CN108251747B - Steel pipe for crane boom and manufacturing method thereof - Google Patents
Steel pipe for crane boom and manufacturing method thereof Download PDFInfo
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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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- 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
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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
- C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
- C21D8/105—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies of ferrous alloys
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- 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
- C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
- C21D9/085—Cooling or quenching
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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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
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- 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
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- 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
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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
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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Abstract
The invention provides a steel pipe for a crane boom and a manufacturing method thereof. The steel pipe comprises, by weight, 0.10-0.20% of a C element, 0.10-0.90% of a Si element, 0.008-0.070% of an Al element, 0.80-3.60% of a Cr element, 0.40-1.80% of a Mo element, 0.03-0.16% of a V element, 0.03-0.35% of a Nb element, 0.10-1.50% of a W element, 0-0.005% of a N element, and the balance of Fe element and inevitable impurities. On the premise of strictly controlling the alloy elements which are easy to generate compact scale on the surface of the steel pipe and bend in the water quenching process, the invention ensures that the steel pipe reaches the requirements of 960 steel grade strength and toughness through dispersion and precipitation of carbides and nitrides of the micro alloy elements, and ensures that the steel pipe has good surface quality, straightness, excellent low-temperature toughness and weldability.
Description
Technical Field
The invention relates to the technical field of pipes for crane booms, in particular to a steel pipe for a crane boom and a manufacturing method thereof.
Background
The crawler crane is a mobile crane which installs a hoisting operation device on a crawler chassis and runs by depending on the crawler device, can carry out the operations of material hoisting, transportation, loading and unloading, installation and the like, and has the advantages of large hoisting capacity, small ground pressure, small turning radius, hoisting and running, low requirement on environment, various combinations of arm frames and the like. The crane jib is formed by welding and combining 3-12 m seamless steel pipes in sections, and is a key component for bearing, transferring and hoisting heavy objects by the crawler crane, so that the crane jib pipe has high strength and high toughness and also has good welding performance.
In recent years, with the increase of the number of large and ultra-large construction projects in the national infrastructure construction, the development of the crawler crane gradually develops towards the severe environments of large tonnage, ultra-low temperature applicable to extremely cold regions and the like. In the weight of the whole crane, the boom occupies a larger specific gravity, and the dead weight of the boom which is too large severely limits the hoisting capacity of the whole crane, so that higher requirements are provided for the main chord tube of the large-tonnage and super-large-tonnage crane. The steel pipe with high strength, high toughness, high ultra-low temperature impact toughness and good welding performance can greatly reduce the self weight of the arm support, improve the hoisting weight and ensure the operation safety under the action of pressure in the ultra-low temperature severe environment in extremely cold regions. Therefore, the development of the high-strength and high-toughness cantilever crane pipe with yield strength reaching 960MPa level has positive effect on large-tonnage and ultra-large-tonnage crawler cranes.
C-Mn-W-V series low-carbon high-strength steel with sufficient strength and good welding performance is mostly adopted at home and abroad to produce the pipe for the crane jib. At present, the highest strength grade of the cantilever crane pipe material is a cantilever crane pipe with the yield strength reaching 890MPa grade, the toughness of a common steel pipe material is weakened to a certain extent along with the improvement of the strength, the toughness index of a steel grade is often more difficult to reach along with the yield strength exceeding 960MPa, and meanwhile, the higher alloying degree of the 960 grade cantilever crane pipe leads to more compact iron scale and difficult removal. Moreover, the strength of the steel pipe is higher, and the straightening machine is more difficult to straighten. Therefore, ensuring good straightness is also one of the production difficulties of 960 grade steel cantilever tubes. Therefore, the technical and production problems of the steel grade crane jib tube with good obdurability matching, excellent surface quality and straightness above 960MPa are solved.
Disclosure of Invention
The invention mainly aims to provide a steel pipe for a crane boom and a manufacturing method thereof, and aims to solve the problems that the steel pipe for the crane boom in the prior art has poor toughness and poor surface quality and straightness after the yield strength exceeds 960 MPa.
In order to achieve the above object, according to one aspect of the present invention, there is provided a steel pipe for a crane boom, which includes, by weight, 0.10 to 0.20% of a C element, 0.10 to 0.90% of a Si element, 0.008 to 0.070% of an Al element, 0.80 to 3.60% of a Cr element, 0.40 to 1.80% of a Mo element, 0.03 to 0.16% of a V element, 0.03 to 0.35% of a Nb element, 0.10 to 1.50% of a W element, and 0 to 0.005% of a N element, and the balance is a Fe element and unavoidable impurities.
Further, the steel pipe for the crane boom further comprises 0.2-1.50% of Ni element in percentage by weight.
Further, the steel pipe for the crane boom comprises, by weight, 0.11-0.15% of a C element, 0.28-0.76% of a Si element, 0.023-0.060% of an Al element, 0.90-1.20% of a Cr element, 0.50-0.60% of a Mo element, 0.056-0.12% of a V element, 0.039-0.12% of a Nb element, 0.565-1.23% of a W element, 0.34-1.32% of a Ni element, and 0-0.005% of a N element, with the balance being Fe element and unavoidable impurities; preferably, the weight ratio of the W element, the Nb element, the V element and the Al element is 20-24: 1.8-2: 2-2.2: 1.
Further, the steel pipe for the crane boom further comprises 1.00-2.50% of Mn element, preferably 1.10-1.41% of Mn element in percentage by weight.
Furthermore, the steel pipe for the crane jib also comprises P element, S element, O element, H element and As element, and the content of the P element is less than or equal to 0.020%, the content of the S element is less than or equal to 0.010%, the content of the O element is less than or equal to 0.003%, the content of the H element is less than or equal to 0.0002%, and the content of the As element is less than or equal to 0.025% by weight percentage of the steel pipe for the crane jib.
Furthermore, the steel pipe for the crane jib further comprises Sn, Pb, Sb and Bi, and the sum of the weight percentages of the Sn, Pb, Sb, Bi and As in the steel pipe for the crane jib is less than or equal to 0.05%.
Further, the carbon equivalent Ceq of the steel pipe for the crane boom is less than or equal to 0.75%, the weight content of C element is represented as a, the weight content of Mn element is represented as b, the weight content of Cr element is represented as C, the weight content of Mo element is represented as d, the weight content of V element is represented as e, and the weight content of Ni element is represented as f, wherein Ceq is a + b/6+ (C + d + e)/5+ f/15.
According to another aspect of the present invention, there is provided a method for manufacturing the steel pipe for the crane boom, which includes the following steps: preparing materials according to chemical components of the steel pipe for the crane boom to obtain a mixed raw material; smelting and casting the mixed raw materials to obtain a blank; rolling the blank to obtain a hot rolled pipe; carrying out quenching and tempering heat treatment on the hot rolled pipe to obtain a heat treated pipe; and straightening the heat-treated pipe to obtain the steel pipe for the crane boom.
Further, the process of rolling the billet comprises: heating the blank to 1230-1280 ℃ in an annular furnace to obtain a hot blank; perforating the hot blank to obtain a capillary; and rolling the hollow billet into a pierced billet, and sizing the pierced billet to obtain the hot rolled pipe.
Further, the process of heating the blank includes: preheating, heating and soaking the blank in sequence to obtain a hot blank, wherein the total time for heating the blank is more than or equal to 190 min; preferably, the preheating process comprises: preheating the blank along with the furnace temperature; the temperature raising process sequentially comprises a first heating section, a second heating section, a third heating section, a fourth heating section and a fifth heating section, wherein the temperature of the first heating section is 1024 +/-10 ℃, and the heating time is more than or equal to 30 min; the temperature of the heating second section is 1138 +/-10 ℃, and the heating time is more than or equal to 40 min; the temperature of the three heating sections is 1250 +/-10 ℃, and the heating time is more than or equal to 20 min; the temperature of the four heating sections is 1267 +/-10 ℃, and the heating time is more than or equal to 20 min; the temperature of the five heating sections is 1263 +/-10 ℃, and the heating time is more than or equal to 20 min; in the soaking process, the soaking temperature is 1260 plus or minus 10 ℃, and the heating time is more than or equal to 40 min.
Further, the step of subjecting the hot-rolled pipe to a quenching and tempering heat treatment includes: preserving heat of the hot rolled pipe at 900-1100 ℃, and then sequentially quenching, descaling for the first time and spraying water on the surface of the heat-preserved hot rolled pipe for cooling to obtain a first treated steel pipe; preferably, the pressure of the descaling water for the first descaling is more than or equal to 25 MPa; tempering the first treated steel pipe for the first time at the temperature of 500-600 ℃, and then descaling for the second time and cooling in air to obtain a second treated steel pipe; preferably, the pressure of the descaling water for the second descaling is more than or equal to 20 MPa; tempering the second treated steel pipe for the second time at the temperature of 600-730 ℃, and then descaling for the third time and cooling in air to obtain a heat treatment pipe; preferably, the descaling water pressure of the third descaling is more than or equal to 20 MPa.
Further, the smelting step comprises the following steps: sequentially carrying out electric furnace smelting and external refining on the mixed raw materials; preferably, the step of casting comprises: carrying out arc continuous casting on the smelted mixed raw material to obtain a blank; more preferably, the manufacturing method further comprises the step of vacuum degassing the mixed raw material after smelting before the arc continuous casting.
Further, a whole-process argon blowing refining process is adopted in the external refining process, and calcium carbide, aluminum particles and carbon powder are added into a refining system for deoxidation; preferably, the step of vacuum degassing comprises: keeping the smelted mixed raw materials under a vacuum condition for 20min or more; preferably, in the step of arc continuous casting, the blank drawing speed is 0.8-1.0 m/min, and the superheat degree is 35-44 ℃.
Further, in the process of straightening the heat-treated tube, the straightening temperature is 600-700 ℃.
The invention provides a steel pipe for a crane boom, which comprises, by weight, 0.10-0.20% of a C element, 0.10-0.90% of a Si element, 0.008-0.070% of an Al element, 0.80-3.60% of a Cr element, 0.40-1.80% of a Mo element, 0.03-0.16% of a V element, 0.03-0.35% of a Nb element, 0.10-1.50% of a W element and 0-0.005% of a N element, and the balance of Fe element and inevitable impurities.
The yield strength of the steel pipe for the crane boom provided by the invention reaches the level of more than 960 MPa. Moreover, by properly adding alloy elements such as Cr, Mo and W and micro alloy elements such as Nb, V and Al and by the synergistic action among the Cr, Mo, W, Nb, V, Al, C and N elements, on the premise of strictly controlling the alloy elements which are easy to generate compact scale on the surface of the steel pipe and bend in the water quenching process, the steel pipe can reach 960 steel-grade strength and toughness requirements by dispersion and precipitation of carbides and nitrides of the micro alloy elements, so that the steel pipe is not easy to generate compact scale and bend in the production process, has good surface quality and straightness, and has excellent low-temperature toughness and weldability while having ultrahigh strength.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.
The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.
As described in the background section, the steel pipe for crane boom in the prior art has too poor toughness after the yield strength exceeds 960MPa, and the surface quality and the straightness of the steel pipe are poor.
In order to solve the problems, the invention provides a steel pipe for a crane boom, which comprises, by weight, 0.10-0.20% of a C element, 0.10-0.90% of a Si element, 0.008-0.070% of an Al element, 0.80-3.60% of a Cr element, 0.40-1.80% of a Mo element, 0.03-0.16% of a V element, 0.03-0.35% of a Nb element, 0.10-1.50% of a W element, 0-0.005% of a N element, and the balance of Fe element and inevitable impurities.
The yield strength of the steel pipe for the crane boom provided by the invention reaches the level of more than 960 MPa. Moreover, by properly adding alloy elements such as Cr, Mo and W and micro alloy elements such as Nb, V and Al and by the synergistic action among the Cr, Mo, W, Nb, V, Al, C and N elements, on the premise of strictly controlling the alloy elements which are easy to generate compact scale on the surface of the steel pipe and bend in the water quenching process, the steel pipe can reach 960 steel-grade strength and toughness requirements by dispersion and precipitation of carbides and nitrides of the micro alloy elements, so that the steel pipe is not easy to generate compact scale and bend in the production process, has good surface quality and straightness, and has excellent low-temperature toughness and weldability while having ultrahigh strength.
C is a carbide forming element, so that the strength and the hardenability of the steel can be effectively improved, the strength of the steel is improved along with the increase of the carbon content, but the impact toughness and the elongation rate are obviously reduced, and the welding performance is particularly unfavorable, therefore, the content of C is controlled to be 0.10-0.20, the strength and the toughness of the steel can be maintained, and the welding performance cannot be adversely affected. Si is an effective element for deoxidizing in steel, can inhibit delta ferrite crystallization, and can improve the toughness of the seamless steel pipe. Meanwhile, silicon exists in the form of solid solution in ferrite or austenite, and the strength of the solid solution is improved, so that the strength of the steel can be improved. However, too high a silicon content significantly reduces the toughness, plasticity and ductility of the steel. Therefore, the content of Si is controlled to be 0.10-0.90%, and the balance of the strength and toughness of the steel pipe is facilitated.
Al is a good deoxidizer in steel, can be matched with Si to remove oxygen in raw materials, can generate highly-finely-divided and ultra-microscopic oxides, can effectively prevent the growth of crystal grains during steel heating, and can refine the crystal grains. Because the deoxidation effect of Al is saturated and the inclusions are prevented from appearing in a bulk form, and meanwhile, excessive Al is added into Cr-containing steel, a layer of more compact iron scale is formed on the surface of the steel pipe and is not easy to remove under high-pressure water. Therefore, the Al content is controlled to be 0.008-0.070%, grains are thinned as much as possible on the basis of keeping good surface quality, and the strength and toughness balance of the steel pipe is improved.
Cr is a carbide forming element, the strength and the hardenability of the steel pipe can be improved, meanwhile, complex carbide formed by Cr and Fe is fine and difficult to dissolve, crystal grains can be refined, the tempering stability can be improved, but the excessive Cr can obviously improve the brittle transition temperature of the steel and reduce the low-temperature impact toughness of the steel. Mo can improve the hardenability of steel, improve the strength of the steel, refine crystal grains and improve the tempering stability of the steel by forming carbides which are dispersed and distributed on grain boundaries, and can reduce or inhibit the tempering brittleness caused by other elements, so the impact toughness of the steel is obviously improved while the strength of the steel is improved, and volatile molybdenum trioxide is formed in the environment with the temperature of more than 800 ℃, so that the formed compact iron oxide film is loose and porous, and is easy to peel off under high pressure water, but the effect of improving the impact toughness is not obvious when the Mo content is too high, and the toughness of the steel is reduced when the Mo content is too high.
V is easy to form extremely stable carbide and nitride with C, N in steel, and vanadium carbide and vanadium nitride are usually present in fine and dispersed form in steel, so that the structure and crystal grains of steel can be obviously refined, the coarsening temperature of the crystal grains is increased, the overheating sensitivity of the steel is reduced, the strength and the toughness of the steel are simultaneously improved, and a secondary hardening phenomenon can be formed in the tempering process when the content is higher, but when the content is too high, the vanadium carbide and the vanadium nitride can be separated out in the interior of the crystal grains to reduce the toughness of the steel. Nb is an action element for strongly refining grains, can form carbide, improves the thermal stability of steel, prevents austenite grains from growing too coarse in the heating stage of a blank, can further refine the grains of the steel in the subsequent rolling, and improves the strength and the toughness of the steel. In the tempering process, highly dispersed Nb C is precipitated to play a role in precipitation strengthening, the yield strength of the material is ensured to reach 960MPa, meanwhile, the material has excellent low-temperature impact toughness, the brittle transition temperature of steel is reduced, and the welding performance is improved.
W is an element with high melting point and strong carbide forming, and forms special carbide with carbon, so that the steel is difficult to be dissolved in solid solution and takes time, thereby the tempering stability and the heat strength of the steel can be increased, the heat sensitivity of the steel is reduced, the tempering stability of the steel after quenching is obviously improved when the W is in a solid solution state, and the special carbide W of the tungsten is in tempering2C dispersion promotes significant secondary hardening of the steel, but too high a W content fixes too much carbon, so that the carbon content of the solid solution portion in austenite is poor, and hardenability of the steel are reduced. The N and the C are combined with Al, Nb and Ti together to form carbon and oxide, and the carbon and the oxide exist in grain boundaries and can play a role in obviously refining grains, so that the toughness of the material is improved.
In a word, the invention plays the comprehensive function of the elements to the greatest extent through the dosage matching of the alloy elements and the micro-alloy elements, so that the steel pipe for the crane boom still has excellent toughness after the yield strength exceeds 960MPa, and the surface quality and the straightness of the steel pipe are improved to a great extent.
In a preferred embodiment, the steel pipe for the crane boom further comprises 0.2-1.50% of Ni element in percentage by weight. Ni is a main alloy element for forming and stabilizing austenite, can exist in steel in a form of being mutually soluble with Fe to improve the strength of the steel, and simultaneously improves the low-temperature toughness of the steel and reduces the low-temperature brittle transition temperature of the steel by refining alpha-phase grains, thereby having an extremely important effect on using 960 steel-grade cantilever crane pipes at low temperature and even ultra-low temperature. Controlling the content of the Ni element within the above range not only can further improve the low temperature performance of the steel pipe, but also can maintain good weldability.
In order to further integrate the performance of the steel pipe in all aspects, in a preferred embodiment, the steel pipe for the crane jib comprises, by weight, 0.11-0.15% of a C element, 0.28-0.76% of a Si element, 0.023-0.060% of an Al element, 0.90-1.20% of a Cr element, 0.50-0.60% of a Mo element, 0.056-0.12% of a V element, 0.039-0.12% of a Nb element, 0.565-1.23% of a W element, 0.34-1.32% of a Ni element, and 0-0.005% of a N element, and the balance of Fe element and inevitable impurities.
More preferably, the weight ratio of W element, Nb element, V element and Al element is 20-24: 1.8-2: 2-2.2: 1. After the elements such as W, Nb, V, Al and the like are added in a synergistic manner, dispersion precipitation is formed during the first tempering in the steel pipe preparation process, and tempering hardening is generated, so that the tempering temperature during the second tempering is favorably improved, the straightening resistance during straightening is favorably reduced, and the straightness is effectively improved. Particularly, the comprehensive performance of the steel pipe can be further improved by matching with the preparation process disclosed by the invention.
In a preferred embodiment, the steel pipe for the crane boom further comprises 1.00-2.50% of Mn element, preferably 1.10-1.41% of Mn element in percentage by weight. Mn is an austenite forming element, can improve the strength of the seamless steel pipe, can improve the hardenability of the steel pipe, can reduce the quenching temperature, has the effects of deoxidation and desulfurization, and can weaken the adverse effect of sulfur. The content of the steel is controlled within the range, so that the strength of the steel pipe is further improved, and the steel pipe can keep grain refinement and good low-temperature impact performance.
In a preferred embodiment, the steel pipe for the crane jib further comprises P element, S element, O element, H element and As element, and the content of the P element is less than or equal to 0.020%, the content of the S element is less than or equal to 0.010%, the content of the O element is less than or equal to 0.003%, the content of the H element is less than or equal to 0.0002%, and the content of the As element is less than or equal to 0.025% by weight percentage of the steel pipe for the crane jib. By controlling the contents of these elements within the above ranges, the influence of impurity elements can be reduced as much as possible.
In order to further improve the performance of the steel pipe, in a preferred embodiment, the steel pipe for the crane jib further comprises Sn, Pb, Sb and Bi, and the sum of the weight percentages of the Sn, Pb, Sb, Bi and As in the steel pipe for the crane jib is less than or equal to 0.05%.
In a preferred embodiment, the carbon equivalent Ceq of the steel pipe for a crane boom is not more than 0.75%, the weight content of C element is represented by a, the weight content of Mn element is represented by b, the weight content of Cr element is represented by C, the weight content of Mo element is represented by d, the weight content of V element is represented by e, and the weight content of Ni element is represented by f, wherein Ceq is a + b/6+ (C + d + e)/5+ f/15. The carbon equivalent is controlled within the range, and the seamless steel pipe has more excellent service performance.
According to another aspect of the present invention, there is provided a method for manufacturing a steel pipe for a crane boom, comprising the steps of: preparing materials according to chemical components of the steel pipe for the crane boom to obtain a mixed raw material; smelting and casting the mixed raw materials to obtain a blank; rolling the blank to obtain a hot rolled pipe; carrying out quenching and tempering heat treatment on the hot rolled pipe to obtain a heat treated pipe; and straightening the heat-treated pipe to obtain the steel pipe for the crane boom.
The yield strength of the steel pipe for the crane boom formed by the manufacturing method reaches the level of more than 960 MPa. Moreover, by properly adding alloy elements such as Cr, Mo and W and micro alloy elements such as Nb, V and Al and by the synergistic action among the Cr, Mo, W, Nb, V, Al, C and N elements, on the premise of strictly controlling the alloy elements which are easy to generate compact scale on the surface of the steel pipe and bend in the water quenching process, the steel pipe can reach 960 steel-grade strength and toughness requirements by dispersion and precipitation of carbides and nitrides of the micro alloy elements, so that the steel pipe is not easy to generate compact scale and bend in the production process, has good surface quality and straightness, and has excellent low-temperature toughness and weldability while having ultrahigh strength.
In order to economically and massively produce seamless steel tubes, improve the quality of blanks and control the content of impurity elements, the invention preferably selects ingredients including various materials of molten iron, tube heads, pure materials, high-quality scrap steel, ferroalloy and aluminum, controls the using amount of the scrap steel and ensures that the adding amount of the high-quality molten iron is more than or equal to 60 percent.
In a preferred embodiment, the process of rolling the billet comprises: heating the blank to 1230-1280 ℃ in an annular furnace to obtain a hot blank; perforating the hot blank to obtain a capillary; and rolling the hollow billet into a pierced billet, and sizing the pierced billet to obtain the hot rolled pipe.
In a preferred embodiment, the process of heating the billet comprises: and (3) preheating, heating up and soaking the blank in sequence to obtain a hot blank, wherein the total time for heating the blank is more than or equal to 190 min. Heating in sections, and controlling the total heating time of the blank to be more than or equal to 190min, which is beneficial to heating the blank more fully.
Preferably, the preheating process comprises: preheating the blank along with the furnace temperature; the temperature raising process sequentially comprises a first heating section, a second heating section, a third heating section, a fourth heating section and a fifth heating section, wherein the temperature of the first heating section is 1024 +/-10 ℃, and the heating time is more than or equal to 30 min; the temperature of the heating second section is 1138 +/-10 ℃, and the heating time is more than or equal to 40 min; the temperature of the three heating sections is 1250 +/-10 ℃, and the heating time is more than or equal to 20 min; the temperature of the four heating sections is 1267 +/-10 ℃, and the heating time is more than or equal to 20 min; the temperature of the five heating sections is 1263 +/-10 ℃, and the heating time is more than or equal to 20 min; in the soaking process, the soaking temperature is 1260 plus or minus 10 ℃, and the heating time is more than or equal to 40 min. Through the sectional heating, the tube blank can be gradually heated to a set temperature, the tube blank can be fully heated, and the defect that the hot rolled steel tube is cracked due to too fast temperature rise is avoided.
In a preferred embodiment, the step of subjecting the hot-rolled pipe to a quenching and tempering heat treatment comprises: preserving heat of the hot rolled pipe at 900-1100 ℃ (preferably preserving heat for 60-90 min), and then sequentially quenching, primary descaling and surface water spray cooling the heat-preserved hot rolled pipe to obtain a first treated steel pipe; preferably, the pressure of the descaling water for the first descaling is more than or equal to 25 MPa; tempering the first treated steel pipe for the first time at the temperature of 500-600 ℃, and then descaling for the second time and cooling in air to obtain a second treated steel pipe; preferably, the pressure of the descaling water for the second descaling is more than or equal to 20 MPa; tempering the second treated steel pipe for the second time at the temperature of 600-730 ℃, and then descaling for the third time and cooling in air to obtain a heat treatment pipe; preferably, the descaling water pressure of the third descaling is more than or equal to 20 MPa.
The heat preservation is carried out for 60-90 min at 900-1100 ℃, which is beneficial to promoting each alloy element (especially the hard-soluble tungsten carbide particles) to be more fully and uniformly dissolved in austenite grains, and is beneficial to the uniformity of austenitizing and the subsequent quenching and cooling effect of the seamless steel pipe; and an internal and external water spraying system is adopted during cooling, so that the sufficiency and uniformity of martensite transformation can be ensured. The secondary tempering process utilizes the special tungsten carbide W which is separated out during the first low-temperature tempering and is dispersed and distributed in the steel grade2The carbide and nitride of C, Nb and V enable the secondary hardening effect of the steel to improve the tempering temperature of the second time, so that the temperature of straightening with temperature carried out after the second tempering is improved, the deformation resistance of the steel pipe during straightening is reduced, and finally the straightness of the 960-grade ultrahigh-strength cantilever crane pipe is improved on the premise of ensuring qualified performance. The steel pipe is subjected to high-pressure water descaling after being taken out of the quenching furnace and the secondary tempering furnace, and the surface quality of the arm support pipe is improved after the steel pipe is subjected to high-pressure water descaling for many times. Then tempering and heat preservation are carried out for 90-130 min at 600-730 ℃, so that alloy elements can be more uniformly and dispersedly precipitated from supersaturated solid solution, and the improvement of the recovery rate is facilitatedStability of fire tissue.
In a preferred embodiment, the step of smelting comprises: sequentially carrying out electric furnace smelting and external refining on the mixed raw materials; preferably, the step of casting comprises: carrying out arc continuous casting on the smelted mixed raw material to obtain a blank; more preferably, the manufacturing method further comprises the step of vacuum degassing the mixed raw material after smelting before the arc continuous casting.
In a preferred embodiment, the whole argon blowing refining process is adopted in the external refining process, and calcium carbide, aluminum particles and carbon powder are added into a refining system for deoxidation; preferably, the step of vacuum degassing comprises: keeping the smelted mixed raw materials under the vacuum condition for 20min or more. Preferably, the vacuum environment of the vacuum degassing process herein is an ultimate vacuum environment.
Preferably, in the step of arc continuous casting, the blank drawing speed is 0.8-1.0 m/min, and the superheat degree is 35-44 ℃. In the arc continuous casting process, the withdrawal speed and the superheat degree are controlled in the ranges, so that the segregation of components in steel is favorably controlled, the tissue segregation degree of a seamless steel tube product is improved, and the impact toughness is favorably improved.
In a preferred embodiment, the straightening temperature is 600 to 700 ℃ during the straightening of the heat-treated pipe.
The beneficial effects of the present invention are further illustrated by the following examples:
examples 1 to 18, comparative examples 1 and 2
The seamless steel pipes were prepared in the above examples and comparative examples, and the preparation processes used were the same, except that the formulations of the chemical elements were different, as follows:
the preparation process comprises the following steps:
and (3) batching according to the chemical components of the steel pipe for the crane boom to obtain the mixed raw material.
And smelting, vacuum degassing and casting the mixed raw materials in sequence to obtain a blank. Specifically, the smelting steps are as follows: and sequentially carrying out electric furnace smelting and external refining on the mixed raw materials, wherein an argon blowing refining process is adopted in the external refining process, and calcium carbide, aluminum particles and carbon powder are added into a refining system for deoxidation. The vacuum degassing step comprises: keeping the smelted mixed raw materials for 30min under the condition of ultimate vacuum. The casting step adopts arc continuous casting, the blank drawing speed is 0.8-1.0 m/min, and the superheat degree is 35-44 ℃.
The blank was heated in a ring furnace with the following procedure: and (3) preheating, heating up and soaking the blank in sequence to obtain a hot blank, wherein the total time for heating the blank is more than or equal to 190 min. The preheating process comprises the following steps: preheating the blank along with the furnace temperature; the temperature rising process sequentially comprises a first heating section, a second heating section, a third heating section, a fourth heating section and a fifth heating section, wherein the temperature of the first heating section is 1024 ℃, and the heating time is 40 min; the temperature of the second heating section is 1138 ℃, and the heating time is 50 min; the temperature of the three heating sections is 1250 ℃, and the heating time is 30 min; the temperature of the four heating sections is 1267 ℃, and the heating time is 30 min; the temperature of the five heating sections is 1263 ℃, and the heating time is 30 min; in the soaking process, the soaking temperature is 1260 ℃, and the heating time is 50min, so as to obtain the hot blank. Perforating the hot blank to obtain a capillary; rolling the rough pipe into a pierced billet, and sizing the pierced billet to obtain a hot-rolled pipe (with the specification phi 168 multiplied by 16 mm).
Carrying out quenching and tempering heat treatment on the hot rolled pipe, specifically, carrying out heat preservation on the hot rolled pipe for 60min at the temperature of 1100 ℃, then sequentially carrying out quenching, primary descaling and surface water spraying cooling on the heat-preserved hot rolled pipe, wherein the descaling water pressure of the primary descaling is more than or equal to 25MPa, and obtaining a first treated steel pipe; tempering the first treated steel pipe for the first time at the temperature of 600 ℃, then performing secondary descaling and air cooling, wherein the descaling water pressure of the secondary descaling is more than or equal to 20MPa, and obtaining a second treated steel pipe; and (3) tempering the second treatment steel pipe for the second time at the temperature of 730 ℃, then carrying out third descaling and air cooling, wherein the descaling water pressure of the third descaling is more than or equal to 20MPa, and obtaining the heat treatment pipe.
Straightening the heat-treated pipe to obtain a steel pipe for the crane boom; wherein the straightening temperature is 600-700 ℃.
The chemical element contents (unit: wt%) of the seamless steel pipes in each of examples and comparative examples are shown in tables 1 to 3:
TABLE 1
TABLE 2
TABLE 3
The properties of the seamless steel pipes obtained in the above examples 1 to 18 and comparative examples 1 and 2 were characterized as follows:
(1) mechanical properties: tensile strength (Rm), yield strength (Rp 0.2), elongation, -40 ℃ impact energy, -60 ℃ impact energy, brittle transition temperature; the test method is carried out according to GB/T229-2007
(2) Straightening performance: and the straightness per meter, namely, a metric ruler or a tightened rope or line with the length of 1m is close to the steel pipe, the maximum distance between the steel pipe and the ruler or the rope or line within the range of 1m is the straightness per meter at the position, the whole steel pipe is measured continuously along the length of 1m of the steel pipe, and the maximum straightness is the straightness per meter of the steel pipe.
(3) Surface properties: visual inspection was carried out.
The test results are shown in tables 4 and 5:
TABLE 4
TABLE 5
As can be seen from the data in the table above, the strength of the seamless steel tube for the crane jib in the comparative examples 1 and 2 can reach 960MPa steel grade by reducing the tempering temperature, but the impact toughness is not good, and the good toughness and toughness matching required by the 960MPa steel grade jib tube cannot be achieved; according to the invention, on the basis of the common seamless steel pipe for the crane boom, the seamless steel pipe with the minimum yield strength of over 960MPa and excellent low-temperature impact toughness can be produced through reasonable component proportion. And the dimensional accuracy data of the steel pipes show that the 960MPa steel grade ultra-high strength arm support pipe after the secondary tempering process has good dimensional accuracy and excellent straightness, and the problem that the ultra-high strength arm support pipe is difficult to straighten is completely solved. By the optimized proportioning of alloy elements and the optimized steel-making and hot-rolling processes and the heat treatment process, the seamless steel tube for the crane jib above 960MPa with good surface quality and excellent straightness can be economically and massively produced.
Example 21
The seamless steel pipe prepared in this example has the same chemical element content and the same preparation process example 5, but the difference lies in that some process conditions in the preparation process are different, specifically as follows:
the blank was heated in a ring furnace with the following procedure: and (3) preheating, heating up and soaking the blank in sequence to obtain a hot blank, wherein the total time for heating the blank is more than or equal to 190 min. The preheating process comprises the following steps: preheating the blank along with the furnace temperature; the temperature rise process sequentially comprises a first heating section, a second heating section, a third heating section, a fourth heating section and a fifth heating section, wherein the temperature of the first heating section is 1014 ℃, and the heating time is 40 min; the temperature of the second heating section is 1128 ℃, and the heating time is 50 min; the temperature of the heating three sections is 1240 ℃, and the heating time is 30 min; the temperature of the four heating sections is 1257 ℃, and the heating time is 30 min; the temperature of the fifth heating section is 1253 ℃, and the heating time is 30 min; in the soaking process, the soaking temperature is 1250 ℃, and the heating time is 50min, so that a hot blank is obtained.
Example 22
The seamless steel pipe prepared in this example has the same chemical element content and the same preparation process example 5, but the difference lies in that some process conditions in the preparation process are different, specifically as follows:
the blank was heated in a ring furnace with the following procedure: and (3) preheating, heating up and soaking the blank in sequence to obtain a hot blank, wherein the total time for heating the blank is more than or equal to 190 min. The preheating process comprises the following steps: preheating the blank along with the furnace temperature; the temperature rise process sequentially comprises a first heating section, a second heating section, a third heating section, a fourth heating section and a fifth heating section, wherein the temperature of the first heating section is 1034 ℃, and the heating time is 40 min; the temperature of the second heating section is 1148 ℃, and the heating time is 50 min; the temperature of the three heating sections is 1260 ℃, and the heating time is 30 min; the temperature of the four heating sections is 1277 ℃, and the heating time is 30 min; the temperature of the fifth heating section is 1273 ℃, and the heating time is 30 min; in the soaking process, the soaking temperature is 1270 ℃, and the heating time is 50min, so as to obtain the hot blank.
Example 23
The seamless steel pipe prepared in this example has the same chemical element content and the same preparation process example 5, but the difference lies in that some process conditions in the preparation process are different, specifically as follows:
the blank was heated in a ring furnace with the following procedure: and (3) preheating, heating up and soaking the blank in sequence to obtain a hot blank, wherein the total time for heating the blank is more than or equal to 190 min. The preheating process comprises the following steps: preheating the blank along with the furnace temperature; the temperature rise process sequentially comprises a first heating section, a second heating section, a third heating section, a fourth heating section and a fifth heating section, wherein the temperature of the first heating section is 1004 ℃, and the heating time is 40 min; the temperature of the second heating stage is 1118 ℃, and the heating time is 50 min; the temperature of the three heating sections is 1230 ℃, and the heating time is 30 min; the temperature of the four heating sections is 1247 ℃, and the heating time is 30 min; the temperature of the fifth heating section is 1243 ℃, and the heating time is 30 min; in the soaking process, the soaking temperature is 1240 ℃, and the heating time is 50min, so as to obtain the hot blank.
Example 24
The blank was heated in a ring furnace with the following procedure: and (3) preheating, heating up and soaking the blank in sequence to obtain a hot blank, wherein the total time for heating the blank is 180 min. The preheating process comprises the following steps: preheating the blank along with the furnace temperature; the temperature rising process sequentially comprises a first heating section, a second heating section, a third heating section, a fourth heating section and a fifth heating section, wherein the temperature of the first heating section is 1024 ℃, and the heating time is 20 min; the temperature of the second heating section is 1138 ℃, and the heating time is 60 min; the temperature of the three heating sections is 1250 ℃, and the heating time is 20 min; the temperature of the four heating sections is 1267 ℃, and the heating time is 30 min; the temperature of the five heating sections is 1263 ℃, and the heating time is 20 min; in the soaking process, the soaking temperature is 1260 ℃, and the heating time is 30min, so that the hot blank is obtained.
The properties of the seamless steel pipes obtained in the above examples 21 to 24 were characterized, and the test results are shown in tables 6 and 7:
TABLE 6
TABLE 7
| Examples | Surface Properties | Accuracy of outer diameter | Wall thickness accuracy | Straightness accuracy |
| 21 | Has smooth surface | 167.5～168.6 | 15.3～16.7 | 1.0mm/m |
| 22 | Has smooth surface | 167.4～168.3 | 15.2～16.6 | 1.2mm/m |
| 23 | Has smooth surface | 167.3～168.4 | 15.1～16.6 | 1.5mm/m |
| 24 | Has smooth surface | 167.2～168.4 | 15.2～16.5 | 1.4mm/m |
From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:
the yield strength of the steel pipe for the crane boom provided by the invention reaches the level of more than 960 MPa. Moreover, by properly adding alloy elements such as Cr, Mo and W and micro alloy elements such as Nb, V and Al and by the synergistic action among the Cr, Mo, W, Nb, V, Al, C and N elements, on the premise of strictly controlling the alloy elements which are easy to generate compact scale on the surface of the steel pipe and bend in the water quenching process, the steel pipe can reach 960 steel-grade strength and toughness requirements by dispersion and precipitation of carbides and nitrides of the micro alloy elements, so that the steel pipe is not easy to generate compact scale and bend in the production process, has good surface quality and straightness, and has excellent low-temperature toughness and weldability while having ultrahigh strength.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (17)
1. The steel pipe for the crane jib is characterized by comprising 0.11 ~ 0.15.15% of C element, 0.28 ~ 0.76.76% of Si element, 0.023 ~ 00.060% of Al element, 0.90 ~ 1.20.20% of Cr element, 0.50 ~ 0.60.60% of Mo element, 0.056 ~ 0.12.12% of V element, 0.039 ~ 0.12.12% of Nb element, 0.565 ~ 1.23.23% of W element, 0.34 ~ 1.32.32% of Ni element, 0 ~ 0.005.005% of N element and 1.10 ~ 1.41.41% of Mn element by weight percentage, and the balance of Fe element and inevitable impurities;
the weight ratio of the W element, the Nb element, the V element and the Al element is 20 ~ 24:1.8 ~ 2:2 ~ 2.2.2: 1.
2. The steel pipe for the crane jib according to claim 1, wherein the steel pipe for the crane jib further comprises P, S, O, H and As, and the content of P is less than or equal to 0.020%, the content of S is less than or equal to 0.010%, the content of O is less than or equal to 0.003%, the content of H is less than or equal to 0.0002%, and the content of As is less than or equal to 0.025% by weight of the steel pipe for the crane jib.
3. The steel pipe for the crane jib according to claim 2, wherein the steel pipe for the crane jib further comprises Sn, Pb, Sb and Bi, and the sum of the Sn, Pb, Sb, Bi and As in the steel pipe for the crane jib is less than or equal to 0.05% by weight.
4. The steel pipe for the crane boom according to claim 1, wherein Ceq is equal to or less than 0.75% in carbon equivalent, a represents a weight content of the C element, b represents a weight content of the Mn element, C represents a weight content of the Cr element, d represents a weight content of the Mo element, e represents a weight content of the V element, and f represents a weight content of the Ni element, and Ceq = a + b/6+ (C + d + e)/5+ f/15.
5. The method for manufacturing the steel pipe for the crane boom as claimed in any one of claims 1 to 4, characterized by comprising the following steps:
batching according to the chemical components of the steel pipe for the crane boom to obtain a mixed raw material;
smelting and casting the mixed raw materials to obtain a blank;
rolling the blank to obtain a hot rolled pipe;
carrying out quenching and tempering heat treatment on the hot rolled pipe to obtain a heat treated pipe; and
and straightening the heat treatment pipe to obtain the steel pipe for the crane boom.
6. The manufacturing method according to claim 5, wherein the process of rolling the billet comprises:
heating the blank to 1230 ~ 1280 ℃ in an annular furnace to obtain a hot blank;
perforating the hot blank to obtain a capillary;
and rolling the hollow billet into a pierced billet, and sizing the pierced billet to obtain the hot rolled pipe.
7. The manufacturing method according to claim 6, wherein the process of heating the blank includes: and sequentially preheating, heating and soaking the blank to obtain the hot blank, wherein the total time for heating the blank is more than or equal to 190 min.
8. The manufacturing method according to claim 7, wherein the preheating process includes: preheating the blank along with the furnace temperature; the temperature raising process sequentially comprises a first heating section, a second heating section, a third heating section, a fourth heating section and a fifth heating section, wherein the temperature of the first heating section is 1024 +/-10 ℃, and the heating time is more than or equal to 30 min; the temperature of the heating second section is 1138 +/-10 ℃, and the heating time is more than or equal to 40 min; the temperature of the three heating sections is 1250 +/-10 ℃, and the heating time is more than or equal to 20 min; the temperature of the four heating sections is 1267 +/-10 ℃, and the heating time is more than or equal to 20 min; the temperature of the five heating sections is 1263 +/-10 ℃, and the heating time is more than or equal to 20 min; in the soaking process, the soaking temperature is 1260 plus or minus 10 ℃, and the heating time is more than or equal to 40 min.
9. The manufacturing method according to any one of claims 5 to 8, wherein the step of subjecting the hot-rolled pipe to a quenching and tempering heat treatment includes:
preserving heat of the hot rolled pipe at 900 ~ 1100 ℃, and then sequentially quenching, primary descaling and surface water spraying cooling the heat-preserved hot rolled pipe to obtain a first treated steel pipe;
tempering the first treated steel pipe for the first time at 500 ~ 600 ℃ and then descaling for the second time and cooling by air to obtain a second treated steel pipe, and
and tempering the second treated steel pipe for the second time at the temperature of 600 ~ 730 ℃ and 730 ℃, and then descaling for the third time and cooling in air to obtain the heat treatment pipe.
10. The method according to claim 9, wherein the first descaling has a descaling water pressure of 25MPa or more; the descaling water pressure of the second descaling is more than or equal to 20 MPa; the descaling water pressure of the third descaling is more than or equal to 20 MPa.
11. The manufacturing method according to any one of claims 5 to 8, wherein the step of smelting comprises: and sequentially carrying out electric furnace smelting and external refining on the mixed raw materials.
12. The method of manufacturing of claim 11, wherein the step of casting comprises: and carrying out arc continuous casting on the smelted mixed raw material to obtain the blank.
13. The manufacturing method according to claim 12, further comprising a step of vacuum degassing the mixed raw material after the smelting, before the arc continuous casting.
14. The manufacturing method of claim 11, wherein the external refining process adopts a whole-process argon blowing refining process, and calcium carbide, aluminum particles and carbon powder are added into a refining system for deoxidation.
15. The method of manufacturing of claim 13, wherein the step of vacuum degassing comprises: and keeping the smelted mixed raw materials under a vacuum condition for more than 20 min.
16. The manufacturing method as set forth in claim 12, wherein in the step of arc continuous casting, the withdrawal speed is 0.8 ~ 1.0.0 m/min and the degree of superheat is 35 ~ 44 ℃.
17. The production method according to any one of claims 5 to 8, wherein a straightening temperature in straightening the heat-treated pipe is 600 ~ 700 ℃.
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| CN109371204A (en) * | 2018-12-22 | 2019-02-22 | 扬州龙川钢管有限公司 | A kind of heavy caliber high-strength BJ890 crane arm support seamless steel pipe and its production method |
| CN114277306B (en) * | 2020-09-27 | 2022-12-16 | 宝山钢铁股份有限公司 | High-strength steel for 1000 MPa-level engineering machinery and production method thereof |
| CN112553526B (en) * | 2020-11-20 | 2022-04-22 | 林州凤宝管业有限公司 | 960 MPa-level ultrahigh-strength structural steel, steel pipe and manufacturing method and application thereof |
| CN115679209B (en) * | 2022-10-14 | 2024-02-09 | 成都先进金属材料产业技术研究院股份有限公司 | Low-alloy tungsten-containing ultra-high-strength steel and production method thereof |
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| DE102008010749A1 (en) * | 2008-02-20 | 2009-09-24 | V & M Deutschland Gmbh | Steel alloy for a low-alloyed steel for the production of high-strength seamless steel tubes |
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