Production method of low-alloy seawater corrosion resistant steel

Abstract

The invention discloses a production method of low-alloy seawater corrosion resistant steel. The production method comprises the steps of molten iron pretreatment, converter smelting, LF furnace refining, VD vacuum degassing and square billet continuous casting production. The design chemical components of the low-alloy seawater corrosion resistant steel comprise, by percentage, 0.10%-0.18% of C, 0.80%-1.00% of Si, 1.00%-1.10% of Mn, smaller than or equal to 0.018% of P, smaller than or equal to 0.008% of S, 0.05%-0.10% of Al, 0.10%-0.20% of Ti, smaller than or equal to 1.30% of Cr, 0.30%-0.40% of Cu, smaller than or equal to 0.30% of Mo and the balance Fe and other inevitable impurities. While the seawater corrosion resistance is ensured, the addition amount of the alloy is controlled as much as possible, the uniform and moderate grain size is obtained, and the requirements of steel for offshore structures are met.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a production method of low-alloy seawater corrosion-resistant steel. Background Art

[0002] The chemical or electrochemical reaction between metal and the surrounding environment medium, which causes deterioration and destruction, is called metal corrosion. From the perspective of thermodynamics, except for a very small number of metals (such as platinum, gold, etc.), general metals have a tendency to gradually change from elemental state to metallic compounds in the environment medium. Therefore, metal corrosion is a spontaneous destructive process, and the phenomenon of metal corrosion is very common.

[0003] Steel materials will be subject to various corrosion in the marine environment, such as corrosion caused by seawater and marine organisms, structural corrosion caused by aging of the coating, pitting corrosion caused by anodic dissolution due to Cl- adsorption on the metal surface, etc. The corrosion characteristics vary in different marine environments, and the corrosion mechanism and corrosion rate of steel vary greatly.

[0004] Generally speaking, the corrosion of marine structures (including fixed and mobile ones) includes different corrosion conditions in five different parts: marine atmosphere zone, splash zone, full immersion zone, tidal zone and sea soil zone, and there are also differences in their composition design. Among them, the marine atmosphere zone is marine atmosphere corrosion, and the other four zones are collectively referred to as seawater corrosion. Therefore, low-alloy corrosion-resistant steel for marine development actually includes two types of steel resistant to atmospheric (marine atmosphere) corrosion and steel resistant to seawater corrosion.

[0005] Metal corrosion brings huge economic losses to mankind. According to statistics, the amount of metal discarded due to corrosion accounts for 20% to 40% of the annual metal production. For marine engineering steel, structural failure caused by corrosion has caused marine shipwrecks, as well as casualties caused by oil transportation, engineering platforms, and submarine oil and gas pipelines. This has caused great physical and mental harm to people, and the indirect economic losses are countless. In addition, the corrosion of marine steel may also cause heavy metal ions to flow into the environment, leading to marine environmental pollution, endangering the life and health of humans, animals and plants, and destroying the ecological balance of the earth.

[0006] Therefore, in order to reduce the various hazards and economic losses caused by corrosion of marine steel, it is of great significance to develop a low-alloy seawater corrosion-resistant steel. Summary of the invention

[0007] The purpose of the present invention is to provide a method for producing low-alloy seawater corrosion-resistant steel, which can control the amount of alloy added as much as possible while ensuring its seawater corrosion resistance, obtain a uniform and moderate grain size, and meet the requirements of steel quality for offshore structures.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] The present invention provides a production method for low alloy seawater corrosion resistant steel, comprising: molten iron pretreatment - converter smelting - LF furnace refining - VD vacuum degassing - billet continuous casting production; wherein:

[0010] Hot metal pretreatment: Before smelting, hot metal is first desulfurized to reduce the sulfur content in the molten steel. Passivated magnesium particles are used for desulfurization. Nitrogen is sprayed into the hot metal. The particle diameter of the passivated magnesium should be controlled at 0.5-2.0 mm. The content exceeding this range is not more than 5%. The spraying amount is 0.4-0.5 kg / t iron. The passivated magnesium reacts with the sulfur in the hot metal to form slag, and the sulfur content in the hot metal is finally reduced to below 0.005%.

[0011] Converter smelting: The focus of this stage is to ensure that the C and P elements meet the target requirements, while controlling the tapping temperature ≥1610℃; in addition, carbon pulling and supplementary blowing, single slag operation, slag blocking tapping, and low-high-low gun position control are adopted for the oxygen supply system, and the gun position is 1.1-1.5m; single slag or double slag is adopted according to the conditions of the molten iron, and the end point basicity is controlled at 2.7-3.5; SiAlMn is used as the final deoxidizer, silicon manganese and manganese iron alloy are added during the tapping process, and the end point control target is to blow once for tapping, the blowing time is ≤1.5min, the tapping carbon is 0.03%≤C≤0.05%, and T≥1610℃;

[0012] LF furnace refining: This stage is mainly to adjust the temperature of molten steel, desulfurize and improve the purity of molten steel. It is heated by graphite electrodes and reduced slag is produced to form a reducing atmosphere in the furnace. At the same time, argon is blown at the bottom for full stirring. According to the steel supply conditions, the composition and temperature are fine-tuned. SiAlCaBa composite deoxidizer is used for deoxidation, and BFe is added after sufficient deoxidation.

[0013] VD vacuum degassing: The molten steel after ladle refining is vacuum degassed in a VD furnace to further reduce the content of harmful gases in the steel and improve the cleanliness of the steel;

[0014] Continuous casting production: This stage is mainly to prevent the secondary oxidation of molten steel and produce ingots with qualified surface and internal quality. The temperature of the first furnace of the upper stage is controlled at 1610-1620℃, and the process furnace is controlled at 1575-1595℃; the baking time of the tundish is 3-3.5h, and the baking temperature is>1250℃; the long nozzle of the protective casting ladle uses an asbestos bowl for each furnace of steel and argon is blown at the long nozzle, so that the T-shaped nozzle does not emit carbon flowers; the covering agent is added to the tundish so that the steel liquid surface does not shine; the immersion nozzle is strictly centered, and the immersion nozzle uses a sealing ring; low-carbon steel protective slag is used; protective slag is added less and more frequently in the crystallizer, and carbon flowers are not allowed on the steel liquid surface; high-pressure water is used for descaling after leaving the furnace;

[0015] The technical parameters controlled in the high-speed wire rolling process are:

[0016] Rolling temperature: 1050±20℃;

[0017] Final rolling temperature 950±20℃;

[0018] The cooling beds are closely packed and the spacing is less than 10mm;

[0019] The designed chemical composition of the low alloy seawater corrosion resistant steel is required to be calculated in percentage as follows: C: 0.10-0.18%, Si: 0.80-1.00%, Mn: 1.00-1.10%, P: ≤0.018%, S: ≤0.008%, Al: 0.05-0.10%, Ti: 0.10-0.20%, Cr: ≤1.30%, Cu: 0.30-0.40%, Mo: ≤0.30%, and the rest is Fe and other unavoidable impurities.

[0020] Furthermore, the designed chemical composition of the low alloy seawater corrosion resistant steel is required to be calculated in percentage as follows: C: 0.105%, Si: 0.85%, Mn: 1.06%, P: 0.015%, S: 0.007%, Al: 0.07%, Cu: 0.33%, and the rest is Fe and other inevitable impurities.

[0021] Furthermore, the designed chemical composition of the low alloy seawater corrosion resistant steel is required to be calculated in percentage as follows: C: 0.10%, Si: 0.87%, Mn: 1.08%, P: 0.017%, S: 0.006%, Al: 0.09%, Ti: 0.18%, Cu: 0.38%, and the rest is Fe and other inevitable impurities.

[0022] Furthermore, the designed chemical composition of the low-alloy seawater corrosion-resistant steel is required to be calculated in percentage as follows: C: 0.12%, Si: 0.95%, Mn: 1.08%, P: 0.018%, S: 0.008%, Al: 0.10%, Ti: 0.19%, Cr: 1.28%, Cu: 0.39%, Mo: 0.27%, and the rest is Fe and other unavoidable impurities.

[0023] Furthermore, the low-alloy seawater corrosion-resistant steel prepared by the present invention has excellent tensile and yield properties, high purity, and long service life.

[0024] Compared with the prior art, the beneficial technical effects of the present invention are:

[0025] The low-alloy seawater corrosion-resistant steel prepared by the present invention has excellent tensile and yield properties, high purity and long service life. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with embodiments:

[0027] This embodiment provides a method for producing low alloy seawater corrosion resistant steel, which comprises the steps of molten iron pretreatment - converter smelting - LF furnace refining - VD vacuum degassing - continuous casting production.

[0028] The specific ingredients of each embodiment are as follows:

[0029] Embodiment 1: The designed chemical composition of the low alloy seawater corrosion resistant steel is required to be calculated in percentage as follows: C: 0.105%, Si: 0.85%, Mn: 1.06%, P: 0.015%, S: 0.007%, Al: 0.07%, Cu: 0.33%, and the rest is Fe and other unavoidable impurities.

[0030] Embodiment 2: The designed chemical composition of the low alloy seawater corrosion resistant steel is required to be calculated in percentage as follows: C: 0.10%, Si: 0.87%, Mn: 1.08%, P: 0.017%, S: 0.006%, Al: 0.09%, Ti: 0.18%, Cu: 0.38%, and the rest is Fe and other unavoidable impurities.

[0031] Example 3: The designed chemical composition of the low-alloy seawater corrosion-resistant steel is required to be calculated in percentage as follows: C: 0.12%, Si: 0.95%, Mn: 1.08%, P: 0.018%, S: 0.008%, Al: 0.10%, Ti: 0.19%, Cr: 1.28%, Cu: 0.39%, Mo: 0.27%, and the rest is Fe and other unavoidable impurities.

[0032] The process parameters for rolling seawater corrosion resistant steel in various embodiments are shown in Table 1:

[0033] Table 1: Process parameters for rolling seawater corrosion resistant steel in various embodiments:

[0034]

[0035] The mechanical properties of the seawater corrosion resistant steel rolled in each embodiment are shown in Table 2:

[0036] Table 2: Mechanical properties of the seawater corrosion resistant steel after rolling in various embodiments:

[0037] Example <![CDATA[R (p0.2) / MPa]]> <![CDATA[R m / MPa]]> A％ Z％ Yield ratio 1 401 710 20.5 29 0.56 2 422 795 24.0 34 0.53 3 788 902 29.8 38 0.87

[0038] The corrosion rates of the seawater corrosion resistant steel after rolling in each embodiment are shown in Table 3:

[0039] Table 3: Corrosion rate of seawater corrosion resistant steel after rolling in various examples (g / m 2 / h)

[0040]

[0041] Through random sampling of the above production results, it can be analyzed from Table 2 that the seawater corrosion-resistant steel has good yield and tensile strength, and it can be analyzed from Table 3 that its corrosion weight loss rate is low and the corrosion resistance effect is good.

[0042] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for producing low alloy seawater corrosion resistant steel, characterized in that: include: Hot metal pretreatment - converter smelting - LF furnace refining - VD vacuum degassing - billet continuous casting production; including: Hot metal pretreatment: Before smelting, hot metal is first desulfurized to reduce the sulfur content in the molten steel. Passivated magnesium particles are used for desulfurization. Nitrogen is sprayed into the hot metal. The particle diameter of the passivated magnesium should be controlled at 0.5-2.0 mm. The content exceeding this range is not more than 5%. The spraying amount is 0.4-0.5 kg / t iron. The passivated magnesium reacts with the sulfur in the hot metal to form slag, and the sulfur content in the hot metal is finally reduced to below 0.005%. Converter smelting: The focus of this stage is to ensure that the C and P elements meet the target requirements, while controlling the tapping temperature ≥1610℃; in addition, carbon pulling and supplementary blowing, single slag operation, slag blocking tapping, and low-high-low gun position control are adopted for the oxygen supply system, and the gun position is 1.1-1.5m; single slag or double slag is adopted according to the conditions of the molten iron, and the end point basicity is controlled at 2.7-3.5; SiAlMn is used as the final deoxidizer, silicon manganese and manganese iron alloy are added during the tapping process, and the end point control target is to blow once for tapping, the blowing time is ≤1.5min, the tapping carbon is 0.03%≤C≤0.05%, and T≥1610℃; LF furnace refining: This stage is mainly to adjust the temperature of molten steel, desulfurize and improve the purity of molten steel. It is heated by graphite electrodes and reduced slag is produced to form a reducing atmosphere in the furnace. At the same time, argon is blown at the bottom for full stirring. According to the steel supply conditions, the composition and temperature are fine-tuned. SiAlCaBa composite deoxidizer is used for deoxidation, and BFe is added after sufficient deoxidation. VD vacuum degassing: The molten steel after ladle refining is vacuum degassed by VD furnace to further reduce the harmful gas content in the steel and improve the cleanliness of the steel; Continuous casting production: This stage is mainly to prevent the secondary oxidation of molten steel and produce ingots with qualified surface and internal quality. The temperature of the first furnace of the upper stage is controlled at 1610-1620℃, and the process furnace is controlled at 1575-1595℃; the baking time of the tundish is 3-3.5h, and the baking temperature is>1250℃; the long nozzle of the protective casting ladle uses an asbestos bowl for each furnace of steel and argon is blown at the long nozzle, so that the T-shaped nozzle does not emit carbon flowers; the covering agent is added to the tundish so that the steel liquid surface does not shine; the immersion nozzle is strictly centered, and the immersion nozzle uses a sealing ring; low-carbon steel protective slag is used; protective slag is added less and more frequently in the crystallizer, and carbon flowers are not allowed on the steel liquid surface; high-pressure water is used for descaling after leaving the furnace; The technical parameters controlled in the high-speed wire rolling process are: Rolling temperature: 1050±20℃; Final rolling temperature 950±20℃; The cooling beds are closely packed and the spacing is less than 10mm; The designed chemical composition of the low alloy seawater corrosion resistant steel is required to be calculated in percentage as follows: C: 0.10-0.18%, Si: 0.80-1.00%, Mn: 1.00-1.10%, P: ≤0.018%, S: ≤0.008%, Al: 0.05-0.10%, Ti: 0.10-0.20%, Cr: ≤1.30%, Cu: 0.30-0.40%, Mo: ≤0.30%, and the rest is Fe and other unavoidable impurities.

2. The method for producing low alloy seawater corrosion resistant steel according to claim 1, characterized in that: The designed chemical composition of the low alloy seawater corrosion resistant steel is required to be calculated in percentage as follows: C: 0.105%, Si: 0.85%, Mn: 1.06%, P: 0.015%, S: 0.007%, Al: 0.07%, Cu: 0.33%, and the rest is Fe and other inevitable impurities.

3. The method for producing low alloy seawater corrosion resistant steel according to claim 1, characterized in that: The designed chemical composition of the low alloy seawater corrosion resistant steel is required to be calculated in percentage as follows: C: 0.10%, Si: 0.87%, Mn: 1.08%, P: 0.017%, S: 0.006%, Al: 0.09%, Ti: 0.18%, Cu: 0.38%, and the rest is Fe and other unavoidable impurities.

4. The method for producing low alloy seawater corrosion resistant steel according to claim 1, characterized in that: The designed chemical composition of the low alloy seawater corrosion resistant steel is required to be calculated in percentage as follows: C: 0.12%, Si: 0.95%, Mn: 1.08%, P: 0.018%, S: 0.008%, Al: 0.10%, Ti: 0.19%, Cr: 1.28%, Cu: 0.39%, Mo: 0.27%, and the rest is Fe and other unavoidable impurities.

5. The method for producing low alloy seawater corrosion resistant steel according to claim 1, characterized in that: The low-alloy seawater corrosion-resistant steel prepared by the present invention has excellent tensile and yield properties, high purity and long service life.

Images