CN110735085A - Manufacturing method of thin Q345qE and Q370qE steel plates - Google Patents
Manufacturing method of thin Q345qE and Q370qE steel plates Download PDFInfo
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- 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
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- 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
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- 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
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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Abstract
The invention discloses a method for manufacturing thin Q345qE and Q370qE steel plates, and belongs to the field of ferrous metallurgy. The steel plate for the bridge steel with the thickness of less than or equal to 10mm is applicable, and comprises the following steps: mechanical stirring desulfurization of molten iron KR, oxygen blowing smelting in a converter, refining in an LF furnace, vacuum dehydrogenation treatment in an RH furnace, calcium line feeding, soft stirring, continuous slab casting, slab heating, cogging rolling, reheating of transition slabs, continuous rolling, natural air cooling of steel plates and straightening of steel plates. Wherein the heating temperature of the heating stage of the plate blank is 1160-1250 ℃, and the furnace time is not less than 1.1 min/mm; and in the cogging stage, rolling an original plate blank into a transition blank of 80-100 mm and naturally cooling, wherein the heating temperature in the reheating stage of the transition blank is 1120-1220 ℃, continuous rolling is adopted in the rolling stage of the transition blank without controlled rolling, and a natural air cooling method is adopted in the cooling stage of the steel plate without water spraying for accelerated cooling. The method has the advantages of good performance, good plate shape control, reduction of the manufacturing difficulty of thin specifications Q345qE and Q370qE, thin applicable thickness specification and the like.
Description
Technical Field
The invention relates to the field of steel manufacturing, in particular to a manufacturing method of thin Q345qE and Q370qE steel plates.
Background
Along with the continuous progress of infrastructure construction of China and countries all over the world, particularly in the field of bridge construction, along with the continuous advancing of bridge engineering in severe cold areas, the requirement on the low-temperature impact toughness of bridge steel plates is higher and higher, along with the continuous deepening of the green development concept, the people and the general application of the TMCP process, more and more bridge steel plates are delivered by adopting the TMCP state, the delivery states of the steel plates used in the current main bridge steel projects at home and abroad are TMCP or TMCP + tempering, the steel grades mainly adopted are Q370 and Q345 strength grades, and the Q420 grade and above are slightly adopted.
The new bridge steel national standard GB/T714-2015 makes the following regulations on the components and carbon equivalent of Q345 and Q370 bridge steel delivered in TMCP or TMCP + tempering state: c is less than or equal to 0.14 percent, Mn is less than or equal to 1.60 percent, carbon equivalent is less than or equal to 0.38 percent, yield ratio is less than or equal to 0.85 percent, and the impact energy of the E-grade bridge steel is required to be more than or equal to 120J at the temperature of minus 40 ℃. For the specification with the thickness less than or equal to 10mm, the main production difficulty is that the steel plate is difficult to roll, the yield ratio is difficult to control, the impact energy is difficult to guarantee, and the control difficulty of the plate type is also very large due to the thin specification, so that the production difficulty of the thin bridge steel is very high at present, and the comprehensive qualified rate is low.
No relevant patents and reports of proprietary for such thin gauge bridge steel are currently retrieved.
Disclosure of Invention
The invention aims to develop production and manufacturing methods of thin Q345qE and Q370qE, which play an important role in reducing the production and manufacturing difficulty of the thin Q345qE and Q370qE and improving the yield.
In order to achieve the purpose, the invention adopts the following technical scheme:
thin Q345qE and Q370qE steel plates are applicable to the bridge steel plate with the thickness less than or equal to 10mm, and the steel plates respectively contain the following components in percentage by mass:
C：0.06～0.09％、
Si：0.10～0.30％、
Mn：1.20～1.50％、
Al：0.020～0.060％、
Nb：0.02～0.04％、
ti: more than 0% and not more than 0.020%,
Cr: more than 0% and not more than 0.20%,
Cu: more than 0% and not more than 0.30%,
P: more than 0% and not more than 0.016%,
S: more than 0% and not more than 0.005%,
N: more than 0% and less than 0.080%, the balance being iron and unavoidable impurities;
carbon equivalent Ceq [ ═ C + Mn/6+ (Cr + Mo + V)/5+ (Cu + Ni)/15] ≦ 0.38%;
weld crack sensitivity index CEpcm[＝C+Si/30+(Mn+Cu+Cr)/20+Ni/60+Mo/15+V/10+5B]≤0.20％；
The method comprises the following steps:
s1, mechanically stirring and desulfurizing molten iron KR, wherein after KR desulfurization treatment, the content of S in the molten iron is less than or equal to 0.010%;
s2, oxygen blowing smelting in a converter, and refining in an LF (ladle furnace), wherein after treatment in the LF, the content of S in the molten steel is less than or equal to 0.005%;
s3, performing vacuum dehydrogenation treatment in an RH furnace, wherein the content of H in steel is less than 2ppm after the RH vacuum treatment;
s4, feeding a calcium wire, feeding a pure Ca wire of 100-300m after the RH furnace vacuum dehydrogenation treatment is finished, and carrying out soft stirring for not less than 10 min;
s5, performing slab continuous casting, and performing non-oxidation protection casting in the slab continuous casting stage, wherein the superheat degree of a tundish is controlled at 25 +/-5 ℃, and the casting speed is 1.4-1.6 m/min;
s6, heating the plate blank, wherein in the plate blank heating stage, the original plate blank is heated to 1120-1200 ℃, and the time of the plate blank in the furnace is not less than 1.1 min/mm;
s7, performing a plate shape regulation rolling process, wherein the rolling process comprises four stages, namely a cogging rolling stage, a transition billet reheating stage, a transition billet continuous rolling stage and a post-rolling natural cooling stage;
s7.1, cogging and rolling a plate blank, wherein the initial plate blank is rolled to a transition blank of 80-100 mm in the cogging stage of the plate blank, and the transition blank is naturally cooled after being rolled;
s7.2, reheating the transition blank, wherein the temperature of the reheating stage of the transition blank is controlled to be 1160-1250 ℃, and the furnace time is not less than 150 min;
s7.3, continuously rolling the transition blank, wherein the transition blank is directly rolled to the thickness of a finished product in a continuous rolling mode without distinguishing austenite recrystallization region rolling and austenite non-crystallization region rolling;
s7.4, naturally cooling the steel plate after rolling without accelerated cooling;
and S8, naturally cooling the steel plate, and performing ultrasonic flaw detection, shearing and warehousing.
The final structure of the steel plate manufactured by the manufacturing method is a ferrite and pearlite structure, and the grain size is more than or equal to 10 grades.
Compared with the prior art, the invention has the beneficial effects that:
(1) thin Q345qE and Q370qE steel plates are applicable to the thickness of less than or equal to 10 mm.
(2) 0.06 to 0.09 percent of C, 0.10 to 0.30 percent of Si, 1.20 to 1.50 percent of Mn, 0.020 to 0.060 percent of Al, 0.02 to 0.04 percent of Nb, less than or equal to 0.020 percent of Ti, less than or equal to 0.20 percent of Cr, less than or equal to 0.30 percent of Cu, less than or equal to 0.016 percent of P, less than or equal to 0.005 percent of S and less than or equal to 0.080 percent of N, and the carbon equivalent Ceq [ ═ C + Mn/6+ (Cr + Mo + V)/5+ (Cu + Ni)/15 percent by strictly controlling the component range]Not more than 0.38%, and welding crack sensitivity index CEpcm[＝C+Si/30+(Mn+Cu+Cr)/20+Ni/60+Mo/15+V/10+5B]Less than or equal to 0.20 percent and meets the requirement that the Ceq of the TMCP delivery state in GB/T714 is less than or equal to 0.38And the mechanical property of the steel plate is ensured by the design of low-carbon microalloying components.
(3) The invention adopts a production mode of twice rolling of the intermediate billet, adopts a continuous rolling mode during the second-stage intermediate billet rolling, does not control rolling, greatly reduces the plate shape control production difficulty of the thin-gauge steel plate, and avoids the problem of poor plate shape after rolling caused by controlling rolling.
(4) The invention adopts the microalloying design of low-carbon high-manganese steel and Nb, Cr and Cu on the components, can effectively prevent the abnormal growth of austenite grains in the heating and rolling stages of the intermediate billet, ensure the grain size of austenite, ensure the grain size of subsequent natural cooling phase change, and the elements Cr and Cu play a strengthening role in the subsequent natural cooling process, thereby improving the strength.
(5) The structure obtained by the invention is a ferrite and pearlite structure, and the grain size grade is more than or equal to grade 9.
In summary, the manufacturing method of the thin gauge Q345qE and Q370qE steel plate has the advantages of good performance, good plate shape control, thin applicable thickness gauge and the like, and has great push value.
Drawings
FIG. 1 is a photograph of the structure of the head of a hot rolled mother plate of Q370qE bridge steel with a thickness of 6mm produced by the method of the present invention;
FIG. 2 is a photograph of the structure of the central portion of a hot rolled mother plate of Q370qE bridge steel having a thickness of 6mm produced by the method of the present invention;
FIG. 3 is a photograph of the structure of the tail of a hot rolled mother plate of Q370qE bridge steel with a thickness of 6mm produced by the method of the present invention.
Detailed Description
The invention relates to a manufacturing method of thin Q345qE and Q370qE steel plates, which is applicable to bridge steel plates with the thickness less than or equal to 10mm, and comprises the following components in percentage by mass:
C：0.06～0.09％、Si：0.10～0.30％、Mn：1.201.50%, Al: 0.020 to 0.060%, Nb: 0.02 to 0.04%, Ti: more than 0% and 0.020% or less, Cr: more than 0% and 0.20% or less, Cu: more than 0% and 0.30% or less, P: more than 0% and 0.016% or less, S: more than 0% and 0.005% or less, N: more than 0% and less than 0.080%, the balance being iron and unavoidable impurities; carbon equivalent Ceq [ ═ C + Mn/6+ (Cr + Mo + V)/5+ (Cu + Ni)/15]Less than or equal to 0.38 percent; weld crack sensitivity index CEpcm[＝C+Si/30+(Mn+Cu+Cr)/20+Ni/60+Mo/15+V/10+5B]≤0.20％。
The design idea of the chemical components of the invention for achieving the above purpose is as follows:
carbon (C) is a main element influencing strength, toughness, hardness and welding performance, can form carbide with Nb, Ti, Cr, Mo and Fe to play a role of precipitation strengthening and grain refinement toughening materials, and the increase of the carbon content has obvious effect on improving the strength and the hardness of the steel, but the increase of the carbon content has negative effect on the ductility, the toughness and the welding performance of the steel, so the carbon content selected by the invention is 0.06-0.09%, the aspect mainly considers that the too low carbon can increase the yield ratio of the steel plate, and the aspect mainly considers the toughness and the excellent welding performance of the steel plate.
Manganese (Mn) is a solid solution strengthening element, can improve the strength and hardness of steel and can also improve the toughness of the steel, moderately improves the hardenability of the steel, enlarges a gamma phase region, reduces the gamma → α phase transformation temperature of the steel, and is beneficial to obtaining a fine phase transformation product, besides, the manganese can also improve the solubility of a microalloy element niobium (Nb) in the steel and inhibit the precipitation of niobium carbonitride, but excessive Mn can cause Mn segregation in the center of a casting blank and has great damage to the toughness of a thick plate, therefore, the manganese content adopted by the steel is 1.2-1.5%.
Niobium (Nb) is an effective grain refining element, can obviously inhibit austenite grain growth and delay gamma → α transformation, thereby obtaining a finer structure, in the hot rolling process, precipitated niobium carbonitride can delay recrystallization and the grain growth process, and niobium carbonitride can retain more dislocation density in a matrix through pinning dislocation, thereby improving the strength and toughness of steel, the niobium in a solid solution state can delay gamma → α transformation, refine ferrite grains, improve the toughness of steel, the niobium in a solid solution state can be continuously precipitated as Nb (CN) in the cooling process, and the strength of steel is further improved by .
Titanium (Ti): titanium is a strong nitrogen fixation element and can form TiN particles in dispersed distribution, so that austenite grain coarsening can be inhibited in the blank heating process and the blank rolling process, the effect of grain refinement is achieved, and the low-temperature toughness of the steel is improved. The addition amount of titanium in the steel is less than or equal to 0.020%.
Chromium (Cr): chromium is a carbide forming element, can improve the hardness of the steel plate and plays a role in precipitation strengthening; chromium is used as a ferrite forming element, so that more acicular ferrite tissues can be obtained in the high-Nb steel; chromium can also improve the corrosion resistance and hydrogen induced cracking resistance of steel, but excessive chromium can reduce the elongation property of the steel plate, promote the growth of crystal grains to influence the toughness, and cause the generation of cold cracks in a welding area. The addition amount of chromium in the steel is 0.10-0.30%.
Copper (Cu): the copper can improve the strength of the steel plate and a welding heat affected zone, the precipitation effect of the copper can also improve the fatigue resistance of the steel, and the addition amount of the copper in the steel is less than or equal to 0.30 percent.
Aluminum (Al): al is a strong N element, forms fine AlN particles to be separated out, can inhibit the growth of crystal grains in the processes of heating, rolling, quenching and heating of a plate blank and welding, and achieves the purposes of refining the crystal grains, improving the low-temperature toughness of the steel plate and improving the welding performance. The content of the selected aluminum is 0.02-0.06%.
The process route is as follows: KR pre-desulfurization of molten iron, smelting in a converter, LF refining, RH vacuum treatment, continuous slab casting, reheating of a slab, primary rolling, intermediate slab cooling to be warm, finish rolling, rapid steel plate cooling, thermal steel plate straightening, offline stacking cooling, ultrasonic flaw detection, shearing and warehousing.
The invention adopts a production mode of twice rolling of the intermediate billet, adopts a continuous rolling mode during the second-stage intermediate billet rolling, does not control rolling, greatly reduces the plate shape control production difficulty of the thin-gauge steel plate, and avoids the problem of poor plate shape after rolling caused by controlling rolling.
The invention adopts a natural cooling mode after rolling, avoids the plate shape problem caused by uneven thin cooling caused by accelerated cooling, and greatly improves the plate shape qualification rate of thin steel plates.
FIG. 1 is a photograph of the structure of a hot rolled mother plate head of Q370qE bridge steel with a thickness of 6mm produced by the method of the present invention, wherein the structure is ferrite + pearlite, and the grain size is 10 grade:
FIG. 2 is a photograph of the structure of the central portion of a hot rolled mother plate of Q370qE bridge steel having a thickness of 6mm produced by the method of the present invention, wherein the structure is ferrite + pearlite, and the grain size is grade 10:
FIG. 3 is a photograph showing the structure of the tail of a hot rolled mother plate of Q370qE bridge steel having a thickness of 6mm produced by the method of the present invention, wherein the structure is ferrite + pearlite and the grain size is grade 10.
The present invention is further described in with reference to the following examples.
Examples 1 to 3:
in the embodiment, the control parameters of the smelting heat and the rolling process of the mother plate are shown in the table 1, the smelting components of the smelting heat are shown in the table 2, the mechanical properties of the hot rolling mother plate are shown in the table 3, and the plate flatness of the mother plate is shown in the table 4.
Table 1: example control parameters of smelting heat and mother plate rolling process
The high quality continuous cast slabs required to produce the thin gauge Q345qE/Q370qE can be found in Table 1.
Table 2: EXAMPLES smelting compositions of smelting furnace
| Practice of Example (b) | C | Si | Mn | P | S | Nb | V | Ti | Cr | N i | Cu | Mo | Al | N | B | Ce q | Pcm |
| Example 1 | 0. 08 | 0. 24 | 1. 45 | 0. 01 0 | 0. 00 2 | 0. 03 5 | 0. 00 1 | 0. 01 3 | 0. 10 | 0 | 0. 21 | 0 | 0. 04 0 | 0.0 038 | 0.0 001 | 0. 35 | 0.17 |
| Example 2 | 0. 07 | 0. 24 | 1. 48 | 0. 00 9 | 0. 00 3 | 0. 03 2 | 0. 00 1 | 0. 01 5 | 0. 10 | 0 | 0. 20 | 0 | 0. 02 8 | 0.0 038 | 0.0 001 | 0. 35 | 0.17 |
| Example 3 | 0. 08 | 0. 24 | 1. 42 | 0. 01 0 | 0. 00 3 | 0. 03 3 | 0. 00 1 | 0. 01 3 | 0. 11 | 0 | 0. 20 | 0. 00 2 | 0. 03 4 | 0.0 026 | 0.0 001 | 0. 38 | 0.18 |
As can be seen from Table 2, the thin gauge Q345qE/Q370qE alloy composition produced by this patent is characterized by the fact that controlled rolling and controlled cooling are not required for the rolling process.
Table 3: examples mechanical properties of hot-rolled master plates:
the examples in Table 3 have a yield strength of > 370MPa, a tensile strength of > 510MPa, a yield ratio of < 0.85 and an impact energy of > 120J at-40 ℃.
Claims (2)
1, thin Q345qE, Q370qE steel plate, applicable thickness not more than 10mm bridge steel use the steel plate, characterized by that, the said steel plate contains by weight percent:
C：0.06~0.09%、
Si：0.10~0.30%、
Mn：1.20~1.50%、
Al：0.020~0.060%、
Nb ：0.02~0.04%、
ti: more than 0% and not more than 0.020%,
Cr: more than 0% and not more than 0.20%,
Cu: more than 0% and not more than 0.30%,
P: more than 0% and not more than 0.016%,
S: more than 0% and not more than 0.005%,
N: more than 0% and less than 0.080%, the balance being iron and unavoidable impurities;
the carbon equivalent Ceq [ = C + Mn/6+ (Cr + Mo + V)/5+ (Cu + Ni)/15] < 0.38%;
weld crack sensitivity index CEpcm[=C+Si/30+(Mn+Cu+Cr)/20+Ni/60+Mo/15+V/10+5B]≤0.20%；
The method comprises the following steps:
s1, mechanically stirring and desulfurizing molten iron KR, wherein after KR desulfurization treatment, the content of S in the molten iron is less than or equal to 0.010%;
s2, oxygen blowing smelting in a converter, and refining in an LF (ladle furnace), wherein after treatment in the LF, the content of S in the molten steel is less than or equal to 0.005%;
s3, performing vacuum dehydrogenation treatment in an RH furnace, wherein the content of H in steel is less than 2ppm after the RH vacuum treatment;
s4, feeding a calcium wire, feeding a pure Ca wire of 100-300m after the RH furnace vacuum dehydrogenation treatment is finished, and carrying out soft stirring for not less than 10 min;
s5, performing slab continuous casting, and performing non-oxidation protection casting in the slab continuous casting stage, wherein the superheat degree of a tundish is controlled at 25 +/-5 ℃, and the casting speed is 1.4-1.6 m/min;
s6, heating the plate blank, wherein in the plate blank heating stage, the original plate blank is heated to 1120-1200 ℃, and the furnace time of the plate blank is not less than 1.1 min/mm;
s7, performing a plate shape regulation rolling process, wherein the rolling process comprises four stages, namely a cogging rolling stage, reheating a transition blank, continuously rolling the transition blank, and naturally cooling the transition blank after rolling;
s7.1, cogging and rolling a plate blank, wherein the initial plate blank is rolled to a transition blank of 80-100 mm in the cogging stage of the plate blank, and the transition blank is naturally cooled after being rolled;
s7.2, reheating the transition blank, wherein the temperature of the reheating stage of the transition blank is controlled to be 1160-1250 ℃, and the furnace time is not less than 150 min;
s7.3, continuously rolling the transition blank, wherein the transition blank is directly rolled to the thickness of a finished product in a continuous rolling mode without distinguishing austenite recrystallization region rolling and austenite non-crystallization region rolling;
s7.4, naturally cooling the steel plate after rolling without accelerating;
and S8, naturally cooling the steel plate, and performing ultrasonic flaw detection, shearing and warehousing.
2. The method for producing a thin Q345qE, Q370qE steel sheet as claimed in claim 1, wherein the final structure of the steel sheet is a ferrite + pearlite structure and the grain size is not less than 10 grade.
Priority Applications (1)
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| CN113481437A (en) * | 2021-06-30 | 2021-10-08 | 重庆钢铁股份有限公司 | Atmospheric corrosion resistant bridge structure steel plate and manufacturing method thereof |
| CN113684415A (en) * | 2021-07-09 | 2021-11-23 | 江苏沙钢集团有限公司 | 6mm EH36 steel and manufacturing method thereof |
| CN114107825A (en) * | 2021-12-02 | 2022-03-01 | 河北普阳钢铁有限公司 | Low-carbon equivalent titanium-containing Q420MD steel plate and preparation method thereof |
| CN114262849A (en) * | 2022-01-03 | 2022-04-01 | 新疆八一钢铁股份有限公司 | Preparation method of ultrahigh-strength low-yield-ratio axle housing steel |
| CN114540580A (en) * | 2022-03-11 | 2022-05-27 | 新疆八一钢铁股份有限公司 | Production method of low-cost Q345Q series bridge steel plate |
| CN115261726A (en) * | 2022-08-04 | 2022-11-01 | 江苏省沙钢钢铁研究院有限公司 | Super-thick Q370qE bridge steel plate and production method thereof |
| CN116034172A (en) * | 2020-07-14 | 2023-04-28 | 杰富意钢铁株式会社 | Dehydrogenation method for steel material and steel product, and method for producing steel material and steel product |
| CN116618435A (en) * | 2023-04-03 | 2023-08-22 | 江苏沙钢集团有限公司 | Production and manufacturing method of extreme thin steel plate |
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| CN115261726A (en) * | 2022-08-04 | 2022-11-01 | 江苏省沙钢钢铁研究院有限公司 | Super-thick Q370qE bridge steel plate and production method thereof |
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