CN113789475A - Method for producing low-alloy hot-rolled steel strip with yield strength of 355MPa at low cost - Google Patents
Method for producing low-alloy hot-rolled steel strip with yield strength of 355MPa at low cost Download PDFInfo
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- CN113789475A CN113789475A CN202111075290.2A CN202111075290A CN113789475A CN 113789475 A CN113789475 A CN 113789475A CN 202111075290 A CN202111075290 A CN 202111075290A CN 113789475 A CN113789475 A CN 113789475A
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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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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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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
-
- 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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
Abstract
The invention relates to a method for producing low-alloy hot-rolled steel strips with 355 MPa-grade yield strength at low cost, which comprises the following steps of 1) producing steel coils with the thickness H less than or equal to 12 mm; controlling the heating temperature of the smelted plate blank to be 1160-1180 ℃, carrying out 1+5 or 3+3 times of rough rolling, wherein the thickness of the intermediate blank after rough rolling is 13-17% of that of the continuous casting blank, and the temperature of the rough rolling RT2 is 1020-1050 ℃; carrying out finish rolling on the intermediate blank, wherein the finish rolling temperature is 850-890 ℃, carrying out finish rolling, then firstly carrying out ultra-fast cooling, and then carrying out laminar cooling to 590-630 ℃ for coiling; 2) producing a steel coil with the thickness of 12mm and H less than or equal to 20 mm; controlling the heating temperature of the smelted plate blank to be 1130-1160 ℃, carrying out 1+5 or 3+3 times of rough rolling, wherein the thickness of the intermediate blank after rough rolling is 17-22% of that of the continuous casting blank, and the temperature of the rough rolling RT2 is 970-1020 ℃; and (3) carrying out finish rolling on the intermediate blank, wherein the finish rolling temperature is 820-850 ℃, carrying out finish rolling, then firstly carrying out ultra-fast cooling, and then carrying out laminar cooling to 550-590 ℃ for coiling. The product has excellent formability.
Description
Technical Field
The invention relates to the technical field of steel rolling processes. In particular to a method for producing low-alloy hot-rolled steel strip with 355MPa grade yield strength at low cost.
Background
The Q355-grade low alloy variety is a main variety of hot-rolled coils, and the steel is mainly based on carbon-manganese steel, and micro-alloy carbon and nitrogen compounds such as Nb, V, Ti and the like are added into the steel to form elements, so that the strength of the steel plate is improved through solid solution strengthening, precipitation strengthening and fine grain strengthening. Statistically, the yield of such steel plates is about 15% of the total yield of hot rolled coils per year.
In general, alloying elements such as Mn, Nb, V, Ti and the like are added in the smelting process in order to meet the requirement of strength performance of Q355 grade. Mn is dissolved in ferrite to increase the strength of the hot-rolled C-Mn steel, and Nb, V and Ti are combined with C, N elements in the steel to form non-deformable second-phase precipitates such as TiC and TiN to increase the strength of the steel. The existence of the elements can also increase the austenite non-recrystallization temperature, increase the deformation amount in the austenite non-recrystallization region and realize fine grain strengthening. The strengthening effect of the alloy elements is obvious, but the dosage and the alloy smelting cost are higher.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for producing a low-alloy hot-rolled steel strip with the yield strength of 355MPa at low cost, reducing alloy addition and improving the product profitability level.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for producing a low-alloy hot-rolled steel strip with 355MPa grade yield strength at low cost comprises the steps of smelting molten iron in a converter, carrying out external refining on the molten iron, pouring into a continuous casting billet, and heating, rough rolling, finish rolling, cooling and coiling the continuous casting billet; the method comprises the following steps:
1) producing a steel coil with the thickness H less than or equal to 12 mm;
a. the chemical components of smelting steel are as follows: 0.15 to 0.20 percent of C, 0.30 to 0.50 percent of Si, 0.80 to 1.00 percent of Mn, less than or equal to 0.050 percent of Als, less than or equal to 0.025 percent of P, less than or equal to 0.015 percent of S, and the balance of Fe and inevitable impurity elements;
b. the heating temperature of the plate blank is controlled to be 1160-1180 ℃, 1+5 or 3+3 passes of rough rolling are adopted for rough rolling, the thickness of the intermediate blank after rough rolling is 13-17% of that of the continuous casting blank, and the temperature of the rough rolling RT2 is 1020-1050 ℃;
c. carrying out finish rolling on the intermediate blank, wherein the finish rolling temperature is 850-890 ℃, carrying out finish rolling, then firstly carrying out ultra-fast cooling, and then carrying out laminar cooling to 590-630 ℃ for coiling;
2) producing the steel coil with the thickness of 12mm and H less than or equal to 20mm
a. The chemical components of smelting steel are as follows: 0.18 to 0.24 percent of C, 0.30 to 0.50 percent of Si, 1.00 to 1.20 percent of Mn, less than or equal to 0.050 percent of Als, less than or equal to 0.025 percent of P, less than or equal to 0.015 percent of S, and the balance of Fe and inevitable impurity elements;
b. the heating temperature of the plate blank is controlled to be 1130-1160 ℃, 1+5 or 3+3 passes of rough rolling are adopted for rough rolling, the thickness of the intermediate blank after rough rolling is 17% -22% of that of the continuous casting blank, and the temperature of the rough rolling RT2 is 970-1020 ℃;
c. and (3) carrying out finish rolling on the intermediate blank, wherein the finish rolling temperature is 820-850 ℃, carrying out finish rolling, then firstly carrying out ultra-fast cooling, and then carrying out laminar cooling to 550-590 ℃ for coiling.
In the step c of the step 1), for the steel coil with the thickness H of less than or equal to 6mm of the finished product, the ultra-fast cold water amount is 2000m3/h～3000m3H, water pressure of 0.20-0.50 MPa, cooling speed of 20-30 ℃/s, finished product thickness of 6-H, H and H of less than or equal to 12mm, and ultrafast cold water amount of 4000m3/h～4500m3H, water pressure 0.50 to 0.75MPa, and a cooling rate of 30 to 40 ℃/s.
In step c of step 2), the amount of ultrafast cold water is 4500m3～5000m3The water pressure is 0.75-0.90 MPa, and the cooling speed is 35-50 ℃/s.
And controlling rolling and cooling to realize grain refinement and grain strengthening. The control of the hardening state of the austenite is realized by controlling the rolling, namely, a large amount of energy is accumulated in the austenite through deformation, the austenite in the hardening state is obtained in the rolling process, and preparation is made for realizing grain refinement in the subsequent phase transformation process. But hardened austenite has a large number of "defects" that more readily increase the likelihood of ferrite nucleation. And adopting a low-temperature heating and low-temperature rolling strategy. The low temperature is to suppress recrystallization of austenite, to keep austenite in a non-recrystallized region, and to maintain its hardened state. The rolling process then increases the stored deformation of the hardened austenite. The controlled cooling is to control the phase transformation process of the hardened austenite, and further refine ferrite grains by controlling the cooling speed after rolling so as to improve the performance of the material.
Compared with the prior art, the invention has the beneficial effects that:
the 355 MPa-grade low-alloy hot-rolled steel strip does not need to be added with Nb and Ti microalloy elements, the addition amount of Mn alloy can be reduced, the same mechanical property as that of the conventional process is realized, the yield strength ReH is more than or equal to 355MPa, the tensile strength Rm is 470-630 MPa, the elongation (transverse) A after fracture is more than or equal to 20%, and the yield ratio is lower compared with that of the product of the conventional process, the yield ratio of the product of the conventional process is generally more than 0.88, while the yield ratio of the product of the invention is generally less than 0.80 and has excellent formability; compared with the traditional process, the cost of each ton of steel is reduced by 60-100 yuan/ton, and the production cost is greatly reduced. The market competitiveness of the product is improved.
Detailed Description
The invention is further illustrated by the following examples:
the following examples describe the invention in detail. These examples are merely illustrative of the best embodiments of the present invention and do not limit the scope of the invention.
The method for producing the low-alloy hot-rolled steel strip with the yield strength of 355MPa at low cost comprises the steps of smelting molten iron in a converter, carrying out external refining on the molten iron, pouring into a continuous casting billet, and heating, rough rolling, finish rolling, cooling and coiling the continuous casting billet;
examples the thickness and chemical composition of the finished product are shown in table 1.
Table 1: thickness and chemical composition of finished product
| Examples | Thickness/mm of finished product | C/wt％ | Si/wt％ | Mn/wt％ | P/wt％ | S/wt％ | Als/wt％ |
| 1 | 2 | 0.15 | 0.30 | 0.80 | 0.023 | 0.010 | 0.050 |
| 2 | 4 | 0.16 | 0.44 | 0.87 | 0.015 | 0.008 | 0.038 |
| 3 | 5 | 0.17 | 0.36 | 0.92 | 0.020 | 0.006 | 0.043 |
| 4 | 6 | 0.17 | 0.38 | 0.91 | 0.025 | 0.015 | 0.030 |
| 5 | 6.5 | 0.18 | 0.50 | 0.86 | 0.022 | 0.004 | 0.025 |
| 6 | 8 | 0.19 | 0.46 | 0.97 | 0.024 | 0.012 | 0.020 |
| 7 | 10 | 0.18 | 0.34 | 0.95 | 0.021 | 0.014 | 0.010 |
| 8 | 12 | 0.20 | 0.48 | 1.00 | 0.019 | 0.003 | 0.047 |
| 9 | 14 | 0.18 | 0.46 | 1.05 | 0.017 | 0.005 | 0.003 |
| 10 | 15 | 0.20 | 0.32 | 1.09 | 0.013 | 0.013 | 0.033 |
| 11 | 16 | 0.19 | 0.45 | 1.13 | 0.018 | 0.008 | 0.025 |
| 12 | 17 | 0.22 | 0.39 | 1.16 | 0.022 | 0.009 | 0.043 |
| 13 | 19 | 0.23 | 0.47 | 1.19 | 0.020 | 0.006 | 0.016 |
| 14 | 20 | 0.24 | 0.35 | 1.20 | 0.012 | 0.010 | 0.024 |
The production process parameters are shown in the table 2.1 and the table 2.2;
table 2.1:
table 2.2:
the properties of the examples are shown in Table 3.
Table 3: examples mechanical Property test results
Claims (3)
1. A method for producing a low-alloy hot-rolled steel strip with 355MPa grade yield strength at low cost comprises the steps of smelting molten iron in a converter, carrying out external refining on the molten iron, pouring into a continuous casting billet, and heating, rough rolling, finish rolling, cooling and coiling the continuous casting billet; the method is characterized by comprising the following steps:
1) producing a steel coil with the thickness H less than or equal to 12 mm;
a. the chemical components of smelting steel are as follows: 0.15 to 0.20 percent of C, 0.30 to 0.50 percent of Si, 0.80 to 1.00 percent of Mn, less than or equal to 0.050 percent of Als, less than or equal to 0.025 percent of P, less than or equal to 0.015 percent of S, and the balance of Fe and inevitable impurity elements;
b. the heating temperature of the plate blank is controlled to be 1160-1180 ℃, the thickness of the intermediate blank after rough rolling is 13-17% of that of the continuous casting blank, and the finish rolling temperature of the rough rolling is 1020-1050 ℃;
c. carrying out finish rolling on the intermediate blank, wherein the finish rolling temperature is 850-890 ℃, carrying out finish rolling, then firstly carrying out ultra-fast cooling at a cooling speed of 20-40 ℃/s, and then carrying out laminar cooling to 590-630 ℃ for coiling;
2) producing the steel coil with the thickness of 12mm and H less than or equal to 20mm
a. The chemical components of smelting steel are as follows: 0.18 to 0.24 percent of C, 0.30 to 0.50 percent of Si, 1.00 to 1.20 percent of Mn, less than or equal to 0.050 percent of Als, less than or equal to 0.025 percent of P, less than or equal to 0.015 percent of S, and the balance of Fe and inevitable impurity elements;
b. the heating temperature of the plate blank is controlled to be 1130-1160 ℃, the thickness of the intermediate blank after rough rolling is 17% -22% of that of the continuous casting blank, and the finish rolling temperature of the rough rolling is 970-1020 ℃;
c. and (3) carrying out finish rolling on the intermediate blank, wherein the finish rolling temperature is 820-850 ℃, carrying out finish rolling, then firstly carrying out ultra-fast cooling at a cooling speed of 35-50 ℃/s, and then carrying out laminar cooling to 550-590 ℃ for coiling.
2. The method for producing a low-alloy hot-rolled steel strip with a yield strength of 355MPa at low cost as claimed in claim 1, wherein in the step c of the step 1), the ultra-fast cold water amount is 2000m for a steel coil with a finished product thickness H less than or equal to 6mm3/h～3000m3H, water pressure of 0.20-0.50 MPa, cooling speed of 20-30 ℃/s, finished product thickness of 6-H, H and H of less than or equal to 12mm, and ultrafast cold water amount of 4000m3/h～4500m3The water pressure is 0.50-0.75 MPa, and the cooling speed is 30-40 ℃/s.
3. The method of claim 1, wherein the amount of ultrafast cold water in step c of step 2) is 4500m3～5000m3The water pressure is 0.75-0.90 MPa.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114959221A (en) * | 2022-06-11 | 2022-08-30 | 新疆八一钢铁股份有限公司 | Manufacturing method of X60-grade micro-alloy wide strip steel for offshore oil conveying pipeline |
| CN115772631A (en) * | 2022-12-12 | 2023-03-10 | 湖南华菱湘潭钢铁有限公司 | Production method of low-alloy high-strength structural steel plate Q355B |
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| JPS60200913A (en) * | 1984-03-26 | 1985-10-11 | Nippon Steel Corp | Manufacture of high tensile invert superior in weldability |
| CN101148735A (en) * | 2007-10-17 | 2008-03-26 | 莱芜钢铁集团有限公司 | Method for rolling thick specification low-alloy structure steel plate by using middle and thin plate blank |
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| CN108315662A (en) * | 2018-03-30 | 2018-07-24 | 湖南华菱涟源钢铁有限公司 | A kind of yield strength 900MPa level hot rolled steel plates and its production technology |
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2021
- 2021-09-14 CN CN202111075290.2A patent/CN113789475B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JPS60200913A (en) * | 1984-03-26 | 1985-10-11 | Nippon Steel Corp | Manufacture of high tensile invert superior in weldability |
| CN101148735A (en) * | 2007-10-17 | 2008-03-26 | 莱芜钢铁集团有限公司 | Method for rolling thick specification low-alloy structure steel plate by using middle and thin plate blank |
| CN101824525A (en) * | 2010-05-07 | 2010-09-08 | 攀钢集团钢铁钒钛股份有限公司 | Production method of hot milling steel plate |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114959221A (en) * | 2022-06-11 | 2022-08-30 | 新疆八一钢铁股份有限公司 | Manufacturing method of X60-grade micro-alloy wide strip steel for offshore oil conveying pipeline |
| CN115772631A (en) * | 2022-12-12 | 2023-03-10 | 湖南华菱湘潭钢铁有限公司 | Production method of low-alloy high-strength structural steel plate Q355B |
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