阅读说明：本技术 一种纵横向冲击韧性良好的大规格建筑用圆钢及生产方法 (Large-size building round steel with good longitudinal and transverse impact toughness and production method thereof ) 是由 赵瑞华 李双居 李秀查 武森 胡云生 任鹏飞 陈良勇 于 2019-10-15 设计创作，主要内容包括：本发明公开了一种纵横向冲击韧性良好的大规格建筑用圆钢及生产方法,圆钢化学成分组成及质量百分含量为：C：0.17～0.22%、Si：0.25～0.45%、Mn：1.00～1.40%、Cr≤0.30%、V：0.02～0.15%、Ti：0.01～0.03%、P≤0.020%、S≤0.010%、Ni≤0.30%、Cu≤0.30%、Al：0.010～0.040%、N：0.007～0.012%,余量为Fe和不可避免的杂质；生产方法包括冶炼、LF精炼、VD真空处理、连铸、加热、轧制工序。本发明产品常温下纵、横向V型冲击功KV2均≥60J,屈服强度Rel：370～435MPa、抗拉强度Rm：545～620MPa。(The invention discloses a large-size round steel for buildings with good longitudinal and transverse impact toughness and a production method thereof, wherein the round steel comprises the following chemical components in percentage by mass: c: 0.17 to 0.22%, Si: 0.25 to 0.45%, Mn: 1.00-1.40%, Cr is less than or equal to 0.30%, V: 0.02 to 0.15%, Ti: 0.01-0.03%, P is less than or equal to 0.020%, S is less than or equal to 0.010%, Ni is less than or equal to 0.30%, Cu is less than or equal to 0.30%, Al: 0.010-0.040%, N: 0.007-0.012%, and the balance of Fe and inevitable impurities; the production method comprises the working procedures of smelting, LF refining, VD vacuum treatment, continuous casting, heating and rolling. The product has vertical and horizontal V-shaped impact energy KV2 of more than or equal to 60J at normal temperature, yield strength Rel: 370-435 MPa, tensile strength Rm: 545-620 MPa.)

1. The round steel for the large-size building with good longitudinal and transverse impact toughness is characterized by comprising the following chemical components in percentage by mass: c: 0.17 to 0.22%, Si: 0.25 to 0.45%, Mn: 1.00-1.40%, Cr is less than or equal to 0.30%, V: 0.02 to 0.15%, Ti: 0.01-0.03%, P is less than or equal to 0.020%, S is less than or equal to 0.010%, Ni is less than or equal to 0.30%, Cu is less than or equal to 0.30%, Al: 0.010-0.040%, N: 0.0070-0.0120% of Fe and the balance of inevitable impurities.

2. The large-size building round steel with good longitudinal and transverse impact toughness as claimed in claim 1, wherein the building round steel has a specification of 130-150 mm.

3. A large-size construction round bar with good longitudinal and transverse impact toughness as claimed in claim 1, wherein the yield strength Rel: 370-435 MPa, tensile strength Rm: 545-620 MPa, and the vertical and horizontal V-shaped impact energy KV2 at normal temperature is more than or equal to 60J.

4. The production method of the large-specification round steel for buildings with good longitudinal and transverse impact toughness is characterized by comprising the working procedures of smelting, LF refining, VD vacuum treatment, continuous casting, heating and rolling; in the LF refining process, 1.5-2.5 kg of ferrovanadium and 0.5-1.5 kg of ferrotitanium are added per ton of steel in the later period of LF refining; in the VD vacuum treatment process, 2.5-4.5 kg of MnN wires and 0.5-1.5 kg of aluminum wires are fed per t of steel after VD vacuum degassing treatment.

5. The method for producing the large-size round steel for buildings with good longitudinal and transverse impact toughness as claimed in claim 4, wherein in the LF refining process, refining slag with high alkalinity R of 5-8 is adopted for refining, and S: 0.002-0.010%.

6. The production method of the large-specification round steel for construction with good longitudinal and transverse impact toughness as claimed in claim 4, wherein the continuous casting process comprises the following chemical components in percentage by mass: c: 0.17 to 0.22%, Si: 0.25 to 0.45%, Mn: 1.00-1.40%, Cr is less than or equal to 0.30%, V: 0.02 to 0.15%, Ti: 0.01-0.03%, P is less than or equal to 0.020%, S is less than or equal to 0.010%, Ni is less than or equal to 0.30%, Cu is less than or equal to 0.30%, Al: 0.010-0.040%, N: 0.0070-0.0120% of Fe and the balance of inevitable impurities.

7. The method for producing large-sized round steel for building use according to any one of claims 4 to 6, wherein the heating step comprises heating the billet to 1140 to 1200 ℃ and maintaining the temperature for 0.8 to 1.1 hours.

8. The method for producing the large-sized round steel for construction use as claimed in any one of claims 4 to 6, wherein the rolling step is performed at a start rolling temperature of 1050 to 1120 ℃ and a finish rolling temperature of 880 to 950 ℃.

Technical Field

The invention belongs to the technical field of metallurgy, and particularly relates to large-specification building round steel with good longitudinal and transverse impact toughness and a production method thereof.

Background

With the continuous expansion of urban scale, a serious situation of urban land shortage appears, and in order to effectively relieve the situation, super high-rise buildings become a main mode for urban construction and development. The urbanization quality is greatly improved at present, the life quality of people is also gradually improved, and the building engineering plays a greater and greater role. Compared with the low-rise building, the super high-rise building has higher requirements on safety and stability, and meanwhile, people put higher requirements on quality and safety of building engineering. Therefore, higher and higher requirements are also put on the constructional steel.

The construction steel is developing in the direction of high strength, high performance and large scale. The steel for modern buildings has the characteristics of high strength, light dead weight, good integral rigidity and strong deformability, so the steel is particularly suitable for building large-span, ultrahigh and overweight buildings; the material has good homogeneity and isotropy, and conforms to the basic assumption of general engineering mechanics; the material has good plasticity and toughness, can have larger deformation, and can well bear dynamic load.

Some modern steel for construction has strict requirements on certain indexes of steel, for example, the requirement on the homogeneity of various items of steel is strict, the longitudinal and transverse impact energy is required to be more than or equal to 60J, and the conventional requirement that the longitudinal KV2 is more than or equal to 27J cannot meet the use requirement and the safety requirement. Therefore, the large-specification building round steel with good longitudinal and transverse impact toughness is urgently needed.

Disclosure of Invention

The technical problem to be solved by the invention is to provide the large-specification round steel for the building, which has good longitudinal and transverse impact toughness; the invention also provides a production method of the large-specification round steel for the building with good longitudinal and transverse impact toughness. According to the chemical composition design, V, Al and N elements are added to form nitride particles, a production process of converter, LF, VD, continuous casting and rolling is adopted, the longitudinal and transverse V-shaped impact energy KV2 of a product in a rolling state at normal temperature is more than or equal to 60J, and the yield strength Rel: 370-435 MPa, tensile strength Rm: 545-620 MPa, and stable performance.

In order to solve the technical problems, the invention adopts the technical scheme that: the round steel for the large-size building with good longitudinal and transverse impact toughness comprises the following chemical components in percentage by mass: c: 0.17 to 0.22%, Si: 0.25 to 0.45%, Mn: 1.00-1.40%, Cr is less than or equal to 0.30%, V: 0.02 to 0.15%, Ti: 0.01-0.03%, P is less than or equal to 0.020%, S is less than or equal to 0.010%, Ni is less than or equal to 0.30%, Cu is less than or equal to 0.30%, Al: 0.010-0.040%, N: 0.0070-0.0120% of Fe and the balance of inevitable impurities.

The action mechanism of each chemical component in the steel is as follows:

c: the main elements for improving the hardness and the strength of the steel are low in C content, and the strength of the material after heat treatment is too low to meet the strength requirement of the round steel for buildings; too high C content is easy to reduce the plasticity and toughness of the material.

Si: the strength of solid solution in steel is improved, the toughness and plasticity of the steel are reduced, and the low strength is not enough; too high causes the ferrite matrix to become brittle and the toughness to decrease.

Mn: in a certain range, Mn can improve the toughness of steel and reduce the brittleness; mn has a remarkable effect of improving the strength of low-carbon and medium-carbon steel and improving the hardenability of the steel; but when the Mn content is higher, the tempering brittleness phenomenon is more obvious, and the function of promoting the growth of crystal grains is realized.

Cr: the strength and the hardness of the steel can be improved, and the hardenability is improved; however, if the Cr content is too high, bainite is easily formed, and the low-temperature impact toughness of the steel is greatly reduced.

N: the most economic and effective alloying elements can form nitrides by combining with V, Ti and Al, and play a role in strengthening precipitation and refining grains; however, when the content of N is too high, more AlN is easily generated, the crack sensitivity of a continuous casting billet is increased, and meanwhile, the content and the size of TiN inclusions in steel are increased, and the toughness of the steel is damaged.

V: not only can improve the strength of the steel and reduce the overheating tendency, but also has obvious influence on the impact toughness of the steel. It reacts with nitrogen in the steel to form compounds and precipitates at grain boundaries, thereby playing a role in refining grains.

Ti: by reasonably controlling the existing form and the forming rule of titanium in steel, the titanium can play a role in refining grains, improving strength, improving toughness and the like. It reacts with nitrogen in the steel to form compounds and precipitates at grain boundaries, thereby playing a role in refining grains. Titanium in a certain range can improve impact toughness, but if the content is too high, the impact toughness of the steel is seriously deteriorated.

Al: is a strong deoxidizing element and plays a role in refining grains. Al and N are combined to refine grains, so that the toughness is improved; when the Al content in the steel is more than 0.50 percent, the effect of the Al on the toughness of the steel is not obviously influenced. Meanwhile, the high Al content easily causes the poor fluidity during continuous casting, and easily causes production accidents such as nozzle nodulation and the like.

S: has harmful effect on the plasticity and the toughness of the steel. Too high control of the S content may degrade the cleanliness of the steel and deteriorate the properties of the steel, particularly anisotropy.

P: increasing the brittleness of the steel and reducing the impact property, so that the content of the P element is controlled in a lower range, and the impact toughness of the steel can be prevented from being reduced.

The round steel for the building has the specification of phi 130-150 mm.

The yield strength Rel of the round steel for the building is as follows: 370-435 MPa, tensile strength Rm: 545-620 MPa, and the vertical and horizontal V-shaped impact energy KV2 at normal temperature is more than or equal to 60J.

The invention also provides a production method of the large-size round steel for the building with good longitudinal and transverse impact toughness, which comprises the working procedures of smelting, LF refining, VD vacuum treatment, continuous casting, heating and rolling; in the LF refining process, 1.5-2.5 kg of ferrovanadium and 0.5-1.5 kg of ferrotitanium are added per ton of steel in the later period of LF refining; in the VD vacuum treatment process, 2.5-4.5 kg of MnN wires and 0.5-1.5 kg of aluminum wires are fed per t of steel after VD vacuum degassing treatment.

In the LF refining process, refining slag with high alkalinity R of 5-8 is adopted for refining, and S in steel is controlled: 0.002-0.010%.

In the continuous casting process, the chemical components and the mass percentage of the ladle sample in the continuous casting are as follows: c: 0.17 to 0.22%, Si: 0.25 to 0.45%, Mn: 1.00-1.40%, Cr is less than or equal to 0.30%, V: 0.02 to 0.15%, Ti: 0.01-0.03%, P is less than or equal to 0.020%, S is less than or equal to 0.010%, Ni is less than or equal to 0.30%, Cu is less than or equal to 0.30%, Al: 0.010-0.040%, N: 0.0070-0.0120% of Fe and the balance of inevitable impurities.

In the heating process, the billet is heated to 1140-1200 ℃ and is kept warm for 0.8-1.1 h. In order to prevent austenite grains from growing excessively, the heating temperature and the heat preservation time are strictly controlled in the heating process of the steel billet.

In the rolling process, the initial rolling temperature is 1050-1120 ℃, and the final rolling temperature is 880-950 ℃.

The standard of the round steel product for large-specification buildings refers to ASTM A572/A572M-07; the performance detection method is referred to GB/T228.1-2010 and GB/T229-2007.

Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: 1. the chemical composition design of the invention forms nitride particles by adding V, Al and N elements, plays a role in refining crystal grains, not only improves the impact toughness of steel, but also improves the strength of the steel, reduces the P, S content in the steel and improves the isotropy of the steel. 2. The invention adopts the production process of converter, LF, VD, continuous casting and rolling, and the production process is simple and convenient. 3. The longitudinal and transverse V-shaped impact energy KV2 of the product in a rolling state at normal temperature is more than or equal to 60J, and the yield strength Rel: 370-435 MPa, tensile strength Rm: 545-620 MPa, and stable performance.

Detailed Description

The present invention will be described in further detail with reference to specific examples.