Steel, high-strength corrosion-resistant steel pipe fitting and pipe manufacturing method

Abstract

The invention discloses steel, a high-strength corrosion-resistant steel pipe fitting and a pipe manufacturing method, and the pipe manufacturing method comprises the following steps: smelting and blank manufacturing; hot rolling; cold rolling; performing hot dipping; manufacturing a pipe; and quenching. On the basis of improvement of steel raw materials, through the design of the pipe manufacturing process, the formability and the strength after forming of the steel pipe fitting are effectively improved, through the design of the hot dipping process, the pipe fitting has excellent corrosion resistance before and after the quenching process, and the pipe manufacturing cost is effectively saved; the strength and corrosion resistance of the steel pipe fitting are improved, meanwhile, the manufacturing cost of the high-strength steel pipe fitting is reduced, and the high-strength corrosion-resistant steel pipe fitting has wide application prospects in the field of high-strength corrosion-resistant pipe fittings.

Description

Technical Field

[0001] The present invention relates to the field of steel pipes, and in particular to a steel material and a high-strength corrosion-resistant steel pipe fitting and a pipe manufacturing method, which can be widely used in the automobile, construction and other industries. Background Art

[0002] There are many types of steel pipe fittings, including round pipes, square pipes, special-shaped pipes, etc. With the development of science and technology, the industry's demand for high-strength steel pipe fittings is increasing.

[0003] High-strength steel plates are necessary raw materials for the preparation of high-strength steel pipe fittings. Chinese patent CN201410209907.9 discloses a high bending performance hot-formed steel for automobiles and a preparation method thereof. The chemical composition mass percentage of the steel pipe is: C: 0.18-0.30%, Si≤0.30%, Mn: 1.00-1.60%, Cr: 0.10-0.30%, Ti: 0.02-0.06%, Al: 0.02-0.06%, Nb: 0.02-0.10%, Mo: 0.15-0.40%, B: 0.0005-0.0040%, P≤0.020%, S≤0.010%, N≤0.006%, and the balance is Fe and unavoidable impurities; after final rolling at 820-890℃, coiling at 540-650℃, and quenching at a cooling rate of ≥40℃ / s, a hot-formed steel with a tensile strength greater than 1450MPa is obtained. This steel plate needs to add expensive microalloying elements Nb and Mo, which has a high production cost. Nb inhibits the dynamic recrystallization of austenite, which increases the hot rolling load and difficulty. In addition, the strength of this steel grade is increased to a certain extent, and its carbon content is low, so the increase will not be much, but the cost will increase a lot.

[0004] Chinese patent CN201110259342.1 discloses a method for preparing a dual-phase hot-formed steel, the chemical composition mass percentage of which is: C: 0.1-0.5%, Si: 0.3-2.5%, Mn: 1.0-3.0%, P≤0.02%, S≤0.01%, the remainder is Fe and unavoidable impurities; through 800-900℃ final rolling, 600-700℃ coiling, 750-850℃ reheating stamping, cooling speed ≥40℃ / s quenching treatment, a dual-phase hot-formed steel with a tensile strength greater than 1150MPa is obtained. The C content of the steel is as high as 0.5%, which makes the steel poor in welding performance and plasticity, and is not conducive to the forming and processing of steel pipe fittings.

[0005] The existing processing methods for high-strength steel pipe fittings mainly include cold processing and hot forming. Among them, cold processing will cause problems such as large springback of high-strength steel plates, easy cracking, and high requirements for processing equipment, which makes pipe making difficult. Hot forming technology refers to the process of first forming the steel plate at high temperature and then quenching it in a mold. This method can solve the above-mentioned problems caused by cold processing, but it has disadvantages such as high equipment investment cost, high mold manufacturing cost, and the popular aluminum-silicon coating does not have incision protection performance. In addition, the steel pipe fittings prepared by the existing processing method have poor corrosion resistance, which seriously affects the service life of the steel pipe fittings. Summary of the invention

[0006] The present invention solves the above-mentioned problems existing in the preparation and use of existing steel pipe fittings by providing a steel material, a high-strength corrosion-resistant steel pipe fitting and a pipe making method.

[0007] To solve the above technical problems, the present invention provides a steel material comprising the following chemical components in percentage by mass: C: 0.15-0.35%, Si: 0.10-0.40%, Mn: 0.20-1.50%, Al: 0.01-0.06%, B: 0.0-0.0035%, P≤0.020%, S≤0.010%, N≤0.006%, and the rest being Fe and unavoidable impurities.

[0008] In order to solve the above technical problems, the present invention also provides a method for manufacturing high-strength corrosion-resistant steel pipe fittings, using the above steel as raw material, comprising the following steps: (1) Smelting and billet making: The steel containing the above chemical composition is smelted in a converter to prepare steel slabs; (2) Hot rolling: After the obtained steel slab is heated and dephosphorized, it is hot rolled to obtain a hot-rolled base plate with a thickness of 2.0 to 6.0 mm, which is then coiled and cooled; (3) Cold rolling: After pickling, the hot-rolled substrate is cold-rolled to obtain a hard-rolled steel plate with a thickness of 0.5 to 3.2 mm, and then annealed; (4) Hot-dip plating: the annealed hard-rolled steel sheet is immersed in a plating solution containing Al, Si and Zn, the temperature of the plating solution is controlled to be 580-640°C, and the immersion temperature of the hard-rolled steel sheet is controlled to be 10-30°C higher than the temperature of the plating solution. After the hot-dip plating is completed, the hard-rolled steel sheet is taken out and cooled to room temperature; (5) Pipe making: using a pipe making machine to bend the hard-rolled steel plate after hot-dip galvanizing, and then welding to obtain steel pipe fittings of the desired shape; (6) Quenching: The steel pipe fittings are quenched by induction heating or radiation heating, and immediately cooled after quenching to obtain the high-strength corrosion-resistant steel pipe fittings.

[0009] In a preferred embodiment of the present invention, in the step (2), the process conditions of hot rolling are: starting rolling temperature 1000-1280°C, and finishing rolling temperature 850-950°C.

[0010] In a preferred embodiment of the present invention, in step (4), the plating solution comprises the following components in percentage by weight: Zn 40-67%, Si 1-6%, Al 25-57%, and the rest are unavoidable impurities.

[0011] In a preferred embodiment of the present invention, in the step (4), the hot-dip immersion time is 1 to 10 seconds.

[0012] In a preferred embodiment of the present invention, in the step (4), after hot-dip dipping, the thickness of the obtained coating is 8 to 30 μm, and a Fe-Al-Si alloy layer with a thickness of 0.5 to 6 μm is formed on the side of the coating facing the steel pipe.

[0013] In a preferred embodiment of the present invention, in the step (4), the temperature of the plating solution is 610-630°C, and the immersion plating temperature of the hard-rolled steel sheet is 620-650°C.

[0014] In a preferred embodiment of the present invention, in the step (6), the quenching process conditions are: temperature 810-920° C., and holding time 1-180 s.

[0015] In a preferred embodiment of the present invention, in step (6), the cooling method is water cooling, oil cooling or air cooling, and the cooling rate is greater than 25°C / s.

[0016] In order to solve the above technical problems, the present invention also provides a high-strength corrosion-resistant steel pipe fitting, which is prepared by the above pipe making method.

[0017] The beneficial effects of the present invention are as follows: the present invention provides a steel material, a high-strength corrosion-resistant steel pipe fitting and a pipe making method. On the basis of improving the steel raw materials, through the design of the pipe making process, the formability of the steel pipe fitting and the strength after forming are effectively improved, and through the design of the hot-dip process, the pipe fitting has excellent corrosion resistance before and after the quenching process, which effectively saves the pipe making cost; the present invention improves the strength and corrosion resistance of the steel pipe fitting, and also reduces the manufacturing cost of the high-strength steel pipe fitting, and has broad application prospects in the field of high-strength corrosion-resistant pipe fittings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a metallographic structure diagram of a hot-rolled substrate prepared in Example 1 of the present invention; Figure 2 This is a metallographic structure diagram of the hot-rolled substrate prepared in Example 1 of the present invention after hot-dip cooling; Figure 3 is a metallographic structure diagram of the steel pipe after quenching prepared in Example 1 of the present invention; Figure 4 is a surface image of the coating after quenching of the steel pipe prepared in Example 1 of the present invention; Figure 5 is a metallographic structure diagram of the coating after quenching of the steel pipe prepared in Example 1 of the present invention; Figure 6 is a metallographic structure diagram of a hot-rolled substrate prepared in Example 2 of the present invention; Figure 7 This is a metallographic structure diagram of the hot-rolled substrate prepared in Example 2 of the present invention after hot-dip cooling; Figure 8 is a metallographic structure diagram of the steel pipe after quenching prepared in Example 2 of the present invention; Fig. 9 This is a metallographic structure diagram of the coating after quenching of the steel pipe prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0019] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0020] The invention discloses a method for manufacturing a high-strength corrosion-resistant steel pipe fitting and the steel raw material used.

[0021] The steel raw material used includes the following chemical components in percentage by mass: C: 0.15-0.35%, Si: 0.10-0.40%, Mn: 0.20-1.50%, Al: 0.01-0.06%, B: 0.0-0.0035%, P≤0.020%, S≤0.010%, N≤0.006%, and the rest is Fe and inevitable impurities. The steel raw material reduces the C content and increases the Mn content, thereby improving the stability and hardenability of austenite, which is beneficial to improving the welding performance and plastic toughness of the steel plate after hot forming, ensuring the effective forming of steel pipe fittings, and avoiding defects such as cracking. In addition, after the steel raw material of this formula is hot formed, it can form a lath martensite microstructure after quenching. The steel of this microstructure has good plasticity, small internal stress, and high strength and hardness, which can meet the use requirements of high-strength steel pipe fittings.

[0022] Using the steel material of the above formula as raw material, the pipe making method specifically comprises the following steps: (1) Smelting and billet making: The steel containing the above chemical composition is smelted in a converter to prepare steel slabs; (2) Hot rolling: After the obtained steel slab is heated to remove phosphorus, it is heated to 1000-1280°C and then hot rolled, and the final rolling temperature is controlled to be 850-950°C. After the hot rolling treatment is completed, a hot-rolled substrate with a thickness of 2.0-6.0 mm is obtained, which is coiled at 550-700°C and finally cooled to room temperature; (3) Cold rolling: The hot-rolled substrate is pickled to remove the iron oxide scale, and then cold-rolled into a hard-rolled steel plate with a thickness of 0.5 to 3.2 mm, coiled, and annealed; (4) Hot-dip plating: The annealed hard-rolled steel sheet is dip-plated into a plating solution containing Al, Si, and Zn. Specifically, the plating solution includes the following components in percentage by mass: Zn 40-67%, Si 1-6%, Al 25-57%, and the rest are unavoidable impurities. The temperature of the plating solution is controlled to be 580-640°C, and the immersion temperature of the hard-rolled steel sheet (i.e., the temperature when entering the plating solution) is controlled to be 10-30°C higher than the temperature of the plating solution. The hot-dip process is performed for 1-10 seconds. After the hot-dip process is completed, the hard-rolled steel sheet is taken out and cooled to room temperature.

[0023] After the hot-dip treatment, a Zn-Al-Si coating with a thickness of 8-30 μm is formed on the surface of the hard-rolled steel plate, and a Fe-Al-Si alloy layer with a thickness of 0.5-6 μm is further formed on the side of the coating facing the hard-rolled steel plate.

[0024] Specifically, in the plating solution, when the mass percentage of zinc is lower than 40%, the sacrificial protection performance of the coating after heat treatment will be reduced. When it is higher than 67%, the zinc element is likely to seriously corrode the austenite grain boundaries during heat treatment, affecting the corrosion resistance of the product after quenching.

[0025] In the zinc-containing plating solution, the addition of aluminum mainly plays the following roles: improving the high-temperature oxidation resistance of the coating; reacting with the hard-rolled steel plate matrix to form an alloy layer during the hot-dip process, reducing the corrosion of the zinc element on the austenite grain boundaries at high temperatures; reducing the iron content of the zinc-rich phase in the coating after austenitization, and improving the corrosion resistance of the coating after quenching.

[0026] The addition of silicon element mainly plays the role of reducing the thickness of the coating alloy and improving the forming performance of the coating; in addition, the presence of silicon element also has the effect of slowing down the diffusion reaction of iron and aluminum elements. When the mass percentage of silicon is 1-6%, a more suitable alloy layer thickness can be formed by controlling the immersion temperature and the plating solution temperature.

[0027] When the bath temperature is 580-640℃ and the immersion temperature is 10-30℃ higher than the bath temperature, the thickness of the alloy structure obtained is relatively thick, between 8-30μm, and more zinc-rich phases will be retained in the coating after heat treatment, which plays a good sacrificial protection role for the hard-rolled steel plate substrate. However, when the coating thickness is less than 8μm, the sacrificial protection performance of the coating after heat treatment is poor; when the coating thickness exceeds 30μm, it is difficult to control the thickness of the coating by air knife blowing, and the thicker coating is prone to sagging during the heat treatment process.

[0028] Through the design of the coating, steel pipe fittings can be directly heated and quenched under air conditions, which effectively reduces the production cost, ensures that no oxide scale is generated during the quenching process, and ensures that the pipe fittings after quenching have good corrosion resistance, especially a certain degree of cut protection performance.

[0029] (5) Pipe making: The hard-rolled steel plate after hot-dip galvanizing is bent by a pipe making machine, and then welded to obtain steel pipe fittings of the desired shape, such as round pipes, square pipes, special-shaped pipes, etc. By adjusting the steel formula and designing the above-mentioned forming method, the tensile strength of the hard-rolled steel plate containing the coating is not more than 650MPa, and the coating has good forming performance, which is conducive to the preparation of pipe fittings. At the same time, the coating has good welding performance.

[0030] (6) Quenching: The steel pipe is heated to 810-920°C by induction heating or radiation heating, and then quenched for 1-180s. After quenching, it is immediately cooled by water cooling, oil cooling or air cooling, and the cooling rate is greater than 25°C / s. The design of the quenching process ensures that the parts have good corrosion resistance and avoids cracks in the matrix. After quenching, the microstructure of the pipe matrix is ​​mainly martensite and a small amount of ferrite and carbide, with high strength and hardness. The coating structure is mainly composed of a diffusion layer, a zinc-rich phase, and an aluminum-zinc-rich phase.

[0031] The above-mentioned pipe making method, through the design of first forming the pipe and then quenching to improve the strength, effectively reduces the difficulty of making the pipe of the high-strength steel plate, improves the forming performance and forming quality of the steel pipe fittings, reduces the investment cost of the forming equipment, and integrates the formability and high strength of the steel pipe fittings. In addition, through the design of the plating solution composition and the hot-dip process, a plating layer and an alloy layer of effective thickness are formed on the surface of the steel pipe fittings, so that the steel pipe fittings have high corrosion resistance before and after quenching, reduce the difficulty of quenching, save the gas protection cost in the austenitization process, and reduce the cost.

[0032] The above-mentioned pipe making method is further described in detail below through specific embodiments. Example 1

[0033] Smelting process: The steel material having the chemical composition ratio corresponding to Example 1 in Table 1 is smelted in a converter and cast into steel slabs.

[0034] Hot rolling process: the obtained steel slab is heated to 1200℃, kept warm for 1 hour and then dephosphorized; then hot rolling is carried out, the hot rolling start temperature is 1100℃, the final rolling temperature is 850℃, and the rolling thickness is 3.0mm. The laminar cooling method of the front cooling mode is used to cool the hot rolled piece to between 600-650℃, and then coiled. The coiled hot rolled coil is kept warm in a slow cooling pit for more than 24 hours, and then cooled to room temperature to obtain a hot rolled substrate. The microstructure of the hot rolled substrate is as follows Figure 1 The mechanical properties after hot rolling are shown in Table 2.

[0035] Cold rolling process: the hot-rolled substrate is pickled to remove the iron oxide scale, and the hot-rolled substrate with a thickness of 3 mm is cold-rolled into a hard-rolled steel plate with a thickness of 1.5 mm using a reversible rolling mill, and then annealed at 700° C. for 3 minutes under the protection of hydrogen atmosphere.

[0036] Hot-dip process: The annealed hard-rolled steel plate is cooled to 650°C and kept at this temperature for 10 seconds to make the plate temperature uniform, and then immediately immersed in a configured plating solution at a temperature of 620°C for hot-dip 3 seconds, and then immediately cooled to room temperature by gas.

[0037] The plating solution includes the following components in percentage by mass: Zn 57%, Si 3%, Al 38%, and the balance is other inevitable impurities.

[0038] The metallographic structure after cooling is Figure 2 As shown, the thickness of the obtained coating is 18 μm and the thickness of the alloy layer is 1.5 μm.

[0039] Forming process: Use a tube making machine to bend the steel plate into a 80*80mm square tube, and then weld the edges of the steel tube to make a square tube.

[0040] Quenching process: the obtained square tube is induction heated to 860℃ and kept at this temperature for 1s; then water-cooled quenching is performed, and the temperature of the square tube after quenching is 110℃, and then air-cooled to room temperature. The structure after quenching is as follows Figure 3 The mechanical properties are shown in Table 3. The surface of the coating after quenching is Figure 4 The corresponding metallographic structure is shown in Figure 5 As shown, the surface quality of the coating is good, there is no thick oxide layer and peeling. The yield strength of the square tube after heat treatment is 1217MPa, the tensile strength is 1318MPa, and the elongation at break is 9%. Example 2

[0041] Smelting process: The steel material having the chemical composition ratio corresponding to Example 2 in Table 1 is smelted in a converter and cast into steel slabs.

[0042] Hot rolling process: the obtained steel slab is heated to 1200℃, kept warm for 1 hour and then dephosphorized; then hot rolling is carried out, the hot rolling start temperature is 1050℃, the final rolling temperature is 900℃, and the rolling thickness is 2.5mm. The hot rolled piece is cooled to between 550-600℃ by the laminar cooling method in the front cooling mode, and then coiled. The coiled hot rolled coil is kept warm in a slow cooling pit for more than 24 hours, and then cooled to room temperature to obtain a hot rolled substrate. The microstructure of the hot rolled substrate is as follows Figure 6 The mechanical properties after hot rolling are shown in Table 2.

[0043] Cold rolling process: The hot-rolled substrate is pickled to remove the iron oxide scale, and the steel plate with a thickness of 2.5 mm is cold-rolled into a hardened steel plate with a thickness of 1 mm using a reversible rolling mill, and then annealed at 700°C for 5 minutes under the protection of a hydrogen atmosphere.

[0044] Hot-dip process: The annealed hard-rolled steel plate is cooled to 640°C and kept at this temperature for 10 seconds to make the plate temperature uniform, and then immediately immersed in a plating solution with a temperature of 580°C for hot-dip for 1.5 seconds, and then immediately cooled to room temperature by gas.

[0045] The plating solution includes the following components in percentage by mass: Zn 45%, Si 2%, Al 51%, and the balance is other inevitable impurities.

[0046] The metallographic structure after cooling is Figure 7 As shown, the coating thickness after hot-dip galvanizing is 28 μm, and the alloy layer thickness is 3.2 μm.

[0047] Forming process: Use a tube making machine to bend the hot-dip galvanized steel plate into a 80*80mm square tube shape, and weld its edges to make a square tube.

[0048] Quenching process: Induction heat the square tube to 830℃, keep it warm for 2s; then water-cooling quench, the temperature of the tube after quenching is 110℃, and then air-cooling to room temperature. The microstructure after quenching is as follows Figure 8 The mechanical properties are shown in Table 3, and the metallographic structure of the coating after quenching is shown in Fig. 9 As shown in the figure, the yield strength of the square tube after heat treatment is 1070MPa, the tensile strength is 1108MPa, and the elongation at break is 11.2%.

[0049] Comparative Example 1 The difference from Example 1 is that the temperature of the plating solution is 560° C., the immersion plating temperature of the hard-rolled steel sheet is 590° C., and the thickness of the obtained coating is 6.5 μm.

[0050] Comparative Example 2 The difference from Example 1 is that the temperature of the plating solution is 680°C, the immersion temperature of the hard-rolled steel sheet is 710°C, the thickness of the obtained coating is uneven, with an average thickness of 33 μm, and sagging occurs during the subsequent heat treatment heating process.

[0051] Comparative Example 3 The difference from Example 1 is that the immersion plating temperature of the hard-rolled steel sheet and the temperature of the plating solution are the same, both of which are 620° C., and the thickness of the obtained coating is 7.5 μm.

[0052] Comparative Example 4 The difference from Example 1 is that the temperature of the plating solution is 620° C., the immersion plating temperature of the hard-rolled steel sheet is 680° C., and the thickness of the obtained coating is 7.3 μm.

[0053] Example 1, Example 2, Comparative Examples 1-4 and commercially available aluminum silicon plates were subjected to an atmospheric exposure test for 3 years. The surface corrosion conditions after exposure are shown in Table 4 below.

[0054] Table 1 Chemical composition of the examples (wt.%)

[0055] Table 2 Mechanical properties of hot-rolled substrate

[0056] Table 3 Mechanical properties of hot-formed parts

[0057] Table 4 Surface corrosion after exposure

[0058] It can be seen from the test results in Table 2 that the hot-rolled substrate prepared by the present invention has moderate strength and good toughness, and is suitable for the forming of pipe fittings. It can not only realize large-scale production and steelmaking, but also ensure that the strength of the material is reduced and the forming performance of the steel pipe fittings is improved during the pipe making process.

[0059] It can be seen from the test results in Table 3 that the yield strength and tensile strength of the steel pipe fittings prepared by the present invention are significantly improved after quenching, both reaching more than 1000 MPa, which can meet the use requirements of high-strength steel pipe fittings.

[0060] It can be seen from the test results in Table 4 above that the coating prepared by the hot-dip coating process of the present invention has good corrosion resistance. The coatings of Comparative Examples 1, 3 and 4 have poor corrosion resistance. The coating of Comparative Example 2 has good corrosion resistance, but the surface is uneven and has a poor appearance quality due to the sagging phenomenon, which does not meet the requirements.

[0061] The steel pipe prepared by the present invention has a microstructure composed of ferrite and pearlite, and the microstructure is mainly composed of lath-shaped martensite, and the tensile strength thereof reaches above 1100 MPa.

[0062] The steel pipe fittings prepared by the method of the present invention have low production cost, ultra-high strength and excellent plasticity, and the material after quenching has good corrosion resistance, can be widely used in construction, automobile structural parts and reinforcements, and have significant economic and social benefits.

[0063] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A steel material, It is characterized in that The chemical composition includes the following mass percentages: C: 0.15-0.35%, Si: 0.10-0.40%, Mn: 0.20-1.50%, Al: 0.01-0.06%, B: 0.0-0.0035%, P≤0.020%, S≤0.010%, N≤0.006%, and the rest are Fe and unavoidable impurities.

2. A method for manufacturing high-strength corrosion-resistant steel pipe fittings, It is characterized in that Using the steel material described in claim 1 as raw material, the method comprises the following steps: (1) Smelting and billet making: the steel material containing the chemical composition described in claim 1 is subjected to converter smelting to prepare steel slabs; (2) Hot rolling: After the obtained steel slab is heated and dephosphorized, it is hot rolled to obtain a hot-rolled base plate with a thickness of 2.0 to 6.0 mm, which is then coiled and cooled; (3) Cold rolling: After pickling the hot-rolled substrate, cold rolling is performed to obtain a hard-rolled steel plate with a thickness of 0.5 to 3.2 mm, and then annealing is performed; (4) Hot-dip plating: the annealed hard-rolled steel sheet is immersed in a plating solution containing Al, Si and Zn, the temperature of the plating solution is controlled to be 580-640°C, and the immersion temperature of the hard-rolled steel sheet is controlled to be 10-30°C higher than the temperature of the plating solution. After the hot-dip plating is completed, the hard-rolled steel sheet is taken out and cooled to room temperature; (5) Pipe making: using a pipe making machine to bend the hard-rolled steel plate after hot-dip galvanizing, and then welding to obtain steel pipe fittings of the desired shape; (6) Quenching: The steel pipe fittings are quenched by induction heating or radiation heating, and immediately cooled after quenching to obtain the high-strength corrosion-resistant steel pipe fittings.

3. The method for manufacturing a high-strength corrosion-resistant steel pipe according to claim 2, It is characterized in that In the step (2), the hot rolling process conditions are: the starting rolling temperature is 1000-1280°C, and the final rolling temperature is 850-950°C.

4. The method for manufacturing a high-strength corrosion-resistant steel pipe according to claim 2, It is characterized in that In the step (4), the plating solution comprises the following components in percentage by weight: Zn 40-67%, Si 1-6%, Al 25-57%, and the rest are unavoidable impurities.

5. The method for manufacturing a high-strength corrosion-resistant steel pipe according to claim 2, It is characterized in that In the step (4), the hot-dip galvanizing time is 1 to 10 seconds.

6. The method for manufacturing a high-strength corrosion-resistant steel pipe according to claim 2, It is characterized in that In the step (4), after hot-dip galvanizing, the thickness of the obtained coating is 8 to 30 μm, and a Fe-Al-Si alloy layer with a thickness of 0.5 to 6 μm is formed on the side of the coating facing the steel pipe.

7. The method for manufacturing a high-strength corrosion-resistant steel pipe according to claim 2, It is characterized in that In the step (4), the temperature of the plating solution is 610-630°C, and the immersion plating temperature of the hard-rolled steel sheet is 620-650°C.

8. The method for manufacturing a high-strength corrosion-resistant steel pipe according to claim 2, It is characterized in that In the step (6), the quenching process conditions are: temperature 810-920° C., and holding time 1-180 s.

9. The method for manufacturing a high-strength corrosion-resistant steel pipe according to claim 2, It is characterized in that In the step (6), the cooling method is water cooling, oil cooling or air cooling, and the cooling rate is greater than 25°C / s.

10. A high-strength, corrosion-resistant steel pipe fitting, It is characterized in that The method is prepared by any one of claims 2 to 9.

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