CN114395690A - A kind of production technology of 300MPa grade high-strength enamel steel - Google Patents

Abstract

The invention discloses a production process of 300MPa grade high-strength enamel steel, which comprises the following steps: designing and controlling components: adding Ti element (about 0.015-0.035%); slab: stacking and slowly cooling; hot rolling: on the hot rolling process, the finish rolling temperature FT 7: 890 ± 20 ℃, coiling temperature CT: 580 ℃ and 640 ℃; cold rolling and annealing: the large compression ratio and low-temperature annealing process is adopted, the yield strength is 350-390MPa, the tensile strength is 465-500MPa, the elongation is more than 28 percent, and the performance is excellent; simulated enameling firing test: the enamel process is simulated, namely the enamel is cooled at room temperature after the temperature is kept at 850 ℃ for 10 minutes, the change degree of mechanical properties is detected, the yield strength is reduced by 2-23MPa, and the tensile strength is reduced by 45-57 MPa. The quality control of the 300MPa grade enamel steel for the water heater liner is completed through the experimental steps, and the scale explosion resistance performance index of the product is ensured to meet the requirements of users and standards.

Description

A kind of production process of 300MPa grade high-strength enamel steel

technical field

The invention relates to the field of enamel steel processing, in particular to a production process of 300MPa-level high-strength enamel steel.

Background technique

In recent years, water heaters have developed rapidly and are more and more favored by consumers. However, due to the increasingly fierce market competition, various water heater liner manufacturers are under the pressure of production costs, requiring lightweight materials, steel plates and strong pressure resistance. Therefore, the material must have high strength and certain formability. It is also required that the strength of the material decreases less after enamelling at a high temperature of 850 °C.

To this end, we propose a production process of 300MPa high-strength enamel steel to solve the above problems.

SUMMARY OF THE INVENTION

The relevant factors that can affect the anti-scale performance of enamelled steel are studied in depth by production test, including 1. The influence of chemical composition on service performance; 2. The influence of cold rolling of slabs on the production and quality of hot rolling; 3. Thermal The influence of rolling process (FT7/CT, etc.) on product performance and subsequent product quality; 4. The optimization of cold rolling reduction rate, the influence of continuous annealing process on performance; 5. The influence of user enamel process on the performance of finished products.

The above-mentioned technical purpose of the present invention is achieved through the following technical solutions:

A production process of 300MPa grade high-strength enamel steel, comprising the following steps:

Step 1, composition design and control: add Ti element (about 0.015-0.035%) in C-Mn steel, increase the amount of TiC and TiN in the steel to improve the hydrogen storage performance of the steel plate;

Step 2: Slab: slow cooling by stacking, the slab will experience a long time at a higher temperature, so that the supersaturated and desolubilized hydrogen diffuses out quickly;

Step 3. Hot rolling: In the hot rolling process, the control idea of high temperature final rolling and low temperature coiling is adopted, the final rolling temperature FT7: 890±20°C, and the coiling temperature CT: 580-640°C;

Step 4, cold rolling and annealing: using a large compression ratio and low temperature annealing process, the yield strength is 350-390MPa, the tensile strength is 465-500MPa, the elongation is more than 28%, and the performance is excellent;

Step 5. Simulated enamel sintering test: Simulate the enamel process, that is, after holding at 850°C for 10 minutes, cool at room temperature to detect the degree of change in mechanical properties, the yield strength is reduced by 2-23MPa, and the tensile strength is reduced by 45-57MPa.

Further, after completing the above steps, it is necessary to carry out the anti-scale explosion performance test: the scale explosion index TH value and the inspection and analysis of the 300MPa-grade high-strength enamel steel for the inner tank of the test water heater are generally considered to be TH≥6.7min/mm. ^2. The anti-scale explosion performance of the tested plate is qualified. The 300MPa grade samples have been tested, and the TH≥8.5min/mm ² has passed the hydrogen permeation test.

Further, the 300MPa grade high-strength enamel steel for the water heater inner tank in the first step includes titanium, and the content of titanium is controlled within the range of 0.015%-0.035%.

Further, the 300MPa grade high-strength enamel steel for the water heater liner in the step 1 includes manganese, and the manganese content is controlled within the range of 0.60-0.90% to ensure the adhesion of the steel plate enamel.

Further, the 300MPa grade high-strength enameled steel for the water heater inner tank in the step 1 includes nitrogen. For the 300MPa grade high-strength enameled steel, the large-size precipitates are TiN particles; as the N content increases, the number of TiN particles in the steel increases. The size increases and the size becomes larger, the hydrogen infiltration time is prolonged, and the anti-scaling performance of the steel plate is improved. Therefore, the nitrogen content is controlled between 0.0040-0.0075%.

Further, the 300MPa grade high-strength enamel steel used for the water heater inner tank in the first step includes carbon, and the carbon content is controlled within the range of 0.04-0.08%. For enamel steel, the higher the carbon content, the higher the baking deformation of enamel products. It is large, and the carbon atoms in the steel plate easily react with the oxygen in the enamel to generate carbon monoxide, which causes bubbles on the surface of the enamel product.

Further, in the step 4, cold rolling and annealing, increasing the cold rolling reduction rate is very beneficial to break the cementite and increase the number of lattice distortion zones. The grains become thinner, and the grain boundaries that prevent hydrogen diffusion increase, which is beneficial to anti-scale explosion. However, according to the rolling capacity of the cold rolling mill, the cold rolling reduction rate of 300MPa high-strength enamel steel for water heater inner tank is set as 55%-75%.

Further, in the step 4, cold rolling and annealing, in the annealing process, an annealing process that is more conducive to the aggregation and growth of the second phase particles is adopted, and the annealing temperature is controlled at 790-810°C.

To sum up, the present invention has the following beneficial effects:

Through the process research on the anti-scale explosion performance of enamel steel, the technicians can master the key process technologies in various production links of 300MPa high-strength enamel steel for water heater inner tank, and ensure that the anti-scale explosion performance index of the product meets the requirements of users and standards, and meets the needs of users. Require.

Description of drawings

Fig. 1 is a metallographic structure diagram of a production process of a 300MPa grade high-strength enameled steel of the present invention.

Detailed ways

The present invention will be clearly and completely described below with four embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

A production process of 300MPa grade high-strength enamel steel, comprising the following steps:

Step 1. Component design and control: Add Ti element (about 0.015-0.035%) to C-Mn steel, increase the amount of TiC and TiN in the steel to improve the hydrogen storage performance of the steel plate,

The 300MPa grade high-strength enameled steel used for the water heater inner tank includes titanium, and the content of titanium is controlled within the range of 0.015%-0.035%. For enamel steel, the higher the carbon content, the greater the baking deformation of the enamel product, and the carbon atoms in the steel plate easily react with the oxygen in the enamel to form carbon monoxide, causing bubbles on the surface of the enamel product.

The 300MPa grade high-strength enamel steel used for the inner tank of the water heater includes manganese. In order to ensure the adhesion of the steel plate enamel, the manganese content is controlled within the range of 0.60-0.90%. The 300MPa grade high-strength enameled steel used for the water heater inner tank includes nitrogen. For the 300MPa grade high-strength enameled steel, the large-sized precipitates are TiN particles; as the N content increases, the number of TiN particles in the steel increases and the size becomes larger, and the hydrogen infiltration time Prolonged, the anti-scalding performance of the steel plate is improved. Therefore, the nitrogen content is controlled between 0.0040-0.0075%;

Step 2. Slab: Slow cooling by stacking, the slab will experience a long time at a higher temperature, so that the supersaturated and desolubilized hydrogen diffuses out quickly, and the whole process is protected by pouring, and the slab is stacked slowly cooled to room temperature ;

Step 3. Hot rolling: in the hot rolling process, the control idea of high temperature final rolling and low temperature coiling is adopted. ±30℃, the casting billet is kept in the furnace for more than 130min, and a seven-stand hot tandem rolling mill is used, the final rolling temperature is controlled at 890±20℃, and the coiling temperature is 580-640℃;

Step 4. Cold rolling and annealing: adopt large compression ratio and low temperature annealing process, the yield strength is 350-390MPa, the tensile strength is 465-500MPa, the elongation is more than 28%, the performance is excellent, and the cold rolling pressure is increased. The reduction rate is very beneficial to break the cementite and increase the number of lattice distortion zones. With the increase of the cold rolling reduction rate, the grains after recrystallization and annealing become finer, and the grain boundaries that prevent hydrogen diffusion increase accordingly, which is beneficial to the resistance to resistance. However, according to the rolling capacity of the cold rolling mill, the relative reduction rate of cold rolling is 55-75%. Therefore, the cold rolling reduction rate of 300MPa high-strength enamel steel for water heater inner tank is set to 55%-75%. In the annealing process, an annealing process that is more conducive to the aggregation and growth of the second phase particles is adopted. (0.8-1.5)%;

Step 5. Simulated enamel firing test: Simulate the enamel process, that is, after holding at 850 ℃ for 10 minutes, cool down at room temperature to test the degree of change in mechanical properties, the yield strength is reduced by 2-23MPa, and the tensile strength is reduced by 45-57MPa. Furnace, that is, 850 ℃ for 10 minutes and then cooled at room temperature, as shown in Figure 1 after sintering.

After completing the above steps, it is necessary to carry out the anti-scale explosion performance test: the scale explosion index TH value and inspection and analysis of the 300MPa high ^- strength enamel steel for the test water heater inner tank are generally considered to be The anti-scale explosion performance of the test plate is qualified, and the 300MPa grade samples have been tested, and the TH≥8.5min/mm ² has passed the hydrogen permeation test.

Table 1 Chemical composition of the embodiment of the present invention

Example C Si Mn P S Ti N Example 1 0.06 0.05 0.69 0.010 0.012 0.025 0.053 Example 2 0.05 0.05 0.69 0.010 0.015 0.028 0.043 Example 3 0.06 0.04 0.66 0.009 0.011 0.024 0.060 Example 4 0.05 0.05 0.70 0.011 0.014 0.021 0.068

Table 2 Slab slow cooling process according to the embodiment of the present invention

Example stacking method Slow cooling time Measured temperature/℃ Example 1 stack, top 72h36min 153 Example 2 stacking, middle layer 73h06min 165 Example 3 stacking, middle layer 73h15min 163 Example 4 stack, bottom 73h46min 173

Table 3 The present invention implements rolling process parameters

Table 4 The present invention implements the mechanical properties of cold rolling

Example Yield strength/MPa Tensile strength/MPa Elongation/% Example 1 377 489 32.8 Example 2 367 481 29.5 Example 3 386 494 27.5 Example 4 385 493 27.4

Table 5 The embodiment of the present invention simulates the performance after enamel sintering

The basic principles and main features of the present invention and the advantages of the present invention have been shown and described above. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments, and the descriptions in the above-mentioned embodiments and the description are only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have Various changes and modifications fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (8)

1. a production technique of 300MPa grade high-strength enamel steel, is characterized in that: comprise the following steps: Step 1, composition design and control: adding Ti element (about 0.015-0.035%) in C-Mn steel, increasing the amount of TiC and TiN in the steel to improve the hydrogen storage performance of the steel plate; Step 2: Slab: slow cooling by stacking, the slab will experience a long time at a higher temperature, so that the supersaturated and desolubilized hydrogen diffuses out quickly; Step 3. Hot rolling: In the hot rolling process, the control idea of high temperature final rolling and low temperature coiling is adopted, the final rolling temperature FT7: 890±20°C, and the coiling temperature CT: 580-640°C; Step 4, cold rolling and annealing: using a large compression ratio and low temperature annealing process, the yield strength is 350-390MPa, the tensile strength is 465-500MPa, the elongation is more than 28%, and the performance is excellent; Step 5. Simulated enamel sintering test: Simulate the enamel process, that is, after holding at 850°C for 10 minutes, cool at room temperature to detect the degree of change in mechanical properties, the yield strength is reduced by 2-23MPa, and the tensile strength is reduced by 45-57MPa. 2. the production technique of a kind of 300MPa grade high-strength enamelled steel according to claim 1, is characterized in that: need to carry out anti-scale explosion performance detection after completing above-mentioned steps: carry out scale explosion index TH value inspection and analysis to test enamelled steel, generally It is considered that the anti-scale explosion performance of the enamel scale explosion sensitivity TH is greater than or equal to 6.7min/mm ² . After testing, the 300MPa high-strength enamel samples are all above 8.5min/mm ² , and all are qualified. 3. The production process of a 300MPa-level high-strength enamelled steel according to claim 2, wherein the 300MPa-level high-strength enamelled steel for the water heater inner tank in the step 1 includes titanium, and the content of titanium is controlled at 0.015% In the range of -0.035%, the titanium is a carbide forming element, and the precipitation phases are TiN, TiC, TiS, Ti4C2S2, etc., the amount of the precipitation phases will affect the hydrogen breakthrough time, and the more the precipitation phases, the longer the hydrogen breakthrough time. long. 4. the production process of a kind of 300MPa grade high-strength enameled steel according to claim 2, it is characterized in that: the water heater inner tank in the described step 1 includes manganese with 300MPa grade high-strength enameled steel, in order to ensure the adhesion of steel plate enamelling The manganese content is controlled within the range of 0.60-0.90%. 5. The production process of a 300MPa-level high-strength enamelled steel according to claim 2, wherein the water heater inner tank in the step 1 includes nitrogen with a 300MPa-level high-strength enamelled steel. It is said that the large-sized precipitates are TiN particles; as the N content increases, the number of TiN particles in the steel increases and the size becomes larger, the hydrogen infiltration time is prolonged, and the scale resistance of the steel plate is improved. Therefore, the nitrogen content is controlled between 0.0040-0.0075%. 6. The production process of a 300MPa-level high-strength enameled steel according to claim 2, characterized in that: the 300MPa-level high-strength enamelled steel for the water heater inner tank in the step 1 includes carbon, and the carbon content is controlled at 0.04-0.08 Within the range of %, for enameled steel, the higher the carbon content, the greater the baking deformation of the enamel product, and the carbon atoms in the steel plate easily react with the oxygen in the enamel to form carbon monoxide, which causes bubbles on the surface of the enamel product. 7. the production technique of a kind of 300MPa grade high-strength enamel steel according to claim 4, is characterized in that: described step 4, cold rolling and annealing, increase cold rolling reduction ratio to broken cementite and increase lattice The number of distortion zones is very favorable. With the increase of the cold rolling reduction rate, the grains after recrystallization and annealing become thinner, and the grain boundaries that prevent hydrogen diffusion increase, which is beneficial to anti-scale explosion. However, according to the rolling capacity of the cold rolling mill , Therefore, the cold rolling reduction rate of 300MPa grade high-strength enamel steel for water heater inner tank is set to 55%-75%. 8. The production process of a 300MPa grade high-strength enamelled steel according to claim 7, characterized in that: in the step 4, cold rolling and annealing, in the annealing process, it is more conducive to second-phase particle aggregation and long Large annealing process, the annealing temperature is controlled at 780-810 ℃.

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