CN114134402A - Large-specification high-strength wind power fastener steel for offshore and rock and manufacturing method thereof - Google Patents
Large-specification high-strength wind power fastener steel for offshore and rock 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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0093—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for screws; for bolts
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- 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
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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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C22C38/06—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
- 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
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
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Abstract
The invention relates to large-specification high-strength wind power fastener steel for sea and rocks and a manufacturing method thereof, belonging to the technical field of iron-based alloy. The tensile strength of the product is 1040-1170 MPa, the yield strength is more than or equal to 940MPa, the elongation after fracture is more than or equal to 9%, and the reduction of area is more than or equal to 48%; the-40 ℃ low-temperature impact energy AKV of the quarter diameter part of the round steel is more than or equal to 27J, and the-20 ℃ low-temperature impact energy AKV is more than or equal to 35J; vickers hardness: the difference HV0.3 between the surface and the core of the round steel is less than or equal to 30, the quarter diameter part HV10 is 320-375, and the surface HV0.3 is less than or equal to 375. The production process adopts a short-flow production process of continuous casting, continuous rolling and continuous heat treatment, and replaces the traditional quenching liquid such as oil, water-soluble quenching medium and the like by high-pressure circulating water quenching and cooling, thereby realizing green, energy-saving and environmental protection.
Description
Technical Field
The invention belongs to the technical field of design, production and manufacturing of steel for the energy wind power generation industry, and particularly relates to large-size high-strength wind power fastener quenched and tempered bright round steel for offshore and rock production and a manufacturing method thereof.
Background
Nowadays, natural resources are increasingly exhausted on the earth, and development of renewable energy and improvement of energy utilization rate have become undisputable strategic targets of countries in the world. Along with the gradual maturity of fan technology and the decline of wind-powered electricity generation cost, the world wind-powered electricity generation installed capacity increases at a high speed, therefore the demand of marine, rock with big specification high strength wind-powered electricity generation fastener quenching and tempering bright round steel is bigger and bigger, but has two characteristics because of its abominable operational environment: 1) extremely cold and extremely hot ambient temperatures; 2) a variable load. Therefore, the harsh technical index requirements are provided for the quenched and tempered steel for the wind power fastener: firstly, an integral tensile sample with the same diameter as the round steel is adopted, the strength, the elongation after fracture and the reduction of area are tested, and the performance indexes are achieved as follows: the tensile strength is 1040-1170 MPa, the yield strength is more than or equal to 940MPa, the elongation after fracture is more than or equal to 9 percent, and the reduction of area is more than or equal to 48 percent; on the basis of meeting the indexes of high strength and plasticity, the low-temperature impact energy AKV (-20 ℃) of a quarter diameter (half radius) part of the round steel is more than or equal to 35J, and the AKV (-40 ℃) is more than or equal to 27J; thirdly, after the steel is quenched, the martensite structure of the core part reaches more than 90 percent, and then the sorbite of more than 90 percent is obtained by high-temperature tempering of the core part; vickers hardness: the difference HV0.3 between the surface and the core of the round steel is less than or equal to 30, and the quarter diameter part HV 10: 320-375, and the surface HV0.3 is less than or equal to 375. If the above-mentioned index requirements are met, the steel should have sufficient hardenability, high strength, ductility and toughness and uniform heat-treated structure stability.
Disclosure of Invention
The large-specification high-strength quenched and tempered silver bright steel for the offshore and rock wind power fasteners is controlled by various process links such as steel element component optimization, smelting, rolling, heat treatment and the like, is used for replacing the traditional 40CrNiMo, 34CrNiMo6 and AISI4340 high Ni steel, and meets the requirements of high-end large-specification fastener quenched and tempered material on through quenching of core tissues, full-section ultralow hardness difference distribution, optimal matching of high toughness and the like.
The technical scheme of the invention is as follows: the large-specification high-strength wind power fastener steel for the offshore and rock comprises the following elements in percentage by mass: c: 0.38-0.45%, Si: 0.20 to 0.40%, Mn: 0.80-1.00%, Cr: 1.15-1.30%, Mo: 0.30-0.45%, Ni: 0.30-0.50%, P: less than or equal to 0.015 percent, S: less than or equal to 0.005 percent, Al: 0.010-0.040%, H: less than or equal to 0.0001 percent, and the balance of Fe and inevitable impurity elements.
The production diameter range of the round steel is 16-78 mm.
The element components of the round steel are determined according to the following principles:
the C has the functions of improving the hardenability of the steel and the strength of the steel, and has the most obvious improvement on the hardenability and the strength compared with other alloys, but the low-temperature impact toughness of the final fastener after quenching and tempering heat treatment is obviously reduced along with the improvement of the C. For this reason, C: 0.38-0.45%.
The alloy elements Si, Mn, Cr, Ni and Mo in the invention have the function of improving the hardenability of the steel firstly, and the alloy elements Mn, Cr, Mo, Ni and Si which have the greatest contribution to the hardenability also contribute to the hardenability. Through multiple comprehensive test analysis of the element components and indexes such as strength, hardness, plasticity, low-temperature impact toughness and the like, the optimal content proportion of each alloy element of Mn, Cr, Mo, Ni and Si is determined.
Mn has the functions of improving the hardenability of steel and improving the strength of the quenched and tempered steel, but Mn is easy to be compatible with S in the steel to form MnS nonmetallic inclusions, so that the toughness of the steel is reduced, and the Mn content is too high and also can be segregated together with impurities such as P, S and the like at the grain boundary of the steel to reduce the toughness of the steel, wherein the Mn: 0.80 to 1.00 percent.
Cr has the functions of improving the hardenability of steel and the strength of the steel after quenching and tempering, and also has the functions of forming carbide with C in the steel, and the Cr in the quenched and tempered steel can also improve the corrosion resistance of the steel, and the Cr: 1.15 to 1.30 percent.
Mo is a strong carbide forming element, the main function of Mo is similar to that of Cr, the hardenability of Mo is improved, the Mo and C form carbide, the other function of Mo is to inhibit the oxidation of steel, so that the impact fracture resistance and overload fatigue resistance of a fastener are improved, and the important fastener materials are generally added with Mo, so that the Mo is preferably selected in consideration of the cost: 0.30-0.45%.
Ni is a non-carbide forming element, its role in steel is to improve impact toughness of steel in addition to hardenability, hardenability is remarkably improved when it is combined with Cr, Mo, and in addition Ni can improve symmetric tensile-compressive fatigue strength σ -1 of fasteners, and Ni: 0.35 to 0.50 percent.
Si is a deoxidizing element in steel and improves the strength of the steel in a solid solution strengthening mode, Si can also improve hardenability and has a tempering softening resistant effect, but the brittleness of the steel is increased when the content of Si is higher, and the invention controls the ratio of Si: 0.20 to 0.40 percent.
Al is a deoxidizing element in steel, Al is combined with oxygen in molten steel to generate Al2O3 which floats to slag, so that the oxygen content in the molten steel is reduced, the other function of Al is to refine grains, and the strength and toughness of a matrix are improved and the symmetric tension-compression fatigue strength sigma-1 is improved by adding a part of Al, so that the invention controls the ratio of Al: 0.010-0.40%.
P is a harmful element in steel, P is particularly easy to be segregated in grain boundaries, the strength and toughness of the grain boundaries are reduced, the impact toughness of the fastener after final quenching and high-temperature tempering is very adversely affected, and the fatigue performance of the material is finally affected, and the preferable ratio of P: less than or equal to 0.015 percent.
S is a harmful element in steel and is easy to form defects of segregation, inclusion and the like. As impurity elements which adversely affect the toughness of steel and significantly reduce hot workability and corrosion resistance of steel, the content thereof should be minimized, and S: less than or equal to 0.005 percent.
H causes defects such as hydrogen embrittlement, white spots and the like in steel, so that the plasticity, toughness and fatigue strength of the steel are remarkably reduced, and H can also cause delayed fracture of the steel, which is particularly sensitive to high-strength fastener materials, and H: less than or equal to 0.0001 percent.
The invention also provides a manufacturing method of the large-size wind power fastener quenched and tempered bright round steel for the offshore and rock, alloy raw materials and molten iron are preferably smelted according to the characteristics of the steel, molten steel meeting the element design requirement is smelted, and the molten steel is cast into a rectangular continuous casting billet by utilizing a continuous casting process.
The rectangular continuous casting slab is slowly heated in a stepping heating furnace in a weak oxidizing atmosphere, the temperature of a preheating section is 650-850 ℃, the temperature of a heating section is 1100-1260 ℃, the temperature of a soaking section is 1230-1260 ℃, descaled by high-pressure water, and then the continuous rolling round steel enters a full continuous rolling mill set automatically controlled by a computer, and is subjected to rough rolling and finish rolling sectional type rolling, the rough rolling reduction reaches more than 30%, the finish rolling total reduction reaches 100%, and the total compression ratio from the continuous casting slab to a hot rolling bar is more than or equal to 20. The initial rolling temperature is 1070-1150 ℃, and the final rolling temperature is 920-970 ℃. After rolling, the bar is slowly cooled like a slow cooling pit, the temperature of the bar entering the slow cooling pit is more than or equal to 450 ℃ while the temperature of the bar leaving the slow cooling pit is less than or equal to 120 ℃. The macrostructure of the rolled bar meets the following standard grading of ASTM E381: s, R, C is not more than 1.0 grade, and the microstructure is ferrite plus pearlite.
Quenching and tempering the rolled and cooled round steel in a continuous roller hearth furnace, controlling the austenitizing temperature to be 850-890 ℃, controlling the heat preservation time t (min) to be more than or equal to 1.0X D (D is the diameter of the steel), using water as a quenching medium, and fully austenitizing the steel and rapidly quenching and cooling the steel to obtain more than 90% of uniform martensite structure; and (3) tempering the martensite structure of the quenched steel at a high temperature of 540-600 ℃, controlling the tempering heat preservation time t (min) to be not less than 3.0 x D (D is the diameter of the steel), and using air as a tempering medium to obtain more than 90% of uniform sorbite structure.
The rolled ferrite and pearlite structure of the steel is changed into a tempered sorbite structure in a balanced state at room temperature after quenching and tempering, the strength, the plasticity and the toughness of the steel are obviously improved, the steel has good comprehensive mechanical properties, and the service performance requirement of a high-quality fastener product can be better met.
And (3) finely rectifying the quenched and tempered bar, and deeply processing the bar into a quenched and tempered bright silver steel bar by using a lathe carriage, so that the standard detection of surface flaw detection (the standard N is 0.1mm), ultrasonic flaw detection (EN 10308 standard 4 grade) and surface roughness Ra of less than or equal to 1.6 mu m is realized, and the qualified product is obtained. Qualified quenched and tempered bright steel bars for flaw detection are not subjected to heat treatment any more and are manufactured into wind power fasteners after threads are turned at two ends, and the wind power fasteners are applied to fan equipment in harsh working environments such as sea and rocks and meet the requirements at the same time:
firstly, an integral tensile sample with the same diameter as the round steel is adopted, the strength, the elongation and the reduction of area are tested, and the tensile property index is as follows: the tensile strength is 1040-1170 MPa, the yield strength is more than or equal to 940MPa, the elongation after fracture is more than or equal to 9 percent, and the reduction of area is more than or equal to 48 percent;
secondly, on the basis of meeting the indexes of high strength and plasticity, the low-temperature impact energy AKV (-40 ℃) of the quarter-diameter part of the round steel is more than or equal to 27J;
thirdly, the martensite structure of the core part of the steel reaches more than 90 percent after quenching, and the whole section structure of the quenched and tempered round steel is sorbite with the uniformity of more than 90 percent after final tempering;
vickers hardness: the difference HV0.3 between the surface and the core of the round steel is less than or equal to 30, the quarter diameter part HV10 is 320-375, and the surface HV0.3 is less than or equal to 375. On the basis of the four requirements, the production cost of the fan is reduced.
Compared with the prior art, the invention has the advantages that:
(1) provides a new material of a high-strength fastener which is suitable for offshore and rock and has the maximum specification of M80 (the diameter of round steel is 78mm) and a manufacturing method thereof.
(2) The optimal proportion of alloy elements C, Mn, Cr, Mo and Ni in the steel replaces the traditional alloy steel with higher Ni content, such as 40CrNiMo, 34CrNiMo6, AISI4340 and the like, so that the hardenability of the round steel is improved.
(3) The wind power fastener product produced by the quenched and tempered bright round steel produced by the method achieves excellent toughness and toughness matching. The mechanical property simultaneously meets the following requirements: firstly, an integral tensile sample with the same diameter as the round steel is adopted, the strength, the elongation and the reduction of area are tested, and the performance is achieved: the tensile strength is 1040-1170 MPa, the yield strength is more than or equal to 940MPa, the elongation after fracture is more than or equal to 9%, and the reduction of area is more than or equal to 48%; on the basis of meeting the indexes of high strength and plasticity, the low-temperature impact energy AKV (-20 ℃) of the quarter-diameter part of the round steel is more than or equal to 35J, and the AKV (-40 ℃) is more than or equal to 27J; thirdly, the martensite structure of the core part of the steel material after quenching reaches more than 90 percent, namely, the subsequent high-temperature tempering core part obtains more than 90 percent sorbite; vickers hardness: the difference HV0.3 between the surface and the core of the round steel is less than or equal to 30, the quarter diameter part HV10 is 320-375, and the surface HV0.3 is less than or equal to 375. The requirements of high strength and toughness, hardenability and tissue uniformity of key parts of wind power generation for sea and rocks are met.
(4) The manufacturing of the round steel adopts a short-flow process of continuous casting-continuous rolling-continuous heat treatment, the quenched and tempered bright steel deep-processing material for large-size wind power fasteners on the sea and rocks is produced, the production process and cost are saved, the quenching and cooling are carried out by high-pressure circulating water, the traditional quenching liquid such as oil, water-soluble quenching medium and the like is replaced, and the green, energy-saving and environment-friendly effects are realized.
Drawings
FIG. 1 shows a tempered core structure (500X) in example 1 of the present invention;
FIG. 2 shows a quenched and tempered core structure (500X) in example 2 of the present invention.
Detailed Description
The present invention is described in further detail below with reference to examples, which are intended to be illustrative and not to be construed as limiting the invention.
Example 1
The fastener that this embodiment relates to is M80 specification (round steel diameter 78mm), and its chemical composition by mass percent is: c: 0.42%, Si: 0.28%, Mn: 0.95%, Cr: 1.25%, Mo: 0.34%, Ni: 0.40, Cu: 0.08%, Al: 0.029%, H: 0.00008% of iron and the balance of inevitable impurity elements. The method is produced according to the steps of KR pretreatment of blast furnace molten iron → electric furnace (EAF) or converter (BOF) primary smelting → ladle LF furnace refining → VD or RH degassing furnace vacuum degassing → argon protection casting rectangular continuous casting blank → continuous rolling round steel → continuous roller hearth furnace quenching and tempering → fine straightening, turning skin → surface and ultrasonic flaw detection, detection and the like.
The method comprises the following specific steps:
1) KR pretreated molten iron with low content of P, S impurity elements is primarily smelted in an electric furnace or a converter, refined in an LF furnace, and subjected to enhanced deoxidation in the process, and a ladle is transferred into a VD or RH furnace for vacuum degassing after the refining is finished, so that gas and impurities are removed.
2) The low superheat degree of the continuous casting molten steel is controlled, and the segregation of a continuous casting billet is reduced and the internal quality is improved by utilizing a crystallizer and the tail end electromagnetic stirring.
3) Slowly cooling the continuous casting blank, heating the continuous casting blank in a stepping heating furnace, wherein the temperature of a preheating section is 760-798 ℃, the temperature of a heating section is 1130-1149 ℃, soaking the continuous casting blank to 1230-1260 ℃, removing scales from the casting blank by high-pressure water after discharging the casting blank, removing iron scales at high temperature, continuously rolling the casting blank into a quenched and tempered bright round steel base material by a full continuous rolling mill set automatically controlled by a computer, the rolling start temperature is 1070-1150 ℃, the finish rolling temperature is 920-970 ℃, and the total reduction ratio of the casting blank to the round steel in the rolling process is 21%. After rolling, the bar is slowly cooled, the temperature of the lower line entering a slow cooling pit is 478 ℃, and the temperature of the slow cooling pit is 112 ℃. The macrostructures of the rolled bars are 0.5 grade according to the ASTM E381 standard rating S, R, C, and the microstructure is ferrite plus pearlite.
4) Putting the rolled bar into a continuous roller bottom heat treatment furnace, and quenching and tempering at high temperature, wherein the austenitizing temperature is 850-870 ℃, the heat preservation time is 86 minutes, the quenching medium is water, and 100% uniform martensite structure is obtained after water quenching; high-temperature tempering is carried out at 565-585 ℃, the heat preservation time is 251 minutes, the tempering medium is air, and finally a 100% uniform sorbite structure is obtained, namely a composite structure (a mixture of ferrite and granular carbide) of spherical granular carbide (including cementite) distributed on a ferrite matrix, the ferrite of the structure has basically no carbon supersaturation, the carbide is also stable carbide, is a balanced structure at normal temperature, and has high comprehensive mechanical properties.
5) And finely straightening the quenched and tempered bar, deeply processing the quenched and tempered bar into bright silver round steel, and realizing the standard detection of surface flaw detection (standard N is 0.1mm +) ultrasonic flaw detection (EN 10308 standard 4 grade) and surface roughness Ra is less than or equal to 1.6 mu m, and the qualified product is obtained.
The mechanical properties of the fastener product manufactured after the threads are turned at the two ends of the round steel are shown in table 1, the metallographic structure is shown in the attached drawing 1 and is a 100% uniform tempering sorbite structure, and the technical specification requirements of the M80 large-specification offshore and rock wind power fastener product are met.
Table 1 example 1 fastener product mechanical properties
The tensile property is measured by adopting a diameter sample of the integral fastener; the low temperature impact work was tested at 1/4 diameter locations on the cross section of the fastener; vickers hardness was measured at the surface of the cross-section of the fastener, the core, and 1/4 diameter locations, respectively.
Example 2
The fastener that this embodiment relates to is M72 (round steel diameter 70mm), and its chemical composition by mass percent is: c: 0.41%, Si: 0.25%, Mn: 0.93%, Cr: 1.23%, Mo: 0.31%, Ni: 0.37, Cu: 0.06%, Al: 0.026%, H: 0.00007% of iron and the balance of inevitable impurity elements. The method is produced according to the steps of KR pretreatment of blast furnace molten iron → electric furnace (EAF) or converter (BOF) primary smelting → ladle LF furnace refining → VD or RH degassing furnace vacuum degassing → argon protection casting rectangular continuous casting blank → continuous rolling round steel → continuous roller hearth furnace quenching and tempering → fine straightening, turning skin → surface and ultrasonic flaw detection, detection and the like.
The method comprises the following specific steps:
1) KR pretreated molten iron with low content of P, S impurity elements is primarily smelted in an electric furnace or a converter, refined in an LF furnace, and subjected to enhanced deoxidation in the process, and a ladle is transferred into a VD or RH furnace for vacuum degassing after the refining is finished, so that gas and impurities are removed.
2) The low superheat degree of the continuous casting molten steel is controlled, and the segregation of a continuous casting billet is reduced and the internal quality is improved by utilizing a crystallizer and the tail end electromagnetic stirring.
3) Slowly cooling the continuous casting blank, heating the continuous casting blank in a stepping heating furnace, wherein the preheating section temperature is 767-803 ℃, the heating section temperature is 1141-1153 ℃, soaking the continuous casting blank to 1230-1260 ℃, removing scales from the continuous casting blank by high-pressure water and removing iron scales at high temperature after discharging, continuously rolling the continuous casting blank into a tempered silver bright round steel base material by a full continuous rolling unit automatically controlled by a computer, the rolling start temperature is 1070-1150 ℃, the final rolling temperature is 920-970 ℃, and the total reduction ratio of the continuous rolling process from the casting blank to the round steel is 25%. After rolling, the bar is slowly cooled, the temperature of the lower line is 471 ℃ in a slow cooling pit, and the temperature of the slow cooling pit is 105 ℃. The macrostructures of the rolled bars are 0.5 grade according to the ASTM E381 standard rating S, R, C, and the microstructure is ferrite plus pearlite.
4) Putting the rolled bar into a continuous roller bottom heat treatment furnace, and quenching and tempering at high temperature, wherein the austenitizing temperature is 850-870 ℃, the heat preservation time is 83 minutes, the quenching medium is water, and 100% uniform martensite structure is obtained after water quenching; tempering temperature is 565-585 ℃, the heat preservation time is 227 minutes, the tempering medium is air, and 100% uniform tempering sorbite structure is obtained after tempering.
5) And finely straightening the quenched and tempered bar, deeply processing the quenched and tempered bar into bright silver round steel, and realizing the standard detection of surface flaw detection (standard N is 0.1mm +) ultrasonic flaw detection (EN 10308 standard 4 grade) and surface roughness Ra is less than or equal to 1.6 mu m, and the qualified product is obtained.
The mechanical properties of the fastener products manufactured after the threads are turned at the two ends of the round steel are shown in table 2, the microstructure is shown in the attached figure 2, the fastener products are 100% of uniform tempering sorbite structures, and the requirements of the technical specifications of the M72 large-specification offshore and rock wind power fasteners are met.
Table 2 mechanical properties of the example 2 fastener product
The tensile property is measured by adopting a diameter sample of the integral fastener; the low temperature impact work was tested at 1/4 diameter locations on the cross section of the fastener; vickers hardness was measured at the surface of the cross-section of the fastener, the core, and 1/4 diameter locations, respectively.
In addition to the above embodiments, the present invention also includes other embodiments, and any technical solutions formed by equivalent transformation or equivalent replacement should fall within the scope of the claims of the present invention.
Claims (5)
1. A manufacturing method of large-specification high-strength wind power fastener steel for offshore and rock is characterized by comprising the following steps of:
preparing a rectangular continuous casting billet which accords with element component design, slowly heating the rectangular continuous casting billet in a weak oxidizing atmosphere heating furnace, wherein the temperature of a preheating section is 650-850 ℃, the temperature of a heating section is 1100-1260 ℃, the temperature of a soaking section is 1230-1260 ℃, descaling with high pressure water, feeding the rectangular continuous casting billet into a full continuous rolling mill set for continuously rolling round steel, performing rough rolling and finish rolling in a sectional type, wherein the rough rolling reduction is more than 30%, the finish rolling total reduction is 100%, the total compression ratio from the continuous casting billet to the hot rolling round steel is more than or equal to 20, the start rolling temperature is 1070-1150 ℃, and the finish rolling temperature is 920-970 ℃; and (3) cooling the rolled round steel in a slow cooling pit: the temperature of the lower line entering the slow cooling pit is more than or equal to 450 ℃, and the temperature of the slow cooling pit leaving is less than or equal to 120 ℃; the macrostructure of the rolled bar meets the following standard grading of ASTM E381: s, R, C is not more than 1.0 grade, and the microstructure is ferrite plus pearlite;
quenching and tempering round steel: quenching: austenitizing, heating at 850-890 ℃, keeping the temperature for more than or equal to 1.0 x D at t/min, wherein D is the diameter/mm of the steel, the quenching medium is water, and the steel is fully austenitized and rapidly quenched with water to obtain more than 90% of uniform martensite structure; tempering the martensite structure of the quenched steel at 540-600 ℃, wherein the tempering heat preservation time t/min is more than or equal to 3.0 x D, D is the diameter/mm of the steel, and the tempering medium is air, so as to obtain a tempered sorbite structure with the room temperature equilibrium state of more than 90 percent;
after the quenching and tempering treatment, the bar is finely rectified and the wagon is deeply processed into a quenched and tempered bright silver steel bar, so that surface flaw detection is realized: and (3) marking N as 0.1mm, performing ultrasonic flaw detection according to EN 10308 standard grade 4, and obtaining a final qualified product after the standard detection of the surface roughness Ra of less than or equal to 1.6 mu m is qualified.
2. The manufacturing method according to claim 1, characterized in that: smelting the molten steel according to the following components in percentage by weight: c: 0.38-0.45%, Si: 0.20 to 0.40%, Mn: 0.80-1.00%, Cr: 1.15-1.30%, Mo: 0.30-0.45%, Ni: 0.30-0.50%, P: less than or equal to 0.015 percent, S: less than or equal to 0.005 percent, Al: 0.010-0.040%, H: less than or equal to 0.0001 percent, and the balance of Fe and inevitable impurity elements.
3. The manufacturing method according to claim 1, characterized in that: the qualified product prepared by the method does not need heat treatment, and the wind power fastener can be manufactured after threads are turned at two ends.
4. The manufacturing method according to claim 1, characterized in that: the qualified product prepared by the method meets the following requirements:
firstly, an integral tensile sample with the same diameter as round steel is adopted to test the strength, the elongation and the reduction of area, wherein the tensile strength is 1040-1170 MPa, the yield strength is more than or equal to 940MPa, the elongation after fracture is more than or equal to 9 percent, and the reduction of area is more than or equal to 48 percent;
② the one-quarter diameter part of the round steel has-40 ℃ low-temperature impact energy AKV which is more than or equal to 27J and-20 ℃ low-temperature impact energy AKV which is more than or equal to 35J;
③ Vickers hardness: the difference HV0.3 between the surface and the core of the round steel is less than or equal to 30, the quarter diameter part HV10 is 320-375, and the surface HV0.3 is less than or equal to 375.
5. The manufacturing method according to claim 1, characterized in that: the production diameter of the qualified product prepared by the method is 16-78 mm.
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| CN115161550A (en) * | 2022-06-01 | 2022-10-11 | 江阴兴澄特种钢铁有限公司 | Steel for high-strength fastener for large hydraulic impact crusher and manufacturing method thereof |
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