of improving the hardenability of the ferroalloy, simultaneously precipitates fine and dispersed carbide particles in the tempering process to play a role of dispersion strengthening so as to improve the strength of the steel, and also has the function of refining the structure, so in order to play the roles of solid solution strengthening and precipitation strengthening of Cr and simultaneously improve the steel structure, the Cr content is set to be 0.75-1.35%.
Mo：0.55％～1.00％
Mo is a ferrite forming element, and is beneficial to improving the hardenability of the steel, so that bainite and martensite are formed in the steel in the quenching process. Because the atomic weight of Mo is larger, the atomic radius is large, and Mo is not easy to diffuse in the ferroalloy, the tempering is carried out at a lower temperature, Mo mainly exists in the steel in a solid solution form to play a solid solution strengthening effect, and fine carbides can be formed by tempering at a higher temperature, so that the strength of the steel is improved, and the tempering resistance of the steel is improved on the whole. The higher tempering temperature can effectively reduce the amount of dislocation and subboundary in the steel, thereby avoiding the delayed cracking caused by the aggregation of hydrogen element at the dislocation and the subboundary, but Mo is a precious alloy element, and the higher content of Mo can cause the cost to rise, therefore, the content of Mo is set to be 0.55-1.00%.
V：0.08％～0.30％
V is a strong carbide forming element, and formed carbides are divided into two types, namely vanadium carbide which is not dissolved in the quenching process, and vanadium carbide which is precipitated in the tempering process. In the quenching process, undissolved vanadium carbide belongs to a high-temperature precipitated phase, the temperature at which the vanadium carbide is completely dissolved is higher than the quenching temperature, and the undissolved vanadium carbide can pin the prior austenite grain boundary, prevent the prior austenite grain from growing up, and achieve the effects of refining the prior austenite grain and refining the martensite structure; fine vanadium carbide particles can be formed in the tempering process, and the fine vanadium carbide belongs to an irreversible hydrogen trap, so that hydrogen in steel can be effectively trapped, and hydrogen is prevented from being accumulated at a position with concentrated stress, so that hydrogen-induced cracking is caused; in addition, the vanadium carbide precipitated phase can block the interaction between hydrogen and dislocation, reduce the increment of dislocation and reduce local plastic deformation. At higher tempering temperatures, too high a V content tends to form coarse vanadium carbide particles, reducing the impact properties of the steel, and therefore, in combination with the other alloying elements of the invention, the V content is set at 0.08% to 0.30%, preferably 0.25% to 0.30%.
Al：0.005％～0.10％
Al is a deoxidizer added in steel, and the content of Al is controlled within the range of 0.005-0.10%, so that grains can be refined, and the toughness of the steel can be improved.
S：0～0.005％
The S content is maintained at a low level because of the hot shortness problem caused by the formation of FeS from S, and is limited to 0.005% or less. The lower limit is not defined because the lower the S content, the better for the same reason.
The method for manufacturing the high-strength bolt steel provided by the invention comprises the following steps:
smelting and casting
Because more Cr, Mo, V and other alloy elements are added into the steel, the alloy elements are easy to segregate in the solidification process, segregation has inheritance, and the segregation of the continuous casting billet or the steel ingot is lost to the wire rod, so that the uniformity of the material is reduced, and compared with the conventional casting process, the casting process has the following requirements on the cross section area of the continuous casting billet or the steel ingot: the ratio of the cross-sectional area of the continuous casting blank or the steel ingot to the cross-sectional area of the wire rod rolling blank is more than 6, the cross-sectional area of the continuous casting blank or the steel ingot is more than or equal to 320 x 425mm, and the cross-sectional area of the continuous casting blank or the steel ingot is measured by adopting a measuring tape at room temperature and the cross-sectional area is calculated.
Soaking and blooming
Compared with the conventional wire rod production process, the invention adds soaking treatment and blooming steps to reduce the segregation of Cr, Mo, V and other alloy elements in steel and improve the uniformity of materials, and the continuous casting billet or steel ingot needs to be subjected to soaking treatment before the blooming step to reduce the segregation of materials, wherein the soaking treatment step of the continuous casting billet or steel ingot is specifically to preserve heat at 1200-1250 ℃ for more than 24h, and the blooming step is specifically to roll the continuous casting billet or steel ingot with larger cross section area into a steel billet with smaller cross section area.
Wire rod rolling
Heating a steel billet to 1000-1080 ℃, rolling a wire rod, wherein the finish rolling temperature is 830-900 ℃, the wire rod spinning temperature is 780-810 ℃, and a stelmor line (the stelmor line is a controlled cooling process designed on the basis of the transformation rule of the structure of steel during cooling) is treated according to the conventional process to obtain the delayed fracture resistant fine-grain high-strength steel wire rod for the bolt.
Thermal refining
The wire rod needs to be subjected to quenching and tempering treatment, the selected quenching temperature is that log { [ V ] [ C ] } > 6.72-9500/T (wherein [ V ] is the mass percent of V in the high-strength bolt steel, [ C ] is the mass percent of C in the high-strength bolt steel, T is the quenching temperature, and the unit of the quenching temperature T is K), the wire rod is subjected to oil quenching after being subjected to heat preservation for 60-80 min at the quenching temperature, mineral oil at 40-60 ℃ is adopted to cool the wire rod to below 80 ℃, then the wire rod is heated for more than 90min at the temperature of not less than 500 ℃ to be tempered, and the high-strength bolt steel is obtained through air cooling.
Through the quenching and tempering steps, the tensile strength of the obtained high-strength bolt steel reaches more than 1400MPa, the yield strength reaches more than 1260MPa, the reduction of area is more than 50%, the microstructure of the high-strength bolt steel is tempered sorbite, and the size of prior austenite crystal grains in the tempered sorbite is less than or equal to 20 mu m.
The invention has the following beneficial effects:
the high-strength bolt steel provided by the invention has the advantages that the tensile strength is more than 1400MPa, the yield strength is more than 1260MPa, the reduction of area is more than 50%, the microstructure of the high-strength bolt steel is tempered sorbite, and the size of prior austenite crystal grains in the tempered sorbite is less than or equal to 20 mu m. The high-strength steel for bolts has low alloy cost, the strength of the high-strength steel for bolts is improved through nanoscale precipitates, meanwhile, the high-strength steel for bolts has good ductility and toughness and delayed fracture resistance, the structure is refined, and the composition and the size of inclusions are controlled, so that the finished bolts have long fatigue life, the requirements of automobile light weight, high strength and long service life in the mechanical industry can be met, the technical level of the industry can be favorably improved, and good economic benefits are achieved.
Hereinafter, the present invention will be described in more detail by way of examples.
Examples
The embodiment of the invention carries out smelting and casting according to the chemical component requirements, and casts the mixture into a continuous casting billet with the diameter of 320 multiplied by 425 mm. 1 to 10 are examples, 11 to 13 are comparative examples, and the chemical compositions are shown in Table 1.
Soaking the continuous casting slab in a soaking furnace at 1200-1250 ℃ for more than 24h, cogging, and rolling into a 142 x 142mm steel slab, wherein the compression ratio is 6.7 and meets the requirement that the compression ratio is more than 6, and the compression ratio is the ratio of the cross-sectional area of the continuous casting slab or the steel ingot to the cross-sectional area of the steel slab.
Rolling a 142mm by 142mm billet into
The wire rod of (1) is subjected to thermal refining and then processed to form a delayed fracture-resistant high-strength bolt steel.
Wherein, the quenching temperature T satisfies the following relation in the quenching and tempering process: log { [ V ] [ C ] } > 6.72-9500/T; wherein [ V ] is the mass percent of V in steel, [ C ] is the mass percent of C in steel, and T is the quenching temperature (unit is K); keeping the temperature for 60-80 min at the quenching temperature T, and cooling to below 80 ℃ by adopting mineral oil at 40-60 ℃; heating for more than 90min at the tempering temperature of more than 500 ℃, and cooling in air.
The parameters of the quenching and tempering process are shown in a table 2, the grain size and the mechanical property of the prior austenite are shown in a table 3, the strength loss rate and the plasticity loss rate of comparative examples 11-13 in a hydrogen charging environment are obviously higher than those of examples 1-10, the V content in the example 2 is within the preferred range of 0.25% -0.30%, and the steel for the high-strength bolt shows better delayed fracture resistance.
The measurement method of the prior austenite crystal grains refers to a straight line intercept point method in the GB/T6394-2017 standard.
The strength loss rate and the plasticity loss rate under the hydrogen charging environment are measured as follows: adopting a slow stretching experiment, placing a sample in a hydrogen-containing environment in the slow stretching process, and soaking the sample in 0.1mol/L hydrochloric acid solution, wherein the strain rate is 10 -6 s -1 And comparing the mechanical property of the high-strength bolt steel in the hydrogen-filled environment with the mechanical property of the steel in the air environment in slow stretching (including tensile strength and reduction of area) to obtain the strength loss rate and the plasticity loss rate of the steel in the hydrogen-filled environment, wherein the following formula is shown in the specification: i is σ ＝(σ 0 -σ H )/σ 0 ×100％；I Z ＝(Z 0 -Z H )/Z 0 X is 100%; in the formula I σ 、I Z Respectively, the strength loss rate and the plasticity loss rate, sigma 0 、σ H Tensile strength of the test specimen in air and in a hydrogen-containing atmosphere, Z 0 、Z H The reduction of area of the sample in air and in a hydrogen-containing atmosphere, respectively.
TABLE 1 chemical composition (unit%)
TABLE 2 thermal refining parameters
| Examples | Thermal refining |
| 1 | Keeping the temperature at 900 ℃ for 60min, and performing oil quenching; keeping the temperature at 530 ℃ for 90min, then tempering and air cooling |
| 2 | Keeping the temperature at 880 ℃ for 80min, and performing oil quenching; keeping the temperature at 600 ℃ for 90min, then tempering and air cooling |
| 3 | Keeping the temperature of 870 ℃ for 70min and then performing oil quenching; keeping the temperature at 530 ℃ for 90min, then tempering and air cooling |
| 4 | Keeping the temperature of 890 ℃ for 75min, and performing oil quenching; keeping the temperature at 520 ℃ for 90min, then tempering and air cooling |
| 5 | Keeping the temperature at 920 ℃ for 70min, and performing oil quenching; keeping the temperature at 580 ℃ for 90min, then tempering and air cooling |
| 6 | Keeping the temperature at 920 ℃ for 60min, and performing oil quenching; keeping the temperature at 570 ℃ for 90min, then tempering and air cooling |
| 7 | Performing oil quenching after keeping the temperature at 910 ℃ for 80 min; keeping the temperature at 560 ℃ for 90min, then tempering and air cooling |
| 8 | Keeping the temperature at 920 ℃ for 65min, and performing oil quenching; tempering after the temperature is preserved for 90min at 590 ℃, and air cooling |
| 9 | Keeping the temperature of 890 ℃ for 75min, and performing oil quenching; keeping the temperature at 560 ℃ for 90min, then tempering and air cooling |
| 10 | Keeping the temperature at 900 ℃ for 70min, and performing oil quenching;keeping the temperature at 500 ℃ for 90min, then tempering and air cooling |
| 11 (comparison example) | Keeping the temperature at 850 ℃ for 70min, and performing oil quenching; keeping the temperature at 400 ℃ for 90min, then tempering and air cooling |
| 12 (comparison example) | Keeping the temperature at 910 ℃ for 70min, and then performing oil quenching; keeping the temperature at 420 ℃ for 90min, then tempering and air cooling |
| 13 (comparison example) | Keeping the temperature of 960 ℃ for 70min, and performing oil quenching; keeping the temperature at 550 ℃ for 90min, then tempering and air cooling |
TABLE 3 prior austenite grain size and mechanical Properties
As can be seen from tables 1 to 3, the steel for bolts of examples 1 to 10 had a prior austenite grain size of 20 μm or less in the tempered sorbite, a tensile strength of 1400MPa or more, a yield strength of 1260MPa or more, a reduction of area of 50% or more, and a strength loss rate of < 20% in a hydrogen-charged environment, the plastic loss rate in the hydrogen-charged environment is less than 50%, while the prior austenite grain size in the tempered sorbite of the steel for bolt of comparative example 11 is more than 20 μm, this is because the content of V element in comparative example 11 is 0.01%, the content of V element is too low, the carbide such as vanadium carbide formed is less, the effect of refining prior austenite grains cannot be achieved, and the reduction of area of the steel for bolt of comparative example 11 is less than 50% in combination with the lower tempering temperature, the strength loss rate under the hydrogen charging environment is more than 20 percent, and the plasticity loss rate under the hydrogen charging environment is more than 50 percent, namely the plasticity and toughness and the delayed fracture resistance are poor.
The lower contents of the Mo element and the V element in the comparative example 12 result in poor hardenability of the bolt steel of the comparative example 12 and the prior austenite grain size in the tempered sorbite is more than 20 μm, and in combination with the lower tempering temperature, result in the bolt steel of the comparative example 12 having a reduction of area of less than 50%, a strength loss rate of more than 20% in a hydrogen-charged environment, and a plastic loss rate of more than 50% in a hydrogen-charged environment, i.e., poor ductility and delayed fracture resistance.
In comparative example 13, the mass percentages of the V element and the C element were 0.22, 0.41, respectively, and the quenching temperature T < 1223.44K, i.e., the quenching temperature T < 950 ℃ was calculated according to the formula log { [ V ] [ C ] } > 6.72-9500/T, whereas, as can be seen from Table 3, comparative example 13 employed a quenching temperature of 960 ℃ exceeding 950 ℃ and, therefore, comparative example 13 employed a higher quenching temperature, resulting in a austenite grain size in tempered sorbite of the steel for bolt of > 20 μm and poor delayed fracture resistance (strength loss rate in hydrogen charged environment of > 20%, plasticity loss rate in hydrogen charged environment of > 50%).
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 more particular description of the invention than is possible with reference to the specific embodiments, which are not to be construed as limiting the invention. Various changes in form and detail, including simple deductions or substitutions, may be made by those skilled in the art without departing from the spirit and scope of the invention.
Claims (7)
1. A high-strength bolt steel, characterized by comprising, in mass percent:
C：0.35％～0.45％；Si：0.15％～0.24％；Mn：0.20％～0.40％；Cr：0.75％～1.35％；Mo：0.55％～1.00％；V：0.08％～0.30％；Al：0.005％～0.10％；S：0～0.005％。
2. the steel for high strength bolts according to claim 1, wherein the balance is Fe and inevitable impurities.
3. The steel for high strength bolts according to claim 2, wherein the mass percent of V, the mass percent of C, and the quenching temperature satisfy the following relational expressions: log { [ V ] [ C ] } > 6.72-9500/T; wherein [ V ] is the mass percent of V in the high-strength bolt steel, [ C ] is the mass percent of C in the high-strength bolt steel, T is the quenching temperature, and the unit of the quenching temperature T is K.
4. The steel for high strength bolts according to claim 2, characterized in that the microstructure of the steel for high strength bolts is tempered sorbite, and the crystal grain size of prior austenite in the tempered sorbite is 20 μm or less.
5. The steel for high-strength bolts according to claim 2, characterized in that the steel for high-strength bolts has a tensile strength of not less than 1400MPa, a yield strength of not less than 1260MPa, and a reduction of area of not less than 50%.
6. The steel for high strength bolts according to claim 2, characterized in that the steel for high strength bolts has a strength loss rate of < 20% in a hydrogen charged environment and a plasticity loss rate of < 50% in a hydrogen charged environment.
7. A manufacturing method of the steel for high strength bolts according to any one of claims 1 to 6, characterized by comprising the steps of:
smelting and casting: smelting and casting the components into a continuous casting billet or a steel ingot, wherein the ratio of the cross sectional area of the continuous casting billet or the steel ingot to the cross sectional area of a wire rod rolling billet is more than 6, and the cross sectional area of the continuous casting billet or the steel ingot is more than or equal to 320 multiplied by 425 mm;
soaking treatment: soaking the continuous casting slab or the steel ingot, wherein the soaking temperature is 1200-1250 ℃, and the heat preservation time is more than or equal to 24 hours;
blooming in the first rolling: rolling the continuous casting billet or the steel ingot to form a billet;
rolling the wire rods: heating the steel billet to 1000-1080 ℃, and rolling a wire rod, wherein the finish rolling temperature is 830-900 ℃, and the wire rod spinning temperature is 780-810 ℃, so as to obtain a wire rod;
quenching and tempering: and (3) quenching and tempering the wire rod, carrying out oil quenching after keeping the temperature for 60-80 min at the quenching temperature T, tempering at the temperature of more than or equal to 500 ℃ for the heating time of more than or equal to 90min, and carrying out air cooling to obtain the high-strength bolt steel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110113145.2A CN114807738B (en) | 2021-01-27 | 2021-01-27 | High-strength steel for bolts and manufacturing method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110113145.2A CN114807738B (en) | 2021-01-27 | 2021-01-27 | High-strength steel for bolts and manufacturing method thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN114807738A true CN114807738A (en) | 2022-07-29 |
| CN114807738B CN114807738B (en) | 2023-06-13 |
Family
ID=82524356
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202110113145.2A Active CN114807738B (en) | 2021-01-27 | 2021-01-27 | High-strength steel for bolts and manufacturing method thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114807738B (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1098145A (en) * | 1993-11-11 | 1995-02-01 | 河南省安阳钢铁公司 | 35SiMnVB spring steel for variable cross-section plate spring |
| JP2000328191A (en) * | 1999-05-13 | 2000-11-28 | Nippon Steel Corp | Steel for high strength bolt and production of high strength bolt |
| CN1900344A (en) * | 2005-07-22 | 2007-01-24 | 新日本制铁株式会社 | High strength bolt excellent in delayed fracture resistance and method of production of same |
| CN111850429A (en) * | 2019-04-30 | 2020-10-30 | 宝山钢铁股份有限公司 | Steel for high-strength weather-resistant fastener and manufacturing method thereof |
-
2021
- 2021-01-27 CN CN202110113145.2A patent/CN114807738B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1098145A (en) * | 1993-11-11 | 1995-02-01 | 河南省安阳钢铁公司 | 35SiMnVB spring steel for variable cross-section plate spring |
| JP2000328191A (en) * | 1999-05-13 | 2000-11-28 | Nippon Steel Corp | Steel for high strength bolt and production of high strength bolt |
| CN1900344A (en) * | 2005-07-22 | 2007-01-24 | 新日本制铁株式会社 | High strength bolt excellent in delayed fracture resistance and method of production of same |
| CN111850429A (en) * | 2019-04-30 | 2020-10-30 | 宝山钢铁股份有限公司 | Steel for high-strength weather-resistant fastener and manufacturing method thereof |
Non-Patent Citations (1)
| Title |
|---|
| 杨才福等: "《钒钢冶金原理与应用》", 30 June 2012, 冶金工业出版社 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN114807738B (en) | 2023-06-13 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP4089197A1 (en) | Chain steel for use in mine and manufacturing method therefor | |
| CN110468340B (en) | Steel wire rod for 14.9-grade high-strength fastener and preparation method thereof | |
| WO2015197007A1 (en) | Carburized alloy steel, method for preparing same, and use thereof | |
| CN110923546B (en) | High-weather-resistance cold forging steel for 10.9-grade fastener and production method thereof | |
| CN111748739B (en) | Heat-resistant spring steel with tensile strength of more than 2100MPa and production method thereof | |
| CN110791715A (en) | Niobium-titanium-containing atmospheric corrosion-resistant 14.9-grade high-strength bolt steel and production method thereof | |
| CN111041356B (en) | Niobium-containing atmospheric corrosion-resistant 14.9-grade high-strength bolt steel and production method thereof | |
| WO2016158361A1 (en) | Wire material for use in bolts that has excellent acid pickling properties and resistance to delayed fracture after quenching and tempering, and bolt | |
| CN111074148B (en) | 800 MPa-level hot stamping axle housing steel and manufacturing method thereof | |
| US20240052470A1 (en) | Non-quenched and Tempered Round Steel with High Strength, High Toughness and Easy Cutting and Manufacturing Method Therefor | |
| JP6232324B2 (en) | Stabilizer steel and stabilizer with high strength and excellent corrosion resistance, and method for producing the same | |
| CN110938732A (en) | Titanium-containing atmospheric corrosion-resistant 14.9-grade high-strength bolt steel and production method thereof | |
| CN111850399B (en) | Corrosion-resistant plastic die steel with good wear resistance and preparation method thereof | |
| CN109957728B (en) | Weather-resistant cold heading steel wire rod for 800 MPa-level fastener and production method thereof | |
| CN112575242B (en) | Steel for alloy structure and manufacturing method thereof | |
| WO2016158343A1 (en) | Steel wire for use in bolts that has excellent cold headability and resistance to delayed fracture after quenching and tempering, and bolt | |
| CN114134431B (en) | 2000 Mpa-grade high-strength high-toughness high-hardenability spring steel by square billet continuous casting and rolling and manufacturing method thereof | |
| CN110923580B (en) | Heat-resistant 12.9-grade steel for fasteners for rail transit and heat treatment process thereof | |
| JP3733229B2 (en) | Manufacturing method of high strength bolt steel bar with excellent cold workability and delayed fracture resistance | |
| CN113737108A (en) | Delay cracking resistant electro-galvanized super-strong dual-phase steel and manufacturing method thereof | |
| CN114807738B (en) | High-strength steel for bolts and manufacturing method thereof | |
| CN111321346B (en) | Ultrahigh-strength spring steel with excellent hydrogen-induced delayed fracture resistance and production method thereof | |
| CN115216700B (en) | 1700 MPa-level steel for fasteners and production method and heat treatment process thereof | |
| CN114525455B (en) | Wire rod, preparation method thereof and prestressed concrete steel bar prepared from wire rod | |
| CN115261724B (en) | Steel for ultrahigh-strength and high-toughness fastener, production method thereof and heat treatment process |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |