CN113637890A - Ultra-fine grain seamless steel pipe and manufacturing method thereof - Google Patents
Ultra-fine grain seamless steel pipe and manufacturing method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 129
- 239000010959 steel Substances 0.000 title claims abstract description 129
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 30
- 238000001816 cooling Methods 0.000 claims abstract description 48
- 238000005096 rolling process Methods 0.000 claims abstract description 18
- 238000010438 heat treatment Methods 0.000 claims abstract description 12
- 229910052729 chemical element Inorganic materials 0.000 claims abstract description 7
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 6
- 238000003303 reheating Methods 0.000 claims abstract description 6
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 5
- 238000004513 sizing Methods 0.000 claims abstract description 5
- 239000012535 impurity Substances 0.000 claims abstract description 4
- 238000000034 method Methods 0.000 claims description 21
- 229910000859 α-Fe Inorganic materials 0.000 claims description 17
- 229910052758 niobium Inorganic materials 0.000 claims description 8
- 229910052719 titanium Inorganic materials 0.000 claims description 8
- 229910052720 vanadium Inorganic materials 0.000 claims description 8
- 229910052804 chromium Inorganic materials 0.000 claims description 6
- 229910052802 copper Inorganic materials 0.000 claims description 6
- 229910052750 molybdenum Inorganic materials 0.000 claims description 6
- 229910052759 nickel Inorganic materials 0.000 claims description 6
- 238000004321 preservation Methods 0.000 claims description 3
- 239000013078 crystal Substances 0.000 abstract description 3
- 230000008569 process Effects 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 10
- 230000000694 effects Effects 0.000 description 6
- 238000012545 processing Methods 0.000 description 6
- 230000002411 adverse Effects 0.000 description 5
- 229910045601 alloy Inorganic materials 0.000 description 5
- 239000000956 alloy Substances 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 230000009286 beneficial effect Effects 0.000 description 4
- 238000013461 design Methods 0.000 description 4
- 229910001562 pearlite Inorganic materials 0.000 description 4
- 229910001566 austenite Inorganic materials 0.000 description 3
- 229910001563 bainite Inorganic materials 0.000 description 3
- 229910000734 martensite Inorganic materials 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 230000009466 transformation Effects 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000003754 machining Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 238000005275 alloying Methods 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 238000004781 supercooling Methods 0.000 description 1
- 238000005496 tempering Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- RMLPZKRPSQVRAB-UHFFFAOYSA-N tris(3-methylphenyl) phosphate Chemical compound CC1=CC=CC(OP(=O)(OC=2C=C(C)C=CC=2)OC=2C=C(C)C=CC=2)=C1 RMLPZKRPSQVRAB-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- 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
-
- 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
-
- 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
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- C—CHEMISTRY; METALLURGY
- 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
- C21D2211/005—Ferrite
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
The invention discloses an ultra-fine grain seamless steel tube, the grain size is above grade 9, and the mass percentages of all chemical elements of the ultra-fine grain seamless steel tube are as follows: c: 0.03-0.1%, Si: 0.2-1%, Mn: 0.5% -1.5%, Al: 0.01-0.05%, N: 0.001-0.01% of S, less than or equal to 0.008% of P, less than or equal to 0.02% of O, and the balance of Fe and other inevitable impurity elements. In addition, the invention also discloses a manufacturing method of the superfine crystal grain seamless steel pipe, which comprises the steps of (1) preparing a pipe blank (2), heating and preserving heat of the pipe blank, then perforating and rolling to prepare a pierced billet (3), cooling the pierced billet at the cooling speed of 10-80 ℃/s, controlling the final cooling temperature to be less than or equal to 600 ℃ (4), reheating the cooled pierced billet to 850-1000 ℃, keeping for 10-60 min, performing tension reducing or sizing, and controlling the section deformation to be not less than 1.2 (5): and controlling the finish rolling temperature to be 800-980 ℃, cooling the steel pipe at a cooling speed of 10-80 ℃/s after finish rolling, and freely cooling the steel pipe to room temperature at the finish cooling temperature of 550-700 ℃ (6).
Description
Technical Field
The invention relates to a metal material and a manufacturing method thereof, in particular to a seamless steel tube and a manufacturing method thereof.
Background
The seamless steel pipe can be applied to the fields of fluid transportation and the like, and has more applications in the manufacturing of various mechanical structure parts due to the hollow characteristic. The seamless steel pipe is often used as a raw material for processing, and needs to be subjected to various deformation processes such as bending, expanding and extruding in subsequent processing, and is applied to a mechanical structure. This makes higher demands on the ductility and toughness of seamless pipes for mechanical construction. Further, since a seamless pipe for a machine structure is often subjected to a certain stress, a certain requirement is also imposed on the strength thereof.
The traditional manufacturing method of the seamless steel tube is perforation-rolling-tension reducing/sizing tube forming, then the tube is air-cooled to room temperature on a cooling bed, the deformation process is carried out in a high-temperature area, and a structural performance regulation and control means similar to a plate TMCP technology is also absent in the process, so that the crystal grains are often thicker than those of similar plate products, and the performance is lower. In recent years, some enterprises begin to explore means of controlling cooling, rolling and the like in the production process of seamless steel pipes, and the measures have good effects on grain refinement and performance improvement.
Ferrite generally exists in steel as a soft phase, the ductility and toughness of the ferrite are good, the ferrite is suitable for subsequent processing, but the strength is low, the refined ferrite grains are an effective method for improving the toughness, but the refined grains of the seamless steel tube basically need to be added with micro alloy elements such as V, Nb, Ti and the like, rare earth and the like, or the refined ferrite grains can be obtained through subsequent heat treatment, but the grain size of the ferrite cannot reach more than 9 grades, and the strengthening effect is limited.
Chinese patent publication No. CN101892441A, published 24/11/2010 entitled "ultra-fine grain semitrailer axle tube material and axle tube processing method", discloses an ultra-fine grain semitrailer axle tube and manufacturing method thereof, which mainly uses the outer wall strong cooling and residual temperature tempering processes to greatly improve the strength and fatigue life, and does not significantly improve the plasticity.
The Chinese patent document with the publication number of CN103290324A and the publication number of 2013, 9, 11 and the name of 'fine-grained ferrite + pearlite type N80-1 non-quenched and tempered seamless oil casing and production method' discloses a fine-grained ferrite + pearlite type non-quenched and tempered N80-1 seamless oil casing and production method thereof, which mainly refine grains and improve toughness through an online normalizing process, and simultaneously need to add refined grain elements such as V/Nb/Ti and the like.
Based on this, it is desired to obtain a seamless steel pipe which has excellent deformation characteristics and low-temperature toughness and also has high strength without adding micro-alloying elements such as V/Nb/Ti.
Disclosure of Invention
One of the objectives of the present invention is to provide an ultra-fine grain seamless steel tube, the microstructure of which is mainly ferrite, the ferrite proportion is not less than 75%, the grain size is above 9 grade, which has excellent deformation characteristic and low temperature toughness (elongation is more than 30%, charpy impact work at-40 ℃ is more than 50J), and the yield strength can reach more than 245 MPa. The superfine grain seamless steel pipe does not need to add various precious alloy elements and heat treatment, has low production cost and can be effectively applied to various machining and manufacturing industries which take steel pipes as raw materials.
In order to achieve the purpose, the invention provides an ultra-fine grain seamless steel pipe, which comprises the following chemical elements in percentage by mass:
c: 0.03-0.1%, Si: 0.2-1%, Mn: 0.5% -1.5%, Al: 0.01-0.05%, N: 0.001-0.01% of S, less than or equal to 0.008% of P, less than or equal to 0.02% of O, and the balance of Fe and other inevitable impurity elements.
In the ultra-fine grain seamless steel pipe of the present invention, the design principle of each chemical element is as follows:
c: in the ultra-fine grained seamless steel pipe of the present invention, C is advantageous for improving the strength of steel, but excessive C also reduces the ductility and toughness of steel, and in order to ensure excellent ductility and toughness of steel, it is necessary to maintain a structure mainly including ferrite to reduce the proportion of pearlite, cementite, etc. in steel. Therefore, the mass percent of C in the ultra-fine grain seamless steel pipe is controlled to be 0.03-0.1%.
In some preferred embodiments, the mass percentage of C can be controlled between 0.03 and 0.08%.
Si: in the ultra-fine grain seamless steel pipe, Si is beneficial to inhibiting pearlite transformation in the steel, so that the content of Si is required to be kept above 0.2%, when the content of Si exceeds 1%, the cold brittleness tendency of the steel is obviously increased, and the mass percent of Si in the ultra-fine grain seamless steel pipe is controlled to be 0.2-1%.
In some preferred embodiments, the mass percentage of Si may be controlled between 0.4 and 0.8%.
Mn: in the ultra-fine grain seamless steel pipe, Mn has the beneficial effects of expanding an austenite phase region, refining grains and the like, when the content of C in the seamless steel pipe is limited to be lower, enough Mn needs to be added to improve the solid solution strengthening effect, but meanwhile, after the content of Mn exceeds a certain amount, the tendency of forming structures such as bainite, martensite and the like during the cooling of the steel is increased. Therefore, the mass percent of Mn in the ultra-fine grain seamless steel pipe is controlled between 0.5 percent and 1.5 percent.
In some preferred embodiments, the mass percent of Mn can be controlled between 0.8 and 1.2%.
Al: in the ultra-fine grain seamless steel pipe, Al is usually brought in by a deoxidizer, and oxynitride of the deoxidizer can play a role in pinning austenite grain boundaries and refining grains in the steel. However, it should be noted that too much Al content in the steel also results in large-particle inclusions, which affect the properties of the steel. Therefore, the mass percent of Al in the ultra-fine grain seamless steel pipe is controlled to be 0.01-0.05%.
In some preferred embodiments, the mass percentage of Al can be controlled between 0.01 and 0.03%.
N: in the ultra-fine grain seamless steel pipe, the strength and the hardness of the steel can be effectively improved by containing a trace amount of N in the steel, but the formation of more inclusions can be caused by excessively high content of N, so that the performance of the steel is not facilitated. The beneficial influence and adverse factors of N element in steel are comprehensively considered, and the mass percent of N in the ultra-fine grain seamless steel pipe is controlled to be 0.001-0.01%.
S: in the ultra-fine grain seamless steel pipe of the present invention, S is a harmful element in steel, and S has adverse effects on corrosion resistance, hot workability, toughness, etc. of steel, so that S is controlled to be not more than 0.008% by mass in the ultra-fine grain seamless steel pipe of the present invention.
In some preferred embodiments, the mass percentage of S may be controlled to be S.ltoreq.0.005%.
P: in the ultra-fine grain seamless steel pipe of the present invention, P is also a harmful element in the steel, and an excessively high content of P adversely affects the corrosion resistance, toughness, etc. of the steel. Therefore, the mass percentage of P in the ultra-fine grain seamless steel pipe is controlled to be less than or equal to 0.02 percent.
In some preferred embodiments, the mass percentage of P may be controlled to be P.ltoreq.0.015%.
O: in the ultra-fine grain seamless steel pipe, O exists in the steel in the form of various oxide inclusions, the existence of the oxide inclusions has adverse effects on the hot workability and the plastic toughness of the steel, and in order to ensure the final performance of the product, the mass percent of O in the ultra-fine grain seamless steel pipe is controlled to be less than or equal to 0.006 percent.
In some preferred embodiments, the mass percent of O may be controlled to be O.ltoreq.0.004%.
Further, in the ultra-fine grain seamless steel pipe of the present invention, it further contains at least one of V, Nb and Ti elements, and the addition amount thereof satisfies: when the ratio of (V + Nb + Ti) is more than 0, the ratio is less than or equal to 0.15 percent. V, Nb and Ti in the formula respectively represent the mass percent of each element.
It should be noted that one of the features of the present technical solution is that without adding micro-alloy elements such as V, Nb, Ti, etc., the steel has excellent deformation characteristics and low temperature toughness, and has high strength, i.e., the elongation of the steel grade is greater than 30% and the charpy impact energy at-40 ℃ is greater than 50J, the yield strength is greater than or equal to 245MPa, and the grain size is greater than 9 grade. In this case, V, Nb and Ti may be added in appropriate amounts to the ultra-fine grained seamless steel pipe of the present invention, thereby further improving the performance of the ultra-fine grained seamless steel pipe. However, since too high a content of V, Nb and Ti is liable to form coarse carbides in the steel, the total amount of the elements V, Nb and Ti added is controlled to 0 < (V + Nb + Ti) > 0.15% in the ultra-fine grained seamless steel pipe according to the present invention.
Further, in the ultra-fine grain seamless steel pipe according to the present invention, at least one of Cr, Ni, Cu, and Mo elements is further contained, and the addition amount thereof satisfies: cr/5+ Mo/5+ (Cu + Ni)/15 is more than 0 and less than or equal to 0.08 percent. In the formula, Cr, Ni, Cu and Mo respectively represent the mass percentage of each element.
In the technical scheme, Cr, Ni, Cu and Mo elements are alloy elements which are often added in steel, but if the content of the Cr, Ni, Cu and Mo elements in the steel is too much, the phase transformation characteristic of the steel is changed, so that brittle phases such as bainite and martensite are generated in the steel making process, according to the research, the total adding amount of the Cr, Ni, Cu and Mo elements is controlled within the range of 0 & lt Cr/5+ Mo/5+ (Cu + Ni)/15 & lt/0.08%, and the adverse effect can be effectively avoided.
Further, in the ultra-fine grain seamless steel pipe of the present invention, the chemical elements thereof may satisfy at least one of the following contents by mass:
C：0.03～0.08％％；
Si：0.4～0.8％；
Mn：0.8～1.2％；
Al：0.01～0.03％；
S≤0.005％；
P≤0.015％；
O≤0.004％。
further, in the ultra-fine grain seamless steel pipe of the present invention, the proportion of ferrite in the microstructure is not less than 75%.
Furthermore, in the ultra-fine grain seamless steel pipe, the elongation is more than 30 percent, the Charpy impact energy at minus 40 ℃ is more than 50J, and the yield strength is more than or equal to 245 MPa.
Accordingly, another object of the present invention is to provide a method for manufacturing an ultra-fine grain seamless steel tube, wherein the ultra-fine grain seamless steel tube obtained by the method has excellent deformation characteristics and low-temperature toughness (elongation > 30%, -40 ℃ Charpy impact energy >50J), and at the same time, has a yield strength of 245MPa or more, and can be effectively applied to various processing and manufacturing industries using steel tubes as raw materials.
In order to achieve the above object, the present invention provides a method for manufacturing the above ultra-fine grain seamless steel pipe, comprising the steps of:
(1) preparing a tube blank;
(2) heating and insulating the tube blank, and then perforating and rolling to prepare a pierced billet;
(3) cooling the pierced billet at a cooling speed of 10-80 ℃/s, and controlling the final cooling temperature to be less than or equal to 600 ℃;
(4) reheating the cooled pierced billet to 850-1000 ℃, keeping for 10-60 min, and then performing tension reducing or sizing, wherein the deformation of the section is controlled to be not less than 1.2;
(5) rolling the steel pipe: controlling the finish rolling temperature to be 800-980 ℃, cooling the steel pipe at a cooling speed of 10-80 ℃/s after finish rolling, and controlling the finish cooling temperature to be 550-700 ℃;
(6) the steel tube was free air cooled to room temperature.
In the method for manufacturing an ultra-fine grain seamless steel pipe according to the present invention, in the step (3), the pierced billet may be cooled by a plurality of rapid cooling means, for example: and rapid cooling means such as water cooling, fog cooling, air cooling and the like. In addition, in the step (3), the cooling speed is controlled to be 10-80 ℃/s, the final cooling temperature is controlled to be less than or equal to 600 ℃, so that the deformed austenite in the steel can be subjected to phase transformation, and the grains are further refined through the subsequent reheating process.
Correspondingly, in the step (5), the finishing temperature is controlled to be more than or equal to 800 ℃, so that the structure of the finally rolled steel can be effectively ensured to be maintained in a fully austenitic structure state. In the step (5), after the finish rolling, the pierced billet can be cooled by adopting various rapid cooling means, for example: and rapid cooling means such as water cooling, fog cooling, air cooling and the like. The cooling speed is controlled to be 10-80 ℃/s, the final cooling temperature is controlled to be 550-700 ℃, the steel pipe can be ensured to have enough phase change supercooling degree, and hard phases such as bainite and martensite are not generated at the same time.
Further, in the manufacturing method of the ultra-fine grain seamless steel tube, in the step (2), the heating temperature is 1150-1280 ℃; and/or the heat preservation time is less than or equal to 4 hours.
In the technical scheme of the invention, according to the conditions of different hot rolling mill groups, the heating temperature is usually not lower than 1150 ℃, so as to ensure that the steel pipe has enough deformability, but it is noted that if the heating temperature exceeds 1280 ℃, the steel pipe can generate grain coarsening and overburning. Therefore, in the method for manufacturing the ultra-fine grain seamless steel tube, the heating temperature is controlled to be 1150-1280 ℃ in the step (2).
Further, in the method for manufacturing an ultra-fine grain seamless steel pipe according to the present invention, in the step (3), the final cooling temperature is 400 to 600 ℃.
In the technical scheme of the invention, in order to avoid overhigh energy consumption of reheating in the subsequent steps due to too low cooling temperature, the final cooling temperature is preferably 400-600 ℃.
Compared with the prior art, the ultra-fine grain seamless steel pipe and the manufacturing method thereof have the advantages and beneficial effects as follows:
1) the microstructure of the ultra-fine grain seamless steel tube is mainly ferrite, the proportion of the ferrite is not less than 75%, the grain size is 9-grade or above, the ultra-fine grain seamless steel tube has excellent ductility and toughness (the elongation is more than 30%, and the Charpy impact power at minus 40 ℃ is more than 50J), and can be effectively convenient for subsequent processing treatment, and the yield strength of the ultra-fine grain seamless steel tube can reach more than 245 MPa;
2) the ultra-fine grain seamless steel pipe can obtain excellent performance without any treatment after rolling, has simple and convenient production flow, does not contain noble alloy elements in the components, and has low cost.
Therefore, the ultra-fine grain seamless steel pipe disclosed by the invention can obtain a ferrite structure with high proportion by adopting reasonable collocation of basic elements such as C, Si, Mn and the like and a proper manufacturing method, and effectively refines grains, so that the ultra-fine grain seamless steel pipe has excellent deformation characteristics and higher strength, is lower in production cost and can be effectively suitable for various processing industries using steel pipes as raw materials.
Detailed Description
The ultra fine grained seamless steel pipe and the method for manufacturing the same according to the present invention will be further explained and illustrated with reference to the following specific examples, which, however, should not be construed to unduly limit the technical aspects of the present invention.
Examples 1 to 6 and comparative examples 1 to 3
Table 1 shows the mass percentages of the respective chemical elements in the ultra-fine grained seamless steel pipes of examples 1 to 6 and the seamless steel pipes of comparative examples 1 to 3.
TABLE 1 (wt%, balance Fe and other unavoidable impurities)
The ultra fine grain seamless steel pipes of examples 1 to 6 and the seamless steel pipes of comparative examples 1 to 3 according to the present invention were manufactured by the following steps:
(1) preparing a tube blank;
(2) heating and insulating the tube blank, and then perforating and rolling to prepare a pierced billet; the preferable heating temperature is 1150-1280 ℃, and the heat preservation time is less than or equal to 4 hours.
(3) Cooling the pierced billet at a cooling speed of 10-80 ℃/s, controlling the final cooling temperature to be less than or equal to 600 ℃, and preferably controlling the final cooling temperature to be 400-600 ℃;
(4) reheating the cooled pierced billet to 850-1000 ℃, keeping for 10-60 min, and then performing tension reducing or sizing, wherein the deformation of the section is controlled to be not less than 1.2;
(5) rolling the steel pipe: controlling the finish rolling temperature to be 800-980 ℃, cooling the steel pipe at a cooling speed of 10-80 ℃/s after finish rolling, and controlling the finish cooling temperature to be 550-700 ℃;
(6) the steel tube was free air cooled to room temperature.
It should be noted that, with reference to table 1, the chemical compositions and related process parameters of the ultra-fine grain seamless steel pipes of examples 1-6 all meet the design specification control requirements of the present invention. Accordingly, the seamless steel pipe of comparative example 1 is only one in which the content of element C is high, and the process parameters satisfy the above requirements in the step of manufacturing the seamless steel pipe. The chemical compositions of comparative example 2 and comparative example 3 can meet the design requirements of the invention, but relevant process parameters can not meet the design requirements of the invention.
Tables 2-1 and 2-2 show the specific process parameters of the respective steps of the manufacturing methods of the ultra fine grained seamless steel pipes of examples 1-6 and the seamless steel pipes of comparative examples 1-3.
Table 2-1.
Table 2-2.
The ultra-fine grained seamless steel pipes of examples 1 to 6 and the seamless steel pipes of comparative examples 1 to 3 were tested for their respective properties such as yield strength and elongation to obtain test data for evaluating the respective properties, which are shown in Table 3.
Table 3 lists the relevant performance parameters of the ultra fine grained seamless steel pipes of examples 1-6 and the seamless steel pipes of comparative examples 1-3.
Table 3.
As can be seen from Table 3, the ultra-fine grained seamless steel pipes of examples 1 to 6 are excellent in properties, and the seamless steel pipes of comparative examples 1 to 3, which were not manufactured using the chemical components and related process parameters required for the specification control according to the present invention, were significantly inferior to those of examples 1 to 6.
As can be seen from Table 3, the yield strengths of the ultra-fine grain seamless steel pipes of examples 1 to 6 are all more than or equal to 250MPa, the elongations are more than or equal to 33%, and the Charpy impact energies at-40 ℃ are all more than 90J. In addition, the microstructures of the seamless steel pipes with ultrafine grains of examples 1 to 6 all had a ferrite phase ratio of 76% or more and a grain size of 9 or more. The superfine crystal grain seamless steel pipe has deformation characteristic, low-temperature toughness and proper yield strength, can be effectively used in various machining and manufacturing industries using steel pipes as raw materials, and has good popularization and application values and market prospects.
It should be noted that the above-mentioned embodiments are only specific embodiments of the present invention. It is apparent that the present invention is not limited to the above embodiments and similar changes or modifications can be easily made by those skilled in the art from the disclosure of the present invention and shall fall within the scope of the present invention.
Claims (9)
1. The seamless steel pipe with the ultrafine grains is characterized in that the grain size is more than 9 grade, and the seamless steel pipe with the ultrafine grains comprises the following chemical elements in percentage by mass:
c: 0.03-0.1%, Si: 0.2-1%, Mn: 0.5% -1.5%, Al: 0.01-0.05%, N: 0.001-0.01% of S, less than or equal to 0.008% of P, less than or equal to 0.02% of O, and the balance of Fe and other inevitable impurity elements.
2. The ultra fine grain seamless steel pipe of claim 1, further comprising at least one of V, Nb and Ti, and added in an amount satisfying: when the ratio of (V + Nb + Ti) is more than 0, the ratio is less than or equal to 0.15 percent.
3. The ultra fine grain seamless steel pipe according to claim 1, further comprising at least one of Cr, Ni, Cu, and Mo elements, and added in an amount satisfying: cr/5+ Mo/5+ (Cu + Ni)/15 is more than 0 and less than or equal to 0.08 percent.
4. The ultra-fine grain seamless steel pipe according to claim 1, wherein the chemical elements are contained in a mass percentage satisfying at least one of the following:
C：0.03～0.08％；
Si：0.4～0.8％；
Mn：0.8～1.2％；
Al：0.01～0.03％；
S≤0.005％；
P≤0.015％；
O≤0.004％。
5. the ultra fine grained seamless steel tube according to claim 1, characterized in that the ferrite phase ratio in the microstructure is 75% or more.
6. The ultra fine grained seamless steel tube according to claim 1, characterized by an elongation of > 30%, a Charpy impact energy of >50J at-40 ℃ and a yield strength of > 245 MPa.
7. A method for manufacturing an ultra fine grained seamless steel tube according to any one of claims 1 to 6, comprising the steps of:
(1) preparing a tube blank;
(2) heating and insulating the tube blank, and then perforating and rolling to prepare a pierced billet;
(3) cooling the pierced billet at a cooling speed of 10-80 ℃/s, and controlling the final cooling temperature to be less than or equal to 600 ℃;
(4) reheating the cooled pierced billet to 850-1000 ℃, keeping for 10-60 min, and then performing tension reducing or sizing, wherein the deformation of the section is controlled to be not less than 1.2;
(5) rolling the steel pipe: controlling the finish rolling temperature to be 800-980 ℃, cooling the steel pipe at a cooling speed of 10-80 ℃/s after finish rolling, and controlling the finish cooling temperature to be 550-700 ℃;
(6) the steel tube was free air cooled to room temperature.
8. The manufacturing method according to claim 7, wherein in the step (2), the heating temperature is 1150 to 1280 ℃; and/or the heat preservation time is less than or equal to 4 hours.
9. The method according to claim 7, wherein in the step (3), the final cooling temperature is 400 to 600 ℃.
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Effective date of registration: 20231207 Address after: 201900 Fujin Road, Baoshan District, Shanghai 885 Patentee after: BAOSHAN IRON & STEEL Co.,Ltd. Patentee after: YANTAI LUBAO STEEL PIPE Co.,Ltd. Address before: 201900 Fujin Road, Baoshan District, Shanghai 885 Patentee before: BAOSHAN IRON & STEEL Co.,Ltd. |