High-strength sulfuric acid dew point corrosion resistant 09CrCuSb round steel and preparation method thereof

Abstract

The invention provides high-strength 09CrCuSb round steel resistant to sulfuric acid dew point corrosion. The 09CrCuSb round steel is prepared from, by mass, 0.05%-0.10% of C, 0.20%-0.36% of Si, 0.45%-0.62% of Mn, smaller than or equal to 0.012% of P, smaller than or equal to 0.012% of S, 0.90%-1.20% of Cr, 0.40%-0.55% of Cu, 0.17%-0.26% of Ni, 0.12%-0.20% of Sn, 0.15%-0.20% of Sb, 0.15%-0.20% of W, 0.35%-0.45% of Mo and the balance Fe and inevitable impurities. Wherein 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 microns, and the volume fraction of yellow block structures is smaller than or equal to 0.70%. By adjusting the element ratio, optimizing the technological process and controlling the cooling speed after rolling, the prepared 09CrCuSb round steel has high strength and sulfuric acid dew point corrosion resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of sulfuric acid dew point corrosion resistant steel, and specifically 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". It is widely used in the environmental protection industry, thermal power plants, etc. 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 chemicals.

[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 while the strength is increased, 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. Incomplete phase transformation products are produced: 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 a yellow block structure is produced in the microstructure that has an adverse effect on the performance.

[0004] Therefore, it is urgently necessary to propose a new solution from the aspects of composition design and performance optimization through low-cost and high-efficiency technical means, and develop a new type of high-strength and high-corrosion-resistant 09CrCuSb steel that meets the requirements of greenness, high application value and reduced 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: 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 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%.

[0007] A method for preparing the above-mentioned 09CrCuSb round steel comprises the following steps: 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 steelmaking process for deoxidation and alloying. Then, the chemical composition is adjusted in the LF furnace, deoxidation and inclusion removal are performed, and the temperature of the molten steel is controlled to be 1600~1650℃. Finally, vacuum degassing is performed in the VD furnace to further remove inclusions and deep desulfurization. S2, continuous casting: using argon seal protection pouring technology, control the tundish superheat at 25~50℃, the crystallizer liquid level fluctuation at ±6mm, and 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 casting is 900~1000℃; S3. Rolling: preheating temperature 540~600℃, two-stage equalizing heat is adopted, rolling start 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 insulation pit for slow cooling.

[0008] Furthermore, in step S1, the oxygen lance oxygen blowing flow rate is 750~800Nm 3 / min.

[0009] 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%.

[0010] Furthermore, deoxidation and removal of inclusions in the LF furnace are achieved by feeding calcium wire into the molten steel and passing argon gas; wherein the argon gas flow rate is 5~20NL / min, and the blowing time is 10~20min.

[0011] Furthermore, in step S2, the argon gas flow rate is 7-22 NL / min.

[0012] Furthermore, the two-stage equalization 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.

[0013] Furthermore, in step S3, the cooling temperature after rolling is 300-420° C., and the cooling rate is 0.5-2° C. / s.

[0014] Compared with the prior art, the present invention has the following beneficial effects: (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 of 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.

[0015] (2) This application has optimized the process flow: optimizing the continuous casting and rolling processes, controlling the superheat of the tundish at 25~50℃, and controlling the soft water flow rate of the crystallizer at 98~103m 3 / h, the soaking temperature is 980~1050℃, to avoid cracks in the ingot and hot-rolled round steel caused by too high temperature, and to improve 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, so as to achieve the best match between performance and surface quality.

[0016] (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

[0017] 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 direction of the shear head indicates the yellow quick structure. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below in conjunction with specific embodiments so that those skilled in the art can understand the present invention more clearly.

[0019] Example 1 The present embodiment provides a high-strength sulfuric acid dew point corrosion resistant 09CrCuSb round steel and a preparation method thereof. The chemical composition of the 09CrCuSb round steel in the present embodiment is as follows by mass percentage: 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 rest is Fe and unavoidable impurities. At this time, Cu / Ni=2.5.

[0020] The specific preparation method is as follows: S1. Steelmaking: First, use top and bottom combined blowing converter to make steel. Oxygen lance blows oxygen into the converter and controls the flow rate at 800Nm 3 / min, deoxidizer (25% metal calcium powder, 10% metal aluminum powder) and alloy are added during the steel tapping process for deoxidation and alloying; then the chemical composition is precisely adjusted in the LF furnace, and deoxidation and inclusion removal are carried out by feeding calcium wire and passing argon gas with a flow rate of 10NL / min for 15 minutes, and the molten steel temperature is controlled at 1600℃; finally, vacuum degassing and further removal of inclusions and deep desulfurization are carried out in the VD furnace; S2, continuous casting: adopt argon seal (argon flow rate is 15NL / min) to protect the pouring technology, control the superheat of the tundish to 25~35℃, the crystallizer liquid level fluctuation is controlled within ±6mm, and the crystallizer soft water flow is controlled at 100m 3 / h, pulling speed 0.95m / min; light pressure reduction 8mm at the end of solidification, corner temperature of the ingot 910℃; ingot size 280*280*mm*6m; (3) Rolling: The preheating temperature is controlled at 550°C, and two-stage equalization 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 cooled to 320°C on the cooling bed and then bundled and collected in the insulation pit for slow cooling for 24 hours. The cooling rate after rolling is controlled at 0.5°C / s.

[0021] The metallographic structure of the prepared 09CrCuSb round steel is shown in Figure 1 The grain statistics software and the statistical organization percentage software were used to obtain the average ferrite grain size of the 09CrCuSb round steel prepared in this embodiment, which was 11.26 μm and the volume fraction of the yellow block organization was 0.00%.

[0022] Example 2 The present embodiment provides a high-strength sulfuric acid dew point corrosion resistant 09CrCuSb round steel and a preparation method thereof. The chemical composition of the 09CrCuSb round steel in the present embodiment is as follows by mass percentage: 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 rest is Fe and unavoidable impurities. At this time, Cu / Ni=2.35.

[0023] The specific preparation method is as follows: S1. Steelmaking: First, use 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% metal calcium powder, 12% metal aluminum powder) and alloy are added during the steel tapping process for deoxidation and alloying; then the chemical composition is precisely adjusted in the LF furnace, and deoxidation and inclusion removal are carried out by feeding calcium wire and passing argon gas with a flow rate of 5NL / min for 20 minutes, and the molten steel temperature is controlled at 1620℃; finally, vacuum degassing and further removal of inclusions and deep desulfurization are carried out in the VD furnace; S2, continuous casting: adopt argon seal (argon flow rate is 7NL / min) to protect the pouring technology, control the superheat of the tundish to 27~38℃, the crystallizer liquid level fluctuation is controlled within ±6mm, and the crystallizer soft water flow is controlled at 98m 3 / h, pulling speed 0.95m / min; light pressure reduction 8mm at the end of solidification, corner temperature of the ingot 973℃; ingot size 240*240*mm*6m; (3) Rolling: The preheating temperature was controlled at 562°C, and two-stage equalization was adopted (the first stage heating temperature was 985°C, the time was 100 min; the second stage heating temperature was 1020°C, the time was 60 min); the starting rolling temperature was 972°C, the final rolling temperature was 857°C, and the rolling target size was 60 mm; after rolling, the steel was closely packed and cooled to 345°C on the cooling bed, and then bundled and collected in the insulation pit for slow cooling for 24 h. The cooling rate after rolling was controlled at 1.0°C / s.

[0024] The metallographic structure of the prepared 09CrCuSb round steel is shown in Figure 2 The grain statistics software and the statistical organization percentage software were used to obtain the average ferrite grain size of the 09CrCuSb round steel prepared in this embodiment of the present invention is 9.50 μm, and the volume fraction of the yellow block organization is 0.12%.

[0025] Example 3 The present embodiment provides a high-strength sulfuric acid dew point corrosion resistant 09CrCuSb round steel and a preparation method thereof. The chemical composition of the 09CrCuSb round steel in the present embodiment is as follows by mass percentage: 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 rest is Fe and unavoidable impurities. At this time, Cu / Ni=2.0.

[0026] The specific preparation method is as follows: S1. Steelmaking: First, use top and bottom combined blowing converter to make steel. Oxygen lance blows oxygen into the converter and controls the flow rate at 900Nm 3 / min, deoxidizer (35% metal calcium powder, 15% metal aluminum powder) and alloy are added during the steel tapping process for deoxidation and alloying; then the chemical composition is precisely adjusted in the LF furnace, and deoxidation and inclusion removal are carried out by feeding calcium wire and passing argon gas with a flow rate of 5NL / min for 20 minutes, and the molten steel temperature is controlled at 1630℃; finally, vacuum degassing and further removal of inclusions and deep desulfurization are carried out in the VD furnace; S2, continuous casting: adopt argon seal (argon flow rate is 7 NL / min) to protect the pouring technology, control the superheat of the tundish to 31~48℃, the crystallizer liquid level fluctuation is controlled within ±6mm, and the crystallizer soft water flow is controlled at 100m 3 / h, pulling speed 0.95m / min; light pressure reduction 8mm at the end of solidification, corner temperature of the ingot 983℃; ingot size 240*240*mm*6m; (3) Rolling: The preheating temperature was controlled at 594°C, and two-stage equalization was adopted (the first stage heating temperature was 1000°C, the time was 100 min; the second stage 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 in the insulation pit for slow cooling for 24 h. The cooling rate after rolling was controlled at 2.0°C / s.

[0027] The metallographic structure of the prepared 09CrCuSb round steel is shown in Figure 3 The grain statistics software and the statistical organization percentage software were used to obtain the average ferrite grain size of the 09CrCuSb round steel prepared in this embodiment of the present invention is 13.82 μm, and the volume fraction of the yellow block organization is 0.69%.

[0028] Comparative Example 1 This comparative example provides a high-strength sulfuric acid dew point corrosion resistant 09CrCuSb round steel and a preparation method thereof, which is basically the same as Example 1 except that: the chemical composition of the 09CrCuSb round steel is Cu=0.30%, Ni=0.20%. At this time, Cu / Ni=1.5.

[0029] The metallographic structure of the prepared 09CrCuSb round steel is shown in Figure 4 Using grain statistics software and statistical organization proportion software, it was found that the average grain size of ferrite in the 09CrCuSb round steel prepared in this comparative example was 28.92μm, and the volume fraction of yellow block organization was 0.62%.

[0030] Comparative Example 2 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.

[0031] The metallographic structure of the prepared 09CrCuSb round steel is shown in Figure 5 The grain statistics software and the statistical organization percentage software were used to obtain the average ferrite grain size of the 09CrCuSb round steel prepared in this embodiment of the present invention is 21.07 μm, and the volume fraction of the yellow block organization is 0.14%.

[0032] Furthermore, in order to understand the performance of the various 09CrCuSb round steels prepared above, the following tests were conducted on their performance.

[0033] The prepared 09CrCuSb round steels were tested for tensile strength, yield strength, elongation and sulfuric acid corrosion resistance rate. Among them, the tensile strength, yield strength and elongation were tested in accordance with GB / T 228.1-2021 "Metallic Materials Tensile Test Part 1: Room Temperature Test Method"; the sulfuric acid corrosion resistance rate test method was tested in accordance with JB / T 7901-1999 "Metallic Materials Laboratory Uniform Corrosion Full Immersion Test Method". The specific results are shown in Table 1 below.

[0034] Table 1 Performance results of various 09CrCuSb round steels

[0035] It can be seen from Table 1 that when the copper content is controlled at 0.40%~0.55%, the nickel content is controlled at 0.17%~0.26%, the ratio of Cu to Ni is controlled between 2~2.5, and the cooling rate after rolling is controlled between 0.5-2℃ / s, the average grain size of the prepared 09CrCuSb round steel is finer, and it has better mechanical properties and corrosion resistance.

[0036] 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 can be well applied to desulfurization equipment, boiler pressure vessels, air preheaters and other equipment, meeting the requirements of greenness, high application value and reduced production costs.

[0037] The specific raw materials not described in the present invention are all existing materials and can be directly purchased from the market.

[0038] The above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A 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%.

2. A method for preparing 09CrCuSb round steel as claimed in claim 1, characterized in that: 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 steelmaking process for deoxidation and alloying. Then, the chemical composition is adjusted in the LF furnace, deoxidation and inclusion removal are performed, and the temperature of the molten steel is controlled to be 1600~1650℃. Finally, vacuum degassing is performed in the VD furnace to further remove inclusions and deep desulfurization. S2, continuous casting: using argon seal protection pouring technology, control the tundish superheat at 25~50℃, the crystallizer liquid level fluctuation at ±6mm, and 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 casting is 900~1000℃; S3. Rolling: preheating temperature 540~600℃, two-stage equalizing heat is adopted, rolling start 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 insulation pit for slow cooling.

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

4. The preparation method according to claim 2, 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%.

5. The preparation method according to claim 2, characterized in that: Deoxidation and removal of inclusions 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.

6. The preparation method according to claim 2, characterized in that: In step S2, the argon gas flow rate is 7-22 NL / min.

7. The preparation method according to claim 2, characterized in that: The two-stage equalization 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.

8. The preparation method according to claim 2, characterized in that: In step S3, the cooling temperature after rolling is 300-420°C, and the cooling rate is 0.5-2°C / s.

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