Galvanized structural steel with export strength grade of 280 MPa and production method

Abstract

The invention discloses galvanized structural steel with the export strength grade of 280 MPa and a production method of the galvanized structural steel. 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 steel products, and in particular relates to a galvanized structural steel with an export strength level of 280MPa and a production method thereof. 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] Prior art patent publication number CN 107419180 A (hereinafter referred to as document 1) discloses a cold-rolled steel sheet for electrogalvanizing with a yield strength of >250MPa and a production method, and its main production process is: hot rolling → pickling → cold rolling → electrolytic degreasing → hood annealing → leveling. The main production process of the present invention is hot rolling → pickling → continuous annealing → galvanizing → skin finishing, straightening → passivation → coiling → finished product. First of all, the hood annealing of the invention is limited to the production of soft steel plates, and is intermittent production, with a long production cycle and low efficiency, and is only suitable for small batch production.

[0004] Prior art patent publication number CN 104018079 A (hereinafter referred to as document 2) discloses a cold-rolled steel sheet and a preparation method thereof and a hot-dip galvanized steel sheet and a preparation method thereof, wherein the chemical composition ratio is C: 0.001-0.005%: Si: 0.01-0.05%: Mn: 0.2-0.7%: P: 0.03-0.08%: S≤0.02%: A1: 0.01-0.08%: Ti: 0.001-0.02%: Nb: 0.003-0.03%. The composition design of the invention improves the strength by reducing the C content and increasing the Ti and Nb content. Due to the high cost of Ti and Nb alloys, the production cost per ton of steel is significantly increased.

[0005] The prior art also discloses a 250MPa hot-dip galvanized high-strength structural steel for container barrels and a production method thereof. This patent is for 250MPa hot-dip galvanized structural steel for container barrels. The product strength levels are different, and there are obvious differences in chemical composition design, hot rolling, acid rolling, and galvanizing processes; the prior art discloses a method for galvanizing low-alloy high-strength structural steel. This patent prepares the steel for galvanizing by treating the surface of the coated steel to avoid the inability to react normally and completely with the steel during the subsequent galvanizing process. This invention can only change the appearance quality of the coating.

[0006] The above-mentioned prior art disclosed, whether it is 250MPa or 400MPa grade or above galvanized high-strength structural steel and its production method, has obvious differences in chemical composition design, hot rolling, acid rolling, and galvanizing process due to different product usage scenarios, and it is difficult to obtain the mechanical properties required for galvanized structural steel, which cannot meet people's needs.

[0007] In view of the above factors, a galvanized structural steel with an export strength level of 280MPa and a production method thereof are provided. By adjusting the hot rolling temperature system, the acid rolling reduction rate, and the process temperature system of the galvanizing furnace area, the optimal configuration of product costs is ensured, and mass production of products with qualified performance and meeting customer requirements is achieved. Summary of the invention

[0008] The object of the present invention is to provide a galvanized structural steel with an export strength level of 280 MPa and a production method thereof, so as to solve the problems raised in the above-mentioned background technology.

[0009] The object of the present invention is achieved through the following technical scheme: a galvanized structural steel for export strength level 280MPa, the chemical composition range of the galvanized structural steel by mass percentage is: C≤0.21%; Si≤0.06%; Mn 0.80~1.50; P≤0.015; S≤0.003; N≤50ppm, and the rest is Fe;

[0010] The chemical composition range of galvanized structural steel by mass percentage also includes: Alt0.033-0.038; Ca0.008-0.015; N0.0032-0.0055.

[0011] Furthermore, the metallographic grain size of the finished galvanized structural steel product is 10-11.

[0012] Furthermore, the mechanical properties of the finished galvanized structural steel product meet the following requirements: yield strength Rp0.2≥300MPa, tensile strength Rm≥420MPa.

[0013] Furthermore, the finished elongation A of the galvanized structural steel meets the requirement of ≥35%.

[0014] A production method for galvanized structural steel with an export strength level of 280 MPa, comprising the following steps;

[0015] 1. Smelting process

[0016] S1 converter smelting: the molten iron is pre-treated and desulfurized before converter smelting, oxygen is blown to decarburize and heat up, ensuring that the tapping temperature is ≥1620℃, and that the composition and temperature are coordinated for tapping;

[0017] S2 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.

[0018] S3 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;

[0019] 2. Hot rolling process

[0020] 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;

[0021] 3. Acid rolling process

[0022] The pickling rolling adopts the F1-F5 stand continuous rolling process to form different finished product thickness rolling specifications;

[0023] 4. Annealing process

[0024] Annealing uses a vertical continuous annealing furnace, which uses a reducing atmosphere and a nitrogen-hydrogen mixed protective atmosphere for cooling, and controls the outlet temperature of each section of the heating furnace;

[0025] Furthermore, in the smelting process, ferrosilicon and ferromanganese are added to deoxidize and alloy in the later stage of converter smelting to control the P and S components to prevent overoxidation of molten steel, and the converter tapping is controlled to have [P]≤0.010% and [S]≤0.008%

[0026] If it is a new tapping port or an abnormal turnover ladle, the tapping temperature will be increased by 10-15℃ based on the upper limit.

[0027] Furthermore, the heating system of the casting billet is as follows;

[0028]

[0029] Further, the rolling procedure of the acid rolling process is as follows;

[0030]

[0031] Furthermore, the annealing process is as follows:

[0032]

[0033] A production method for exporting galvanized structural steel with a strength level of 280 MPa is used to produce galvanized structural steel products suitable for export with a thickness of 0.80-2.50 mm and a strength level of 280 MPa;

[0034] Stable mass production of galvanized structural steel with a full thickness of 0.80-2.50mm that meets the export product standards. 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 lowest manufacturing cost;

[0035] The production method of galvanized structural steel ensures that the elongation A of the finished galvanized structural steel meets ≥35%, the grain size of the finished metallographic structure is grade 10-11, and the mechanical properties of the finished galvanized structural steel meet the following requirements: yield strength Rp0.2 ≥300MPa, tensile strength Rm ≥420MPa.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The present invention can be used to stably produce galvanized structural steel with a full thickness of 0.80-2.50 mm in large quantities and in compliance with export product standards. According to different later uses, the present invention can effectively match upstream and downstream processes to produce galvanized structural steel products that meet standards and are suitable for use at the optimal manufacturing cost, and has good promotion value.

[0038] The present invention adopts a production method of galvanized structural steel with an export strength level of 280MPa, combines the needs proposed by users, fully identifies customer requirements for products, product service environment, and product inspection requirements, and ensures product mechanical properties by adding C, Mn elements and micro-alloying elements. At the same time, by adjusting the hot rolling temperature system, acid rolling reduction rate, and galvanizing furnace area process temperature system, the product cost is optimized, and mass production of products with qualified performance and meeting customer requirements is achieved.

[0039] The products and methods of the present invention have the purpose of low cost and high applicability, and have a directional guiding role for similar production lines. The 280MPa-level products can meet the requirements of general use, and have lower costs and selling prices, which meet market needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of the metallographic structure of the finished product of the present invention. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0042] like Figure 1As shown, a galvanized structural steel with an export strength level of 280MPa, the chemical composition range of the galvanized structural steel by mass percentage is: C≤0.21%; Si≤0.06%; Mn0.80~1.50; P≤0.015; S≤0.003; N≤50ppm, and the rest is Fe;

[0043] The chemical composition range of galvanized structural steel in mass percentage also includes: Alt0.033-0.038, Ca0.008-0.015, N0.0032-0.0055.

[0044] The finished galvanized structural steel has a metallographic structure with a grain size of 10-11.

[0045] The mechanical properties of the finished galvanized structural steel meet the following requirements: yield strength Rp0.2≥300MPa, tensile strength Rm≥420MPa.

[0046] The finished product elongation A of the galvanized structural steel meets the requirement of ≥35%. Specific embodiment one:

[0048] like Figure 1 As shown, a production method for galvanized structural steel with an export strength level of 280 MPa comprises:

[0049] 1. Smelting process

[0050] S1 converter smelting: molten iron is pre-treated for desulfurization and then smelted in converter, oxygen is blown for decarburization and temperature is raised, ferrosilicon and ferromanganese are added for deoxidation and alloying in the later stage of smelting, P and S components are controlled to prevent overoxidation of molten steel, and the tapping temperature is ≥1620℃ to ensure that the composition and temperature are coordinated for tapping. If there is a new tapping port or abnormal turnover ladle, the tapping temperature shall be increased by 10-15℃ on the basis of the upper limit, and the converter tapping [P] ≤0.015%, [S] ≤0.010%.

[0051] S2 refining: LF full-process argon blowing process is adopted, a good reducing atmosphere is maintained during the refining process, Al wire is used for deoxidation, ferromanganese and ferrotitanium are added for alloying in the later stage of LF, and calcium treatment is carried out after the end of LF.

[0052] S3 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.

[0053]

[0054] 2 Hot rolling process

[0055] 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.

[0056] Table 1 Billet heating system

[0057]

[0058] Table 2 Rolling process

[0059]

[0060] 3. Acid rolling process

[0061] The pickling rolling adopts the F1-F5 stand continuous rolling process, and the rolling procedures for different finished product thicknesses are shown in Table 3.

[0062] Table 3 Pickling rolling procedures

[0063] 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

[0064] 4 Annealing process

[0065] 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.

[0066] Table 4 Annealing process

[0067]

[0068] Table 5 Leveling machine process

[0069] Thickness range(mm) 1.00-2.00 Elongation(%) 1.80±0.10

[0070] Example Analysis

[0071] Steelmaking ingredients:

[0072] According to the above steelmaking process requirements, the actual slab chemical composition (mass percentage) is shown in Table 5 below.

[0073] Table 5 Example chemical composition is as follows:

[0074]

[0075] Finished product performance:

[0076] 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 .

[0077] Table 7 Mechanical properties of finished products

[0078] Specific embodiment 2:

[0080] A production method for galvanized structural steel with a strength level of 280 MPa for export is used to produce galvanized structural steel products with a thickness of 0.80-2.50 mm and a strength level of 280 MPa suitable for export;

[0081] Stable mass production of galvanized structural steel with a full thickness of 0.80-2.50mm that meets the export product standards. 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 lowest manufacturing cost;

[0082] The production method of galvanized structural steel ensures that the elongation A of the finished galvanized structural steel meets ≥35%, the grain size of the finished metallographic structure is grade 10-11, and the mechanical properties of the finished galvanized structural steel meet the following requirements: yield strength Rp0.2 ≥300MPa, tensile strength Rm ≥420MPa.

[0083] 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.

[0084] 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.

[0085] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0086] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A galvanized structural steel with an export strength level of 280MPa, characterized by: The chemical composition range of galvanized structural steel by mass percentage: C ≤ 0.21%; Si ≤ 0.06%; Mn 0.80 ~ 1.50; P ≤ 0.015; S≤0.003; N≤50ppm, the rest is Fe; The chemical composition range of galvanized structural steel by mass percentage also includes: Alt0.033-0.038; Ca0.008-0.015; N0.0032-0.0055.

2. The galvanized structural steel for export with a strength level of 280 MPa according to claim 1, characterized in that: The finished galvanized structural steel has a metallographic structure with a grain size of 10-11.

3. The galvanized structural steel for export with a strength level of 280 MPa according to claim 2, characterized in that: The mechanical properties of the finished galvanized structural steel meet the following requirements: yield strength Rp0.2≥300MPa, tensile strength Rm≥420MPa.

4. The galvanized structural steel for export with a strength level of 280 MPa according to claim 3, characterized in that: The finished product elongation A of the galvanized structural steel meets the requirement of ≥35%.

5. A method for producing galvanized structural steel with an export strength level of 280 MPa according to any one of claims 1 to 4, characterized in that: The method comprises the following steps:

1. Smelting process S1 converter smelting: the molten iron is pre-treated and desulfurized for converter smelting, oxygen is blown for decarburization and heating, to ensure that the tapping temperature is ≥1620℃, and the composition and temperature are coordinated for tapping; S2 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. S3 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; 3. Acid rolling process The pickling rolling adopts the F1-F5 stand continuous rolling process to form different finished product thickness rolling specifications; 4. Annealing process Annealing uses a vertical continuous annealing furnace, which is cooled by a reducing atmosphere and a nitrogen-hydrogen mixed protective atmosphere to control the outlet temperature of each section of the heating furnace.

6. The method for producing galvanized structural steel with an export strength level of 280 MPa according to claim 5, characterized in that: In the smelting process, ferrosilicon and ferromanganese are added to the converter for deoxidation and alloying in the later stage of converter smelting to control the P and S components and prevent the molten steel from being overoxidized. The converter tapping is controlled to have [P]≤0.010% and [S]≤0.008%; If it is a new tapping port or an abnormal turnover ladle, the tapping temperature will be increased by 10-15℃ based on the upper limit.

7. The method for producing galvanized structural steel with an export strength level of 280 MPa according to claim 5, characterized in that: The heating system of the casting billet is as follows:

8. The method for producing galvanized structural steel with an export strength level of 280 MPa according to claim 5, characterized in that: The rolling procedure of the acid rolling process is as follows:

9. The method for producing galvanized structural steel with an export strength level of 280 MPa according to claim 5, characterized in that: The annealing process is as follows:

10. A method for producing galvanized structural steel with a strength level of 280 MPa for export according to any one of claims 5 to 9, which is applied to the production of galvanized structural steel products suitable for export with a thickness of 0.80-2.50 mm and a strength level of 280 MPa; Stable mass production of galvanized structural steel with a full thickness of 0.80-2.50mm that meets the export product standards. 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 lowest manufacturing cost; The production method of galvanized structural steel ensures that the elongation A of the finished galvanized structural steel meets ≥35%, the grain size of the finished metallographic structure is grade 10-11, and the mechanical properties of the finished galvanized structural steel meet the following requirements: yield strength Rp0.2 ≥300MPa, tensile strength Rm ≥420MPa.

Images