KR20230059825A - Low-cost, high-performance Q500 bridge steel and production method - Google Patents

Abstract

The present invention discloses low-cost, high-performance Q500 bridge steel and relates to the field of steel production technology, the chemical composition and mass percentage thereof being C≤0.035%, Si: 0.31%-0.40%, Mn: 1.71%-1.80%, P≤ 0.015%, S≤0.0030%, Nb: 0.030%~0.050%, V: 0.020%~0.050%, Ti: 0.010%~0.018%, Cr: 0.70%~0.80%, Ni: 0.10%~0.20%, remaining Mo ≤0.05%, Cu: 0.10% to 0.20%, B≤0.0005%, N≤0.0005%, Al: 0.020% to 0.050%. It effectively reduces the yield ratio of the product by reducing the yield strength and improving the tensile strength of the product at the same time.

Description

Low-cost, high-performance Q500 bridge steel and production method

The present invention relates to the field of steel production technology, and more particularly to low-cost, high-performance Q500 bridge steel and production methods.

High-performance bridge steel sheet Q500 is widely used in road bridges, railway bridges, and road-rail bridges. Since 2010, with the active development of China's transportation construction, in the background of the continuous increase in bridge steel, in the wide span Q500 grade bridge steel For the normalized steel sheet that is mainly used, the smelting process cost of the normalizing heat treatment process is more than 200 yuan, not including the transshipment cost. quality problems may occur.

In order to solve the above technical problem, the present invention provides a low-cost and high-performance Q500 bridge steel.

In order to solve the above technical problem, the present invention provides a low-cost and high-performance Q500 bridge steel, the chemical composition and mass percentage of which are C ≤ 0.035%, Si: 0.31% ~ 0.40%, Mn: 1.71% ~ 1.80%, P ≤ 0.015%, S≤0.0030%, Nb: 0.030%~0.050%, V: 0.020%~0.050%, Ti: 0.010%~0.018%, Cr: 0.70%~0.80%, Ni: 0.10%~0.20%, remaining Mo ≤0.05%, Cu: 0.10% to 0.20%, B≤0.0005%, N≤0.0005%, Al: 0.020% to 0.050%, the rest being Fe and impurities.

After studying the National Bridge Structural Steel GB/T 714 standard in depth, the present invention achieves a structure structure containing more ferrite through the unique design of low carbon micro niobium titanium alloy bridge components, promoting the soft tissue formation of the product, It effectively increases the secondary rolling and final rolling temperature, appropriately changes the crystal grain size of the structure, and promotes the transformation of carbides and chromium elements through water cooling conditions to reduce the yield strength and improve the tensile strength of the product at the same time to improve the quality of the product. Effectively lowers the yield ratio.

The technical solution further defined by the present invention is as follows.

In the aforementioned low-cost and high-performance Q500 bridge steel, its chemical composition and mass percentage are C≤0.030%, Si: 0.31%~0.38%, Mn: 1.71%~1.77%, P≤0.013%, S≤0.0020%, Nb: 0.030 %~0.040%, V: 0.020%~0.030%, Ti: 0.010%~0.016%, Cr: 0.70%~0.75%, Ni: 0.10%~0.15%, remaining Mo≤0.05%, Cu: 0.10%~0.15% , B≤0.0005%, N≤0.0005%, Al: 0.020% to 0.050%, the rest being Fe and impurities.

In the aforementioned low-cost and high-performance Q500 bridge steel, its chemical composition and mass percentage are C≤0.025%, Si: 0.33%~0.40%, Mn: 1.73%~1.80%, P≤0.012%, S≤0.0020%, Nb: 0.040 %~0.050%, V: 0.030%~0.040%, Ti: 0.012%~0.018%, Cr: 0.75%~0.80%, Ni: 0.15%~0.20%, remaining Mo≤0.05%, Cu: 0.15%~0.20% , B≤0.0005%, N≤0.0005%, Al: 0.020% to 0.050%, the rest being Fe and impurities.

In the aforementioned low-cost and high-performance Q500 bridge steel, its chemical composition and mass percentage are C≤0.035%, Si: 0.31%~0.40%, Mn: 1.71%~1.80%, P≤0.015%, S≤0.0030%, Nb: 0.035 %~0.045%, V: 0.040%~0.050%, Ti: 0.010%~0.018%, Cr: 0.73%~0.78%, Ni: 0.13%~0.18%, Residual Mo≤0.05%, Cu: 0.13%~0.18% , B≤0.0005%, N≤0.0005%, Al: 0.020% to 0.050%, the rest being Fe and impurities.

In the aforementioned low-cost, high-performance Q500 bridge steel, the thickness of the steel plate is 10 to 60 mm.

In the aforementioned low-cost, high-performance Q500 bridge steel, the microstructure of the steel sheet includes polygonal ferrite and 20% to 30% of bainite.

Another object of the present invention is to provide a method for producing low-cost and high-performance Q500 bridge steel that does not require tempering treatment, the production method comprising:

Step S1 in which molten iron is pretreated by the KR method, but S<0.010% of the molten iron entering the converter;

Step S2 of smelting the pretreated molten iron by removing dregs, putting it into a converter, and using a top-and-bottom combined blowing method;

After the molten steel is tapped, it is sent to RH to remove vacuum decarburization, degassing and inclusions, but the vacuum time is 20 to 30 minutes (min) Step S3;

Step S4 of sending the vacuum-treated molten steel to LF to perform refining and deoxidation alloying, and after alloying, calcium treatment to purify the molten steel and improve the purity of the molten steel through static stirring;

Step S5 of casting the refined molten steel by sending it to a continuous casting machine, using electromagnetic stirring and a dynamic soft reduction process, and having a tensile speed of 0.6 to 1.3 m/min;

Sending the casting billet that passed the surface inspection to a heating furnace for heating, but the heating temperature is 1120 ~ 1140 ℃ Step S6;

Rolling proceeds with the TMCP rolling process, but the rough rolling start temperature is 1000 ~ 1100 ℃, the secondary start temperature is controlled at 820 ~ 990 ℃, the final rolling temperature is 820 ± 20 ℃, ultra-high-speed cooling 580 ~ 690 ℃ Step S7 cooling until;

Step S8 of sending the rolled steel sheet to an annealing kiln for slow cooling for 24 hours; and

Step S9 of controlling the flatness of the steel sheet by cold-calibrating the laminated cooled steel sheet, and carrying out shearing, marking, surface inspection, and flaw detection, and then storing the sheet.

The present invention has the following advantageous effects.

(1) According to the Chinese National Standard GB/T 714 Structural Bridge Steel, the present invention uses low-carbon micro-niobium-titanium alloy to improve product flexibility, and uses high manganese element to increase product tensile strength and improve product quality. Replace the existing TMCP+ tempering process with TMCP rolling technology based on component design by ensuring yield ratio, improving welding performance of products using element Cu, and improving impact performance of high-grade products using element Ni. This effectively lowers the manufacturing cost of the product and greatly improves the competitiveness of the enterprise.

(2) The low-temperature austenitization technology of the present invention reduces the grain size of initial austenite to ensure stability of low-temperature impact toughness of the product.

(3) The present invention controls the secondary starting temperature and the final rolling temperature and combines with the water cooling process to effectively lower the yield strength of the product to ensure the stability of the tensile strength and stabilize the stability of the yield ratio of the product.

(4) The present invention effectively refines the crystal grain size of the structure by controlling the controlled cooling process, and ensures the transformation of the structure through the secondary starting temperature and the water temperature to convert polygonal ferrite and 20 to 30% of bainite into a substructure form. It effectively removes the internal stress of the steel plate and improves the stability of the secondary processing performance of the product through the steel plate lamination cooling and cold straightening process.

(5) The present invention effectively lowers the manufacturing cost through component and process design, and reduces the cost by 300 to 500 yuan/ton from the initial steel manufacturing cost, effectively improving market competitiveness.

1 is a typical structure morphology of the steel sheet obtained in Example 1 under a metallographic microscope.

Table 1 shows the chemical composition and mass percentage of the low-cost, high-performance Q500 bridge steel provided in the following examples.

Table 1 Chemical composition (wt%) of the steel sheet according to each example

Example 1

The thickness of the steel sheet is 20mm, the production method does not require tempering treatment, the following steps,

Step S1 in which molten iron is pretreated by the KR method, but S<0.010% of the molten iron entering the converter;

Step S2 of smelting the pretreated molten iron by removing dregs, putting it into a converter, and using a top-and-bottom combined blowing method;

After the molten steel is tapped, it is sent to RH to remove vacuum decarburization, degassing, and inclusions, but the vacuum time is 22 minutes. Step S3;

Step S4 of sending the vacuum-treated molten steel to LF to perform refining and deoxidation alloying, and after alloying, calcium treatment to purify the molten steel and improve the purity of the molten steel through static stirring;

Step S5 where the refined molten steel is sent to a continuous casting machine to be cast, using electromagnetic stirring and a dynamic soft reduction process, and a tensile speed of 1.1 m/min;

Sending the casting billet that passed the surface inspection to a heating furnace for heating, but the heating temperature is 1126 ℃ Step S6;

Rolling proceeds with the TMCP rolling process, the rough rolling start temperature is 1098 ° C, the secondary starting temperature is controlled to 960 ° C, the final rolling temperature is 838 ° C, and cooling to 680 ° C by ultra-high speed cooling Step S7;

Step S8 of sending the rolled steel sheet to a slow cooling kiln for slow cooling for 24 hours, effectively removing harmful gases in the steel sheet through layer cooling, reducing internal stress of the steel sheet, and improving secondary processing performance of the steel sheet; and

Step S9 of controlling the flatness of the steel sheet by cold-calibrating the laminated cooled steel sheet, and carrying out shearing, marking, surface inspection, and flaw detection, and then storing the sheet.

Example 2

The thickness of the steel sheet is 33mm, the production method does not require tempering treatment, the following steps,

Step S1 in which molten iron is pretreated by the KR method, but S<0.010% of the molten iron entering the converter;

Step S2 of smelting the pretreated molten iron by removing dregs, putting it into a converter, and using a top-and-bottom combined blowing method;

Step S3 of vacuum decarburization, degassing, and removal of inclusions by sending the molten steel to RH after the tap is finished, but the vacuum time is 26 minutes;

Step S4 of sending the vacuum-treated molten steel to LF to perform refining and deoxidation alloying, and after alloying, calcium treatment to purify the molten steel and improve the purity of the molten steel through static stirring;

Step S5 where the refined molten steel is sent to a continuous casting machine to be cast, using electromagnetic stirring and a dynamic light reduction process and a tensile speed of 0.9 m/min;

Sending the casting billet that has passed the surface inspection to a heating furnace for heating, but the heating temperature is 1133 ℃ Step S6;

Rolling proceeds with the TMCP rolling process, the rough rolling start temperature is 1055 ° C, the secondary starting temperature is controlled to 855 ° C, the final rolling temperature is 820 ° C, and cooling to 630 ° C by ultra-high speed cooling Step S7;

Step S8 of sending the rolled steel sheet to a slow cooling kiln for slow cooling for 24 hours, effectively removing harmful gases in the steel sheet through layer cooling, reducing internal stress of the steel sheet, and improving secondary processing performance of the steel sheet; and

Step S9 of controlling the flatness of the steel sheet by cold-calibrating the laminated cooled steel sheet, and carrying out shearing, marking, surface inspection, and flaw detection, and then storing the sheet.

Example 3

The thickness of the steel sheet is 50 mm, the production method does not require tempering treatment, the following steps,

Step S1 in which molten iron is pretreated by the KR method, but S<0.010% of the molten iron entering the converter;

Step S2 of smelting the pretreated molten iron by removing dregs, putting it into a converter, and using a top-and-bottom combined blowing method;

After the molten steel is tapped, it is sent to RH to remove vacuum decarburization, degassing, and inclusions, but the vacuum time is 28 minutes. Step S3;

Step S4 of sending the vacuum-treated molten steel to LF to perform refining and deoxidation alloying, and after alloying, calcium treatment to purify the molten steel and improve the purity of the molten steel through static stirring;

Step S5 where the refined molten steel is cast by sending it to a continuous casting machine, using electromagnetic agitation and a dynamic light reduction process, with a tensile speed of 0.7 m/min;

Sending the casting billet that has passed the surface inspection to a heating furnace for heating, but the heating temperature is 1139 ℃ Step S6;

Rolling proceeds with the TMCP rolling process, but the rough rolling start temperature is 1020 ° C, the secondary starting temperature is controlled to 828 ° C, the final rolling temperature is 819 ° C, and cooling to 596 ° C by ultra-high speed cooling Step S7;

Step S8 of sending the rolled steel sheet to a slow cooling kiln for slow cooling for 24 hours, effectively removing harmful gases in the steel sheet through layer cooling, reducing internal stress of the steel sheet, and improving secondary processing performance of the steel sheet; and

Step S9 of controlling the flatness of the steel sheet by cold-calibrating the laminated cooled steel sheet, and carrying out shearing, marking, surface inspection, and flaw detection, and then storing the sheet.

The mechanical performance according to each embodiment is shown in Table 2.

Table 2 Mechanical performance of the steel sheet according to each example

As can be seen in Figure 1, the structure of the steel sheet is mainly composed of lumpy ferrite and contains a small amount of bainite, and the structure is uniform, fine and dense, resulting in high strength, low yield ratio, high toughness, easy welding, fatigue resistance, etc. advantageous to

Summarizing the above, the present invention uses TMCP rolling technology and applies a short process and low-cost manufacturing method to effectively remove the internal stress of steel sheets, thereby providing a bridge factory for high-performance bridge steel sheets that are easy to weld, have high toughness, and have stable quality. meet the needs of Through cost optimization, it effectively reduces the manufacturing cost of products, enhances the competitiveness of enterprises, and improves the enterprise's manufacturing profit rate.

In addition to the above-described embodiments, the present invention may have other embodiments. All technical solutions formed by equivalent substitution or equivalent transformation are included in the claims of the present invention.

Claims (7)

In low-cost, high-performance Q500 bridge steel,
Its chemical composition and mass percentage are C≤0.035%, Si: 0.31%~0.40%, Mn: 1.71%~1.80%, P≤0.015%, S≤0.0030%, Nb: 0.030%~0.050%, V: 0.020% ~0.050%, Ti: 0.010%~0.018%, Cr: 0.70%~0.80%, Ni: 0.10%~0.20%, Residual Mo≤0.05%, Cu: 0.10%~0.20%, B≤0.0005%, N≤0.0005 Low-cost, high-performance Q500 bridge steel, characterized in that %, Al: 0.020% to 0.050%, the rest being Fe and impurities. According to claim 1,
Its chemical composition and mass percentage are C≤0.030%, Si: 0.31%~0.38%, Mn: 1.71%~1.77%, P≤0.013%, S≤0.0020%, Nb: 0.030%~0.040%, V: 0.020% ~0.030%, Ti: 0.010%~0.016%, Cr: 0.70%~0.75%, Ni: 0.10%~0.15%, remaining Mo≤0.05%, Cu: 0.10%~0.15%, B≤0.0005%, N≤0.0005 Low-cost, high-performance Q500 bridge steel, characterized in that %, Al: 0.020% to 0.050%, the rest being Fe and impurities. According to claim 1,
Its chemical composition and mass percentage are C≤0.025%, Si: 0.33%~0.40%, Mn: 1.73%~1.80%, P≤0.012%, S≤0.0020%, Nb: 0.040%~0.050%, V: 0.030% ~0.040%, Ti: 0.012%~0.018%, Cr: 0.75%~0.80%, Ni: 0.15%~0.20%, Residual Mo≤0.05%, Cu: 0.15%~0.20%, B≤0.0005%, N≤0.0005 Low-cost, high-performance Q500 bridge steel, characterized in that %, Al: 0.020% to 0.050%, the rest being Fe and impurities. According to claim 1,
Its chemical composition and mass percentage are C≤0.035%, Si: 0.31%~0.40%, Mn: 1.71%~1.80%, P≤0.015%, S≤0.0030%, Nb: 0.035%~0.045%, V: 0.040% ~0.050%, Ti: 0.010%~0.018%, Cr: 0.73%~0.78%, Ni: 0.13%~0.18%, remaining Mo≤0.05%, Cu: 0.13%~0.18%, B≤0.0005%, N≤0.0005 Low-cost, high-performance Q500 bridge steel, characterized in that %, Al: 0.020% to 0.050%, the rest being Fe and impurities. According to claim 1,
Low-cost, high-performance Q500 bridge steel, characterized in that the thickness of the steel plate is 10 to 60 mm. According to claim 1,
Low-cost, high-performance Q500 bridge steel, characterized in that the microstructure of the steel sheet contains polygonal ferrite and 20% to 30% bainite. In the production method of low-cost high-performance Q500 bridge steel,
Applied to any one of claims 1 to 6, tempering treatment is not required; the steps below,
Step S1 in which molten iron is pretreated by the KR method, but S<0.010% of the molten iron entering the converter;
Step S2 of smelting the pretreated molten iron by removing dregs, putting it into a converter, and using a top-and-bottom combined blowing method;
After the molten steel is tapped, it is sent to RH to remove vacuum decarburization, degassing and inclusions, but the vacuum time is 20 to 30 minutes (min) Step S3;
Step S4 of sending the vacuum-treated molten steel to the LF to perform refining and deoxidation alloying, and after alloying, calcium treatment to purify the molten steel and improve the purity of the molten steel through static stirring;
Step S5 of casting the refined molten steel by sending it to a continuous casting machine, using electromagnetic stirring and a dynamic soft reduction process, and having a tensile speed of 0.6 to 1.3 m/min;
Sending the casting billet that passed the surface inspection to a heating furnace for heating, but the heating temperature is 1120 ~ 1140 ℃ Step S6;
Rolling proceeds with the TMCP rolling process, the rough rolling start temperature is 1000 ~ 1100 ℃, the secondary start temperature is controlled at 820 ~ 990 ℃, the final rolling temperature is 820 ± 20 ℃, ultra-high-speed cooling 580 ~ 690 ℃ Step S7 cooling until;
Step S8 of sending the rolled steel sheet to an annealing kiln for slow cooling for 24 hours; and
A method for producing low-cost, high-performance Q500 bridge steel, characterized in that it comprises a step S9 of cold-calibrating the laminated cooled steel sheet to control the flatness of the steel sheet, and then carrying out shearing, marking, surface inspection, and flaw detection.

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