Production method of Q355NE steel plate

Abstract

The invention discloses a production method of a Q355NE steel plate. The Q345NE steel plate comprises the following chemical components in percentage by weight: 0.15-0.17% of C; s : 0.3 to 0.4%; 1.4 to 1.5 percent of Mn; 0.01% to 0.02% of Nb; p is less than or equal to 0.014%; s < = 0.003%; the content of Ca is 0.0011 to 0.0026 percent; 0.017 to 0.033 percent of Al < s >; and the balance of iron and inevitable impurities. The Q345NE steel plate with good comprehensive performance is produced through proper continuous casting, heating and rolling processes. The steel plate is excellent in mechanical property, the yield strength of the steel plate ranges from 398 MPa to 436 MPa, the tensile strength ranges from 525 MPa to 556 MPa, the ductility ranges from 26% to 31%, and the impact energy at the temperature of minus 40 DEG C ranges from 178 J to 235 J.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of structural steel, and particularly relates to a production method of Q355NE steel plate. BACKGROUND

[0002] Q355NE is a yield strength 355MPa grade low alloy high strength structural steel produced by normalizing rolling method, and is widely applied in engineering machinery, wind power and other fields. The national standard of Q355NE steel plate requires that the impact energy at-40 DEG C is not less than 34J, the steel plate has high strength, and also needs good low temperature impact toughness. Since the steel plate produced by normalizing rolling has better uniformity of microstructure and performance than other methods, the finish rolling temperature is usually higher than that of other controlled rolling methods, and the steel plate is not rapidly cooled after rolling, so it is difficult to obtain good toughness.

[0003] The patent with publication number CN 102312156 A "60mm or less low alloy Q345E+B steel plate and production method thereof" provides a production method of Q345E steel plate with thickness of 60mm or less. The steel plate produced by the method meets the strength requirement, and has good toughness. However, the method needs the steel plate to enter the holding box after rolling, and it is difficult to mass produce.

[0004] The patent with publication number CN 106521333 A "Large thickness and super wide Q345E-Z35 steel plate and production method thereof" provides a production method of Q345E thick steel plate. The steel plate produced by the method meets the strength requirement, and has good toughness. However, the method needs to add Nb, V and other micro alloys, and the alloy cost is high. Meanwhile, the steel plate needs to be heat treated after rolling, and the process is more and the manufacturing cost is higher.

[0005] The patent with publication number CN 107739992 A "Normalizing type yield 345MPa grade weathering steel plate and production method thereof" provides a production method of steel plate with yield strength of 345MPa. The steel plate produced by the method meets the strength requirement, and has good toughness. However, the method needs to add Nb, Cu, Cr and other alloys, and the alloy cost is high. The steel plate needs to be normalized after rolling, and the process cost is high. SUMMARY

[0006] The purpose of the application is to provide a production method of Q345NE steel plate with good surface quality, simple production process, low manufacturing cost, and good matching of strength and toughness.

[0007] To solve the above technical problems, the application adopts the following technical scheme:

[0008] The application provides a production method of Q355NE steel plate, which comprises the following steps:

[0009] The thickness of the continuous casting billet is 300 mm, electromagnetic stirring and light pressing are used during continuous casting, the electromagnetic stirring frequency is 5 Hz, the current is 360 A, the pressing position is 7, 8 and 9, and the total pressing amount is 8.1 mm.

[0010] Heating process: the production is carried out by using a 300 mm thick continuous casting billet, and a three-stage walking beam furnace is used for slab heating. The first heating stage furnace temperature is 1170-1200℃, the second heating stage furnace temperature is 1220-1260℃, the continuous casting billet discharge temperature is 1200-1240℃, and the heating time is 210-280 minutes.

[0011] Rolling process: after the slab is heated, controlled rolling is carried out, two-stage controlled rolling is adopted, the first stage rolling thickness is the slab thickness, the first stage rolling temperature is 1190-1230℃, the first stage final rolling temperature is ≥1050℃, the first stage rolling is 7-9 passes, the first stage rolling is rolled to the second stage rolling thickness, and the first stage rolling speed is 2.0 m / s. The second stage slab rolling thickness is 80-100 mm, the second stage slab rolling temperature is 870-890℃, the second stage final rolling temperature is 800-820℃, the second stage rolling is rolled to the finished slab thickness, and the second stage rolling is 8 passes;

[0012] The mass percentage of the chemical composition of the Q345NE steel plate is: C: 0.15-0.17%; Si: 0.3-0.4%; Mn: 1.4-1.5%; Nb: 0.01-0.02%; P≤0.014%; S≤0.003%; Ca: 0.0011-0.0026%; Als: 0.017-0.033%; the rest is iron and unavoidable impurities.

[0013] Further, the thickness of the steel plate is 20-30 mm thick.

[0014] Further, the mass percentage of the chemical composition of the Q345NE steel plate is: C 0.15%, Si 0.3%, Mn 1.5%, Nb 0.01%, P 0.014%, S 0.003%, Als 0.017%, Ca 0.0011%, the balance being Fe and unavoidable impurities.

[0015] Further, the mass percentage of the chemical composition of the Q345NE steel plate is: C 0.17%, Si 0.4%, Mn 1.4%, Nb 0.02%, P 0.011%, S 0.001%, Als 0.033%, Ca 0.0026%, the balance being Fe and unavoidable impurities.

[0016] Further, the Q345NE steel plate has the following chemical components in percentage of mass: C 0.16%, Si 0.35%, Mn 1.42%, Nb 0.012%, P 0.012%, S 0.002%, Als 0.031%, Ca 0.0022%, and the balance of Fe and inevitable impurities.

[0017] Further, the steel plate has the following properties: yield strength between 398MPa and 436MPa, tensile strength between 525MPa and 556MPa, elongation between 26% and 31%, and impact energy at-40℃ between 178J and 235J.

[0018] Compared with the prior art, the present application has the following beneficial technical effects:

[0019] 1) The present application adopts low-cost component design, and uses cheap Si and Mn as the main components, and adds a small amount of alloy such as Nb, so that the Q355ND steel plate with good comprehensive performance and similar comprehensive performance to the normalized steel plate is obtained through suitable heating and controlled rolling. The alloy cost and manufacturing cost are low.

[0020] 2) The steel plate has good strength, plasticity and toughness, and the structure is fine ferrite + pearlite. The yield strength of the steel plate is between 398MPa and 436MPa, the tensile strength is between 525MPa and 556MPa, the elongation is between 26% and 31%, and the impact energy at-40℃ is between 178J and 235J. BRIEF DESCRIPTION OF DRAWINGS

[0021] The present application will be further described below in combination with the drawings.

[0022] Figure 1 Fig. 1 is a metallographic structure diagram of the steel plate of the present application example 1;

[0023] Figure 2 Fig. 2 is a metallographic structure diagram of the steel plate of the present application example 2;

[0024] Figure 3 Fig. 3 is a metallographic structure diagram of the steel plate of the present application example 3. DETAILED DESCRIPTION

[0025] The present application will be further described below in combination with the drawings.

[0026] Example 1

[0027] The slab with thickness of 300 mm is used, the frequency of electromagnetic stirring during continuous casting of the slab is 5 Hz, the current is 360 A, the reduction position is 7, 8, 9, and the total reduction is 8.1 mm. The three-stage walking beam furnace is used for heating the slab, the furnace temperature of the first heating stage is 1170 °C, the furnace temperature of the second heating stage is 1220 °C, the temperature of the continuous casting slab when leaving the furnace is 1200 °C, and the heating time is 210 minutes. The chemical composition (in weight percent) of the slab is: C 0.15%, Si 0.3%, Mn 1.5%, Nb 0.01%, P 0.014%, S 0.003%, Als 0.017%, Ca 0.0011%, and the balance is Fe and inevitable impurities. The Q345NE steel plate with thickness of 20 mm is rolled, the detailed rolling and cooling process is shown in Table 1, and the mechanical properties are shown in Table 2.

[0028] Table 1 Rolling and cooling process

[0029]

[0030] Table 2 Mechanical properties of the steel plate

[0031]

[0032] Example 2

[0033] The slab with thickness of 300 mm is used, the frequency of electromagnetic stirring during continuous casting of the slab is 5 Hz, the current is 360 A, the reduction position is 7, 8, 9, and the total reduction is 8.1 mm. The three-stage walking beam furnace is used for heating the slab, the furnace temperature of the first heating stage is 1170 °C, the furnace temperature of the second heating stage is 1220 °C, the temperature of the continuous casting slab when leaving the furnace is 1200 °C, and the heating time is 210 minutes. The chemical composition (in weight percent) of the slab is: C 0.15%, Si 0.3%, Mn 1.5%, Nb 0.01%, P 0.014%, S 0.003%, Als 0.017%, Ca 0.0011%, and the balance is Fe and inevitable impurities. The Q345NE steel plate with thickness of 20 mm is rolled, the detailed rolling and cooling process is shown in Table 1, and the mechanical properties are shown in Table 2.

[0034] Table 3 Rolling and cooling process

[0035]

[0036] Table 4 Mechanical properties of the steel plate

[0037]

[0038] Example 3

[0039] The slab with thickness of 300 mm is used, the frequency of electromagnetic stirring during continuous casting of the slab is 5 Hz, the current is 360 A, the reduction position is 7, 8, 9, and the total reduction is 8.1 mm. The three-stage step-type heating furnace is used during heating of the slab, the furnace temperature of the first heating stage is 1195℃, the furnace temperature of the second heating stage is 1238℃, the continuous casting slab exit temperature is 1229℃, and the heating time is 271 minutes. The chemical composition (wt.%) of the slab is: C 0.16%, Si 0.35%, Mn 1.42%, Nb 0.012%, P 0.012%, S 0.002%, Al 0.031%, Ca 0.0022%, and the balance is Fe and inevitable impurities. The Q345NE steel plate with thickness of 25 mm is rolled, the detailed rolling and cooling process is shown in Table 5, and the mechanical properties are shown in Table 6.

[0040] Table 5 Rolling and cooling process

[0041]

[0042] Table 6 Mechanical properties of the steel plate

[0043]

[0044] The above-described embodiments are only to describe the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A production method of a Q355NE steel plate, characterized in that: Comprise: The thickness of the continuous casting billet is 300 mm, electromagnetic stirring and light pressing are used during continuous casting, the frequency of electromagnetic stirring is 5 Hz, the current is 360 A, the pressing position is 7, 8, 9, and the total pressing amount is 8.1 mm; The heating process: using 300 mm thick continuous casting billet for production, three-stage walking beam furnace is used for slab heating; the first heating stage furnace temperature is 1170-1200℃, the second heating stage furnace temperature is 1220-1260℃, the continuous casting billet discharge temperature is 1200-1240℃, and the heating time is 210-280 minutes; The rolling process: after the slab is heated, controlled rolling is carried out, two-stage controlled rolling is adopted, the first stage rolling thickness is the slab thickness, the first stage rolling temperature is 1190-1230℃, the first stage final rolling temperature is ≥1050℃, the first stage rolling is 7-9 passes, the first stage rolling is stopped until the second stage rolling thickness, the first stage rolling speed is 2.0 m / s, the second stage slab opening rolling thickness is 80-100 mm, the second stage slab opening rolling temperature is 870-890℃, the second stage final rolling temperature is 800-820℃, the second stage rolling is stopped until the finished steel plate thickness, and the second stage rolling is 8 passes; The mass percentage chemical composition of the Q345NE steel plate is: C: 0.15-0.17%; Si: 0.3-0.4%; Mn: 1.4-1.5%; Nb ：0.01～0.02％；P≤0.014％； S≤0.003%; Ca: 0.0011-0.0026%; Als: 0.017-0.033%; the rest is iron and unavoidable impurities.

2. The method of producing a Q355NE steel plate according to claim 1, characterized in that: The thickness of the steel plate is 20-30 mm thick.

3. The method of producing a Q355NE steel plate according to claim 1, characterized in that: The mass percentage chemical composition of the Q345NE steel plate is: C 0.15%, Si 0.3%, Mn 1.5%, Nb 0.01%, P 0.014%, S 0.003%, Als 0.017%, Ca 0.0011%, and the balance is Fe and unavoidable impurities.

4. The method of producing a Q355NE steel plate according to claim 1, characterized in that: The mass percentage chemical composition of the Q345NE steel plate is: C 0.17%, Si 0.4%, Mn 1.4%, Nb 0.02%, P 0.011%, S 0.001%, Als 0.033%, Ca 0.0026%, and the balance is Fe and unavoidable impurities.

5. The method of producing a Q355NE steel plate according to claim 1, characterized in that: The mass percentage chemical composition of the Q345NE steel plate is: C 0.16%, Si 0.35%, Mn 1.42%, Nb 0.012%, P 0.012%, S 0.002%, Als 0.031%, Ca 0.0022%, and the balance is Fe and unavoidable impurities.

6. The method of producing a Q355NE steel plate according to claim 1, characterized in that: The properties of the steel plate meet: the yield strength is between 398 MPa and 436 MPa, the tensile strength is between 525 MPa and 556 MPa, the elongation is between 26% and 31%, and the-40℃ impact energy is between 178 J and 235 J.

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