Production method of steel for high-corrosion-resistance and high-toughness zinc-aluminum-magnesium corrugated pipe

Abstract

The invention discloses a production method of steel for a high-corrosion-resistance and high-toughness zinc-aluminum-magnesium corrugated pipe. The production method is characterized by comprising the following steps: a steelmaking process: KR desulfurization, converter treatment, RH (Ruhrstahl Heraeus) refining and slab continuous casting; the steel comprises the following chemical components in percentage by mass: less than or equal to 0.003% of C, less than or equal to 0.03% of S , less than or equal to 0.20% of Mn, less than or equal to 0.020% of P, less than or equal to 0.010% of S, less than or equal to 0.0030% of N, less than or equal to 0.0030% of O, more than or equal to 0.04% of T and the balance of A hot rolling process; acid rolling process; and a galvanization process. According to the invention, the production cost is low, and international ROSH and Reach environmental protection requirements are met; the yield strength is controlled to be 145-190 MPa, the tensile strength is controlled to be 280-330 MPa, the elongation is larger than or equal to 42%, the value r is larger than or equal to 2.3, and the value n is larger than or equal to 0.21.

Description

Technical Field

[0001] The invention belongs to the technical field of research and development of steel products, and in particular relates to a production method of steel for high-corrosion-resistant and high-toughness zinc-aluminum-magnesium corrugated pipes. Background Art

[0002] A bellows is a piping system used to transfer liquids or gases and other media, which is characterized by a corrugated elastic structure. Bellows are widely used in many industrial fields, including petroleum, chemical, machinery and other industries. Their main function is to connect, buffer and absorb shock in the pipeline system. With the vigorous development of the petroleum and chemical industries, the market size has steadily increased. The working environment of the petrochemical industry is usually harsh, with problems such as high temperature, high humidity, corrosion, and safety hazards. Therefore, there is no domestic production experience in the development of high corrosion-resistant and high-toughness zinc-aluminum-magnesium corrugated pipe steel, which is a blank product. The steel for corrugated pipes is favored by the majority of users for its high corrosion resistance, high toughness and excellent forming properties. In order to achieve the above indicators, we at Baosteel have carried out research on the metallurgical process route for zinc-aluminum-magnesium steel for corrugated pipes.

[0003] The existing literature and patent research are as follows:

[0004] The searched patent "A bellows production and manufacturing process" describes a bellows production and manufacturing process, in which a support plate, a side plate, a support unit, a rotation unit and an auxiliary unit cooperate to complete the production and manufacturing of the bellows; it does not explain the production and manufacturing method of the steel used for the bellows.

[0005] The searched patent "A high-strength corrugated pipe" describes that a reinforcing shell is arranged on the main body of the corrugated pipe and reinforcing ribs are arranged at the upper and lower ends of the reinforcing shell, thereby protecting the main body of the corrugated pipe, making it able to withstand greater pressure and more widely used. This is not the same category as the production method of steel for corrugated pipes described in this article. Summary of the invention

[0006] The purpose of the present invention is to provide a production method for high corrosion resistance and high toughness zinc aluminum magnesium corrugated pipe steel, which is designed and developed from the whole process of chemical composition, smelting, hot rolling, cold rolling and hot dip galvanizing, and the development process is explained in a relatively systematic and perfect manner. Not only is the production cost low, but it also meets the international ROSH and Reach environmental protection requirements. The yield strength is controlled at 145-190MPa, the tensile strength is controlled at 280-330MPa, the elongation is ≥42%, the r value is ≥2.3, and the n value is ≥0.21.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for producing steel for zinc-aluminum-magnesium corrugated pipes with high corrosion resistance and high toughness, comprising:

[0009] Steelmaking process: KR desulfurization → converter → RH refining → slab continuous casting; its chemical composition by mass percentage is: C≤0.003%, Si≤0.03%, Mn≤0.20%, P≤0.020%, S≤0.010%, N≤0.0030%, O≤0.0030%, Ti≥0.04%, and the rest is Fe and unavoidable impurities;

[0010] Hot rolling process: heating furnace → rough rolling high-pressure water descaling machine → fixed width press → E1R1 rough rolling mill → E2R2 rough rolling mill → insulation cover → flying shear → finishing high-pressure water descaling machine → F1-F7 finishing mill → encrypted laminar cooling → coiler; during the rolling process of the finishing mill, the actual rolling oil flow of each stand of F2, F3, and F4 is controlled at 140-240ml / min;

[0011] Pickling process: Pickling uncoiling → welding → straightening → pickling → rinsing → drying → trimming → rolling → coiler → pickling reduction rate ≥ 70%;

[0012] Galvanizing process: hot-dip galvanizing uncoiling → welding → entrance looper → cleaning → annealing furnace → zinc pot → cooling after plating → water quenching → intermediate looper → skin-passing machine → straightening machine → roller coater → dryer → air cooling device → exit looper → trimming → surface inspection → oiling → sampling → coiling; galvanizing entrance process:; the conductivity control range of 1# brush washing tank is 30-70ms / cm, the conductivity control range of 2# brush washing tank (deionized water) is ≤200ms / cm, the conductivity control range of electrolytic tank is 40-60ms / cm, and the conductivity control range of rinsing tank is ≤200ms / cm.

[0013] Furthermore, the zinc liquid composition is controlled as follows: Al content: 5.0-6.0%, magnesium content: 2.0-3.0%, Zn>90% and the zinc pot temperature is 420-450℃.

[0014] Further, air knife process: In order to ensure the thickness of zinc-aluminum-magnesium galvanized strip steel, the air knife height is controlled at 400-600mm.

[0015] The air knife pressure is controlled at 200-300mbar (adjusted according to the thickness of the zinc layer), and the air knife gap is controlled in the range of 7.5-8.0mm.

[0016] Furthermore, the roller coater adopts reverse coating, the linear speed ratio of the coating roller to the steel strip is controlled at 100-150, the linear speed ratio of the dipping roller to the steel strip is controlled at 50-100, and the thickness of the fingerprint-resistant film is controlled at 0.9-1.3 μm.

[0017] Furthermore, the outlet temperature of the galvanizing annealing / soaking section is 795-810°C, the outlet temperature of the slow cooling section is 670-690°C, the elongation of the leveling machine is 1.05-1.10%, and the production line speed is 90-120m / min.

[0018] Furthermore, the chemical composition of the zinc-aluminum-magnesium corrugated pipe steel in mass percentage is: C 0.0020%, Si 0.004%, Mn 0.12%, P 0.013%, S 0.008%, N 0.0022%, O 0.0017%, Ti 0.057%, and the rest is Fe and unavoidable impurities.

[0019] Furthermore, the chemical composition of the zinc-aluminum-magnesium corrugated pipe steel in mass percentage is: C 0.0023%, Si 0.006%, Mn 0.13%, P 0.010%, S 0.007%, N 0.0018%, O 0.0020%, Ti 0.059%, and the rest is Fe and unavoidable impurities.

[0020] Furthermore, the chemical composition of the zinc-aluminum-magnesium corrugated pipe steel in mass percentage is: C 0.0022%, Si 0.004%, Mn 0.15%, P 0.015%, S 0.006%, N 0.0024%, O 0.0020%, Ti 0.059%, and the rest is Fe and unavoidable impurities.

[0021] Furthermore, the chemical composition of the zinc-aluminum-magnesium corrugated pipe steel in mass percentage is: C 0.0024%, Si 0.004%, Mn 0.16%, P 0.013%, S 0.009%, N 0.0020%, O 0.0019%, Ti 0.058%, and the rest is Fe and unavoidable impurities.

[0022] Compared with the prior art, the beneficial technical effects of the present invention are:

[0023] According to the chemical composition, hot rolling process, acid rolling process and galvanizing process of the present invention, a steel strip having good mechanical property stability, good corrosion resistance and other indicators and meeting the requirements of the corrugated pipe can be manufactured. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below in conjunction with the accompanying drawings.

[0025] Figure 1 The metallographic structure of the steel for the high corrosion resistance and high toughness zinc-aluminum-magnesium corrugated pipe of the present invention;

[0026] Figure 2 This is the macroscopic morphology before the test;

[0027] Figure 3 This is a photo of 2800 hours of salt spray corrosion;

[0028] Figure 4 It is a zinc-aluminum-magnesium bellows. DETAILED DESCRIPTION

[0029] A method for producing steel for zinc-aluminum-magnesium corrugated pipes with high corrosion resistance and high toughness, comprising:

[0030] Smelting process:

[0031] KR desulfurization process: The molten iron needs to be treated with KR desulfurization. The sulfur content of the molten iron entering the converter is required to be less than 0.004%, and the slag removal area of ​​the molten iron is required to be greater than 95% (the surface of the molten iron is cleaner after slag removal).

[0032] Converter smelting process: converter tapping temperature ≥ 1660℃, must use turnover ladle tapping, tapping temperature drop requirement is less than 70℃. Add top slag modifier according to the oxygen content of molten steel and the amount of slag.

[0033] RH process: Decarburization is carried out according to the composition and temperature of the RH molten steel supplied by the converter. After decarburization, aluminum particles are added for deoxidation and alloying according to the oxygen setting conditions. After 4 minutes of circulation, ferromanganese, ferrotitanium and other alloys are added to adjust the molten steel composition to the target value. After the composition adjustment is completed, ensure that the vacuum cycle is ≥6 minutes.

[0034] Continuous casting process: The superheat of the casting machine is controlled at 25-45, and the casting machine adopts constant casting speed control with a casting speed range of 1.0-1.8m / min.

[0035] Hot rolling process:

[0036] The ingot was heated in a walking beam heating furnace. The heating process is shown in Table 1. The rough rolling adopted the 3+3 mode, and the pass reduction rate is shown in Table 2.

[0037] Table 1 Billet heating system

[0038]

[0039] Table 2 Roughing pass reduction rate

[0040] Rolling Mill Pass reduction rate / % R1 ≥13 R1 ≥15 R1 ≥18 R2 ≥20 R2 ≥30 R2 ≥30

[0041] Finishing rolling adopts F1-F7 continuous rolling, and the cooling method is front concentrated. The specific hot rolling process is shown in Table 3. During the rolling process of the finishing mill, the actual rolling oil flow rate of each stand of F2, F3, and F4 is controlled at 140-240ml / min.

[0042] Table 3 Hot rolling process

[0043]

[0044] Galvanizing process:

[0045] Galvanizing entrance process:

[0046] In order to ensure the cleaning effect of the strip steel plate surface, the conductivity control range of 1# scrubbing tank is 30-70ms / cm, the conductivity control range of 2# scrubbing tank (deionized water) is ≤200ms / cm, the conductivity control range of electrolytic tank is 40-60ms / cm, and the conductivity control range of rinsing tank is ≤200ms / cm.

[0047] Furnace area process:

[0048] The outlet temperature control conditions of each section of the galvanizing annealing furnace are shown in Table 4, and the elongation setting of the leveling mill is shown in Table 5.

[0049] Table 4 Galvanizing annealing process

[0050]

[0051] Table 5 Leveling machine process

[0052]

[0053] Zinc liquid composition and temperature control:

[0054] Zinc liquid composition control: Al content: 5.0-6.0%, magnesium content: 2.0-3.0%, Zn>90%;

[0055] Zinc pot temperature 420-450℃.

[0056] Air knife process:

[0057] In order to ensure the thickness of zinc-aluminum-magnesium galvanized strip, the air knife height is controlled at 400-600mm, the air knife pressure is controlled at 200-300mbar (adjusted according to the thickness of the zinc layer), and the air knife gap is controlled in the range of 7.5-8.0mm.

[0058] Roller coating process:

[0059] The roller coater adopts reverse coating, the linear speed ratio of the coating roller and the strip steel is controlled at 100-150, the linear speed ratio of the dipping roller and the strip steel is controlled at 50-100, and the thickness of the fingerprint-resistant film is controlled at 0.9-1.3μm.

[0060] Example Analysis

[0061] Steelmaking ingredients

[0062] According to the above steelmaking process requirements, the actual slab chemical composition (mass percentage) is shown in Table 6.

[0063] Table 6 Chemical composition of the examples wt.%

[0064]

[0065]

[0066] Hot rolling process is based on the above-mentioned thermal process requirements, and the hot rolling process control is shown in Table 7.

[0067] Table 7 Hot rolling process

[0068]

[0069] Galvanizing process

[0070] The galvanizing process control is shown in Table 8, which meets the design requirements.

[0071] Table 8 Galvanizing process

[0072]

[0073] Roller coating process

[0074] The process parameters of the roller coater and the thickness of the zinc-aluminum-magnesium anti-fingerprint film are shown in Table 9.

[0075] Table 9 Roller coating process parameters and fingerprint resistant film

[0076]

[0077] Finished product performance

[0078] Mechanical properties:

[0079] The room temperature tensile mechanical properties of the finished product are shown in Table 10. The yield and tensile strength of the product are stable, meeting the user's requirements. The metallographic structure is equiaxed ferrite, and the organizational morphology is shown in Table 10. Figure 1 .

[0080] Table 10 Tensile mechanical properties of finished products

[0081]

[0082] Zinc layer weight:

[0083] Zinc layer weight requirement ≥275g / m 2 The actual test value is 279-284g / m 2 .

[0084] Table 7 Zinc layer weight

[0085] Serial number Average value of double-sided three-point detection Example 1 282 Example 2 279 Example 3 283 Example 4 284

[0086] Salt spray performance:

[0087] The product's cyclic salt spray corrosion test can meet 2800h visible black spots, white rust, and edge red rust; the red rust area is 1.5%, and the red rust area is ≤5%. Figure 2 and Figure 3 As shown, it meets the requirements of users and the market.

[0088] Usage

[0089] The products manufactured according to the present invention are processed by users into bellows and their parts such as Figure 4 As shown, it meets the user's requirements.

[0090] In summary, the performance indicators and formability of this product meet user requirements and are now available.

[0091] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for producing steel for high corrosion resistance and high toughness zinc-aluminum-magnesium corrugated pipes, characterized in that: include: Steelmaking process: KR desulfurization → converter → RH refining → slab continuous casting; Its chemical composition by mass percentage is: C≤0.003%, Si≤0.03%, Mn≤0.20%, P≤0.020%, S≤0.010%, N≤0.0030%, O≤0.0030%, Ti≥0.04%, and the rest is Fe and unavoidable impurities; Hot rolling process: heating furnace → rough rolling high-pressure water descaling machine → fixed width press → E1R1 rough rolling mill → E2R2 rough rolling mill → insulation cover → flying shear → finishing high-pressure water descaling machine → F1-F7 finishing mill → encrypted laminar cooling → coiler; during the rolling process of the finishing mill, the actual rolling oil flow of each stand of F2, F3, and F4 is controlled at 140-240ml / min; Pickling process: Pickling uncoiling → welding → straightening → pickling → rinsing → drying → trimming → rolling → coiler → pickling reduction rate ≥ 70%; Galvanizing process: hot-dip galvanizing uncoiling → welding → entrance looper → cleaning → annealing furnace → zinc pot → cooling after plating → water quenching → intermediate looper → skin-passing machine → straightening machine → roller coater → dryer → air cooling device → exit looper → trimming → surface inspection → oiling → sampling → coiling; galvanizing entrance process:; the conductivity control range of 1# brush washing tank is 30-70ms / cm, the conductivity control range of 2# brush washing tank (deionized water) is ≤200ms / cm, the conductivity control range of electrolytic tank is 40-60ms / cm, and the conductivity control range of rinsing tank is ≤200ms / cm.

2. The method for producing high corrosion-resistant and high-toughness zinc-aluminum-magnesium corrugated pipe steel according to claim 1, characterized in that: Zinc liquid composition control: Al content: 5.0-6.0%, magnesium content: 2.0-3.0%, Zn>90%; zinc pot temperature 420-450℃.

3. The production method of high corrosion resistance and high toughness zinc-aluminum-magnesium corrugated pipe steel according to claim 1 is characterized in that: Air knife process: In order to ensure the thickness of zinc-aluminum-magnesium galvanized strip, the air knife height is controlled at 400-600mm, the air knife pressure is controlled at 200-300mbar, and the air knife gap is controlled in the range of 7.5-8.0mm.

4. The method for producing high corrosion resistant and high toughness zinc-aluminum-magnesium corrugated pipe steel according to claim 1, characterized in that: The roller coater adopts reverse coating, the linear speed ratio of the coating roller and the strip steel is controlled at 100-150, the linear speed ratio of the dipping roller and the strip steel is controlled at 50-100, and the thickness of the fingerprint-resistant film is controlled at 0.9-1.3μm.

5. The method for producing high corrosion resistant and high toughness zinc-aluminum-magnesium corrugated pipe steel according to claim 1, characterized in that: The outlet temperature of the galvanizing annealing / soaking section is 795-810℃, the outlet temperature of the slow cooling section is 670-690℃, the elongation of the leveling machine is 1.05-1.10%, and the production line speed is 90-120m / min.

6. The method for producing high corrosion resistant and high toughness zinc-aluminum-magnesium corrugated pipe steel according to claim 1, characterized in that: The chemical composition of the zinc-aluminum-magnesium corrugated pipe steel in mass percentage is: C 0.0020%, Si 0.004%, Mn 0.12%, P 0.013%, S 0.008%, N 0.0022%, O 0.0017%, Ti 0.057%, and the rest is Fe and unavoidable impurities.

7. The method for producing high corrosion resistant and high toughness zinc-aluminum-magnesium corrugated pipe steel according to claim 1, characterized in that: The chemical composition of the zinc-aluminum-magnesium corrugated pipe steel in mass percentage is: C 0.0023%, Si 0.006%, Mn 0.13%, P 0.010%, S 0.007%, N 0.0018%, O 0.0020%, Ti 0.059%, and the rest is Fe and unavoidable impurities.

8. The method for producing high corrosion resistant and high toughness zinc-aluminum-magnesium corrugated pipe steel according to claim 1, characterized in that: The chemical composition of the zinc-aluminum-magnesium corrugated pipe steel in mass percentage is: C 0.0022%, Si 0.004%, Mn 0.15%, P 0.015%, S 0.006%, N 0.0024%, O 0.0020%, Ti 0.059%, and the rest is Fe and unavoidable impurities.

9. The method for producing high corrosion resistant and high toughness zinc-aluminum-magnesium corrugated pipe steel according to claim 1, characterized in that: The chemical composition of the zinc-aluminum-magnesium corrugated pipe steel by mass percentage is: C 0.0024%, Si 0.004%, Mn 0.16%, P 0.013%, S 0.009%, N 0.0020%, O 0.0019%, Ti 0.058%, and the rest is Fe and unavoidable impurities.

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