CN112458375A - Special steel for ASTM A656 Gr70 support pipe and preparation method thereof - Google Patents
Special steel for ASTM A656 Gr70 support pipe and preparation 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
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0006—Adding metallic additives
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/072—Treatment with gases
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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
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
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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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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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
- 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
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
Abstract
The invention relates to a special steel for an ASTM A656 Gr70 support tube and a preparation method thereof, wherein the special steel for the ASTM A656 Gr70 support tube is prepared from the following components in percentage by mass: 0.05-0.25%, Si: 0.15 to 0.35%, Mn: 1.30-1.70%, S: 0.0010-0.0050%, P: 0.005-0.015%, Al: 0.015-0.065%, O: 0.0008-0.0030%, N: 0.0010-0.0040%, Ca: 0.0010-0.0040%, Nb: 0.040-0.10%, Ti: 0.01-0.06%, V: 0.01-0.06%, and the balance of Fe and other inevitable impurities. On the basis of carbon-manganese steel, niobium, vanadium and titanium are added for composite strengthening, so that the grain size can be effectively refined, austenite recrystallization is inhibited, the fatigue resistance of the steel special for the ASTM A656 Gr70 support tube is improved, expensive nickel is not added on the basis, the production cost of the steel special for the ASTM A656 Gr70 support tube is reduced, and the economic benefit of enterprises is improved.
Description
Technical Field
The invention relates to the technical field of special steel for support pipes, in particular to special steel for ASTM A656 Gr70 support pipes and a preparation method thereof.
Background
For a long time, the domestic support pipe adopts the traditional medium carbon seamless steel pipe, and the production capacity can not meet the requirement far. With the development of microalloying and controlled rolling and controlled cooling technologies of steel, high-grade hot rolled plate coils obtain excellent comprehensive performance, and the hot rolled plate coils are used for manufacturing straight seam Electric Resistance Welding (ERW) sleeves to replace traditional seamless steel pipes abroad in the eighties, so that success is achieved, and better economic benefits are obtained. According to the statistics of the American automobile society, the steel special for the straight slit supporting tube accounts for 50-60% of the total amount of the supporting tube, and according to the Japanese statistical data, the following data are shown: the support tube produced by the ERW welding method accounts for 70 percent, and the yield ratio of the straight seam resistance welding sleeve to the seamless sleeve in other industrially developed countries is at least 3: 7. the straight welded pipe has the advantages that: the seamless sleeve pipe has the advantages of high geometric dimension precision, uniform wall thickness, 10-15% higher fatigue resistance and external extrusion pressure capability in service than the same steel grade seamless sleeve pipe, low carbon content of the material, no tearing after forming and low price.
China introduces seamless supporting tubes from abroad since the last 90 years, the seamless supporting tubes are tried on truck frames, supports and crane frames, the using effect is good, in order to reduce import, China automobile industry encourages ERW welded tubes to replace seamless tubes, but the current steel special for ASTM A656 supporting tubes has the defects of high cost, low dimensional precision, uneven wall thickness, poor collapse and crushing resistance, poor fatigue resistance, poor welding performance and the like.
Therefore, there is a need to develop a steel special for supporting tubes in ASTM a656 Gr70 and a preparation method thereof, which can overcome the above disadvantages.
Disclosure of Invention
The present invention is directed to solving one of the technical problems of the prior art or the related art.
The invention provides the special steel for the support tube in ASTM A656 Gr70 and the preparation method thereof.
In view of the above, one aspect of the present invention provides a steel special for ASTM a656 Gr70 support tubes, which steel special for ASTM a656 Gr70 support tubes is composed of, by mass percent, C: 0.05-0.25%, Si: 0.15 to 0.35%, Mn: 1.30-1.70%, S: 0.0010-0.0050%, P: 0.005-0.015%, Al: 0.015-0.065%, O: 0.0008-0.0030%, N: 0.0010-0.0040%, Ca: 0.0010-0.0040%, Nb: 0.040-0.10%, Ti: 0.01-0.06%, V: 0.01-0.06%, and the balance of Fe and other inevitable impurities.
Further, the ASTM A656 Gr70 supports the thickness of the tube-dedicated steel from 2.0mm to 20.0 mm.
Further, the ASTM A656 Gr70 support tube special steel has the tensile strength of 600MPa to 670MPa, the yield strength of 510MPa to 580MPa and the elongation of 28 percent to 40 percent.
The invention also provides a preparation method of the steel special for the support tube in ASTM A656 Gr70, which comprises the following steps:
pretreating molten iron, wherein after the molten iron is pretreated, the molten iron S is less than or equal to 0.005 percent, and completely slagging off;
a converter working procedure, namely, loading fine material scrap steel into a furnace, pouring the treated molten iron into the furnace to form molten steel, blowing a steel ladle through argon before tapping, and injecting the molten steel into the steel ladle to ensure that Alt is more than or equal to 0.015% and less than or equal to 0.045% in the steel ladle;
a refining process, namely refining the molten steel in the ladle by adopting an LF (ladle furnace) refining process to ensure that the nitrogen increment N is less than or equal to 5ppm, manufacturing reducing slag with fluidity, controlling the argon blowing strength, and adopting calcium treatment to obtain refined molten steel;
a continuous casting process, pouring the refined molten steel into a tundish, purging the tundish by adopting argon before casting to ensure that the nitrogen increment N is less than or equal to 5ppm, and controlling the target continuous casting superheat degree to be 20-25 ℃;
heating in a heating furnace at 1220-1260 ℃, and keeping the temperature for 30 mim-50 min to obtain a plate blank;
hot continuous rolling, including rough rolling and finish rolling, wherein the thickness of a plate blank is not less than 55mm during the rough rolling, and the compression ratio of the finish rolling is more than 4.0;
controlling the cooling to be intermittent cooling;
coiling at a coiling temperature of not lower than 500 ℃.
Further, the carbon is drawn in the converter process for one time, so that the phenomenon that the oxygen content in steel is too high due to point blowing and complementary blowing is avoided, high manganese and ferrosilicon are added in the tapping process, and the high manganese and the ferrosilicon are added in the tapping process.
And further, adding ferrovanadium and ferroniobium alloy during tapping.
Further, in the refining process, active lime and fluorite are adopted to manufacture reducing slag with fluidity, and the calcium treatment is to feed CaSi wires of 400m to 500 m.
Further, Al is added for deoxidation in the refining process, and Ti-Fe, Nb-Fe and V-Fe are added.
Further, the finishing temperature in the hot continuous rolling is not more than 880 ℃.
Further, the converter process adopts a top-bottom combined blown converter.
The technical scheme provided by the embodiment of the invention can have the following beneficial effects:
on the basis of carbon-manganese steel, Nb, V and Ti with a certain proportion are added into the steel for composite strengthening, the composite strengthening is combined with thermomechanical control rolling, the P, S content and the gas H, N and O content in the steel are strictly controlled, the steel is pure, calcium treatment is carried out after refining is finished, oxides and sulfides in the steel are distributed in a spherical shape, the problems that the level of inclusions in special steel is high and a banded structure exceeds the standard are well solved, the special steel has good obdurability matching and excellent fatigue resistance, ferrite pearlite can be obtained by the preparation method, and the structure ensures that the steel plate has excellent forming performance, cold bending performance and welding performance while having good obdurability and fatigue resistance.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.
In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.
Fig. 1 shows a schematic flow chart of a preparation method of steel special for ASTM a656 Gr70 support pipes according to one embodiment of the present invention.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the invention, as detailed in the appended claims.
Example 1
The embodiment provides a special steel for supporting pipes in ASTM A656 Gr70, which is prepared from the following components in percentage by mass: 0.05-0.25%, Si: 0.15 to 0.35%, Mn: 1.30-1.70%, S: 0.0010-0.0050%, P: 0.005-0.015%, Al: 0.015-0.065%, O: 0.0008-0.0030%, N: 0.0010-0.0040%, Ca: 0.0010-0.0040%, Nb: 0.040-0.10%, Ti: 0.01-0.06%, V: 0.01-0.06%, and the balance of Fe and other inevitable impurities.
On the basis of carbon-manganese steel, niobium, vanadium and titanium are added for composite strengthening, the grain size can be effectively refined, austenite recrystallization is inhibited, the fatigue resistance of the steel special for the ASTM A656 Gr70 support tube is improved, on the basis, vanadium replaces nickel, on one hand, vanadium element can enable the steel to obtain more and finer pearlite at the same cooling speed by reducing the carbon content of a eutectoid point and improving the stability of super-cooled austenite, so that the strength of the steel is improved, on the other hand, V replaces Ni, the production cost of the steel special for the ASTM A656 Gr70 support tube is reduced, and the economical efficiency of enterprises is improved.
Specifically, Mn, Nb, V and Ti have the dragging action of solute in solid solution, the pinning action of fine precipitates in gamma grain boundary and the dislocation arrangement action in deformed grains in steel, and the results of the actions delay austenite recrystallization until austenite bears larger deformation, so that the critical deformation amount required for the start of the gamma grain boundary is greatly improved, once recrystallization occurs, the higher nucleation rate is obtained, the fine and uniform grain size is obtained, austenite recrystallization is inhibited, the excessive coarseness of original austenite grains is avoided, the final structure of the steel plate is finer, and the fatigue resistance, the forming performance and the welding performance of the steel plate are further improved.
Further, ASTM A656 Gr70 supports the thickness of the tube-specific steel from 2.0mm to 20.0 mm.
Through the special steel for the ASTM A656 Gr70 support tube, the original 345 MPa-level steel plate with the thickness of 5.0mm can be replaced by the steel with the thickness of 4.0mm, and the original 345 MPa-level steel plate with the thickness of 6.0mm is replaced by the steel with the thickness of 5.0mm, so that the weight of the support tube is reduced by 15%, the steel consumption is reduced, and energy conservation and environmental protection are realized.
Further, the ASTM A656 Gr70 support tube special steel has the tensile strength of 600MPa to 670MPa, the yield strength of 510MPa to 580MPa and the elongation of 28 percent to 40 percent.
The performance of each parameter of the steel special for the ASTM A656 Gr70 support tube can meet the requirement of the ASTM A656, the finished steel tube has no thread gluing phenomenon through a make-up test and a break-out test, the optimal torque requirement of the ASTM A656 is met, and the thread parameter, the failure pressure and the failure load of the steel tube meet the standard requirement of the ASTM A656.
Example 2
Fig. 1 shows a schematic flow chart of a preparation method of steel special for ASTM a656 Gr70 support pipes according to one embodiment of the present invention.
As shown in fig. 1, this example proposes a preparation method of steel special for ASTM a656 Gr70 support tube, which includes the following steps:
pretreating molten iron, wherein after the molten iron is pretreated, the molten iron S is less than or equal to 0.005 percent, and completely slagging off;
a converter process, namely, loading fine material scrap steel into a furnace, pouring the treated molten iron into the furnace to form molten steel, blowing a steel ladle through argon before tapping, and injecting the molten steel into the steel ladle to ensure that Alt is more than or equal to 0.015% and less than or equal to 0.045% in the steel ladle;
a refining process, namely refining the molten steel in the ladle by adopting an LF (ladle furnace) refining process to ensure that the nitrogen increment N is less than or equal to 5ppm, manufacturing reducing slag with fluidity, controlling the argon blowing strength, and adopting calcium treatment to obtain refined molten steel;
a continuous casting process, pouring the refined molten steel into a tundish, purging the tundish by adopting argon before casting to ensure that the nitrogen increment N is less than or equal to 5ppm, and controlling the target continuous casting superheat degree to be 20-25 ℃;
heating in a heating furnace at 1220-1260 ℃, and keeping the temperature for 30 mim-50 min to obtain a plate blank;
hot continuous rolling, including rough rolling and finish rolling, wherein the thickness of a plate blank is not less than 55mm during the rough rolling, and the compression ratio of the finish rolling is more than 4.0;
controlling the cooling to be intermittent cooling;
coiling at a coiling temperature of not lower than 500 ℃.
Wherein, in order to ensure the tissue to be fine and uniform, a finishing mill group is rolled by an F1-F7 frame, the finish rolling compression ratio is required to be more than 4.0, namely, a plate blank is rolled from 55mm to 28mm by F1, and the reduction rate reaches 50%; rolling the steel plate from 28mm to 14mm through F2, rolling the steel plate from 14mm to 8.4mm through F3, and finally rolling the steel plate into the finished product with the thickness of 4.0mm required by a user through F4, F5 and F6.
Specifically, the heating temperature is increased to 1220-1260 ℃, so that alloy elements are fully dissolved, Nb, V and Ti in the steel are fully melted, the composite effects of fine grain strengthening, precipitation strengthening and precipitation strengthening are achieved, better obdurability matching and good plate shape are ensured during hot continuous rolling, and the requirements of the rolling process are met; the thickness of the plate blank is not less than 55mm during rough rolling, and the compression ratio of finish rolling is more than 4.0, namely the plate blank is rolled from 55mm to 28mm through F1, and the reduction rate reaches 50%; rolling the steel plate into a thickness of 14mm from 28mm through F2, rolling the steel plate into a thickness of 8.4mm from 14mm through F3, and finally rolling the steel plate into a thickness of a finished product required by a user through F4, F5 and F6, so that the metallographic structure, the mechanical property and the physical property of the finished steel plate are ensured, the surface quality and the internal quality of the steel plate are ensured, and the quality of the finished product is improved; the method has the advantages that the whole-process protective pouring is adopted during the continuous casting process, the pouring process ensures that no molten steel is exposed, the function is realized under the condition that the molten steel is put into the steel pouring process, the constant drawing speed is kept during the steel pouring process, the superheat degree control target of continuous casting is 20-25 ℃, isometric crystals in steel fully grow to avoid excessive columnar crystals, the continuous casting blank adopts a hot-delivery hot-charging process, the energy consumption is saved, the surface weight of the plate blank is favorably improved, the residual plate blank is placed in a slow cooling area in a warehouse, and the crack defect caused by the excessively fast cooling speed of the continuous casting blank is avoided.
The soft reduction is a process method for applying small pressure to a liquid-cored casting blank in order to obtain a defect-free casting blank when the continuous casting and rolling blank is straightened by adopting liquid core straightening in the continuous casting and iron making process, wherein solidification and cooling shrinkage can cause solidification shrinkage force to suck S, P enriched liquid among dendritic crystals around to generate center segregation, the formation of the center segregation is caused by the fact that a bridge is formed at the solidification front edge of inward growth to obstruct the downward conveying of molten steel, and the center segregation can seriously influence the internal quality of the casting blank. In order to reduce the center segregation, a soft reduction technology is applied to a section (casting blank solidification end section) where the center segregation is generated, that is, a casting blank is slightly reduced at a position where the casting blank is nearly completely solidified, so that the center segregation is reduced.
Wherein the constant drawing speed is generally 1m/min to 4 m/min.
The ferrite pearlite can be obtained by the preparation method, and the structure ensures that the steel plate has excellent forming performance, cold bending performance and welding performance while ensuring good toughness and fatigue resistance.
Furthermore, in the converter process, carbon is drawn for one time, point blowing and complementary blowing are avoided, and high manganese and ferrosilicon are added in the tapping process, so that the manganese and silicon contents reach the tapping component control range in the tapping process.
The carbon in the molten steel is reduced to the range of target components, the over-high oxygen content in the steel caused by point blowing and complementary blowing is avoided, and the high manganese and ferrosilicon are added in the tapping process, so that the manganese and silicon content in the tapping process reaches the tapping component control range.
Further, ferrovanadium and ferroniobium alloy are added during tapping.
Because V, Nb is stable in steel, VFe and NbFe alloy is added during tapping, so that V, Nb content in a ladle meets requirements, and the V, Nb deficiency is added during refining.
Further, in the refining process, active lime and fluorite are adopted to manufacture reducing slag with fluidity, and calcium treatment is to feed CaSi wires of 400m to 500 m.
In the refining process, an LF refining process is adopted, and the gas in the steel is strictly limited. The LF treatment is required to keep micro-positive pressure, the LF N increasing amount is strictly controlled, and the CaSi wire is fed to 400m to 500m, so that inclusions are fully spheroidized, and the forming property, the fatigue property and the welding property of the steel plate are improved.
Wherein, Al is added for deoxidation in the refining process, and Ti-Fe, Nb-Fe and V-Fe are added.
Adding Ti-Fe to make the Ti content in the steel meet the target requirement, and supplementing Nb-Fe and V-Fe to the internal control standard range.
Because Ti is very active in steel, Ti alloying is carried out in refining, and Ti-Fe alloy is added in the refining process during refining, so that Ti in the steel meets the requirement of a finished product; the argon blowing strength is strictly controlled, and the exposure of molten steel is avoided as much as possible, so that the oxygen content in the molten steel is too high.
Further, the finishing temperature in the hot continuous rolling is not more than 880 ℃.
The finish rolling temperature and the coiling temperature are controlled, so that sufficient time is provided for obtaining ferrite and pearlite structures, crystal grains are refined, and the welding performance and the fatigue resistance of the steel special for the ASTM A656 Gr70 support tube are improved while the toughness is ensured.
Further, the converter process adopts a top-bottom combined blown converter for smelting.
The top-bottom combined blown converter supplies oxygen from the upper part of a converter molten pool, supplies inert gas from the bottom and simultaneously carries out blowing at the top and the bottom, and compared with the existing top blowing process, the combined blown converter has the following advantages: reducing the oxygen content in molten steel and the TFe content in slag; improving the manganese content of molten steel at the blowing end point; the dephosphorization and desulfurization efficiency is improved; the blowing is stable and the splashing is reduced.
Three sets of sample steels were prepared according to the preparation method of this example, and their performance parameters are shown in table 1.
TABLE 1 data sheet of the Performance parameters of three groups of sample steels
Wherein the heating temperature of the sample 1 is 1220 ℃, the heat preservation time is 35min, the finish rolling temperature is 875 ℃, the coiling temperature is 550 ℃, the heating temperature of the sample 2 is 1240 ℃, the heat preservation time is 40min, the finish rolling temperature is 870 ℃, the coiling temperature is 560 ℃, the heating temperature of the sample 3 is 1260 ℃, the heat preservation time is 50min, the finish rolling temperature is 860 ℃ and the coiling temperature is 580 ℃.
As can be seen from Table 1, the supporting tube special steel prepared by the preparation method of the embodiment meets the requirements of the grade special steel in ASTM A656 Gr70, and has better product quality.
In Table 1, KV2 represents the impact absorption energy of a V-notch sample at a weight edge of 2mm, and the larger the value, the better the surface toughness, and ASTM A656 Gr70 supports tube special steel 60J at-20 ℃ standard, and the actual values are 110J, 96J and 95J, which shows that the toughness of the special steel is good.
Comparative example
The performance parameters of the support tube special steel of the application and the support tube special steel of other preparation methods of the same grade are compared and shown in table 2.
TABLE 2 comparison table of performance parameters of the supporting tube special steel and other steel tubes
Wherein, the sample 1 is the special steel according to the invention with the chemical components, and the rolling process is as follows: the heating temperature is 1220 ℃, the heat preservation time is 35min, the finishing temperature is 875 ℃, and the coiling temperature is 550 ℃.
The sample 2 as a comparison sample adopts the original component design, common low alloy steel, the heating temperature of 1210 ℃, the heat preservation time of 50min, the finish rolling temperature of 840 ℃ and the coiling temperature of 620 ℃.
The sample 3 as a comparison sample adopts the original component design, common low alloy steel, the heating temperature is 1200 ℃, the heat preservation time is 60min, the finish rolling temperature is 835 ℃, and the coiling temperature is 600 ℃.
As can be seen from Table 2, the ASTM A656 Gr70 support tube special steel produced by the components and the method is superior to the original 345MPa grade steel plate in all properties.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
It is to be understood that the present invention is not limited to what has been described above, and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.
Claims (10)
1. The steel special for the support tube of ASTM A656 Gr70 is characterized in that the steel special for the support tube of ASTM A656 Gr70 is prepared from the following components in percentage by mass: 0.05-0.25%, Si: 0.15 to 0.35%, Mn: 1.30-1.70%, S: 0.0010-0.0050%, P: 0.005-0.015%, Al: 0.015-0.065%, O: 0.0008-0.0030%, N: 0.0010-0.0040%, Ca: 0.0010-0.0040%, Nb: 0.040-0.10%, Ti: 0.01-0.06%, V: 0.01-0.06%, and the balance of Fe and other inevitable impurities.
2. The ASTM A656 Gr70 steel special for support tubes according to claim 1, wherein the ASTM A656 Gr70 steel special for support tubes has a thickness of 2.0mm to 20.0 mm.
3. The ASTM A656 Gr70 steel special for supporting tubes as claimed in claim 1, wherein the ASTM A656 Gr70 steel special for supporting tubes has a tensile strength of 600MPa to 670MPa, a yield strength of 510MPa to 580MPa and an elongation of 28% to 40%.
4. A method for preparing steel special for supporting tubes according to ASTM a656 Gr70 in any one of claims 1 to 3, wherein the method comprises the following steps:
pretreating molten iron, wherein after the molten iron is pretreated, the molten iron S is less than or equal to 0.005 percent, and completely slagging off;
a converter working procedure, namely, loading fine material scrap steel into a furnace, pouring the treated molten iron into the furnace to form molten steel, blowing a steel ladle through argon before tapping, and injecting the molten steel into the steel ladle to ensure that Alt is more than or equal to 0.015% and less than or equal to 0.045% in the steel ladle;
a refining process, namely refining the molten steel in the ladle by adopting an LF (ladle furnace) refining process to ensure that the nitrogen increment N is less than or equal to 5ppm, manufacturing reducing slag with fluidity, controlling the argon blowing strength, and adopting calcium treatment to obtain refined molten steel;
a continuous casting process, pouring the refined molten steel into a tundish, purging the tundish by adopting argon before casting to ensure that the nitrogen increment N is less than or equal to 5ppm, and controlling the target continuous casting superheat degree to be 20-25 ℃;
heating in a heating furnace at 1220-1260 ℃, and keeping the temperature for 30 mim-50 min to obtain a plate blank;
hot continuous rolling, including rough rolling and finish rolling, wherein the thickness of a plate blank is not less than 55mm during the rough rolling, and the compression ratio of the finish rolling is more than 4.0;
controlling the cooling to be intermittent cooling;
coiling at a coiling temperature of not lower than 500 ℃.
5. The method for preparing the steel special for the ASTM A656 Gr70 support tube according to claim 4, wherein the carbon drawing is hit once in the converter process, the point blowing and the complementary blowing are avoided, and high manganese and ferrosilicon are added in the tapping process.
6. The method for preparing the steel special for the ASTM A656 Gr70 support tube according to claim 4, wherein V-Fe and Nb-Fe are added during tapping.
7. The method for preparing the steel special for the ASTM A656 Gr70 support tube as claimed in claim 4, wherein in the refining process, the reducing slag with fluidity is prepared by adopting active lime and fluorite, and the calcium is processed by feeding 400m to 500m of CaSi line.
8. The method for preparing the steel special for the ASTM A656 Gr70 support tube according to claim 4, wherein Al is added for deoxidation during refining in the refining procedure, and Ti-Fe, Nb-Fe and V-Fe are added.
9. The method for preparing the steel special for the ASTM A656 Gr70 support pipe according to claim 4, wherein the finishing temperature in the hot continuous rolling is not more than 880 ℃.
10. The method for preparing the steel special for the ASTM A656 Gr70 support tube according to any one of claim 4 and 9, wherein the converter procedure adopts a top-bottom combined blown converter.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011441370.0A CN112458375A (en) | 2020-12-08 | 2020-12-08 | Special steel for ASTM A656 Gr70 support pipe and preparation method thereof |
Applications Claiming Priority (1)
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Cited By (1)
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Application publication date: 20210309 |