CN113088824A - High-construction steel and manufacturing method thereof - Google Patents

Abstract

The invention discloses high building steel which comprises the following chemical components in percentage by weight: c: 0.05-0.20%, N is less than or equal to 0.025%, and Si: 0.05-0.30%, Mn 0.50-0.80%, P not more than 0.045%, S not more than 0.045%, Cr 3.5-4.5%, Ni 1.0-2.0%, B0.0003-0.0010%, Al 0.4-0.6%, Cu: 0.04-0.06%, and the balance of iron and unavoidable impurities. According to the invention, by adjusting the numerical range of the components of the conventional high-construction steel, the contents of Cr and Ni elements are increased, the content of Al is increased by more than ten times of the original content, the consumption of Cu is reduced, the surface processing quality and the strength of the product are ensured, and thus the yield of the high-construction steel is improved and the thickness of the high-construction steel can be reduced.

Description

High-construction steel and manufacturing method thereof

Technical Field

The invention relates to a stainless steel smelting process, in particular to high-construction steel and a manufacturing method thereof.

Background

The high-construction steel greatly saves the material consumption due to the good physical properties, can ensure the safety of a building structure, and is the trend of the current building materials. The materials used for high-rise building structures generally require high strength and toughness and good weldability, so that preheating is not needed before welding and stress relief treatment is not needed after welding, and if the materials have certain heat resistance, the application field can be further widened.

At present, the high-strength structural steel for buildings mainly comprises Q550GJ, Q620GJ and Q690GJ types of steel, the maximum value of the yield strength is 690, the tensile strength range is 690-860, the elongation after fracture is more than or equal to 14, the strength is improved along with the increase of the thickness, but the elongation performance is poor, and in order to ensure the mechanical property of a steel plate, the thickness of the structural steel plate for high-rise buildings is usually not less than 8mm, so that the weight of the structural steel plate cannot be further reduced. Meanwhile, cracks are easily generated on the surface of the steel continuous casting billet for high-rise buildings produced by most domestic steel mills, and the cracks are amplified in the heating and rolling processes of steel rolling to generate larger cracks and reduce the performance of a steel plate. Therefore, it is a subject to be studied how to control the surface processing quality of a thin high-construction steel sheet and to combine the strength, yield strength and elongation of a thick sheet.

Disclosure of Invention

The invention aims to provide high-construction steel.

The technical scheme for realizing the purpose of the invention is as follows: the high-construction steel comprises the following chemical components in percentage by weight: c: 0.05-0.20%, N is less than or equal to 0.025%, and Si: 0.05-0.30%, Mn 0.50-0.80%, P not more than 0.045%, S not more than 0.045%, Cr 3.5-4.5%, Ni 1.0-2.0%, B0.0003-0.0010%, Al 0.4-0.6%, Cu: 0.04-0.06%, and the balance of iron and unavoidable impurities.

In the component design of the invention:

c: 0.05-0.20%, N: less than or equal to 0.025 percent to control the martensite content in the slab cooling process and reduce brittle phase. Wherein, nitrogen is a gap atom of the steel grade, the content of the nitrogen can influence the plasticity of the material, and the N is required to be less than or equal to 0.025 percent in the component design.

3.5-4.5% of Cr, ensures the strength of the steel, has certain corrosion resistance, cannot play a role when being too low, and is too high, thereby relating to the cost problem.

Si: 0.20-0.30%, silicon is a parameter related to the strength of a finished product, and in addition, a certain silicon content ensures that molten steel is not oxidized excessively.

0.4 to 0.6 percent of Al. The Al content of the same type of high-construction steel in the market is 0.02-0.04%, and the Al element is used for fixing nitrogen in the steel and protecting boron. However, the inventor finds that the insufficient Al can cause the problem of slab surface cracks in the machining process in the structural steel thinning research. The invention improves the generation amount of ferrite and inhibits the generation of carbide by improving the content of Al element, thereby reducing the generation of martensite to the maximum extent and reducing the generation of cracks caused by over-quick cooling of a plate blank when the cooling speed is relatively high. However, under the condition of ensuring single phase of a plate blank under the quenching condition, the surface crack probability of the plate blank is increased due to the over-high content of a certain amount of aluminum element, so that the content range is limited to 0.4-0.6%. Meanwhile, the aluminum content is kept in the range, the oxygen content in the molten steel is reduced, the purity of the molten steel is improved, and magnesium-aluminum systems in the molten steel are mixed in the plastic deformable range.

Cu: 0.04-0.06%, copper element can increase the proportion of goldenrain crystal, the surface area of crystal grain is increased, and the strength of the material is improved. Too high a content increases the production cost.

Mn: the molten steel is prevented from being oxidized.

Ni: the corrosion resistance is improved.

The contents of P and S are controlled within 0.045%, and the P and the S are impurity elements in the steel, so that the ductility and the welding performance can be obviously improved by controlling the contents.

And B, improving the bonding force of the grain boundary and reducing the occurrence of edge crack.

According to the invention, by adjusting the numerical range of the components of the conventional high-construction steel, the contents of Cr and Ni elements are increased, the content of Al is increased by more than ten times of the original content, the consumption of Cu is reduced, the surface processing quality and the strength of the product are ensured, and thus the yield of the high-construction steel is improved and the thickness of the high-construction steel can be reduced.

The invention also aims to provide a manufacturing method of the high-construction steel, which comprises the following steps:

(1) carrying out converter smelting according to the chemical components of the first object of the invention;

(2) refining;

(3) continuous casting: the temperature of the tundish is controlled to be 1535-1545 ℃; setting according to the liquidus of the molten steel at 25-30 ℃ to ensure the internal quality of the plate blank;

(4) slowly cooling or heaping the steel billet;

(5) hot rolling: heating the steel billet in a heating furnace at 1150-1200 ℃, and finishing at 850-920 ℃; within the finish rolling temperature range, the steel grade is rolled in an austenite single-phase region, and the generation of hot rolling defects is reduced;

(6) carrying out laminar cooling and coiling to obtain hot-rolled strip steel: wherein the coiling temperature is 550-650 ℃. The coiling temperature can reduce the precipitation of carbide and increase the hardness of the material, and the toughness of the material is reduced when the coiling temperature exceeds the range, so that the mechanical property of the product is poor;

(7) and air-cooling to room temperature.

The process steps are not limited by the process parameters, and all the process parameters are the conventional general process parameters.

The high-construction steel prepared by the second aim of the invention has high strength, excellent extensibility and surface processing quality, has excellent corrosion resistance, can greatly reduce steel plates with the same performance requirements, replaces part of existing products in the fields of construction structural steel and the like, and has wide application prospect.

Detailed Description

The following is a detailed description of preferred embodiments of the invention.

Example 1:

the high-construction steel comprises the following chemical components in percentage by weight: c: 0.141%, Si: 0.28%, Mn: 0.76%, P: 0.032, S: 0.013%, Cu: 0.047%, Cr: 3.63%, Ni: 1.38%, N: 0.020%, Al: 0.42%, B: 0.0008% and the balance Fe and unavoidable impurities.

The manufacturing process of the high-construction steel comprises the following steps:

(1) carrying out converter smelting according to the chemical components;

(2) refining: fine adjustment of components is carried out in an LF furnace, the temperature is adjusted, when smelting components meet requirements, an Al wire is fed, the wire feeding length is 200 m/furnace, a B wire is fed, the wire feeding length is 10-15 m/furnace, argon is blown after a ferroboron wire is fed, soft stirring is carried out for 10-15 min, and then the sedation time is kept to be more than or equal to 10 min;

(3) continuous casting: the temperature of the tundish is controlled to be 1535-1545 ℃;

(4) slowly cooling or heaping the steel billet;

(5) hot rolling: the slab is fed into a heating furnace in a hot feeding mode, the precipitation of martensite in the rapid cooling process of the slab is reduced to the maximum extent, the billet is heated in the heating furnace at 1150 ℃, the finish rolling temperature is 880 ℃, the carbide is ensured to be completely dissolved into a matrix, and the rolling in a single-phase region is ensured;

(6) carrying out laminar cooling and coiling to obtain hot-rolled strip steel: wherein the coiling temperature is 630 ℃, and carbide precipitation is reduced;

(7) air cooling to room temperature: martensite precipitation is reduced to the maximum extent.

The examples 2 to 16 adopt the same smelting method as the examples, and are different in the ratio of each component, which is specifically shown in table 1. Wherein table 1 simultaneously gives the compositions of the structural steels which have been developed so far as comparative examples.

Table 1 units: weight percent of

Composition (I)	C	Si	Mn	P	S	Cu	Ni	Cr	N	Al	B
												Example 1	0.141	0.28	0.76	0.032	0.013	0.047	1.38	3.63	0.020	0.42	0.0008
Example 2	0.115	0.2	0.97	0.04	0.009	0.046	1.37	3.89	0.023	0.45	0.0005
												Example 3	0.141	0.23	0.83	0.035	0.026	0.047	1.41	3.98	0.016	0.48	0.0006
Example 4	0.138	0.16	0.85	0.036	0.035	0.044	1.39	3.95	0.017	0.51	0.0006
												Example 5	0.15	0.18	0.93	0.04	0.041	0.044	1.39	4.15	0.030	0.40	0.0005
Example 6	0.183	0.15	0.84	0.042	0.049	0.046	1.39	3.87	0.040	0.52	0.0005
												Example 7	0.089	0.28	0.65	0.033	0.039	0.051	1.38	3.13	0.022	0.55	0.0005
Example 8	0.085	0.32	0.72	0.036	0.045	0.051	1.37	3.36	0.019	0.44	0.0005
												Example 9	0.094	0.32	0.78	0.036	0.027	0.04	1.38	3.6	0.022	0.50	0.0005
Example 10	0.146	0.27	0.76	0.037	0.029	0.049	1.38	3.55	0.026	0.47	0.0007
												Example 11	0.111	0.11	0.8	0.037	0.033	0.041	1.41	3.67	0.027	0.45	0.0008
Example 12	0.156	0.2	0.82	0.04	0.033	0.042	1.43	4.01	0.015	0.42	0.0005
												Example 13	0.123	0.21	0.74	0.036	0.04	0.043	1.43	3.68	0.033	0.48	0.0007
Example 14	0.169	0.07	0.71	0.04	0.051	0.047	1.37	3.46	0.039	0.45	0.0005
												Example 15	0.121	0.02	0.73	0.035	0.048	0.047	1.44	3.69	0.025	0.46	0.0005
Example 16	0.159	0.2	0.74	0.041	0.061	0.044	1.43	3.48	0.024	0.56	0.0006
												Comparative example 1	0.150	0.40	1.70	0.023	0.021	0.004	0.50	1.20	0.010	0.001	0.0005
Comparative example 2	0.139	0.50	1.80	0.031	0.030	0.005	0.42	1.10	0.012	0.002	0.0007

Table 2 shows the main process parameters of examples 1 to 16 and comparative examples.

TABLE 2

The mechanical properties and surface finish qualities of the finished products of examples 1-16 and comparative examples 1-2 are shown in table 3, wherein the mechanical properties are obtained from hot rolled sheets.

TABLE 3

Numbering	Cooling method	Specification/mm	Yield strength	Tensile strength	Elongation after fracture	Cold bending	Hardness of	Surface cracking
									Example 1	Heap cooling	6.0*1015	750	980	18	Combination of Chinese herbs	78	Is free of
Example 2	Heap cooling	6.0*1015	760	985	17	Combination of Chinese herbs	75.5	Is free of
									Example 3	Heap cooling	6.0*1015	765	970	17.5	Combination of Chinese herbs	79	Is free of
Example 4	Heap cooling	6.0*1015	782	1013	16.5	Combination of Chinese herbs	80	Is free of
									Example 5	Heap cooling	6.0*1015	770	978	19.5	Combination of Chinese herbs	79.5	Is free of
Example 6	Heap cooling	6.0*1015	785	990	18.5	Combination of Chinese herbs	80.5	Is free of
									Example 7	Heap cooling	6.0*1015	755	960	18	Combination of Chinese herbs	77.5	Is free of
Example 8	Heap cooling	6.0*1015	803	1002	17.5	Combination of Chinese herbs	76.5	Is free of
									Example 9	Heap cooling	6.0*1015	806	997	16.6	Combination of Chinese herbs	74.5	Is free of
Example 10	Air cooling	6.0*1015	810	1018	15.5	Combination of Chinese herbs	81.5	Is free of
									Example 11	Air cooling	6.0*1015	820	1026	15.0	Combination of Chinese herbs	82.0	Is free of
Example 12	Air cooling	6.0*1015	830	1008	16.0	Combination of Chinese herbs	80.5	Is free of
									Example 13	Water cooling	6.0*1015	850	1020	14.5	Incompatibility of	83.5	Is free of
Example 14	Water cooling	6.0*1015	835	1035	15.0	Incompatibility of	82.5	Is free of
									Example 15	Water cooling	6.0*1015	840	1050	15.5	Incompatibility of	84.5	Is free of
Example 16	Water cooling	6.0*1015	870	1050	15.5	Incompatibility of	84.5	Is free of
									Comparative example 1	Heap cooling	8.0*1015	805	875	14.5	Combination of Chinese herbs	80.5	Is provided with
Comparative example 2	Heap cooling	8.0*1015	835	860	15.0	Combination of Chinese herbs	77.5	Is provided with

The results of comparing the weather resistance of the finished products of examples 1 to 4 and comparative examples 1 to 2 with Q235 are shown in Table 4.

TABLE 4

Material	Corrosion rate, g/m 2. h	Weather resistance is multiple of Q235
			Example 1	1.05	3.78
Example 2	1.02	4.02
			Example 3	1.12	4.22
Example 4	1.08	4.15
			Comparative example 1	1.82	2.21
Comparative example 2	1.89	2.25
			Q235B	4.15	1.00

As can be seen from Table 3, compared with comparative examples 1-2, the sheet products of examples 1-16 of the present invention having a thickness of 6mm had yield strengths not lower than those of the existing high construction steels having a thickness of 8mm, tensile strengths superior to those of the existing high construction steels having a thickness of 8mm, no significant decrease in elongation after fracture, and no cracks on the surfaces. Table 4 shows that the corrosion resistance of the high-construction steel obtained by the invention is also greatly superior to that of the existing high-strength steel product. Therefore, the performance of the high-construction steel is improved, the steel plates with the same performance requirements can be greatly thinned, and then partial existing products are replaced in the fields of building structural steel and the like, so that the high-construction steel has a wide market prospect.

The converter-LF-CC smelting and the continuous rolling mill hot rolling adopted by the embodiment of the invention can also select other conventional smelting processes and equipment in the field of steel smelting in the actual production.

In order to maintain high strength, the steel grade has higher chromium and carbon elements, which can cause the generation of martensite in the cooling process of a steel billet or a steel coil, so that the inhibition of the generation of martensite brittle phase is a key point of the production process of the steel grade. Therefore, the C content is controlled within the required range in the smelting implementation process, the conventional increase of the Al element content in the high-construction steel is broken through, the generation amount of ferrite is increased, the generation of carbide is inhibited, the generation of martensite is reduced to the greatest extent when the cooling speed is high, and the generation of cracks caused by the over-quick cooling of the plate blank is reduced. After the billet is produced, the hot-feeding hot-rolling mode is adopted as much as possible, and if the site does not have conditions, the billet is slowly cooled. In the production process of the steel strip, a laminar cooling mode is required, and meanwhile, the produced hot steel strip is slowly cooled in the air.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent flow transformations made by the present specification, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims (2)

1. The high-construction steel is characterized in that: the weight percentage of the chemical components is as follows: c: 0.05-0.20%, N is less than or equal to 0.025%, and Si: 0.05-0.30%, Mn 0.50-0.80%, P not more than 0.045%, S not more than 0.045%, Cr 3.5-4.5%, Ni 1.0-2.0%, B0.0003-0.0010%, Al 0.4-0.6%, Cu: 0.04-0.06%, and the balance of iron and unavoidable impurities.

2. A manufacturing method of high building steel comprises the following steps:

(1) converter smelting according to the chemical composition of claim 1;

(2) refining;

(3) continuous casting: the temperature of the tundish is controlled to be 1535-1545 ℃;

(4) slowly cooling or heaping the steel billet;

(5) hot rolling: heating the steel billet in a heating furnace at 1150-1200 ℃, and finishing at 850-920 ℃;

(6) carrying out laminar cooling and coiling to obtain hot-rolled strip steel: wherein the coiling temperature is 550-650 ℃;

(7) air cooling to room temperature;

the process steps are not limited by the process parameters, and all the process parameters are the conventional general process parameters.