Production method for 400MPa galvanized structural steel with export strength grade

Abstract

The invention discloses a production method for galvanized structural steel with the export strength grade of 400MPa. The production method comprises the following steps: (1) a smelting process; 2) a hot rolling process; 3) an acid rolling process; 4) annealing process; the galvanized structural steel comprises the following chemical components in percentage by mass: less than or equal to 0.21% of C; less than or equal to 0.06% of Si; mn < = 1.50%; less than or equal to 0.015% of P; s is less than or equal to 0.005%, and the balance is Fe and inevitable impurities. According to the method, the requirements proposed by users are combined, the requirements of customers for products, the service environment of the products and the inspection requirements of the products are fully recognized, and the mechanical properties of the products are guaranteed by adding C and Mn elements and microalloy elements. Meanwhile, by means of the measures of adjusting the hot rolling temperature system, the acid rolling reduction rate and the galvanizing furnace area process temperature system, on the basis that the optimal configuration of the product cost is guaranteed, products which are qualified in performance and meet the use requirements of customers can be produced in batches.

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 for galvanized structural steel with an export strength level of 400MPa. Background Art

[0002] Galvanized structural steel is mainly used for civil purposes in China, involving many fields and a wide range of specifications. Galvanized structural steel products rely on the full process (steelmaking, hot rolling, acid rolling, galvanizing) production process, according to the use requirements of different downstream users, combined with its own process adjustment characteristics, and on the premise of fully identifying the process characteristics of other products on the production line, the product production process system and the transition process principles between products and other products have been formulated, so as to achieve mass production of products with qualified performance and in line with customer requirements.

[0003] The existing patent research is as follows:

[0004] The patent "A galvanized high-strength structural steel with a grade of 400MPa or above and its production method" has obvious differences in chemical composition design, hot rolling, acid rolling and galvanizing processes due to different product usage scenarios. Summary of the invention

[0005] The purpose of the present invention is to provide a production method for galvanized structural steel with an export strength level of 400MPa, which combines the needs of users, fully identifies the customer's requirements for products, the product service environment, and product inspection requirements, and ensures the mechanical properties of the products by adding C, Mn elements and micro-alloying elements. At the same time, by adjusting the hot rolling temperature system, the acid rolling reduction rate, and the galvanizing furnace area process temperature system, the product cost is optimized, and the batch production of products with qualified performance and meeting the customer's use requirements is achieved.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The present invention provides a production method for galvanized structural steel with an export strength level of 400MPa, and the main process flow comprises:

[0008] Steelmaking process: KR desulfurization → converter smelting → LF refining → slab continuous casting;

[0009] Hot rolling process: slab heating → high-pressure water descaling → fixed width press → E1R1 roughing mill rolling → E2R2 roughing mill rolling → (insulation cover) → flying shear head and tail → high-pressure water descaling → F1~F7 finishing mill rolling → encrypted laminar cooling → coiling → pallet transportation system → weighing → storage;

[0010] Pickling process: Pickling uncoiling → welding → straightening → pickling → rinsing → drying → trimming → rolling → coiling → weighing → marking → bundling → storage

[0011] Galvanizing process: hot-dip galvanizing uncoiling → welding → entrance looper → cleaning → annealing furnace → zinc pot → cooling after plating → water quenching → intermediate looper → skin pass machine → stretch straightening machine → roller coating machine → dryer → air cooling device → exit looper → trimming → surface inspection → oiling → sampling and inspection → coiling → bundling and weighing → packaging → storage;

[0012] Specifically include:

[0013] 1). Smelting process

[0014] 1.1). Converter smelting: The molten iron is pre-treated for desulfurization and then smelted in the converter. Oxygen is blown for decarburization and temperature is raised. In the later stage of smelting, ferrosilicon and ferromanganese are added for deoxidation and alloying. The P and S components are controlled to prevent overoxidation of the molten steel. The tapping temperature is ≥1620℃ to ensure that the composition and temperature are coordinated for tapping. If there is a new tapping port or an abnormal turnover ladle, the tapping temperature is increased by 10-15℃ on the basis of the upper limit as appropriate. The converter tapping [P] ≤0.015%, [S] ≤0.010%;

[0015] 1.2) Refining: Adopt argon blowing process throughout LF, maintain good reducing atmosphere during the refining process, use Al wire for deoxidation, add ferromanganese and ferrotitanium for alloying in the later stage of LF, and carry out calcium treatment after LF;

[0016] 1.3 Continuous casting: The temperature of molten steel entering the tundish is controlled at 1545-1580℃, the superheat is 25-40℃, and the casting speed is controlled at 1.00-1.50m / min;

[0017] 2). Hot rolling process

[0018] The billet is heated by a walking beam heating furnace, the rough rolling adopts a double-stand R1 and R2 reciprocating rolling, the rough rolling mode adopted is 3+3 or 1+5, and the finishing rolling adopts the F1-F7 continuous rolling process;

[0019] in:

[0020] The heating system of the casting billet is as follows:

[0021]

[0022] The rolling process is as follows:

[0023] Serial number Thickness mm Finish rolling temperature℃ Coil temperature(℃ Cooling Mode / Code 1 2.3-3.5 890±15 590±20 Pre-dispersion / 11

[0024] 3). Acid rolling process

[0025] The pickling rolling adopts the F1-F5 stand continuous rolling process;

[0026] Acid rolling procedures:

[0027] Thickness mm Hot rolling stock thickness mm Reduction rate % 1.00-﹤1.20 3.5 65.7-71.4 1.20-﹤1.40 3.8 63.2-68.4 1.40-﹤1.60 4.3 62.8-67.4 1.60-﹤2.00 4.6 60.9-65.2

[0028] 4). Annealing process

[0029] Annealing uses a vertical continuous annealing furnace, which is cooled by a reducing atmosphere and a nitrogen-hydrogen mixed protective atmosphere;

[0030] Annealing process:

[0031]

[0032] Leveling machine process:

[0033] Thickness range mm 1.00-2.00 Elongation % 1.80±0.10 .

[0034] Furthermore, the metallographic structure of the finished product is equiaxed ferrite + a small amount of pearlite.

[0035] Furthermore, the finished product has a metallographic grain size of 10-11.

[0036] Furthermore, the mechanical properties of the finished product meet the following requirements: yield strength Rp0.2 ≥ 300MPa, tensile strength Rm

[0037] ≥420MPa.

[0038] Furthermore, the elongation A of the finished product satisfies ≥35%.

[0039] Compared with the prior art, the beneficial technical effects of the present invention are:

[0040] The advantage of the present invention is that it introduces a process method for stably producing galvanized structural steel with a full thickness of 0.5 to 2.5 mm in large quantities and meeting the export product standard requirements. According to different later uses, the upstream and downstream processes are effectively matched to produce galvanized structural steel products that meet the standards and are suitable for use at the optimal manufacturing cost, and the method has good promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention will be further described below in conjunction with the accompanying drawings.

[0042] Figure 1 This is the metallographic structure of the finished product. DETAILED DESCRIPTION

[0043] A production method for galvanized structural steel with an export strength level of 400 MPa, comprising:

[0044] 1. Smelting process

[0045] 1.1 Converter smelting: The molten iron is pre-treated for desulfurization and then smelted in the converter. Oxygen is blown for decarburization and temperature is raised. In the later stage of smelting, ferrosilicon and ferromanganese are added for deoxidation and alloying. The P and S components are controlled to prevent the molten steel from being over-oxidized. The tapping temperature is ≥1620℃ to ensure that the components and temperature are coordinated for tapping. If there is a new tapping port or an abnormal turnover ladle, the tapping temperature shall be increased by 10-15℃ on the basis of the upper limit. The tapping temperature of the converter [P] is ≤0.015%, and [S] is ≤0.010%.

[0046] 1.2 Refining: The LF whole process argon blowing process is adopted, and a good reducing atmosphere is maintained during the refining process. Al wire is used for deoxidation. Manganese iron and titanium iron are added for alloying in the later stage of LF. Calcium treatment is carried out after the end of LF.

[0047] 1.3 Continuous casting: The temperature of molten steel entering the tundish is controlled at 1545-1580℃, the superheat is 25~40℃, and the casting speed is controlled at 1.00-1.50m / min.

[0048]

[0049] 2 Hot rolling process

[0050] The ingot is heated in a walking-beam heating furnace (the heating process is shown in Table 1). The rough rolling adopts double-stand R1 and R2 reciprocating rolling. The rough rolling mode adopted is 3+3 or 1+5. The finishing rolling adopts F1~F7 continuous rolling process. The specific hot rolling process is shown in Table 2.

[0051] Table 1 Billet heating system

[0052]

[0053] Table 2 Rolling process

[0054]

[0055] 3. Acid rolling process

[0056] The pickling rolling adopts the F1~F5 frame continuous rolling process, and the rolling procedures for different finished product thicknesses are shown in Table 3.

[0057] Table 3 Pickling rolling procedures

[0058] Thickness mm Hot rolling stock thickness mm Reduction rate % 1.00～﹤1.20 3.5 65.7～71.4 1.20～﹤1.40 3.8 63.2～68.4 1.40～﹤1.60 4.3 62.8～67.4 1.60～﹤2.00 4.6 60.9～65.2

[0059] 4 Annealing process

[0060] Annealing uses a vertical continuous annealing furnace, and the furnace is cooled by a reducing atmosphere and a nitrogen-hydrogen mixed protective atmosphere. The outlet temperature control of each section of the heating furnace is shown in Table 4, and the elongation control of the flattening machine at different thicknesses is shown in Table 5.

[0061] Table 4 Annealing process

[0062]

[0063] Table 5 Leveling machine process

[0064] Thickness range(mm) 1.00～2.00 Elongation(%) 1.80±0.10

[0065] Example Analysis

[0066] Steelmaking ingredients:

[0067] According to the above steelmaking process requirements, the actual slab chemical composition (mass percentage) is shown in Table 5 below.

[0068] Table 5 Chemical composition of examples

[0069]

[0070]

[0071] Finished product performance:

[0072] Based on the hot-rolled mechanical properties, the finished product is produced according to the above-designed acid rolling process and annealing process. The room temperature tensile mechanical properties of the finished product are shown in Table 7. The metallographic structure is equiaxed ferrite + a small amount of pearlite, the grain size is 10-11, and the organizational morphology is shown in Figure 1 .

[0073] Table 7 Mechanical properties of finished products

[0074]

[0075] Product application areas: The galvanized structural steel series products are mainly exported to Europe, Japan, South Korea, Southeast Asia and other regions, and are mainly used in construction, electronics, light industry, agriculture and other industries. The products are mostly made into square tubes, round tubes, structural panels, cable trays, scaffolding, protective pipes, etc.

[0076] In summary, this product has passed performance tests and user experience and its various performances meet the current market demand, and has been widely used in various civil structural parts and reinforcement plates.

[0077] 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 galvanized structural steel with an export strength level of 400 MPa, characterized by comprising: 1). Smelting process 1.1). Converter smelting: The molten iron is pre-treated for desulfurization and then smelted in the converter. Oxygen is blown for decarburization and temperature is raised. In the later stage of smelting, ferrosilicon and ferromanganese are added for deoxidation and alloying. The P and S components are controlled to prevent overoxidation of the molten steel. The tapping temperature is ≥1620℃ to ensure that the composition and temperature are coordinated for tapping. If there is a new tapping port or an abnormal turnover ladle, the tapping temperature is increased by 10-15℃ on the basis of the upper limit as appropriate. The converter tapping [P] ≤0.015%, [S] ≤0.010%; 1.2) Refining: Adopt argon blowing process throughout LF, maintain good reducing atmosphere during the refining process, use Al wire for deoxidation, add ferromanganese and ferrotitanium for alloying in the later stage of LF, and carry out calcium treatment after LF; 1.3 Continuous casting: The temperature of molten steel entering the tundish is controlled at 1545-1580℃, the superheat is 25-40℃, and the casting speed is controlled at 1.00-1.50m / min; 2). Hot rolling process The billet is heated by a walking beam heating furnace, the rough rolling adopts a double-stand R1 and R2 reciprocating rolling, the rough rolling mode adopted is 3+3 or 1+5, and the finishing rolling adopts the F1-F7 continuous rolling process; in: The heating system of the casting billet is as follows: The rolling process is as follows: 3). Acid rolling process The pickling rolling adopts the F1-F5 stand continuous rolling process; Acid rolling procedures: 4). Annealing process Annealing uses a vertical continuous annealing furnace, which is cooled by a reducing atmosphere and a nitrogen-hydrogen mixed protective atmosphere; Annealing process: Leveling machine process: The chemical composition of the galvanized structural steel in terms of mass percentage is: C≤0.21%; Si≤0.06%; Mn≤1.50%; P≤0.015%; S≤0.005%, and the rest is Fe and unavoidable impurities.

2. The method for producing galvanized structural steel with an export strength level of 400 MPa according to claim 1, characterized in that: The metallographic structure of the finished product is equiaxed ferrite + a small amount of pearlite.

3. The production method for export strength grade 400MPa galvanized structural steel according to claim 1, characterized in that: The grain size of the finished metallographic structure is 10-11.

4. The method for producing galvanized structural steel with an export strength level of 400 MPa according to claim 1, characterized in that: The mechanical properties of the finished product meet the following requirements: yield strength Rp0.2≥300MPa, tensile strength Rm≥420MPa.

5. The method for producing galvanized structural steel with an export strength level of 400 MPa according to claim 1, characterized in that: The elongation A of the finished product meets ≥35%.

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