CN113564481A

CN113564481A - Low-cost sulfate acid dew point corrosion resistant steel plate and manufacturing method thereof

Info

Publication number: CN113564481A
Application number: CN202110891223.1A
Authority: CN
Inventors: 石践; 胡学文; 何博; 王海波; 郭锐; 汪飞; 朱涛; 李雄杰
Original assignee: Maanshan Iron and Steel Co Ltd
Current assignee: Maanshan Iron and Steel Co Ltd
Priority date: 2021-08-04
Filing date: 2021-08-04
Publication date: 2021-10-29

Abstract

The invention provides a low-cost sulfate acid dew point corrosion resistant steel plate and a manufacturing method thereof, and the steel plate comprises the following components: c: 0.05-0.10%; si: 0.30% -0.70%; mn: 0.60-0.90%; p: less than or equal to 0.025 percent; s: less than or equal to 0.006 percent; cr: 0.60-1.00%; ni: 0.10-0.25%; cu: 0.20-0.40%; and Als: 0.020-0.050%; ti: 0.010-0.040%; sb: 0.04-0.10%; the balance of Fe and inevitable impurities; the weather resistance index I is more than or equal to 6.0, the alloy of the invention has lower cost, does not add noble metal Mo, reduces the production and manufacturing cost, and has excellent obdurability matching. And the paint has good atmospheric corrosion resistance and good sulfate acid dew point corrosion resistance.

Description

Low-cost sulfate acid dew point corrosion resistant steel plate and manufacturing method thereof

Technical Field

The invention belongs to the field of steel materials and manufacturing thereof, and particularly relates to a low-cost sulfate acid dew point corrosion resistant steel plate and a manufacturing method thereof.

Background

In the fields of electric power, petrifaction, metallurgy and the like, coal, petroleum and household garbage are combusted to generate byproducts such as water, sulfur dioxide, sulfur trioxide, hydrogen chloride, nitrogen oxide, carbon dioxide and the like, and the byproducts are condensed when the byproducts are lower than the dew point temperature of sulfuric acid (about 100-150 ℃) and the dew point temperature of hydrochloric acid (about 50-80 ℃), so that the hydrochloric acid and the sulfuric acid are formed to cause serious corrosion to equipment, perforation and leakage occur, and the hidden danger is very large.

At present, most of the existing similar products of domestic enterprises are sulfuric acid dew point corrosion resistant steel, but the similar products are often corroded by sulfuric acid and hydrochloric acid on a conveying pipeline, a flue and a chimney in the industries of metallurgy, electric power, petrochemical industry and the like, so that the research and development of steel materials capable of resisting the sulfuric acid and hydrochloric acid dew point corrosion simultaneously have important significance.

CN 107868919A published in 2018, 4 and 3 discloses steel resistant to hydrochloric acid and sulfuric acid corrosion and a preparation method thereof, wherein the steel comprises the following chemical components: c: 0.02% -0.04%, Si: 0.2-0.4%, Mn: 0.8% -1.0%, P: less than or equal to 0.01 percent, S: 0.005-0.015%, Cu: 0.25-0.35%, Cr: 0.3% -0.4%; ni: 0.1 to 0.2 percent; sb: 0.05-0.15%, Sn: 0.05-0.15%, Mo: 0.05 to 0.15%, and the balance of Fe and inevitable impurities. However, Sb and Sn deteriorate the manufacturability, particularly hot workability, and the billet has severe surface cracks during continuous casting and heating, and the addition of Mo greatly increases the alloy cost.

CN104451457A published 3, 25.2015 discloses a hot-rolled steel strip resistant to hydrochloric acid and sulfuric acid corrosion and a production method thereof, and is characterized in that the hot-rolled steel strip comprises the following components in percentage by mass: less than or equal to 0.060% of C, less than or equal to 0.55% of Si, 0.50-1.20% of Mn, less than or equal to 0.035% of P, less than or equal to 0.035% of S, less than or equal to 0.35% of Ni, less than or equal to 0.10% of Cr, Cu: 0.20-0.50%, Nb is less than or equal to 0.060%, Sb is less than or equal to 0.15%, Ca: 0.0005 to 0.0040 percent of Al, less than or equal to 0.060 percent of N, less than or equal to 0.0080 percent of N, and the balance of Fe and inevitable impurities. In order to further improve the corrosion resistance to hydrochloric acid and sulfuric acid, the invention also requires that: contains one or two or more elements selected from the following groups (1) to (2): (1) mo: 0.01-0.25%, RE: 0.001 to 0.060%, Sn: 0.01-0.15% of one or more elements; (2) ti: 0.001 to 0.060%, V: 0.001 to 0.060%. The addition of noble metals such as Mo, RE, V, Sn, alone or in combination, further increases the cost.

The prior art contains one or more of Mo, Sn, RE, V and Nb, and has higher cost and high casting blank crack sensitivity.

Disclosure of Invention

The invention aims to provide a low-cost sulfate acid dew point corrosion resistant steel plate, which has low cost and excellent sulfate acid dew point corrosion resistance by optimizing the proportion of key alloy elements.

The invention also aims to provide a manufacturing method of the low-cost sulfate acid dew point corrosion resistant steel plate, which designs a production process matched with a formula, and produces the steel plate with good atmospheric corrosion resistance and good sulfate acid dew point corrosion resistance.

The specific technical scheme of the invention is as follows:

a low-cost sulfate acid dew point corrosion resistant steel plate comprises the following components in percentage by mass:

c: 0.05-0.10%; si: 0.30% -0.70%; mn: 0.60-0.90%; p: less than or equal to 0.025 percent; s: less than or equal to 0.006 percent; cr: 0.60-1.00%; ni: 0.10-0.25%; cu: 0.20-0.40%; and Als: 0.020-0.050%; ti: 0.010-0.040%; sb: 0.04-0.10%; the balance of Fe and inevitable impurities.

Controlling the Cu/Sb: 3-6; ensure sufficient Cu generation₂Sb, improving the sulfuric acid corrosion resistance. Considering that the yield of Sb is only about 85 percent, and in addition, part of Sb also participates in Sb₂O₃And Sb₂O₅The invention controls the Cu/Sb: 3-6, ensuring sufficient Cu generation₂Sb。

The low-cost sulfate acid dew point corrosion resistant steel plate meets the weather resistance index I of more than or equal to 6.0;

preferably, the weather resistance index I is more than 6.5, and the paint has good atmospheric corrosion resistance. The acid corrosion resistance is improved through the matching design of Cu-Cr-Ni-Sb elements.

The weathering index I of this steel grade was calculated with reference to the formula Legault-Leckie modified in American society for testing and materials Standard ASTM G101-01, I ═ 26.01 (% Cu) +3.88 (% Ni) +1.20 (% Cr) +1.49 (% Si) +17.28 (% P) -7.29 (% Cu) x (% Ni) -9.10 (% Ni) x (% P) -33.39 (% Cu)²≥6.0。

The low-cost sulfate acid dew point corrosion resistant steel plate has a metallographic structure of ferrite and pearlite, and the grain size of the ferrite is 9-11 grades; the pearlite area accounts for 12-18%.

The low-cost sulfate acid dew point corrosion resistant steel plate has the yield strength of more than or equal to 345MPa, the tensile strength of more than or equal to 470MPa, the elongation of more than or equal to 26 percent, the transverse Charpy V-shaped impact energy KV2 of more than 180J (sample size: 10mm multiplied by 55mm) at the temperature of minus 40 ℃, and has excellent obdurability matching.

The invention provides a manufacturing method of a low-cost sulfate acid dew point corrosion resistant steel plate, which comprises the steps of pretreating molten iron;

the molten iron is pretreated and deeply desulfurized until the [ S ] is less than or equal to 0.006%;

the manufacturing method also comprises refining, wherein the refining adopts an LF furnace for treatment, the content of non-metallic inclusions is reduced, the content of S is controlled to be below 0.006 percent, and the cleanliness of the molten steel is improved.

The manufacturing method also comprises the step of cleaning corners piece by piece after the casting blank is slowly cooled, so that the risk of cracks at the hot edge curling part is reduced.

The manufacturing method also comprises the step of heating the plate blank, wherein the heating temperature is 1200-1250 ℃.

The manufacturing method also comprises hot continuous rolling, and specifically comprises the following steps: after heating, the plate blank is taken out of the furnace, and then rough rolling and finish rolling are carried out after high-pressure water descaling; in the rough rolling stage, 2 four-roller reversible rolling mills are adopted for rolling back and forth, and the final rolling temperature of rough rolling in the rough rolling stage is controlled to be above 1050 ℃; and in the finish rolling stage, a 7-frame four-roller CVC rolling mill is adopted for continuous rolling, and the finish rolling temperature is 850-890 ℃.

And further, after finishing the finish rolling, performing controlled cooling and coiling, wherein the coiling temperature is controlled to be 600-670 ℃, and the hot rolled coil is air-cooled to room temperature. The chloride ion has small radius and strong penetrability to the oxide rust layer, and then the chloride ion diffuses to the grain boundary and is enriched in the grain boundary to further corrode the steel matrix. Therefore, the invention takes the regulation and control of ferrite as an important means for resisting the dew point corrosion of hydrochloric acid, and adopts the coiling at 600-670 ℃ to control the grain size of the ferrite to be 9-11 grade. The method avoids the size of excessively fine grains, shortens the length of a crystal boundary which can be eroded by chloride ions, and reduces the degree of corrosion of hydrochloric acid along the crystal.

Compared with the prior art, the invention realizes the dual effect of sulfate acid dew point corrosion resistance only by adding Sb in the conventional hot continuous rolling plate and strip production line, and meanwhile, the alloy has lower cost and is more competitive in the similar products. According to the invention, through the matching design of Cu-Cr-Ni-Sb elements, noble metals Mo and Sn are not added, and the production and manufacturing cost is reduced. The mechanical property of the material is as follows: the yield strength is more than or equal to 345MPa, the tensile strength is more than or equal to 470MPa, the elongation is more than or equal to 26 percent, the transverse Charpy V-shaped impact energy KV2 at minus 40 ℃ is more than 180J (the sample size is 10mm multiplied by 55mm), and the high-strength high-toughness composite material has excellent strength and toughness matching. And the paint has good atmospheric corrosion resistance and good sulfate acid dew point corrosion resistance.

Drawings

FIG. 1 is a metallographic structure diagram of the structure of example 1 of the present invention;

FIG. 2 is a metallographic structure diagram according to example 2 of the present invention;

FIG. 3 is a metallographic structure chart according to example 3 of the present invention;

FIG. 4 is a metallographic structure diagram of comparative example 4 of the present invention;

FIG. 5 is a metallographic structure diagram of comparative example 5 of the present invention;

FIG. 6 is a comparison graph of the micro-corrosion morphology of the surfaces of examples 1 to 3, comparative examples 4 to 5 and carbon steel Q235B according to the present invention;

FIG. 7 is a graph comparing the side macro corrosion of example 2 of the present invention with carbon steel Q235B.

Detailed Description

The invention provides a low-cost sulfate acid dew point corrosion resistant steel plate and a manufacturing method thereof, wherein the steel plate comprises the following chemical components in percentage by weight: 0.05-0.10%; si: 0.30% -0.70%; mn: 0.60-0.90%; p: less than or equal to 0.025 percent; s: less than or equal to 0.006 percent; cr: 0.60-1.00%; ni: 0.10-0.25%; cu: 0.20-0.40%; and Als: 0.020-0.050%; ti: 0.010-0.040%; sb: 0.04-0.10%; the balance of Fe and inevitable impurities.

The invention adopts the following method for improving the sulfate acid dew point corrosion resistance and the atmospheric corrosion resistance of the steel plate:

1) cu, Cr and Ni are main alloy elements for improving the corrosion resistance of the steel. Cr: obviously improve the passivation effect of steel and promote the formation of Cr on the surface of the steel₂O₃Designing the Cr content to be 0.60-1.00% in the case of an isodense passive film; cu: the rust layer on the steel surface is compact, the adhesion is improved, and fine second phase particles are separated out in the cooling process to improve the strength. But the melting point of Cu is low, and the billet is easy to crack in the heating and rolling processes due to excessively high content, so that the content of Cu is designed to be 0.20-0.40%; ni: improve the self-corrosion potential of the machine body and reduce the corrosion rate of the matrix, but Ni is a noble metal element, so as to avoid obviously increasing the manufacturing cost of steel, therefore, the content of Ni is controlled to be 0.10 to 0.25 percent. The Cu, Cr and Ni elements are reasonably matched, so that the alloy has good atmospheric corrosion resistance.

2) Sb element is added into the chemical components. Under the acid environment, a compact outer film rich in Sb element which is several times higher than the matrix is formed on the steel-containing surface, Sb is greatly enriched in the rust-containing layer, and Sb is₂O₃And Sb₂O₅The formation of the rust layer improves the compactness of the rust layer, promotes the surface passivation and inhibits the anode dissolution. Co-addition of Cu and Sb to form Cu₂The Sb film can effectively inhibit cathode reaction. Therefore, the sulfate acid corrosion resistance is good. However, too high a content thereof deteriorates hot workability and weldability of the steel. Therefore, the Sb content is designed to be 0.04-0.10%.

3) And Si is used for replacing Ni, so that the manufacturing cost is reduced. Si is one of effective elements for improving corrosion resistance, and has certain effect on resisting chloride ion corrosion. However, since the welding performance of the steel is lowered by excessively high Si content, the Si content is designed to be 0.30 to 0.70% in the present invention.

In addition, the chemical composition design of the invention also needs to meet the following requirements of weather resistance index I:

Furthermore, the matching design of elements ensures that the weather resistance index I is more than 6.5 and has good atmospheric corrosion resistance; controlling the Cu/Sb: 3-6; ensure sufficient Cu generation₂Sb, improving the sulfuric acid corrosion resistance.

The manufacturing method of the sulfate acid dew point corrosion resistant steel plate is produced by adopting a traditional hot continuous rolling process, and the process flow is molten iron pretreatment → converter smelting → LF external refining → continuous casting → slab heating → hot continuous rolling → laminar cooling → coiling, and specifically comprises the following steps:

1) the molten iron is pretreated and deeply desulfurized until the [ S ] is less than or equal to 0.006 percent, and the LF furnace is adopted for refining, so that the content of non-metallic inclusions is reduced, and the cleanliness of the molten steel is improved. The method adopts a high-quality clean steel smelting process control technology, controls the S content to be below 0.006 percent, and improves the purity of the molten steel by external refining.

2) After the casting blank is slowly cooled, corner parts are cleaned piece by piece, and the risk of cracks at the hot edge curling part is reduced.

3) The hot continuous rolling firstly heats the plate blank at 1200-1250 ℃, and the plate blank is taken out of a furnace and then is descaled by high-pressure water, and then is subjected to rough rolling and finish rolling. And in the rough rolling stage, 2 four-roller reversible rolling mills are adopted for rolling back and forth, the rolling temperature in the rough rolling stage is controlled to be more than 1050 ℃, and in the finish rolling stage, 7 four-roller CVC rolling mills are adopted for continuous rolling. And the finish rolling temperature is 850-890 ℃, after finish rolling, the cooling and coiling are controlled, the coiling temperature is controlled at 600-670 ℃, and the hot rolled coil is cooled to room temperature by air.

The steel plate produced by the method has a metallographic structure of ferrite and pearlite, and the grain size of the ferrite is 9-11 grades. Avoid the too fine grain size, reduce the hydrochloric acid along the crystal degree of corroding. The reason is that the radius of the chloride ion is small, the penetrating ability is strong, the compact structure of the rust layer is easy to damage, after the chloride ion penetrates through the rust layer, the chloride ion continuously diffuses to the matrix and finally gathers in the grain boundary, if the grain size is too small, the total length of the grain boundary is greatly increased, and the corrosion degree is also greatly increased. The yield strength of the obtained product is more than or equal to 345MPa, the tensile strength is more than or equal to 470MPa, the elongation is more than or equal to 26 percent, the transverse Charpy V-shaped impact energy KV2 at minus 40 ℃ is more than 180J (the sample size is 10mm multiplied by 55mm), and the product has excellent obdurability matching.

The specific steel plate produced by the above method is further illustrated by the following examples.

Example 1 to example 3

The invention provides a low-cost sulfate acid dew point corrosion resistant steel plate, which is smelted by adopting a molten iron pretreatment → converter steelmaking → LF external refining → a continuous casting process according to the chemical component requirements provided by the invention. Of these, 3 furnaces of steel were used as 3 examples of the present invention. After LF external refining, the chemical components in the steel meet the following weight percentages (wt%): c: 0.05-0.10%; si: 0.30% -0.70%; mn: 0.60-0.90%; p: less than or equal to 0.025 percent; s: less than or equal to 0.006 percent; cr: 0.60-1.00%; ni: 0.10-0.25%; cu: 0.20-0.40%; and Als: 0.020-0.050%; ti: 0.010-0.040%; sb: 0.04-0.10%; the balance of Fe and inevitable impurities.

Chemical components of the examples of the present invention are shown in table 1, and the balance not shown in table 1 is Fe and inevitable impurities. The weather resistance index I is more than 6.0. The component detection is carried out according to GB/T4336 atomic emission spectrometry (conventional method) for spark sources of carbon steel and medium and low alloy steel.

Comparative example 4

A low-cost sulfate acid dew point corrosion resistant steel sheet has chemical compositions as shown in Table 1, and the balance not shown in Table 1 is Fe and inevitable impurities.

Comparative example 5

TABLE 1 chemical composition of examples of the invention

After the continuous casting of the product, the rolling process adopts slab heating → high-pressure water descaling → 2 frame rough rolling → 7 frame finish rolling → laminar cooling → coiling, and the production process of the low-cost sulfate acid dew point corrosion resistant steel plate in the embodiment 1 comprises the following steps:

1) the molten iron is pretreated and deeply desulfurized to 0.004 percent of S, and LF furnace treatment is adopted for refining, so that the content of non-metallic inclusions is reduced, and the cleanliness of the molten steel is improved.

3) The hot continuous rolling firstly heats a plate blank at the heating temperature of 1243 ℃, and after the plate blank is taken out of a furnace, the plate blank is descaled by high-pressure water and then is subjected to rough rolling and finish rolling. And in the rough rolling stage, 2 four-roller reversible rolling mills are adopted for rolling back and forth, the finishing temperature in the rough rolling stage is controlled at 1065 ℃, and in the finish rolling stage, 7 four-roller CVC rolling mills are adopted for continuous rolling. And the finish rolling temperature of the finish rolling is 872 ℃, after the finish rolling is finished, the controlled cooling and coiling are carried out, the coiling temperature is controlled to be 634 ℃, and the hot rolled coil is air-cooled to the room temperature.

The production of low-cost sulfate acid dew point corrosion resistant steel sheets of examples 2 and 3 and comparative examples 4 and 5 is the same as that of example 1, except for the main rolling process parameters, which are shown in table 2. The properties of the test steels of the respective examples are shown in tables 2 and 3. Tensile properties test according to GB/T228.1-2010 "metallic materials tensile test part 1: the room temperature test method, the impact performance test is carried out according to GB/T229-.

The low-cost sulfate acid dew point corrosion resistant steel plate produced in the example 1 has a ferrite + pearlite structure, and the ferrite grain size is grade 10; pearlite area proportion is 13.7%;

the low-cost sulfate acid dew point corrosion resistant steel plate produced in example 2 has a ferrite plus pearlite structure, and the ferrite grain size is 9.5 grade; pearlite area percentage 14.8%;

the low-cost sulfate acid dew point corrosion resistant steel plate produced in example 3 has a ferrite plus pearlite structure, and the ferrite grain size is 11 grades; the pearlite area proportion was 17.9%.

The low-cost sulfate acid dew point corrosion resistant steel plate produced by the comparative example 4 has a structure of ferrite and pearlite, and the grain size of the ferrite is 11 grades; the pearlite area proportion was 15.9%.

The low-cost sulfate acid dew point corrosion resistant steel plate produced by the comparative example 5 has the structure of ferrite, bainite and pearlite, and the grain size of the ferrite is grade 12; the bainite area accounts for 14.2%; the pearlite area occupied ratio was 4.8%.

TABLE 2 Main Process parameters and mechanical Properties of the Rolling procedure in the examples

The soaking test of sulfuric acid and hydrochloric acid is carried out according to JB/T7901 'method for testing uniform corrosion and full immersion in metal material laboratories' and GB/T28907-. Table 4 shows the corrosion rates of examples 1 to 3, comparative examples 4 to 5, and comparative examples 1 to 3 (example 1 to example 3 of CN 104451457A). The invention has excellent sulfate acid dew point corrosion resistance at lower alloy cost.

TABLE 4 Corrosion rates for examples 1-3 and comparative examples 1-5

The invention can still have excellent corrosion resistance performance on the premise of economy due to the regulation and control of Cu/Sb and grain size.

In conclusion, the yield strength of the steel obtained by the embodiment of the invention according to the design range of the chemical components of the steel grade and the rolling process control technology is more than or equal to 345MPa, the tensile strength is more than or equal to 470MPa, the elongation is more than or equal to 26 percent, and the transverse Charpy V-shaped impact energy KV2 at minus 40 ℃ is more than 180J (the sample size is 10mm multiplied by 55 mm); compared with comparative examples 1-3 (CN104451457A), the steel has excellent sulfate acid dew point corrosion resistance under lower alloy cost, and can be widely applied to various fields of sulfate acid dew point corrosion resistance.

Comparative example 4Cu/Sb 2.15, lower than examples 1, 2, 3(4.63, 5.14, 3.25) (Cu/Sb: 3-6 is required); the grain size 11 was higher than those of examples 1 and 2(10, 9.5), and was the same as that of example 3 (requirements 9 to 11). The corrosion resistance is lower than that of examples 1, 2 and 3, and shows that under the condition of the same grain size, the higher the Cu/Sb ratio is, the better the corrosion resistance is, and the comparative example 4 is that the Cu/Sb ratio is 2.15 which is lower than that of the invention: 3 to 6, resulting in comparative example 4 having lower corrosion resistance than examples 1, 2, and 3.

Comparative example 5Cu/Sb 3.22, lower than examples 1, 2, 3(4.63, 5.14, 3.25) (Cu/Sb: 3-6 is required), and the same level as example 3. The grain size 12 is higher than that of examples 1, 2 and 3(10, 9.5 and 11) (9 to 11 are required). The corrosion resistance was lower than that of examples 1, 2 and 3, indicating that the smaller the grain size, the better the corrosion resistance, and the higher the grain size of comparative example 5 under the condition of the same level of Cu/Sb, resulting in that the corrosion resistance of comparative example 5 was lower than that of examples 1, 2 and 3.

The effect of Cu/Sb and grain size on corrosion resistance was found compared to comparative examples 4-5. I.e., the higher the Cu/Sb ratio, the better the corrosion resistance. The smaller the grain size, the better the corrosion resistance. Particularly, in the aspect of hydrochloric acid resistance dew point corrosion, the grain size has more remarkable influence on the hydrochloric acid resistance compared with Cu/Sb.

FIG. 6 is a comparison (2000 times) of the surface micro-corrosion morphology of examples 1 to 3, comparative examples 4 to 5 and carbon steel Q235B according to the present invention. The experimental conditions were: 20% sulfuric acid (24h) at 20 ℃. The surface of the steel plate is relatively flat in the embodiment 1, and a small amount of corrosion particle products and microcracks exist on the surface; example 2, the surface was smooth with only few corrosion particle products and no obvious cracks; example 3 generated a small amount of corrosion particles and microcracks, and examples 1-3 all exhibited better corrosion resistance; comparative examples 4 and 5 show a further increase in corrosion particle production and microcracking than example 3, and comparative example 5 shows a fractured morphology with a surface corrosion layer. The surface of the carbon steel has a large amount of loose granular corrosion products, and the corrosion resistance is poor.

FIG. 7 is a graph comparing the side macro corrosion of example 2 of the present invention and carbon steel, wherein the upper 3 samples are the products of example 2 and the lower 3 samples are carbon steel samples. The experimental conditions were: 20% sulfuric acid (24h) at 20 ℃. It can be seen that a large number of corrosion pits and holes appear on the side surface of the carbon steel, and the side surface of the embodiment 2 is complete and has no obvious holes.

Claims

1. The low-cost sulfate acid dew point corrosion resistant steel plate is characterized by comprising the following components in percentage by mass:

2. The low-cost sulfate acid dew point corrosion resistant steel sheet as claimed in claim 1, wherein the Cu/Sb: 3 to 6.

3. The low-cost sulfate acid dew point corrosion resistant steel sheet according to claim 1 or 2, wherein the low-cost sulfate acid dew point corrosion resistant steel sheet satisfies a weather resistance index I.gtoreq.6.0.

4. The low-cost sulfate acid dew point corrosion resistant steel sheet according to any one of claims 1 to 3, wherein the low-cost sulfate acid dew point corrosion resistant steel sheet has a metallographic structure of ferrite + pearlite, and a ferrite grain size of 9 to 11 grades; the pearlite area accounts for 12-18%.

5. A method for manufacturing a low-cost sulfate acid dew point corrosion resistant steel plate according to any one of claims 1 to 4, wherein the manufacturing method comprises a molten iron pretreatment; the molten iron is pretreated and deeply desulfurized until the [ S ] is less than or equal to 0.006 percent.

6. The manufacturing method according to claim 5, characterized in that the manufacturing method comprises slab heating, the heating temperature being 1200-1250 ℃.

7. The manufacturing method according to claim 5 or 6, characterized in that it further comprises hot continuous rolling, in particular: after heating, the slab is taken out of the furnace and is descaled by high pressure water, and then is subjected to rough rolling and finish rolling.

8. The manufacturing method according to claim 7, wherein the rough rolling and the final rolling are controlled to a temperature of 1050 ℃ or higher.

9. The manufacturing method according to claim 7 or 8, wherein the finish rolling is performed at a finish rolling temperature of 850 to 890 ℃.

10. The production method according to any one of claims 7 to 9, wherein the coiling temperature is controlled to 600 to 670 ℃.