CN113201685A - Economical low-yield-ratio hot-rolled weather-resistant steel plate and manufacturing method thereof - Google Patents
Economical low-yield-ratio hot-rolled weather-resistant steel plate and manufacturing method thereof Download PDFInfo
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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
- 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
- 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
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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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
- 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
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following 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
- 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
- C22C38/04—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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
Abstract
The invention discloses an economical low-yield-ratio hot-rolled weather-resistant steel plate and a manufacturing method thereof, belonging to the field of steel materials and production thereof. The steel plate comprises the following chemical components: c: 0.11-0.13%; si: 0.20 to 0.50 percent; mn: 0.20-0.60%; p: less than or equal to 0.15 percent; s: less than or equal to 0.005 percent; cr: 0.30-0.50%; ni: less than or equal to 0.07 percent; cu: 0.25-0.40%, and Cr + Ni + Cu is less than or equal to 0.90%; and (3) Alt: 0.020-0.045%; the balance being Fe and unavoidable impurities. The invention aims at the current situation that 345 MPa-level hot-rolled weathering steel has high yield ratio and high production cost, and provides 345 MPa-level economical low yield ratio hot-rolled weathering steel plate and a manufacturing method thereof.
Description
Technical Field
The invention belongs to the technical field of steel materials and production thereof, and particularly relates to an economical hot-rolled weather-resistant steel plate with a low yield ratio and a manufacturing method thereof.
Background
The hot-rolled weathering steel has excellent atmospheric corrosion resistance and longer service life, and is widely applied to the fields of railway vehicles, containers, power towers and the like. Part of the weathering steel, especially thin gauge series, is often used for roll bending or stamping shaped parts, and therefore should have good ductility and cold formability. Yield ratio is one of the important indicators for the formability, and a low yield ratio means a higher work hardening index and good formability. Under the severe market competition environment, how to realize the low yield ratio stable control of 345 MPa-grade weathering steel through component design and process optimization on the basis of ensuring the economy is a technical key and difficulty for improving the cold forming performance of the weathering steel.
At present, a great number of patents are disclosed in the industry about the manufacturing technology of low yield ratio weathering steel, for example, the invention patent with the patent publication number of CN108728740A discloses a hot rolled steel strip for low yield ratio railway vehicles and a production method thereof, and the hot rolled steel strip comprises the following chemical components: c: 0.09-0.12%; si: 0.25 to 0.50 percent; mn: 0.30-0.50%; p: 0.060 to 0.100%; s is less than or equal to 0.012 percent; cr: 0.60-1.00%; cu: 0.25-0.40%; ni: 0.12-0.25%; b: 0.0010-0.0025%, Ti: 0.015-0.030 percent of the total weight of the alloy, the balance of Fe and inevitable impurities, the thickness of a steel plate is 4.5-12 mm, the outlet temperature of finish rolling of the application is 820-870 ℃, the coiling temperature is 660-710 ℃, the alloy cost is high, and the ductility and toughness of Ti microalloying are poor.
Also for example, patent publication No. CN110093568 discloses weather-resistant steel for a high-strength low-yield-ratio weather-resistant carriage, which comprises the following chemical components: c: 0.10-0.12%; si: 0.30-0.50%; mn: 0.30-0.50%; p is less than or equal to 0.015 percent; s is less than or equal to 0.005 percent; al is less than or equal to 0.050 percent; cu: 0.26-0.36%; cr: 0.50-0.60%; ni: 0.15-0.25%; n is less than or equal to 50ppm, the balance is Fe and inevitable impurities, the finishing temperature is 860-900 ℃, the coiling temperature is 700-730 ℃, slow cooling needs to be carried out by matching with a 48-hour heat preservation cover in a warehouse, and the addition amounts of Cr, Ni and Cu are high. The above heat treatment processes and alloy designs all increase production costs.
Also, for example, the invention patent with application number 2020110522728 discloses a hot-rolled low yield ratio high-strength acid corrosion resistant steel plate and a production method thereof, wherein the hot-rolled low yield ratio high-strength acid corrosion resistant steel plate comprises the following chemical components: c: 0.06-0.08%; si: 0.20 to 0.40 percent; mn: 0.80-1.20%; p is less than or equal to 0.012 percent; s is less than or equal to 0.005 percent; cr: 0.70-1.20%; ni: 0.10-0.30%; cu: 0.20-0.40%; and (3) Alt: 0.020-0.045%; nb: 0.015-0.030%; ti: 0.010-0.025%; sb: 0.06-0.12%; the balance of Fe and inevitable impurities; the application adopts the microalloying control technology combined with the controlled rolling and the controlled cooling principle to develop a high-strength acid-resistant steel product with low yield ratio and excellent forming performance and acid corrosion resistance.
345 MPa-grade hot-rolled weathering steel is still the weathering series product with the largest market demand at present, and how to realize the stable industrial production of the hot-rolled weathering steel with low cost, no need of heat treatment, low yield ratio and high ductility and toughness is a technical difficulty and a key starting from the aspects of key component design, steel making and steel rolling process parameter control and the like aiming at the strength grade.
Disclosure of Invention
1. Problems to be solved
Aiming at the defects that the production cost of the existing 345 MPa-grade hot-rolled weather-resistant steel is higher and the performance still needs to be optimized, the invention provides an economical low-yield-ratio hot-rolled weather-resistant steel plate and a manufacturing method thereof, in particular to a 345 MPa-grade economical low-yield-ratio hot-rolled weather-resistant steel plate and a manufacturing method thereof, the weather-resistant steel plate has the advantages of low cost, high ductility and toughness, easiness in forming and the like, and is mainly used for manufacturing stamping and roll bending formed parts in the industries of railway vehicles, containers, electric power towers and the like; the manufacturing method of the invention has the advantages of easy operation, low cost and suitable popularization and application.
2. Technical scheme
In order to solve the above problems, the present invention adopts the following technical solutions.
The invention relates to an economical hot-rolled weather-resistant steel plate with low yield ratio, which comprises the following chemical components in percentage by weight: c: 0.11-0.13%; si: 0.20 to 0.50 percent; mn: 0.20-0.60%; p: less than or equal to 0.15 percent; s: less than or equal to 0.005 percent; cr: 0.30-0.50%; ni: less than or equal to 0.07 percent; cu: 0.25-0.40%, and Cr + Ni + Cu is less than or equal to 0.90%; and (3) Alt: 0.020-0.045%; the balance being Fe and unavoidable impurities.
Furthermore, the thickness specification H of the finished hot-rolled weather-resistant steel plate is 3-20mm, and when the thickness H of the hot-rolled weather-resistant steel plate is more than or equal to 10mm, the components also comprise Nb: less than or equal to 0.030 percent.
Furthermore, the mechanical properties of the hot-rolled weather-resistant steel plate are as follows: reL≥345MPa，RmGreater than or equal to 480MPa, the yield ratio is less than or equal to 0.75, the elongation A after fracture is greater than or equal to 30.0 percent, the KV2 at minus 40 ℃ is greater than or equal to 60J, and the low yield ratio and the good matching of strength and plasticity and toughness are realized. And has excellent cold bendingAnd the forming performance is that no crack appears on the outer side surface of the bending sample after 180-degree cold bending (d is 0a), and the forming processing requirements such as stamping, roll bending and the like in the manufacturing process of products such as railway vehicles, containers and the like are met.
Further, the hot-rolled weather-resistant steel plate has a structure of polygonal ferrite and pearlite, wherein the area fraction of the pearlite structure is 9-11%, and the grain size of the ferrite is 7-9 grades.
According to the low-yield-ratio hot-rolled weather-resistant steel plate, the proportion of hard phase pearlite in a microstructure is closely related to the content of C, the proper content of C is favorable for improving the strength, particularly the tensile strength, of the steel plate, and is one of key elements influencing the yield ratio, but the higher content of C has obvious influence on longitudinal cracking of a casting blank and the forming performance of the steel plate, the content of C is strictly controlled to be 0.11-0.13%, and the effective balance of the low yield ratio and the forming performance can be realized.
Secondly, by the composite addition of Cr, Ni and Cu and the synergistic effect of Cr, Ni and Cu, a compact stable rust layer is formed on the surface in an enrichment manner, so that a corrosive medium is prevented from diffusing to a matrix, and the corrosion resistance of the material is improved; in addition, Cr: 0.30-0.50%; ni: less than or equal to 0.07 percent; cu: 0.25-0.40%, Cr + Ni + Cu is less than or equal to 0.90%, the lower limit requirement on noble metal Ni is not made, and the preferable addition of a proper amount of Ni can reduce the risks of casting blank cracks and hot-rolled sawtooth edges caused by C, Cu and other elements, and is beneficial to reducing the production cost on the basis of guaranteeing the performance.
Secondly, Nb in the invention is a strong carbonitride forming element, the strength deficiency caused by thick specification is mainly compensated by precipitation strengthening and fine grain strengthening, the low-temperature toughness of the steel plate is effectively improved, and when the thickness H of the steel plate is more than 10mm, Nb: less than or equal to 0.030 percent, in particular Nb: 0.020-0.030%; when H is less than or equal to 10mm, no Nb element is needed to be added.
The invention relates to a manufacturing method of an economical low-yield-ratio hot-rolled weather-resistant steel plate, which comprises the working procedures of converter smelting → refining → continuous casting → slab heating → controlled rolling → controlled cooling → coiling, wherein a low-temperature quick-firing mode is adopted in the slab heating stage.
Furthermore, the content of C is controlled to be 0.11-0.13% in the converter refining process; electromagnetic stirring and dynamic soft reduction are applied in the continuous casting process, the highest pulling speed is not more than 1.3m/s, the casting blank needs to be checked when being off-line, and flame cleaning is carried out if longitudinal cracking is found.
Furthermore, the casting blank can be heated in a furnace by hot charging or cold charging, and a low-temperature quick-firing mode is adopted, so that the quality of a hot-rolled edge part is effectively guaranteed, and Cu brittleness is avoided in the heating process; specifically, the slab heating procedure comprises a first heating section, a second heating section and a soaking section, wherein the end temperature of the first heating section is controlled to be less than or equal to 1050 ℃; the final temperature of the second heating section is controlled at 1180-1220 ℃; the sum of the time of the two heating sections and the soaking section is controlled to be less than or equal to 120min, and the tapping temperature of the casting blank is controlled to be 1170-1210 ℃.
Furthermore, the controlled rolling adopts a rough rolling and finish rolling mode, the rough rolling adopts 3+5 times of large reduction rate rolling, the reduction rate is more than or equal to 85 percent, the effect of further reducing the yield ratio is achieved by reducing the thickness of the intermediate billet, and specifically, the thickness h of the intermediate billet of the steel plate is controlled according to the following standard: when the thickness H of the finished product is more than or equal to 3mm and less than or equal to 6mm, the thickness H of the corresponding intermediate blank is more than or equal to 30mm and less than or equal to 33 mm; when the thickness H of the finished product is more than 6mm and less than or equal to 10mm, the thickness H of the corresponding intermediate blank is more than 33mm and less than or equal to 40 mm; when the thickness H of the finished product is more than 10mm and less than or equal to 20mm, the thickness H of the corresponding intermediate blank is more than 40mm and less than or equal to 45 mm.
In the invention, the finish rolling adopts continuous rolling of F1-F7, the outlet temperature of the finish rolling is 880-930 ℃, and the outlet speed of F7 is less than or equal to 8 m/s.
Furthermore, the control cooling adopts a rear-section sparse cooling mode, and the opening and closing proportion of the cooling water nozzles is as follows: correlation is less than or equal to 1: 5, wherein the cooling water nozzles in the front section are all closed, and the cooling water nozzles in the rear section are set to be in an interval type opening and closing state. Specifically, a laminar cooling area in actual practice operation in the industry is generally divided into a manually controlled fine adjustment area and an automatically controlled fine adjustment area, wherein the cooling control in the fine adjustment area has a particularly obvious influence on the performance of a steel plate, cooling water nozzles of 5/6 cooling line lengths in front of the fine adjustment area are all closed, cooling water nozzles of 1/6 cooling line lengths in back are opened, and the cooling water of the length controls the interval open state of on/off/on/off between adjacent nozzles, so that the back-section sparse cooling is realized.
Furthermore, the coiling temperature is 680-730 ℃, and then the steel is cooled to room temperature.
According to the invention, through the component design and the optimization of the rolling and cooling control process, the optimized combination of the strength and the ductility and toughness of the steel plate can be obtained, the microstructure of the steel plate is accurately regulated, the area fraction of pearlite is controlled to be 9-11%, and the grain size of ferrite is controlled to be 7-9 levels, so that the soft phase is a polygonal ferrite structure with a certain size and area ratio and lower strength, the hard phase is a pearlite structure with a higher strength in an accurate range, and meanwhile, the grain size is reduced by 2 grain size levels compared with the conventional process. The deformation of an austenite recrystallization region is effectively increased by controlling the high pressure in the rough rolling stage, and the deformation of an austenite non-recrystallization region is reduced to weaken the grain refinement of austenite; the high-temperature final rolling, the high-temperature coiling and the rear-section sparse cooling mode are matched, so that ferrite grains can fully grow in an austenite region and a ferrite high-temperature region. Finally, the yield ratio of the material is reduced, and simultaneously, good plasticity and toughness are ensured.
3. Advantageous effects
Compared with the prior art, the invention has the beneficial effects that:
(1) the economical hot-rolled weather-resistant steel plate with low yield ratio has the following mechanical properties: reL≥345MPa，RmGreater than or equal to 480MPa, yield ratio less than or equal to 0.75, A greater than or equal to 30.0 percent, and KV at minus 40 DEG C2Not less than 60J, low yield ratio and good matching of strength and plasticity and toughness; the bending test piece has excellent cold-bending forming performance, no crack appears on the outer side surface of the bending test piece after 180-degree cold bending (d is 0a), and the forming processing requirements of stamping, roll bending and the like in the manufacturing process of products such as railway vehicles, containers and the like are met.
(2) The manufacturing method of the economical hot-rolled weather-resistant steel plate with the low yield ratio is simple to practice and operate, low in processing cost and easy to popularize and apply.
Drawings
FIG. 1 is a schematic diagram of the microstructure morphology of the weathering steel plate under an optical microscope, wherein the microstructure of the steel plate is a polygonal ferrite + pearlite structure, the area fraction of the pearlite structure is 9-11%, and the ferrite grain size is 7-9 grade.
Detailed Description
The invention is further described with reference to specific examples.
Example 1
As shown in table 1, the economical hot-rolled weather-resistant steel sheet with low yield ratio of the embodiment comprises the following chemical components in percentage by weight: c: 0.12 percent; si: 0.32 percent; mn: 0.25 percent; p: 0.09%; s: 0.003%; cr: 0.48 percent; ni: 0.03 percent; cu: 0.26%, Alt: 0.04 percent; the balance being Fe and unavoidable impurities.
As shown in table 2, the thickness H of the finished steel plate of the embodiment is 3mm, and the preparation method thereof includes converter smelting → refining → continuous casting → slab heating → controlled rolling → controlled cooling → coiling, wherein the slab heating stage adopts a low-temperature fast burning mode, the end temperature of the first heating section is 1047 ℃, the end temperature of the second heating section is 1220 ℃, then the steel plate enters the soaking section, the sum of the time of the second heating section and the soaking section is controlled to be 116min, and the final tapping temperature is 1208 ℃; 3+ 5-pass rough rolling and F1-F7 continuous rolling are matched in the rolling stage, and the thickness h of the intermediate billet is controlled to be 30 mm; the outlet temperature of the finish rolling is 880 ℃, the outlet speed of the F7 is 8m/s, and the coiling temperature is 697 ℃.
As shown in Table 3, the steel sheet obtained in this example has R propertieseL：406MPa；Rm: 546MPa, yield ratio 0.74, A: 31.5%, and after 180 ° cold bending (d is 0a), no cracks appear on the outer side of the bent sample.
The weather-resistant steel plate has the advantages of low cost, high ductility and toughness, easiness in forming and the like, has good atmospheric corrosion resistance and low-temperature toughness, is suitable for severe service environments such as extremely cold environments, and is mainly used for manufacturing the forming processing requirements of stamping, roll bending forming parts and the like of railway vehicles, containers, power towers and the like.
Example 2
As shown in table 1, the economical hot-rolled weather-resistant steel sheet with low yield ratio of the embodiment comprises the following chemical components in percentage by weight: c: 0.11 percent; si: 0.38 percent; mn: 0.55 percent; p: 0.11 percent; s: 0.002%; cr: 0.41 percent; ni: 0.07 percent; cu: 0.3%, Alt: 0.03 percent; the balance being Fe and unavoidable impurities.
The thickness H of the steel plate finished product is 6mm, and the preparation method comprises the working procedures of converter smelting → refining → continuous casting → slab heating → controlled rolling → controlled cooling → coiling, wherein a low-temperature fast burning mode is adopted in the slab heating stage, the end temperature of a first heating section is 1050 ℃, the end temperature of a second heating section is 1212 ℃, then the steel plate finished product enters a soaking section, the sum of the time of the second heating section and the soaking section is controlled to be 100min, and the final tapping temperature is 1210 ℃; controlling the thickness h of the intermediate billet to be 33mm in the rolling stage; the outlet temperature of the finish rolling is 915 ℃, the outlet speed of F7 is 7m/s, and the coiling temperature is 730 ℃.
The steel plate finally obtained in the embodiment has the property ReL：361MPa；Rm: 496MPa, yield ratio 0.73, A: 32%, and the impact energy at-40 ℃ is as follows: 70/75/82J (55x10x5mm), and after 180 DEG cold bending (d is 0a), no crack appears on the outer side surface of the bending sample, and the forming processing requirements such as punching and roll bending in the manufacturing process of products such as railway vehicles and containers are met.
Example 3
As shown in table 1, the economical hot-rolled weather-resistant steel sheet with low yield ratio of the embodiment comprises the following chemical components in percentage by weight: c: 0.12 percent; si: 0.25 percent; mn: 0.42 percent; p: 0.01 percent; s: 0.002%; cr: 0.32 percent; cu: 0.35%, Alt: 0.025 percent; nb: 0.02%, and the balance of Fe and inevitable impurities.
The thickness H of the finished steel plate in the embodiment is 16mm, the preparation method is basically the same as the embodiment, except that the final tapping temperature in the heating stage of the steel plate blank in the embodiment is 1170 ℃; controlling the thickness h of the intermediate billet to be 41mm in the rolling stage; the outlet temperature of the finish rolling is 904 ℃, the coiling temperature is 703 ℃, and the performance of the steel plate finally obtained in the embodiment is ReL：392MPa；Rm: 537MPa, yield ratio 0.73, A: 30.5 percent, and the impact energy at-40 ℃ is as follows: 108/119/126J (55x10x10mm), and after 180 DEG cold bending (d is 0a), no crack appears on the outer side surface of the bending sample, and the forming processing requirements such as punching and roll bending in the manufacturing process of products such as railway vehicles and containers are met.
Example 4
As shown in table 1, the economical hot-rolled weather-resistant steel sheet with low yield ratio of the embodiment comprises the following chemical components in percentage by weight: c: 0.13 percent; si: 0.5 percent; mn: 0.6 percent; p: 0.08 percent; s: 0.002%; cr: 0.3 percent; ni: 0.02 percent; cu: 0.25%, Alt: 0.02 percent; the balance being Fe and unavoidable impurities.
The thickness H of the finished steel plate product in the embodiment is 10mm, the preparation method is basically the same as that in the embodiment, but the final tapping temperature in the heating stage of the steel plate blank in the embodiment is 1206 ℃; controlling the thickness h of the intermediate billet to be 40mm in the rolling stage; the outlet temperature of the finish rolling is 883 ℃, the coiling temperature is 680 ℃, and the performance of the finally obtained steel plate in the embodiment is ReL：451MPa；Rm: 607MPa, yield ratio 0.74, A: 31%, and the impact energy at-40 ℃ is as follows: 88/90/76J (55x10x7.5mm), and after 180 DEG cold bending (d is 0a), no crack appears on the outer side surface of the bending sample, and the forming processing requirements such as punching, roll bending and the like in the manufacturing process of products such as railway vehicles, containers and the like are met.
Example 5
As shown in table 1, the economical hot-rolled weather-resistant steel sheet with low yield ratio of the embodiment comprises the following chemical components in percentage by weight: c: 0.11 percent; si: 0.2 percent; mn: 0.2 percent; p: 0.015 percent; s: 0.005 percent; cr: 0.5 percent; cu: 0.4%, Alt: 0.045%; nb: 0.03%, and the balance of Fe and inevitable impurities.
The thickness H of the finished steel plate is 20mm, the preparation method is basically the same as that of the embodiment, except that the steel plate blank in the embodiment adopts a low-temperature fast burning mode in the heating stage, the end temperature of the first heating section is 1018 ℃, the end temperature of the second heating section is 1180 ℃, then the steel plate blank enters a soaking section, the sum of the time of the second heating section and the time of the soaking section is controlled to be 120min, and the final tapping temperature is 1175 ℃; controlling the thickness h of the intermediate billet to be 45mm in the rolling stage; the outlet temperature of the finish rolling is 930 ℃, and the coiling temperature is 727 ℃. The steel plate finally obtained in the embodiment has the property ReL：346MPa；Rm: 481MPa, yield ratio of 0.72, A: 32.5%, and the impact energy at-40 ℃ is as follows: 92/104/110J (55x10x10mm), and after 180 DEG cold bending (d is 0a), no crack appears on the outer side surface of the bending sample, and the requirements of railway vehicles and railway container are metThe forming processing requirements such as stamping, roll bending and the like in the manufacturing process of products such as boxes and the like.
Comparative example 1
As shown in Table 1, the hot rolled steel sheet of the present comparative example had a chemical composition comprising, in weight percent: c: 0.08 percent; si: 0.3 percent; mn: 0.34 percent; p: 0.03 percent; s: 0.003%; cr: 0.35 percent; ni: 0.04 percent; cu: 0.32%, Alt: 0.028%; the balance being Fe and unavoidable impurities.
The thickness H of the finished hot-rolled steel plate product of the comparative example is 4mm, and the preparation method also adopts the working procedures of converter smelting → refining → continuous casting → slab heating → controlled rolling → controlled cooling → coiling, wherein as shown in Table 2, the final tapping temperature in the slab heating stage is 1186 ℃; controlling the thickness h of the intermediate billet to be 32mm in the rolling stage; the finish rolling outlet temperature was 862 ℃ and the coiling temperature was 632 ℃. As shown in Table 3, the yield ratio of the steel plate finally obtained by the comparative example is 0.79, which is obviously increased, and the performance requirement of the low yield ratio steel plate in the current industry is difficult to meet.
Comparative example 2
The hot rolled steel sheet of this comparative example had a chemical composition comprising, in weight percent: c: 0.12 percent; si: 0.36 percent; mn: 0.5 percent; p: 0.06 percent; s: 0.004%; cr: 0.4 percent; cu: 0.36%, Alt: 0.022%; the balance being Fe and unavoidable impurities.
The thickness H of the finished hot rolled steel plate product of the comparative example is 5mm, the preparation method also adopts the working procedures of converter smelting → refining → continuous casting → slab heating → controlled rolling → controlled cooling → coiling, wherein the final tapping temperature in the slab heating stage is 1190 ℃ as shown in Table 2; controlling the thickness h of the intermediate billet to be 39mm in the rolling stage; the outlet temperature of the finish rolling is 865 ℃, and the coiling temperature is 625 ℃. As shown in table 3, the yield ratio of the steel sheet finally obtained in this comparative example is 0.76, which is significantly increased, and it is difficult to meet the performance requirement of the low yield ratio steel sheet in the industry at present, and after 180 ° cold bending (d ═ 0a), cracks appear on the outer side surface of the bent sample.
The chemical compositions, rolling processes, mechanical properties of the resulting steel sheets, and the like of the above examples and comparative examples are shown in tables 1, 2, and 3, respectively.
TABLE 1 chemical compositions of inventive and comparative examples
Table 2 main process parameters of the rolling process of the examples and comparative examples
TABLE 3 mechanical Properties of the examples and comparative examples
The examples described herein are merely illustrative of the preferred embodiments of the present invention and do not limit the spirit and scope of the present invention, and various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the design concept of the present invention shall fall within the protection scope of the present invention.
Claims (10)
1. An economical hot-rolled weather-resistant steel plate with low yield ratio is characterized in that: the chemical components of the material comprise the following components in percentage by weight: c: 0.11-0.13%; si: 0.20 to 0.50 percent; mn: 0.20-0.60%; p: less than or equal to 0.15 percent; s: less than or equal to 0.005 percent; cr: 0.30-0.50%; ni: less than or equal to 0.07 percent; cu: 0.25-0.40%, and Cr + Ni + Cu is less than or equal to 0.90%; and (3) Alt: 0.020-0.045%; the balance being Fe and unavoidable impurities.
2. An economical low yield ratio hot rolled weather resistant steel sheet as claimed in claim 1 wherein: the thickness specification H of the finished hot-rolled weather-resistant steel plate is 3-20mm, and when the thickness H of the hot-rolled weather-resistant steel plate is more than 10mm, the hot-rolled weather-resistant steel plate further comprises Nb: less than or equal to 0.030 percent.
3. According to claim 1 or 2The economical hot-rolled weather-resistant steel plate with the low yield ratio is characterized in that: the mechanical properties of the hot-rolled weather-resistant steel plate are as follows: reL≥345MPa，RmGreater than or equal to 480MPa, the yield ratio is less than or equal to 0.75, the elongation A after fracture is greater than or equal to 30.0 percent, and the KV2 at minus 40 ℃ is greater than or equal to 60J.
4. An economical hot-rolled weather-resistant steel sheet with a low yield ratio according to claim 1 or 2, wherein: the hot-rolled weather-resistant steel plate is composed of polygonal ferrite and pearlite, wherein the area fraction of the pearlite structure is 9-11%, and the grain size of the ferrite is 7-9 grades.
5. The manufacturing method of the economical hot-rolled weather-resistant steel plate with low yield ratio is characterized by comprising the following steps of: the method comprises the working procedures of converter smelting → refining → continuous casting → slab heating → controlled rolling → controlled cooling → coiling, wherein the slab heating stage adopts a low-temperature quick-burning mode.
6. The method of claim 5, wherein the hot-rolled weather-resistant steel sheet has a low yield ratio, and further comprises: controlling the content of C to be 0.11-0.13% in the converter refining process; in the continuous casting process, electromagnetic stirring and dynamic soft reduction are used, and the highest drawing speed is not more than 1.3 m/s.
7. The method of claim 5, wherein the hot-rolled weather-resistant steel sheet has a low yield ratio, and further comprises: the slab heating procedure comprises a first heating section, a second heating section and a soaking section, wherein the final temperature of the first heating section is controlled to be less than or equal to 1050 ℃; the final temperature of the second heating section is controlled at 1180-1220 ℃; the sum of the time of the two heating sections and the soaking section is controlled to be less than or equal to 120min, and the tapping temperature of the casting blank is controlled to be 1170-1210 ℃.
8. The method of claim 5, wherein the hot-rolled weather-resistant steel sheet has a low yield ratio, and further comprises: in the rolling control procedure, the thickness h of the steel plate intermediate blank is controlled according to the following standard: when the thickness H of the finished product is more than or equal to 3mm and less than or equal to 6mm, the thickness H of the corresponding intermediate blank is more than or equal to 30mm and less than or equal to 33 mm; when the thickness H of the finished product is more than 6mm and less than or equal to 10mm, the thickness H of the corresponding intermediate blank is more than 33mm and less than or equal to 40 mm; when the thickness H of the finished product is more than 10mm and less than or equal to 20mm, the thickness H of the corresponding intermediate blank is more than 40mm and less than or equal to 45 mm.
9. The method of claim 5, wherein the hot-rolled weather-resistant steel sheet has a low yield ratio, and further comprises: the controlled rolling adopts a rough rolling and finish rolling mode, the rough rolling adopts 3+5 times of large reduction rate rolling, the reduction rate is more than or equal to 85 percent, the finish rolling adopts F1-F7 continuous rolling, the outlet temperature of the finish rolling is 880-930 ℃, and the outlet speed of F7 is less than or equal to 8 m/s; and in the coiling step, the coiling temperature is 680-730 ℃, and then the temperature is cooled to room temperature.
10. The method of any one of claims 5-9, wherein the method further comprises: the control cooling adopts a rear-section sparse cooling mode, and the opening and closing proportion of the cooling water nozzles is as follows: correlation is less than or equal to 1: 5, wherein the cooling water nozzles in the front section are all closed, and the cooling water nozzles in the rear section are set to be in an interval type opening and closing state.
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