CN111575583A - High-strength hot-rolled section and temperature and cooling control process thereof - Google Patents
High-strength hot-rolled section and temperature and cooling control process thereof Download PDFInfo
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- CN111575583A CN111575583A CN202010417835.2A CN202010417835A CN111575583A CN 111575583 A CN111575583 A CN 111575583A CN 202010417835 A CN202010417835 A CN 202010417835A CN 111575583 A CN111575583 A CN 111575583A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/08—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling structural sections, i.e. work of special cross-section, e.g. angle steel
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
Abstract
The invention provides a high-strength hot-rolled section, which comprises the following chemical components in percentage by weight: c: 0.14-0.25%, Mn: 1.40-1.80%, Si: 0.40-0.60%, V: 0.075-0.095%, P/S is less than or equal to 0.045, N: 0.0215-0.025%, Nb: 0.015-0.020%, and the balance of Fe and inevitable impurities. The V/N ratio in the chemical components of the hot-rolled section is 3.49-3.83. The hot-rolled section also comprises chemical components B and Cr, wherein the chemical components B are in the following ratio: 0.0015 to 0.005 percent; the chemical composition ratio of Cr is as follows: 0.6 to 0.7 percent. The invention adjusts the chemical components and the rolling process on the basis of the common section bar, and improves the comprehensive performance of the section bar.
Description
Technical Field
The invention relates to the technical field of section bar manufacturing processes, in particular to a high-strength hot-rolled section bar and a temperature and cooling control process thereof.
Background
The low-strength section bars in the market are saturated at present, the improvement condition can not occur in a short time, and the section bars with the high strength grade of 500MPa and above are high-grade section bars in China at present, and are widely used for various building structures, particularly large, heavy and light structures. Compared with the section bar with low strength, the section bar with high strength of 500MPa and above can save more than 30 percent of steel. The development and application of the novel material can also promote the popularization and application of the novel material with high performance, energy conservation and environmental protection, greatly improve the variety and structure of the current products for construction, and provide powerful support for resource-saving and environment-friendly enterprises.
In the prior art, a microalloying route is adopted, the strength requirement is difficult to meet by a single production process, and the technical problem of high cost exists.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a high-strength hot-rolled section and a temperature and cooling control process thereof, which adjust chemical components and a rolling process on the basis of a common section and improve the comprehensive performance of the section.
The present invention achieves the above-described object by the following technical means.
A high-strength hot-rolled section comprises the following chemical components in percentage by weight:
c: 0.14-0.25%, Mn: 1.40-1.80%, Si: 0.40-0.60%, V: 0.075-0.095%, P/S is less than or equal to 0.045, N: 0.0215-0.025%, Nb: 0.015-0.020%, and the balance of Fe and inevitable impurities.
Furthermore, V/N in the chemical composition ratio of the hot-rolled section is 3.49-3.83.
Furthermore, V/N in the chemical composition ratio of the hot-rolled section is 3.56.
Further, the hot-rolled section also comprises chemical components B and Cr, wherein the chemical components B are in the following ratio: 0.0015 to 0.005 percent; the chemical composition ratio of Cr is as follows: 0.6 to 0.7 percent.
Further, the crystal grains in the hot-rolled section are not more than 4 μm; the yield strength of the hot-rolled section is not lower than 500 MPa.
A temperature control and cooling control process for a high-strength hot-rolled section comprises the following steps:
smelting to prepare rough molten steel;
refining the crude steelmaking water through a refining furnace to obtain refined molten steel;
rolling the refined molten steel through a continuous casting machine to obtain a continuous casting special-shaped blank;
conveying the continuous casting special-shaped blank to a steel rolling heating furnace for heating, wherein the heating temperature is 1150-1200 ℃, and then entering a frame rough rolling unit for rough rolling operation to obtain a rough rolling special-shaped blank;
after the rough rolling special-shaped blank is sheared and broken, the rough rolling special-shaped blank enters a rack middle rolling unit to be subjected to middle rolling operation, and a middle rolling special-shaped blank is obtained;
after the pre-water cooling section of the medium-rolling special-shaped blank is subjected to low-temperature finish rolling, shearing and breaking are carried out, and the medium-rolling special-shaped blank enters a rack finishing mill group to carry out finish rolling operation to obtain a finish-rolling special-shaped blank;
and cooling and processing the finish-rolled special-shaped blank.
Further, cooling control devices are arranged in front of and behind the finishing mill unit, so that the rolled section is cooled to 800-950 ℃.
Further, a heat preservation cover is additionally arranged above the cooling bed, and the heat preservation time of the finish rolling section at 800-950 ℃ is 40-50S.
The invention has the beneficial effects that:
1. the high-strength hot-rolled section and the temperature and cooling control process thereof effectively control the V/N ratio within the range of 3.49-3.83, fully exert the strengthening effect of vanadium, and improve the yield ratio and ultimate strength of the section by a niobium-vanadium composite strengthening mechanism.
2. The high-strength hot-rolled section and the temperature and cooling control process thereof adjust chemical components and rolling process on the basis of common sections, and improve the comprehensive performance of the sections.
3. The high-strength hot-rolled section and the temperature and cooling control process thereof refine steel-making raw materials through a converter to obtain rough molten steel; refining the crude steelmaking water through a refining furnace to obtain refined molten steel; rolling the refined molten steel through a continuous casting machine to obtain a section; conveying the section to a heating furnace for heating, and then entering a frame roughing mill set for roughing operation to obtain a roughing section; after the rough rolling section is sheared and broken, the rough rolling section enters a rack middle rolling unit to perform middle rolling operation, and a middle rolling section is obtained; after the middle rolling section is subjected to a pre-water cooling section to realize low-temperature finish rolling, shearing and breaking are carried out, and the middle rolling section enters a rack finishing mill unit to carry out finish rolling operation to obtain a finish rolling section; and cooling and shearing the finish-rolled section, and finishing and warehousing.
Drawings
FIG. 1 is a flow chart of the high-strength hot-rolled section and the temperature and cooling control process thereof according to the present invention.
Figure 2 is a metallographic picture of a prior art profile.
Figure 3 is a metallographic picture of the profile according to the invention.
Detailed Description
The invention will be further described with reference to the following figures and specific examples, but the scope of the invention is not limited thereto.
The invention relates to a high-strength hot-rolled section, which comprises the following chemical components in percentage by weight:
c: 0.14-0.25%, Mn: 1.40-1.80%, Si: 0.40-0.60%, V: 0.075-0.095%, P/S is less than or equal to 0.045, N: 0.0215-0.025%, Nb: 0.015-0.020%, and the balance of Fe and inevitable impurities.
Wherein C is one of the most economic strengthening elements in steel, and the strength of the material is ensured through the control of the content of C, the solid solution strengthening is realized, and the yield strength is improved. Si is a deoxidizing element and is subjected to solid solution strengthening in the steel, so that the strength of the steel is ensured. Mn is a solid solution strengthening element, improves the yield strength and ensures the obdurability. P is an impurity element in steel, and too high P lowers weldability and formability of steel. S is an impurity element in steel, and influences the low-temperature toughness of the steel. The dissolved N can improve the strength, and the plasticity and the toughness of the material are seriously deteriorated if the content is too high, particularly for heat-treated high-strength steel. Nb is a second phase forming element, exerts a precipitation strengthening action, and has an action of suppressing recovery of austenite and grain growth of recrystallization in the hot rolling step to make the ferrite phase a desired particle size, and the second phase particles belong to a hard phase to increase the wear resistance of the matrix. V is a second phase forming element and exerts a precipitation strengthening effect, and a certain amount of V improves the strength of an incomplete recrystallization zone of welding. Because the content of common alloy elements such as C, Si, Mn and the like in the existing section products is close to the upper limit value of the national industry standard. The up-regulation space of C, Si and Mn is not large when developing high strength. Therefore, a micro-alloying route is needed, and the adopted fine grain strengthening is to refine grains on the basis of a special process approach of controlled cooling after rolling, the actual situation is often much more complicated, and the grains are difficult to reach below 4 mu m only by depending on a single production process approach; however, in practical production, when the vanadium content exceeds 0.10%, the nitrogen content in the steel is relatively low, the V/N ratio is generally more than 5 and is far higher than the ideal ratio of 3.64, and the strengthening effect of the vanadium cannot be fully exerted, so that the V/N ratio in the chemical composition of the hot-rolled section is 3.49-3.83.
In order to improve the hardenability of the section bar, the hot-rolled section bar also comprises chemical components B and Cr, wherein the chemical component B comprises the following chemical components in percentage by weight: 0.0015 to 0.005 percent; the chemical composition ratio of Cr is as follows: 0.6 to 0.7 percent. The crystal grains in the hot-rolled section are not more than 4 mu m; the yield strength of the hot-rolled section is not lower than 500 MPa. Cr is an element for improving hardenability, and the Cr can reduce the phase change driving force and effectively improve the hardenability of the material. In addition, chromium can also promote the "C curve" to move to the right, and can enlarge the region in which full martensite is formed during quenching. N is combined with boron element to form large-particle boron nitride in the smelting continuous casting process, so that the plasticity and toughness of steel are reduced, and the hardenability of boron is reduced.
As shown in fig. 1, the temperature and cooling control process of the high-strength hot-rolled section bar of the present invention comprises:
step 10: the coarsely refined molten steel is obtained by a smelting method.
Step 20: and refining the crude steelmaking water through a refining furnace to obtain refined molten steel.
Step 30: and rolling the refined molten steel through a continuous casting machine to obtain a continuous casting special-shaped blank.
Step 40: and conveying the continuous casting special-shaped blank to a heating furnace for heating, and then entering a frame rough rolling unit for rough rolling operation to obtain a rough rolling special-shaped blank.
Before the continuous casting special-shaped blank is conveyed to a heating furnace to be heated, the method comprises the following steps: inspecting the continuous casting special-shaped blank; and conveying the continuous casting beam blank qualified by inspection to the heating furnace through a conveying roller way for heating.
Step 50: and after shearing and breaking the rough-rolled special-shaped blank, feeding the rough-rolled special-shaped blank into a rack middle rolling unit for middle rolling operation to obtain a middle-rolled special-shaped blank.
The rough rolling special-shaped blank is sheared and broken, and the method comprises the following steps: and cutting off the rough-rolled special-shaped blank after cutting the head and the tail of the special-shaped blank by the crank arm.
Step 60: and after the pre-water cooling section of the medium-rolling special-shaped blank is subjected to low-temperature finish rolling, shearing and breaking are performed, and the medium-rolling special-shaped blank enters a rack finishing mill group to be subjected to finish rolling operation, so that a finish-rolling special-shaped blank is obtained.
After the pre-water cooling section of the medium rolling special-shaped blank is subjected to low-temperature finish rolling, shearing and breaking are carried out, and the method comprises the following steps: and performing rotary shearing on the finish-rolled special-shaped blank to cut the head and the tail of the profile, and then performing fragmentation.
Step 70: and the rolled section steel is cooled to 800-950 ℃ by the cold control device, then enters a cooling bed for centralized cooling, a heat preservation cover is additionally arranged above the cooling bed, the heat preservation time of the finish rolled section steel at 800-950 ℃ is 40-50S, and then the finish rolled section steel is straightened in a straightener after being air-cooled or water-cooled and the temperature is reduced to below 100 ℃.
In the rolling process, chemical component regulation is combined, the temperature control of each stage is distributed by utilizing the mechanisms of microalloy fine grain strengthening, recrystallization rolling, non-recrystallization rolling and deformation induced ferrite according to the difference of the rolling speed and the reduction of a rough rolling mill, a medium rolling mill and a finishing rolling mill, and the refining and the homogenization of the microstructure of the steel are realized through the continuous temperature control and deformation rolling process. In the aspect of process arrangement, the defects of the traditional process are overcome, the temperature control sections are arranged among all the units, the setting of the recovery sections is not needed, and various control mechanisms can be comprehensively utilized and the requirements of controlled rolling of different specifications and components can be met. The heating temperature is controlled to 1150-1200 ℃ during rolling heating, so that the microalloy elements are fully dissolved and the excessive coarsening of original austenite grains is avoided. According to the difference of the rolling speed and the rolling reduction of the rough, medium and finishing mill groups, the temperature control of each stage is distributed by fully utilizing the micro-alloy fine grain strengthening, recrystallization rolling, non-recrystallization rolling and deformation induced ferrite phase change mechanisms, and the refining and homogenization of the microstructure of the steel bar are realized through the continuous temperature control and deformation rolling process. After rolling, moderate cooling is adopted to reach 950 ℃ to avoid crystal grain growth. In the aspect of process arrangement, the defects of the traditional process are overcome, rolling control and cooling control devices are arranged at the front and the back of a bar finishing mill group, various control mechanisms are comprehensively utilized, and the rolling control requirements of different specifications and materials are met. The heat preservation cover is additionally arranged above the cooling bed to prolong the high-temperature heat preservation time, so that the time of the reinforcing steel bars between 800 and 950 ℃ is prolonged from the original 25-30S to 40-50S. Ensuring the full precipitation of nitrogen-containing compounds and preventing the rapid cooling of an austenite region from forming low-temperature structures such as bainite, martensite and the like. By adopting the high-temperature heating and controlled rolling and controlled cooling technology, the deformation system is optimized, and finally the fine-grain high-strength steel bar with the best structure performance is obtained.
Examples
Table 1 shows the chemical composition comparison table of the high-strength hot-rolled section bar of the present invention and the conventional section bar. Table 2 shows the comparison of the sample block of the high strength hot rolled section of the present invention with the existing section in terms of mechanical properties. In Table 2, Rm is tensile strength, Rel is lower yield strength, A is elongation after breakage, and Agt is elongation.
TABLE 1
TABLE 2
As can be seen from tables 1 and 2, the V/N is controlled to be 3.49, 3.56 and 3.83, the niobium content is controlled to be 0.015 percent and 0.025 percent, and the smelted steel billet is rolled to obtain the corresponding mechanical property, and by comparison, the V/N is the most stable when being 3.56, and the utilization effect of V, Nb is the best. Compared with the existing material, the yield strength is obviously improved, and the anti-seismic performance is better.
The present invention is not limited to the above-described embodiments, and any obvious improvements, substitutions or modifications can be made by those skilled in the art without departing from the spirit of the present invention.
Claims (8)
1. A high-strength hot-rolled section is characterized by comprising the following chemical components in percentage by weight:
c: 0.14-0.25%, Mn: 1.40-1.80%, Si: 0.40-0.60%, V: 0.075-0.095%, P/S is less than or equal to 0.045, N: 0.0215-0.025%, Nb: 0.015-0.020%, and the balance of Fe and inevitable impurities.
2. A high strength hot rolled section as claimed in claim 1, wherein V/N in chemical composition ratio of the hot rolled section is 3.49 to 3.83.
3. A high strength hot rolled section as claimed in claim 1, wherein the hot rolled section has a chemical composition ratio wherein V/N is 3.56.
4. The high-strength hot-rolled section according to claim 1, further comprising chemical components B and Cr, wherein the chemical components B are in the following ratio: 0.0015 to 0.005 percent; the chemical composition ratio of Cr is as follows: 0.6 to 0.7 percent.
5. The high strength hot rolled section as claimed in claim 1, wherein the crystal grains in the hot rolled section are not more than 4 μm; the yield strength of the hot-rolled section is not lower than 500 MPa.
6. A temperature controlled cooling process for a high strength hot rolled section according to any one of claims 1 to 5, comprising the steps of:
smelting to prepare rough molten steel;
refining the crude steelmaking water through a refining furnace to obtain refined molten steel;
rolling the refined molten steel through a continuous casting machine to obtain a continuous casting special-shaped blank;
conveying the continuous casting special-shaped blank to a steel rolling heating furnace for heating, wherein the heating temperature is 1150-1200 ℃, and then entering a frame rough rolling unit for rough rolling operation to obtain a rough rolling special-shaped blank;
after the rough rolling special-shaped blank is sheared and broken, the rough rolling special-shaped blank enters a rack middle rolling unit to be subjected to middle rolling operation, and a middle rolling special-shaped blank is obtained;
after the pre-water cooling section of the medium-rolling special-shaped blank is subjected to low-temperature finish rolling, shearing and breaking are carried out, and the medium-rolling special-shaped blank enters a rack finishing mill group to carry out finish rolling operation to obtain a finish-rolling special-shaped blank;
and cooling and processing the finish-rolled special-shaped blank.
7. The temperature-controlled and cold-controlled process for high-strength hot-rolled section as claimed in claim 6, wherein cold-controlled devices are arranged before and after the finishing mill set to cool the rolled section to 800-950 ℃.
8. The temperature-controlled and cold-controlled process for the high-strength hot-rolled section as claimed in claim 7, wherein a heat-preserving cover is additionally arranged above the cooling bed, and the heat-preserving time of the finish-rolled section at 800-950 ℃ is 40-50S.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112501497A (en) * | 2020-10-20 | 2021-03-16 | 包头钢铁（集团）有限责任公司 | 500MPa V + Nb-containing composite high-strength alloy steel and manufacturing method thereof |
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| CN110565016A (en) * | 2019-09-20 | 2019-12-13 | 江苏联峰实业有限公司 | 630MPa high-strength anti-seismic index reinforcing steel bar and production method thereof |
| CN110938777A (en) * | 2019-10-12 | 2020-03-31 | 河钢股份有限公司承德分公司 | Hot-rolled ribbed steel bar for 700 MPa-grade high-strength anchor rod and production method |
| CN111088451A (en) * | 2019-12-24 | 2020-05-01 | 江苏永钢集团有限公司 | 600 MPa-level steel bar for reinforced concrete and production method thereof |
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2020
- 2020-05-18 CN CN202010417835.2A patent/CN111575583A/en active Pending
Patent Citations (5)
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|---|---|---|---|---|
| US20020003008A1 (en) * | 2000-05-24 | 2002-01-10 | Alkan Goecmen | Martensitic-hardenable heat-treated steel with improved resistance to heat and ductility |
| US20050173030A1 (en) * | 2001-11-16 | 2005-08-11 | Strapack Corporation | Method for manufacturing steel plate having superior toughness in weld heat-affected zone |
| CN110565016A (en) * | 2019-09-20 | 2019-12-13 | 江苏联峰实业有限公司 | 630MPa high-strength anti-seismic index reinforcing steel bar and production method thereof |
| CN110938777A (en) * | 2019-10-12 | 2020-03-31 | 河钢股份有限公司承德分公司 | Hot-rolled ribbed steel bar for 700 MPa-grade high-strength anchor rod and production method |
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| CN112501497A (en) * | 2020-10-20 | 2021-03-16 | 包头钢铁（集团）有限责任公司 | 500MPa V + Nb-containing composite high-strength alloy steel and manufacturing method thereof |
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Application publication date: 20200825 |