09CrCuSb round steel with high strength and sulfuric acid dew point corrosion resistance and preparation method thereof

Abstract

The application provides a 09CrCuSb round steel with high strength and sulfuric acid dew point corrosion resistance, and the chemical components of the 09CrCuSb round steel are as follows in terms of mass percentage: C: 0.05%-0.10%, Si: 0.20%-0.36%, Mn: 0.45%-0.62%, P: ≤0.012%, S: ≤0.012%, Cr: 0.90%-1.20%, Cu: 0.40%-0.55%, Ni: 0.17%-0.26%, Sn: 0.12%-0.20%, Sb: 0.15%-0.20%, W: 0.15%-0.20%, Mo: 0.35%-0.45%, and the balance is Fe and inevitable impurities; wherein the mass ratio of Cu and Ni is 2-2.5, the average ferrite grain size of the 09CrCuSb round steel is 9-14 mu m, and the volume fraction of proeutectoid ferrite is ≤0.70%. The 09CrCuSb round steel prepared by adjusting the element ratio, optimizing the process flow and controlling the cooling rate after rolling has the properties of high strength and sulfuric acid dew point corrosion resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of sulfuric acid dew point corrosion resistant steel preparation, and in particular relates to high-strength sulfuric acid dew point corrosion resistant 09CrCuSb round steel and a preparation method thereof. Background Art

[0002] 09CrCuSb steel is widely used in the production of desulfurization equipment, boiler pressure vessels, air preheaters and other equipment due to its excellent "resistance to low-temperature dew point corrosion of sulfuric acid" performance. It is widely used in the environmental protection industry, thermal power plants, etc. In order to ensure the long-term stability of the equipment, the material is required to have excellent mechanical properties and corrosion resistance, and be able to resist the erosion of acidic media, high temperature and chemical substances.

[0003] In the prior art, 09CrCuSb round steel usually faces the following problems. Strength and plasticity cannot be well matched: The commonly used method is to increase the strength of steel by adding alloying elements, etc., but as the strength increases, the plasticity of the steel will decrease, so the service life of the steel will be greatly affected during use. Insufficient corrosion resistance: Since the corrosion-resistant elements Cu and Ni are not well matched, and there is no strict control over elements such as P and S, the corrosion resistance does not achieve the best effect. Poor surface quality: The increase in the content of corrosion-resistant elements will have a certain impact on the quality of the ingot, and further have an adverse effect on the surface quality of the steel, increasing production costs. Produce incomplete phase transformation products: In order to ensure that the performance and surface quality of the round steel are good, more ferrite-forming elements such as Cr and W are added to the steel, which further affects the phase diagram, and finally produces a yellow block structure in the microstructure that has an adverse effect on the performance.

[0004] Therefore, it is urgent to use low-cost and high-efficiency technical means to propose a new solution from the aspects of composition design and performance optimization, and develop a new type of high-strength, high-corrosion-resistant 09CrCuSb steel that meets the requirements of being green, high in application value and reducing production costs. Summary of the Invention

[0005] In view of this, the present invention provides a high-strength 09CrCuSb round steel resistant to sulfuric acid dew point corrosion and a preparation method thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A high-strength 09CrCuSb round steel resistant to sulfuric acid dew point corrosion, wherein the chemical composition of the 09CrCuSb round steel is as follows, calculated by mass percentage: C: 0.05%-0.10%, Si: 0.20%-0.36%, Mn: 0.45%-0.62%, P≤0.012%, S≤0.012%, Cr: 0.90%-1.20%, Cu: 0.40%-0.55%, Ni: 0.17%-0.26%, Sn: 0.12%-0.20%, Sb: 0.15%-0.20%, W: 0.15%-0.20%, Mo: 0.35%-0.45%, and the balance being Fe and unavoidable impurities;

[0008] The mass ratio of Cu to Ni is 2-2.5, the average grain size of ferrite in the 09CrCuSb round steel is 9-14 μm, and the volume fraction of yellow block structure is ≤0.70%.

[0009] A method for preparing the above-mentioned 09CrCuSb round steel comprises the following steps:

[0010] S1. Steelmaking: First, steelmaking is carried out in a top-bottom combined-blowing converter. Oxygen is blown into the converter using an oxygen lance. Deoxidizers and alloys are added during the tapping process for deoxidation and alloying. Then, the chemical composition is adjusted, deoxidation and inclusion removal are carried out in an LF furnace, and the molten steel temperature is controlled at 1600-1650°C. Finally, vacuum degassing is carried out in a VD furnace to further remove inclusions and achieve deep desulfurization.

[0011] S2, continuous casting: using argon seal protection pouring technology, control the tundish superheat at 25~50℃, the crystallizer liquid level fluctuation at ±6mm, the crystallizer soft water flow at 98~103m 3 / h, the pulling speed is 0.9~1.0m / min, and the temperature of the corner of the billet is 900~1000℃;

[0012] S3. Rolling: Preheating temperature 540~600℃, two-stage soaking is adopted, rolling starting temperature 950~1100℃, three-roll rolling mill is used, initial rolling reduction accounts for 45~50% of the total deformation, final rolling temperature 840~900℃, after cooling after rolling, it is sent to the holding pit for slow cooling.

[0013] Furthermore, in step S1, the oxygen lance oxygen blowing rate is 750~800Nm 3 / min.

[0014] Furthermore, in step S1, the mass content of the metal calcium powder in the deoxidizer is 25% to 35%, and the mass content of the metal aluminum powder is 10% to 15%.

[0015] Furthermore, deoxidation and inclusion removal in the LF furnace are achieved by feeding calcium wire into the molten steel and introducing argon gas; wherein, the argon gas flow rate is 5~20NL / min, and the blowing time is 10~20min.

[0016] Furthermore, in step S2, the argon flow rate is 7-22 NL / min.

[0017] Furthermore, the two-stage soaking in step S3 is specifically as follows: the first stage heating temperature is 980°C~1000°C, and the time is 100 minutes; the second stage heating temperature is 1000°C~1050°C, and the time is 40~80 minutes.

[0018] Furthermore, in step S3, the cooling temperature after rolling is 300-420° C., and the cooling rate is 0.5-2° C. / s.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) This application optimizes the element ratio: in order to achieve the best comprehensive effect of mechanical properties and corrosion resistance, the carbon content is controlled within 0.1% to avoid the decrease in plasticity and corrosion resistance caused by excessive carbon content. The copper content is controlled within 0.40%~0.55%, and the nickel content is controlled within 0.17%~0.26%. The ratio of Cu to Ni is controlled between 2~2.5 to ensure the comprehensive performance of the steel.

[0021] (2) This application has optimized the process flow: optimized the continuous casting and rolling processes, controlled the tundish superheat at 25~50℃, controlled the crystallizer soft water flow at 98~103m 3 / h, and the soaking temperature is 980~1050℃ to avoid cracks in the ingot and hot-rolled round steel caused by excessively high temperature, thereby improving the mechanical properties and corrosion resistance of the steel. The cooling rate after rolling is controlled at 0.5~2℃ / s, the volume fraction of the yellow block structure in the microstructure is controlled within 0.70%, and the ferrite grain size is controlled at 9~14μm to achieve the best match between performance and surface quality.

[0022] (3) The 09CrCuSb round steel prepared by the present invention has excellent performance, with a tensile strength of 548~565MPa, a yield strength of 426~436MPa, an elongation of 28.28~32.63%, and a sulfuric acid corrosion resistance rate of 0.301~0.348mg / cm 2 ·h. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1-5 The metallographic micrographs of 09CrCuSb round steel prepared in Examples 1-3 of the present invention and Comparative Examples 1 and 2 are shown in sequence; wherein the area pointed by the shear head indicates the yellow quick structure. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below with reference to specific embodiments so that those skilled in the art can understand the present invention more clearly.

[0025] Example 1

[0026] This embodiment provides high-strength 09CrCuSb round steel that is resistant to sulfuric acid dew point corrosion and a method for preparing the same. The chemical composition of the 09CrCuSb round steel in this embodiment, measured by mass percentage, is as follows: C = 0.05%, Si = 0.26%, Mn = 0.47%, P = 0.010%, S = 0.002%, Cr = 0.93%, Mo = 0.35%, Cu = 0.45%, Ni = 0.18%, Sn = 0.13%, Sb = 0.15%, W = 0.16%, and the remainder is Fe and unavoidable impurities. In this case, the Cu / Ni ratio is 2.5.

[0027] The specific preparation method is as follows:

[0028] S1. Steelmaking: First, use the top and bottom double-blowing converter to make steel. Oxygen lance blows oxygen into the converter and controls the flow rate at 800Nm 3 / min, deoxidizer (25% metallic calcium powder, 10% metallic aluminum powder) and alloy are added during the tapping process for deoxidation and alloying. Then, the chemical composition is precisely adjusted in the LF furnace. Deoxidation and inclusion removal are carried out by feeding calcium wire and passing argon gas at a flow rate of 10NL / min for 15 minutes, and the molten steel temperature is controlled at 1600℃. Finally, vacuum degassing, further inclusion removal and deep desulfurization are carried out in the VD furnace.

[0029] S2, continuous casting: adopt argon seal (argon flow rate is 15NL / min) to protect the pouring technology, control the tundish superheat at 25~35℃, control the crystallizer liquid level fluctuation within ±6mm, and control the crystallizer soft water flow at 100m 3 / h, pulling speed 0.95m / min; soft reduction 8mm at the end of solidification, temperature of the corner of the billet 910℃; billet size 280*280*mm*6m;

[0030] (3) Rolling: The preheating section temperature is controlled at 550°C, and a two-stage equalizing heat treatment is adopted (the first stage heating temperature is 980°C, the time is 100 min; the second stage heating temperature is 1000°C, the time is 55 min); the starting rolling temperature is 960°C, the final rolling temperature is 843°C, and the rolling target size is 60 mm; after rolling, the steel is closely packed and cooled to 320°C on the cooling bed, and then bundled and collected into the insulation pit for slow cooling for 24 hours. The cooling rate after rolling is controlled at 0.5°C / s.

[0031] The metallographic structure of the prepared 09CrCuSb round steel is shown in Figure 1Using grain statistics software and tissue proportion statistics software, it was found that the average ferrite grain size in the 09CrCuSb round steel prepared in this embodiment was 11.26 μm, and the volume fraction of the yellow block structure was 0.00%.

[0032] Example 2

[0033] This embodiment provides high-strength 09CrCuSb round steel that is resistant to sulfuric acid dew point corrosion and a method for preparing the same. The chemical composition of the 09CrCuSb round steel in this embodiment, measured by mass percentage, is as follows: C = 0.06%, Si = 0.29%, Mn = 0.49%, P = 0.009%, S = 0.003%, Cr = 0.95%, Mo = 0.36%, Cu = 0.47%, Ni = 0.20%, Sn = 0.15%, Sb = 0.17%, W = 0.18%, and the remainder is Fe and unavoidable impurities. In this case, the Cu / Ni ratio is 2.35.

[0034] The specific preparation method is as follows:

[0035] S1. Steelmaking: First, use the top and bottom combined blowing converter to make steel. Oxygen lance blows oxygen into the converter and controls the flow rate at 750Nm 3 / min, deoxidizer (30% metallic calcium powder, 12% metallic aluminum powder) and alloy are added during the tapping process for deoxidation and alloying. Then, the chemical composition is precisely adjusted in the LF furnace. Deoxidation and inclusion removal are carried out by feeding calcium wire and passing argon at a flow rate of 5NL / min for 20 minutes, and the molten steel temperature is controlled at 1620℃. Finally, vacuum degassing, further inclusion removal and deep desulfurization are carried out in the VD furnace.

[0036] S2, continuous casting: using argon seal (argon flow rate of 7NL / min) to protect the pouring technology, controlling the tundish superheat at 27~38℃, the crystallizer liquid level fluctuation within ±6mm, and the crystallizer soft water flow at 98m 3 / h, pulling speed 0.95m / min; soft reduction 8mm at the end of solidification, temperature of the corner of the billet 973℃; billet size 240*240*mm*6m;

[0037] (3) Rolling: The preheating section temperature is controlled at 562 °C, and two-stage equalization is adopted (the first section heating temperature is 985 °C, the time is 100 min; the second section heating temperature is 1020 °C, the time is 60 min); the starting rolling temperature is 972 °C, the final rolling temperature is 857 °C, and the rolling target size is 60 mm; after rolling, the cooling bed is closely packed and cooled to 345 °C, and then the bundles are collected and slowly cooled in the insulation pit for 24 hours. The cooling rate after rolling is controlled at 1.0 °C / s.

[0038] The metallographic structure of the prepared 09CrCuSb round steel is shown in Figure 2Using grain statistics software and tissue proportion statistics software, it was found that the average ferrite grain size in the 09CrCuSb round steel prepared in this embodiment was 9.50 μm, and the volume fraction of the yellow block structure was 0.12%.

[0039] Example 3

[0040] This embodiment provides high-strength 09CrCuSb round steel that is resistant to sulfuric acid dew point corrosion and a method for preparing the same. The chemical composition of the 09CrCuSb round steel in this embodiment, measured by mass percentage, is as follows: C = 0.07%, Si = 0.34%, Mn = 0.53%, P = 0.009%, S = 0.004%, Cr = 0.98%, Mo = 0.44%, Cu = 0.48%, Ni = 0.24%, Sn = 0.13%, Sb = 0.19%, W = 0.18%, and the remainder is Fe and unavoidable impurities. In this case, the Cu / Ni ratio is 2.0.

[0041] The specific preparation method is as follows:

[0042] S1. Steelmaking: First, use the top and bottom double-blowing converter to make steel. Oxygen lance blows oxygen into the converter and controls the flow rate at 900Nm 3 / min, deoxidizer (35% metallic calcium powder, 15% metallic aluminum powder) and alloy are added during the tapping process for deoxidation and alloying. Then, the chemical composition is precisely adjusted in the LF furnace. Deoxidation and inclusion removal are carried out by feeding calcium wire and passing argon gas at a flow rate of 5NL / min for 20 minutes, and the molten steel temperature is controlled at 1630℃. Finally, vacuum degassing, further inclusion removal and deep desulfurization are carried out in the VD furnace.

[0043] S2, continuous casting: using argon seal (argon flow rate of 7 NL / min) to protect the pouring technology, controlling the tundish superheat at 31~48℃, the crystallizer liquid level fluctuation within ±6mm, and the crystallizer soft water flow rate at 100m 3 / h, pulling speed 0.95m / min; soft pressure reduction 8mm at the end of solidification, temperature of the corner of the billet 983℃; billet size 240*240*mm*6m;

[0044] (3) Rolling: The preheating section temperature was controlled at 594°C, and two-stage equalization was adopted (the first section heating temperature was 1000°C, the time was 100 min; the second section heating temperature was 1040°C, the time was 80 min); the starting rolling temperature was 1006°C, the final rolling temperature was 882°C, and the rolling target size was 60 mm; after rolling, the steel was closely packed and cooled to 381°C on the cooling bed, and then bundled and collected into the insulation pit for slow cooling for 24 h. The cooling rate after rolling was controlled at 2.0°C / s.

[0045] The metallographic structure of the prepared 09CrCuSb round steel is shown in Figure 3Using grain statistics software and tissue proportion statistics software, it was found that the average ferrite grain size in the 09CrCuSb round steel prepared in this embodiment was 13.82 μm, and the volume fraction of the yellow block structure was 0.69%.

[0046] Comparative Example 1

[0047] This comparative example provides a high-strength, sulfuric acid dew-point corrosion-resistant 09CrCuSb round steel and a preparation method thereof. The comparative example is substantially the same as Example 1, except that the chemical composition of the 09CrCuSb round steel is 0.30% Cu and 0.20% Ni, with a Cu / Ni ratio of 1.5.

[0048] The metallographic structure of the prepared 09CrCuSb round steel is shown in Figure 4 Using grain statistics software and statistical organization percentage software, it was found that the average ferrite grain size in the 09CrCuSb round steel prepared in this comparative example was 28.92μm, and the volume fraction of the yellow block organization was 0.62%.

[0049] Comparative Example 2

[0050] This comparative example provides a high-strength 09CrCuSb round steel resistant to sulfuric acid dew point corrosion and a preparation method thereof, which is basically the same as Example 1 except that the cooling rate after rolling is 2.5°C / s, and the rest remain unchanged.

[0051] The metallographic structure of the prepared 09CrCuSb round steel is shown in Figure 5 Using grain statistics software and tissue proportion statistics software, it was found that the average ferrite grain size in the 09CrCuSb round steel prepared in this embodiment was 21.07 μm, and the volume fraction of the yellow block structure was 0.14%.

[0052] Furthermore, in order to understand the properties of the various 09CrCuSb round steels prepared above, the following tests were conducted on their properties.

[0053] The prepared 09CrCuSb round steel was tested for tensile strength, yield strength, elongation, and sulfuric acid corrosion rate. The tensile strength, yield strength, and elongation were measured in accordance with GB / T 228.1-2021, "Metallic Materials - Tensile Tests - Part 1: Room Temperature Test Methods." The sulfuric acid corrosion rate was tested in accordance with JB / T 7901-1999, "Metallic Materials - Laboratory Uniform Corrosion Full Immersion Test Method." The results are shown in Table 1 below.

[0054] Table 1 Performance results of various 09CrCuSb round steels

[0055]

[0056] It can be seen from Table 1 that when the copper content is controlled between 0.40% and 0.55%, the nickel content is controlled between 0.17% and 0.26%, the ratio of Cu to Ni is controlled between 2 and 2.5, and the cooling rate after rolling is controlled between 0.5 and 2°C / s, the average grain size of the prepared 09CrCuSb round steel is finer and has better mechanical properties and corrosion resistance.

[0057] The 09CrCuSb round steel prepared by the present invention has an average grain size of 9-14 μm, a yellow block structure volume fraction of ≤0.70%, a tensile strength of 548-565 MPa, a yield strength of 426-436 MPa, an elongation of 28.28-32.63%, and a sulfuric acid corrosion resistance rate of 0.301-0.348 mg / cm 2 h; It is well suited for desulfurization equipment, boiler pressure vessels, air preheaters and other equipment, meeting the requirements of greenness, high application value and reduced production costs.

[0058] The raw materials not specifically described in the present invention are all existing materials that can be directly purchased from the market.

[0059] The above is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing high-strength 09CrCuSb round steel resistant to sulfuric acid dew point corrosion, characterized in that: The chemical composition of the 09CrCuSb round steel is as follows by mass percentage: C: 0.05%-0.10%, Si: 0.20%-0.36%, Mn: 0.45%-0.62%, P≤0.012%, S≤0.012%, Cr: 0.90%-1.20%, Cu: 0.40%-0.55%, Ni: 0.17%-0.26%, Sn: 0.12%-0.20%, Sb: 0.15%-0.20%, W: 0.15%-0.20%, Mo: 0.35%-0.45%, and the balance is Fe and unavoidable impurities; The mass ratio of Cu to Ni is 2-2.5, the average grain size of ferrite in the 09CrCuSb round steel is 9-14 μm, and the volume fraction of yellow block structure is ≤0.70%; The following steps are involved: S1. Steelmaking: First, steelmaking is carried out in a top-bottom combined-blowing converter. Oxygen is blown into the converter using an oxygen lance. Deoxidizers and alloys are added during the tapping process for deoxidation and alloying. Then, the chemical composition is adjusted, deoxidation and inclusion removal are carried out in an LF furnace, and the molten steel temperature is controlled at 1600-1650°C. Finally, vacuum degassing is carried out in a VD furnace to further remove inclusions and achieve deep desulfurization. S2, continuous casting: Use argon seal to protect casting, control the tundish superheat at 25~50℃, the crystallizer liquid level fluctuation is controlled at ±6mm, and the crystallizer soft water flow is controlled at 98~103m 3 / h, the pulling speed is 0.9~1.0m / min, and the temperature of the corner of the billet is 900~1000℃; S3, rolling: preheating temperature 540 ~ 600 ℃, using two-stage soaking, rolling starting temperature 950 ~ 1100 ℃, using three-roll mill rolling, initial rolling reduction accounts for 45 ~ 50% of the total deformation, final rolling temperature 840 ~ 900 ℃, after cooling after rolling, sent to the holding pit for slow cooling; In step S3, the cooling temperature after rolling is 300-420° C., and the cooling rate is 0.5-2° C. / s.

2. The preparation method according to claim 1, characterized in that The oxygen flow rate of the oxygen lance in step S1 is 750~800Nm 3 / min.

3. The preparation method according to claim 1, characterized in that In step S1, the mass content of the metal calcium powder in the deoxidizer is 25% to 35%, and the mass content of the metal aluminum powder is 10% to 15%.

4. The preparation method according to claim 1, characterized in that Deoxidation and inclusion removal in the LF furnace are achieved by feeding calcium wire into the molten steel and passing argon gas; the argon gas flow rate is 5~20NL / min and the blowing time is 10~20min.

5. The preparation method according to claim 1, characterized in that In step S2, the argon flow rate is 7-22 NL / min.

6. The preparation method according to claim 1, characterized in that The two-stage soaking in step S3 is specifically as follows: the first stage heating temperature is 980°C~1000°C, and the time is 100 minutes; the second stage heating temperature is 1000°C~1050°C, and the time is 40~80 minutes.

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