High-strength corrosion-resistant hot-rolled narrow strip steel and preparation method thereof

Abstract

The invention discloses a high-strength corrosion-resistant hot-rolled narrow strip steel which comprises the following components in percentage by weight: 0.06%-0.12% of C, 0.15%-0.3% of Si, 1.2%-1.8% of Mn, less than or equal to 0.015% of P, less than or equal to 0.003% of S, 1.5%-2.5% of Cr, 0.3%-0.6% of Ni, 0.3%-0.6% of Cu, 0.15%-0.45% of Al, 0.06%-0.12% of Ti, 0.03%-0.06% of Nb, 0.0045%-0.0085% of N and the balance of Fe. And the balance of Fe and inevitable impurity elements. Meanwhile, the invention discloses a preparation method of the high-strength corrosion-resistant hot-rolled narrow strip steel. Through component specific design and preparation process control, the hot-rolled narrow strip steel has the characteristic of high strength and also has high atmospheric corrosion resistance.

Description

Technical Field

[0001] The invention relates to the field of steel, and in particular to a high-strength corrosion-resistant hot-rolled narrow strip steel and a preparation method thereof. Background Art

[0002] Due to its versatility, hot-rolled narrow strip steel is widely used in many core fields such as welded pipes, cold-bent and welded steel sections, highway guardrails, carriage structures, building frames and automobile manufacturing. With the wave of accelerated global economic growth, the demand for narrow strip steel in infrastructure construction, transportation network expansion and energy development has increased sharply, and the application environment has become more complex and harsh, and the requirements for corrosion resistance and high strength of narrow strip steel have become more urgent.

[0003] Traditional hot-rolled narrow strip steels are often unable to simultaneously meet the requirements of the above-mentioned high-end applications in terms of strength and corrosion resistance. Although high-strength narrow strip steels can improve the load-bearing capacity of structural parts, they are easily corroded in the atmosphere, causing structural damage. Therefore, they often need to undergo surface treatment to improve corrosion resistance. However, once the surface is damaged, it is very easy to accelerate rust and cause structural damage. Corrosion-resistant steels such as stainless steel, although they have good corrosion resistance, are relatively expensive and have limited strength, making them expensive. Therefore, the development of a hot-rolled narrow strip steel that has both high strength characteristics and the ability to maintain long-term stability in a variety of corrosive environments has become a hot topic in materials science research. Summary of the invention

[0004] Purpose of the invention: In view of the shortcomings and defects of the prior art, the present invention provides a high-strength, corrosion-resistant hot-rolled narrow strip steel and a preparation method thereof. Through component-specific design and preparation process control, the hot-rolled narrow strip steel is achieved to have high strength characteristics and high atmospheric corrosion resistance.

[0005] Technical solution: A high-strength, corrosion-resistant hot-rolled narrow strip steel of the present invention comprises the following components in weight percentage: C: 0.06%-0.12%, Si: 0.15%-0.3%, Mn: 1.2%-1.8%, P≤0.015%, S≤0.003%, Cr: 1.5%-2.5%, Ni: 0.3%-0.6%, Cu: 0.3%-0.6%, Al: 0.15%-0.45%, Ti: 0.06%-0.12%, Nb: 0.03%-0.06%, N: 0.0045%-0.0085%; the rest are Fe and unavoidable impurity elements.

[0006] The method for preparing high-strength and corrosion-resistant hot-rolled narrow strip steel of the present invention is characterized in that: the high-strength and corrosion-resistant hot-rolled narrow strip steel is prepared by adopting the preparation method of molten iron pretreatment → converter smelting → refining → continuous casting → heating and dephosphorization → rolling → ultra-fast cooling → curling → heat preservation → slow cooling.

[0007] Wherein, in the molten iron pretreatment, the KR method is used to pre-treat and desulfurize the molten iron.

[0008] Among them, in the converter smelting, in the early stage of smelting, slag is made by utilizing the conditions of low temperature and good P removal conditions to achieve rapid P removal; in the later stage of smelting, C removal is strengthened and the boiling of molten steel is strengthened to remove inclusions in the molten steel; when C≤0.04%, P≤0.010%, S≤0.015%, and the residual elements and temperature meet the preparation requirements, steel is tapped.

[0009] Among them, in the refining, the LF refining process adopts the method of adding Al blocks for deoxidation, feeding Al wire for alloying Al, and then adding ferromanganese, ferrochrome, ferronickel and copper blocks for alloying; after RH alloying, high vacuum treatment is carried out, the vacuum degree is ≤3mbar, the vacuum time is 10min~15min, and after RH vacuum breaking, according to the Ti component requirements, Ti-Mg composite alloy wire is fed to increase Ti, forming Ti (C, N) nanocompounds for precipitation, and preventing the precipitates from aggregating and growing; then 80m~150m pure calcium wire is fed for calcium treatment, argon is blown at the bottom for stirring throughout the process, and the soft argon blowing time is ≥10min, followed by continuous casting.

[0010] Among them, in the continuous casting, protective pouring is adopted throughout the whole process, the superheat is controlled at 8°C ~ 20°C, and electromagnetic stirring is adopted at 300A ~ 500A × 2Hz; the light pressure reduction technology at the end of solidification is adopted to improve the segregation and looseness of the casting, the total pressure reduction is 6mm ~ 14mm, the protective slag adopts low-reaction peritectic protective slag, the pulling speed is controlled at 1m / min ~ 1.4m / min, and the continuous casting is into a 150mm × 260mm rectangular billet.

[0011] Among them, in the heating dephosphorization, the ingot is heated to 1120°C to 1180°C, the soaking time is 25min to 40min, the total heating time is 160min to 240min, and the heated ingot is dephosphorized with high-pressure water, and the dephosphorization system pressure is ≥22MPa to ensure that the surface iron oxide is completely removed.

[0012] Among them, in the rolling, the starting temperature of rough rolling is 1020℃~1120℃, the finishing temperature of rough rolling is 960℃~1060℃, and the cast billet is rolled into an intermediate billet with a thickness of 30mm~50mm by adopting large reduction technology, and then undergoes 5 to 9 passes of finishing rolling, the starting temperature of finishing rolling is 880℃~960℃, and the finishing temperature of finishing rolling is 820℃~900℃.

[0013] Wherein, in the ultra-fast cooling, the temperature of the strip steel is rapidly reduced from 820°C to 900°C to 460°C to 580°C, with a cooling rate of 30°C to 60°C / s.

[0014] Among them, in the coiling, heat preservation and slow cooling, the ultra-fast cooling is followed by coiling, and after heat preservation, the steel coil is slowly cooled in a slow cooling pit, thereby completing the preparation of high-strength and corrosion-resistant hot-rolled narrow strip steel.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The present invention adopts the corrosion-resistant chemical composition design of ultra-high-strength steel, and improves the material strength by phase transformation strengthening, solid solution strengthening, fine grain strengthening and precipitation strengthening through alloy elements such as Mn, Al, Cr, Ti, Nb, etc.

[0016] The present invention adopts protective pouring, low superheat, electromagnetic stirring, and light pressure reduction technology at the end of solidification to improve the segregation, looseness, and shrinkage of the ingot. The carbon segregation is ≤1.0 level, the center looseness is ≤1.5 level, and the center shrinkage is ≤1.0 level.

[0017] The present invention adopts low-temperature heating, two-phase rolling and ultra-fast cooling, which can avoid Cu precipitation and the aggregation and growth of Ti and Ni precipitates, and can also refine the grains to obtain bainite + martensite + a small amount of ferrite and residual austenite structure, thereby improving the strength and toughness of the material.

[0018] The present invention adopts low-temperature coiling of steel coils and slow cooling in a slow cooling pit, which can improve the strength and toughness of the material. At the same time, the alloy elements Cr, Ni, Cu, Al, etc. on the surface of the steel strip can fully react with O2 to form a dense composite oxide film passivation layer, thereby improving the corrosion resistance. In addition, the annealing heat treatment process is reduced, reducing the production cost.

[0019] The high-strength corrosion-resistant hot-rolled narrow strip steel of the present invention has high strength characteristics and high atmospheric corrosion resistance through component-specific design and preparation process control, with yield strength ≥750Mpa, tensile strength ≥860Mpa, elongation ≥17.0%, and neutral salt spray corrosion resistance corrosion rate ≤0.25g / m 2 *h, meeting the needs of high strength and corrosion resistance for welding pipes, cold-formed steel, highway guardrails, car panels, construction and automotive steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the finished product structure of the present invention. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific implementation methods.

[0022] The high-strength corrosion-resistant hot-rolled narrow strip steel of the present invention comprises the following components in weight percentage: C: 0.06%-0.12%, Si: 0.15%-0.3%, Mn: 1.2%-1.8%, P≤0.015%, S≤0.003%, Cr: 1.5%-2.5%, Ni: 0.3%-0.6%, Cu: 0.3%-0.6%, Al: 0.15%-0.45%, Ti: 0.06%-0.12%, Nb: 0.03%-0.06%, N: 0.0045%-0.0085%; the rest are Fe and inevitable impurity elements.

[0023] The method for preparing high-strength and corrosion-resistant hot-rolled narrow strip steel of the present invention adopts the preparation method of molten iron pretreatment → converter smelting → refining → continuous casting → heating and dephosphorization → rolling → ultra-fast cooling → curling → heat preservation → slow cooling to prepare high-strength and corrosion-resistant hot-rolled narrow strip steel.

[0024] Among them, the KR method is used for pretreatment and desulfurization of molten iron in the pretreatment of molten iron. In converter smelting, in the early stage of smelting, slag is made by taking advantage of low temperature and good dephosphorization conditions to achieve rapid dephosphorization; in the later stage of smelting, carbon removal is strengthened and the boiling of molten steel is strengthened to remove inclusions in the molten steel; when C≤0.04%, P≤0.010%, S≤0.015%, and the residual elements and temperature meet the preparation requirements, steel is tapped. During refining, the LF refining process adopts the method of adding Al blocks for deoxidation, feeding Al wire for alloying Al, and then adding ferromanganese, ferrochrome, ferronickel, and copper blocks for alloying; after RH alloying, high vacuum treatment is carried out, the vacuum degree is ≤3mbar, and the vacuum time is 10min~15min. After RH vacuum breaking, according to the Ti component requirements, Ti-Mg composite alloy wire is fed to increase Ti, forming Ti(C,N) nano-compound precipitation to prevent the precipitates from aggregating and growing; then 80m~150m pure calcium wire is fed for calcium treatment, argon is blown at the bottom for stirring throughout the process, and the soft argon blowing time is ≥10min, followed by continuous casting. During continuous casting, protective pouring is used throughout the process, the superheat is controlled at 8℃~20℃, and electromagnetic stirring is used at 300A~500A×2Hz; the light pressure reduction technology at the end of solidification is used to improve the segregation and looseness of the ingot, the total pressure reduction is 6mm~14mm, the protective slag uses low-reaction peritectic protective slag, the pulling speed is controlled at 1m / min~1.4m / min, and the ingot is continuously cast into a 150mm×260mm rectangular ingot. During heating and dephosphorization, the ingot is heated to 1120℃~1180℃, the soaking time is 25min~40min, and the total heating time is 160min~240min. The heated ingot is dephosphorized by high-pressure water, and the dephosphorization system pressure is ≥22MPa to ensure that the surface iron oxide is removed cleanly. During rolling, the starting temperature of rough rolling is 1020℃~1120℃, the final rolling temperature of rough rolling is 960℃~1060℃, and the large reduction technology is used to roll the ingot into an intermediate billet with a thickness of 30mm~50mm, and then it undergoes 5 to 9 passes of finishing rolling, the starting temperature of finishing rolling is 880℃~960℃, and the final rolling temperature of finishing rolling is 820℃~900℃. In ultra-fast cooling, the strip temperature is rapidly reduced from 820℃~900℃ to 460℃~580℃, and the cooling rate is 30℃~60℃ / s. In coiling, heat preservation, and slow cooling, the coiling is carried out after ultra-fast cooling, and after heat preservation, the steel coil is slowly cooled in the slow cooling pit, thereby completing the preparation of high-strength and corrosion-resistant hot-rolled narrow strip steel.

[0025] Neutral salt spray corrosion test method: The test is carried out according to GB / T 10125 artificial atmosphere corrosion test salt spray test. The sample is processed into 150×70×4mm and weighed, and then placed in the Q-FOG salt spray corrosion test box. The solution used in the experiment is 50g / L NaCl, the pH value is 6.5-7.2, the test temperature is 35℃, and the sodium chloride solution is atomized by the spray tower so that the salt spray can evenly cover the surface of the specimen. The salt spray corrosion time is 48h, 96h, 240h, 480h, and 720h. Then take out the sample and dry it for 24h, remove the rust layer by chemical method and clean the sample. The chemical cleaning solution is prepared by mixing 500m hydrochloric acid + 500mL distilled water + 5g hexamethylenetetramine, and the cleaning temperature is room temperature. After all the corrosion products are removed, they are cleaned with alcohol and acetone in turn, dried with hot air, placed in a dryer for 24h, taken out and weighed, and the weighing results are recorded to calculate the average corrosion rate.

[0026] Embodiment 1:

[0027] The high-strength, corrosion-resistant hot-rolled narrow strip steel of this embodiment includes the following components in weight percentage: C: 0.091%, Si: 0.26%, Mn: 1.71%, P: 0.01%, S: 0.0013%, Cr: 1.8%, Ni: 0.47%, Cu: 0.58%, Al: 0.27%, Ti: 0.11%, Nb: 0.039%, N: 0.0069%; the rest are Fe and unavoidable impurity elements.

[0028] The preparation parameters and product performance of this embodiment are as follows: finished product thickness is 3mm, rough rolling start temperature is 1090℃, rough rolling final rolling temperature is 985℃, finishing rolling start temperature is 915℃, finishing rolling final rolling temperature is 868℃, water entry temperature is 845℃, curling temperature is 483℃, yield strength is 822MPa, tensile strength is 997MPa, elongation is 17%, corrosion rate is 0.197g / m 2 *h.

[0029] Embodiment 2:

[0030] The high-strength, corrosion-resistant hot-rolled narrow strip steel of this embodiment includes the following components in weight percentage: C: 0.088%, Si: 0.18%, Mn: 1.33%, P: 0.008%, S: 0.0021%, Cr: 1.6%, Ni: 0.52%, Cu: 0.43%, Al: 0.24%, Ti: 0.089%, Nb: 0.042%, N: 0.0055%; the rest are Fe and unavoidable impurity elements.

[0031] The preparation parameters and product performance of this embodiment are as follows: finished product thickness is 3mm, rough rolling start temperature is 1090℃, rough rolling final rolling temperature is 1003℃, finishing rolling start temperature is 890℃, finishing rolling final rolling temperature is 835℃, water entry temperature is 823℃, curling temperature is 495℃, yield strength is 808MPa, tensile strength is 983MPa, elongation is 18.5%, corrosion rate is 0.215g / m 2 *h.

[0032] Embodiment 3:

[0033] The high-strength, corrosion-resistant hot-rolled narrow strip steel of this embodiment includes the following components in weight percentage: C: 0.063%, Si: 0.23%, Mn: 1.56%, P: 0.013%, S: 0.0016%, Cr: 2.3%, Ni: 0.35%, Cu: 0.35%, Al: 0.2%, Ti: 0.068%, Nb: 0.057%, N: 0.0047%; the rest are Fe and unavoidable impurity elements.

[0034] The preparation parameters and product performance of this embodiment are as follows: the finished product thickness is 3.5mm, the rough rolling start temperature is 1110℃, the rough rolling final rolling temperature is 1040℃, the finishing rolling start temperature is 945℃, the finishing rolling final rolling temperature is 874℃, the water entry temperature is 856℃, the curling temperature is 527℃, the yield strength is 787MPa, the tensile strength is 949MPa, the elongation is 20.5%, and the corrosion rate is 0.178g / m 2 *h.

[0035] Embodiment 4:

[0036] The high-strength, corrosion-resistant hot-rolled narrow strip steel of this embodiment includes the following components in weight percentage: C: 0.075%, Si: 0.29%, Mn: 1.59%, P: 0.012%, S: 0.0011%, Cr: 2.1%, Ni: 0.48%, Cu: 0.42%, Al: 0.18%, Ti: 0.074%, Nb: 0.041%, N: 0.0052%; the rest are Fe and unavoidable impurity elements.

[0037] The preparation parameters and product performance of this embodiment are as follows: the finished product thickness is 3.5mm, the rough rolling start temperature is 1110℃, the rough rolling final rolling temperature is 1051℃, the finishing rolling start temperature is 938℃, the finishing rolling final rolling temperature is 890℃, the water entry temperature is 867℃, the curling temperature is 510℃, the yield strength is 793MPa, the tensile strength is 951MPa, the elongation is 19%, and the corrosion rate is 0.184g / m 2 *h.

[0038] Table 1: Chemical compositions of Examples 1 to 4

[0039]

[0040] Table 2: Mechanical properties of Examples 1 to 4

[0041]

[0042]

[0043] The high-strength corrosion-resistant hot-rolled narrow strip steel of the present invention has high strength characteristics and high atmospheric corrosion resistance through component-specific design and preparation process control, with yield strength ≥750Mpa, tensile strength ≥860Mpa, elongation ≥17.0%, and neutral salt spray corrosion resistance corrosion rate ≤0.25g / m 2 *h, meeting the needs of high strength and corrosion resistance for welding pipes, cold-formed steel, highway guardrails, car panels, construction and automotive steel.

Claims

1. A high-strength, corrosion-resistant, hot-rolled narrow strip steel, characterized in that: The invention comprises the following components in weight percentage: C: 0.06% to 0.12%, Si: 0.15% to 0.3%, Mn: 1.2% to 1.8%, P≤0.015%, S≤0.003%, Cr: 1.5% to 2.5%, Ni: 0.3% to 0.6%, Cu: 0.3% to 0.6%, Al: 0.15% to 0.45%, Ti: 0.06% to 0.12%, Nb: 0.03% to 0.06%, N: 0.0045% to 0.0085%; The rest is Fe and inevitable impurity elements.

2. The method for preparing high-strength corrosion-resistant hot-rolled narrow strip steel according to claim 1, characterized in that: The high-strength and corrosion-resistant hot-rolled narrow strip steel is prepared by adopting the preparation method of molten iron pretreatment → converter smelting → refining → continuous casting → heating and dephosphorization → rolling → ultra-fast cooling → curling → heat preservation → slow cooling.

3. The method for preparing high-strength corrosion-resistant hot-rolled narrow strip steel according to claim 2, characterized in that: In the molten iron pretreatment, the KR method is used to pre-treat and desulfurize the molten iron.

4. The method for preparing high-strength corrosion-resistant hot-rolled narrow strip steel according to claim 2, characterized in that: In the converter smelting, in the early stage of smelting, slag is made by utilizing the conditions of low temperature and good P removal conditions to achieve rapid P removal; in the later stage of smelting, C removal is strengthened and the boiling of molten steel is strengthened to remove inclusions in the molten steel; when C≤0.04%, P≤0.010%, S≤0.015%, and the residual elements and temperature meet the preparation requirements, steel is tapped.

5. The method for preparing high-strength corrosion-resistant hot-rolled narrow strip steel according to claim 2, characterized in that: In the refining, the LF refining process adopts the method of adding Al blocks for deoxidation, feeding Al wire for alloying Al, and then adding ferromanganese, ferrochrome, ferronickel and copper blocks for alloying; after RH alloying, high vacuum treatment is carried out, the vacuum degree is ≤3mbar, the vacuum time is 10min~15min, and after RH vacuum breaking, according to the Ti component requirements, Ti-Mg composite alloy wire is fed to increase Ti, forming Ti (C, N) nano-compound precipitation to prevent the precipitates from aggregating and growing; then 80m~150m pure calcium wire is fed for calcium treatment, argon is blown at the bottom for stirring throughout the whole process, and the soft argon blowing time is ≥10min, followed by continuous casting.

6. The method for preparing high-strength corrosion-resistant hot-rolled narrow strip steel according to claim 2, characterized in that: In the continuous casting, protective pouring is adopted throughout the whole process, the superheat is controlled at 8°C to 20°C, and electromagnetic stirring is adopted at 300A to 500A×2Hz; the light reduction technology at the end of solidification is adopted to improve the segregation and looseness of the casting, the total reduction is 6mm to 14mm, the protective slag adopts low-reaction peritectic protective slag, the pulling speed is controlled at 1m / min to 1.4m / min, and the continuous casting is into a 150mm×260mm rectangular billet.

7. The method for preparing high-strength corrosion-resistant hot-rolled narrow strip steel according to claim 2, characterized in that: In the heating dephosphorization, the ingot is heated to 1120°C to 1180°C, the soaking time is 25min to 40min, the total heating time is 160min to 240min, and the heated ingot is dephosphorized with high-pressure water. The dephosphorization system pressure is ≥22MPa to ensure that the surface iron oxide is completely removed.

8. The method for preparing high-strength corrosion-resistant hot-rolled narrow strip steel according to claim 2, characterized in that: In the rolling, the starting temperature of rough rolling is 1020℃~1120℃, the finishing temperature of rough rolling is 960℃~1060℃, and the cast billet is rolled into an intermediate billet with a thickness of 30mm~50mm by adopting large reduction technology, and then undergoes 5 to 9 passes of finishing rolling, the starting temperature of finishing rolling is 880℃~960℃, and the finishing temperature of finishing rolling is 820℃~900℃.

9. The method for preparing high-strength corrosion-resistant hot-rolled narrow strip steel according to claim 2, characterized in that: In the ultra-fast cooling, the temperature of the strip steel is rapidly reduced from 820°C to 900°C to 460°C to 580°C, with a cooling rate of 30°C to 60°C / s.

10. The method for preparing high-strength corrosion-resistant hot-rolled narrow strip steel according to claim 2, characterized in that: In the coiling, heat preservation and slow cooling, the steel coil is coiled after ultra-fast cooling, and after heat preservation, the steel coil is slowly cooled in a slow cooling pit, thereby completing the preparation of high-strength and corrosion-resistant hot-rolled narrow strip steel.

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