Corrosion-resistant steel as well as preparation method and application thereof

Abstract

The invention relates to the technical field of steel and iron smelting, in particular to corrosion-resistant steel and a preparation method and application thereof, and the corrosion-resistant steel contains C, Si, Mn, P, S, Cr, Ni, Cu and Fe. The corrosion-resistant steel is prepared from, by weight, 0.15%-0.20% of C, 0.18%-0.28% of Si, 0.75%-0.85% of Mn, smaller than or equal to 0.020% of P, smaller than or equal to 0.010% of S, 0.85%-0.95% of Cr, 0.26%-0.32% of Ni, 0.20%-0.36% of Cu, and the sum of the content of Cr, the content of Ni and the content of Cu gt. 1.25%, 1.25%; and the model number of the corrosion-resistant steel is 15CrNiCu. By adjusting element components in the corrosion-resistant steel and optimizing process parameters, the problems of cracking, embrittlement and descaling in the prior art are effectively solved, and meanwhile, the corrosion resistance and the mechanical property of the steel are improved.

Description

Technical Field

[0001] The invention relates to the technical field of steel smelting, and in particular to corrosion-resistant steel and a preparation method and application thereof. Background Art

[0002] 15CrNiCu is a typical low-carbon alloy cold heading steel resistant to atmospheric corrosion. It is mainly used to make corrosion-resistant special-shaped bolts for pipelines and flange connections. It is used in conjunction with 08CrNiCu nut materials. The products are mainly exported to European and American countries. A small amount of Cr, Ni, and Cu elements are added in the composition design to form a protective film on the surface of the steel, replacing the surface galvanizing / painting layer, so that it has good corrosion resistance in the atmosphere. At the same time, the alloy elements can enhance the mechanical properties of the material. However, on the one hand, Ni and Cu steels have strong crack sensitivity in continuous casting billets, and transverse cracks are prone to occur at the corners, and star-shaped cracks are very likely to appear on the surface of the billet; on the other hand, after the billet is heated at high temperature, Cu is prone to precipitation embrittlement at the grain boundary, affecting the hot rolling plasticity. At the same time, the presence of Ni significantly increases the adhesion of the oxide scale, resulting in increased difficulty in descaling the billet after it comes out of the heating furnace. At the same time, customer processing requires that the oxide scale on the surface of the rolled disc is free of red rust and no shedding. These problems limit the further improvement of its production efficiency and product quality. Therefore, it is particularly important to develop a new preparation method for 15CrNiCu steel that meets the requirements. Summary of the invention

[0003] The purpose of the present invention is to solve the problems in the prior art that the continuous casting billet has strong crack sensitivity, transverse cracks are prone to occur at the corners, and star-shaped cracks are extremely prone to occur on the surface of the billet. At the same time, after the billet is heated at high temperature, Cu is easily precipitated at the grain boundary and embrittled, affecting the hot rolling plasticity. The presence of Ni significantly increases the adhesion of the oxide scale, resulting in increased difficulty in descaling the billet after it comes out of the heating furnace. Thus, a corrosion-resistant steel and a preparation method and application thereof are provided. By adjusting the element composition in the corrosion-resistant steel and optimizing the process parameters, the crack, embrittlement and descaling problems in the prior art are effectively solved, and the corrosion resistance and mechanical properties of the steel are improved.

[0004] In order to achieve the above-mentioned object, in a first aspect, the present invention provides a corrosion-resistant steel, which contains C, Si, Mn, P, S, Cr, Ni, Cu and Fe; wherein:

[0005] The contents of the elements in the corrosion-resistant steel are as follows by weight percentage: C content is 0.15-0.20%, Si content is 0.18-0.28%, Mn content is 0.75-0.85%, P content is ≤0.020%, S content is ≤0.010%, Cr content is 0.85-0.95%, Ni content is 0.26-0.32%, Cu content is 0.20-0.36%, and Cr content + Ni content + Cu content>1.25%;

[0006] The type of the corrosion-resistant steel is 15CrNiCu.

[0007] Preferably, the atmospheric corrosion resistance index I of the corrosion-resistant steel is ≥ 6.0; wherein,

[0008] I=26.01(%Cu)+3.88(%Ni)+1.20(%Cr)+1.49(%Si)+17.28(%P)-7.29(%Cu)(%Ni)-9.10(%Ni)(%P)-33.39(%Cu) 2 .

[0009] In a second aspect, the present invention provides a method for preparing corrosion-resistant steel, which comprises: converter smelting, LF furnace refining, continuous casting, heating, descaling, rolling, controlled cooling and coiling.

[0010] Preferably, the converter smelting comprises: adding scrap steel, copper blocks and nickel plates into a converter for smelting, wherein the C content in the obtained molten steel is 0.04-0.08wt%, the P content is ≤0.018wt%, and deoxidizer, alloy and lime are added during steel tapping.

[0011] Preferably, the LF furnace refining includes: the inlet temperature of the molten steel is ≥1530°C, the refining cycle is 35-40min, the soft blowing time is ≥15min, lime and slag-reducing agent are added to adjust the slag, and finally silicon carbide and carbon powder are added for deoxidation.

[0012] Preferably, 100-200m of pure calcium wire is fed before the soft blowing.

[0013] Preferably, the continuous casting conditions include: the target superheat of the tundish is 20-30°C, the cooling water volume is 115m 3 / h, the secondary cooling water ratio is 0.70L / kg, the basicity of the protective slag is 0.75-1.15, the viscosity of the protective slag is 1.65-2.25, and the melting point of the protective slag is 1200-1300℃.

[0014] Preferably, the heating conditions include: furnace time <150 min, maximum temperature of soaking section <1080° C., air-to-coal ratio of soaking section 0.55-0.6:1, and residual oxygen content <2%.

[0015] Preferably, the phosphorus removal method is high-pressure water phosphorus removal.

[0016] Preferably, the rolling conditions include: a starting rolling temperature of 1000-1020°C and a spinning temperature of 880-910°C.

[0017] More preferably, the cooling control method is to delay the cooling by opening the first three groups of heat preservation covers of the Stelmore air cooling line after the rolling.

[0018] In a third aspect, the present invention provides a corrosion-resistant steel prepared by the preparation method described in the second aspect.

[0019] In a fourth aspect, the present invention provides a use of the corrosion-resistant steel described in the first aspect or the third aspect in the preparation of corrosion-resistant special-shaped bolts.

[0020] According to the above technical scheme, the corrosion-resistant steel of the present invention adjusts the ratio of the main chemical elements of Cr, Ni, and Cu in the steel to ensure the strength performance requirements of the steel and the atmospheric corrosion resistance index I≥6.0; then by selecting appropriate crystallizer and continuous casting cooling process parameters, the superheat is controlled at the same time to reduce the star-shaped cracks of the ingot; further by adjusting the melting point and viscosity of the protective slag, the uniform heat transfer of the meniscus is controlled to reduce the crack defects of the ingot; then by controlling the heating temperature and selecting the appropriate rolling temperature, the precipitation embrittlement of the grain boundary after copper heating is reduced; the furnace time is controlled to avoid long-term high-temperature combustion, and at the same time, the heating technology of low residual oxygen, low air-to-coal ratio in the soaking section and appropriate reduction of the temperature in the high-temperature section is adopted to improve the descaling property of Ni-containing steel. The corrosion-resistant steel of the present invention has better atmospheric corrosion resistance, and also ensures its good mechanical properties and surface quality, so that it can be more widely used in the production of parts.

[0021] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0023] Figure 1 This is a pickling image of the corrosion-resistant steel ingot surface of Example 1 of the present invention;

[0024] Figure 2 This is the pickling image of the corrosion-resistant steel ingot surface of Comparative Example 1;

[0025] Figure 3 This is a pickling diagram of the finished product of the corrosion-resistant steel of Example 1 of the present invention;

[0026] Figure 4 This is the pickling diagram of the finished product of the corrosion-resistant steel of Comparative Example 1;

[0027] Figure 5 This is a diagram showing the effect of water descaling of the corrosion-resistant steel before rolling according to Example 1 of the present invention;

[0028] Figure 6 The effect diagram of water descaling of the corrosion-resistant steel of Comparative Example 2 before rolling;

[0029] Figure 7 is the thickness of the finished oxide scale of the corrosion-resistant steel of Example 1 of the present invention;

[0030] Figure 8 The thickness of the finished oxide scale of the corrosion-resistant steel of Comparative Example 2. DETAILED DESCRIPTION

[0031] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0032] In a first aspect, the present invention provides a corrosion-resistant steel comprising C, Si, Mn, P, S, Cr, Ni, Cu and Fe; wherein:

[0033] The contents of the elements in the corrosion-resistant steel are as follows by weight percentage: C content is 0.15-0.20%, Si content is 0.18-0.28%, Mn content is 0.75-0.85%, P content is ≤0.020%, S content is ≤0.010%, Cr content is 0.85-0.95%, Ni content is 0.26-0.32%, Cu content is 0.20-0.36%, and Ni, Cr and Cu are designed by comprehensive micro-alloying composition, and Cr content + Ni content + Cu content>1.25%;

[0034] The type of the corrosion-resistant steel is 15CrNiCu.

[0035] The corrosion-resistant steel of the present invention adjusts the ratio of the main chemical elements of Cr, Ni and Cu in the steel to ensure the strength performance requirements of the steel and the atmospheric corrosion resistance index I of the steel ≥ 6.0; then by selecting appropriate crystallizer and continuous casting cooling process parameters, the superheat is controlled at the same time to reduce the star-shaped cracks of the ingot; further by adjusting the melting point and viscosity of the protective slag, the uniform heat transfer of the meniscus is controlled to reduce the crack defects of the ingot; then by controlling the heating temperature and selecting the appropriate start rolling temperature, the precipitation embrittlement of the grain boundary after the copper is heated is reduced; the furnace time is controlled to avoid long-term high-temperature combustion, and at the same time, the heating technology of low residual oxygen, low air-coal ratio in the soaking section and appropriately reduced temperature in the high-temperature section is adopted to improve the descaling property of Ni-containing steel. The corrosion-resistant steel of the present invention has better atmospheric corrosion resistance, and also ensures its good mechanical properties and surface quality, so that it can be more widely used in the production of parts.

[0036] In a preferred embodiment of the present invention, the atmospheric corrosion resistance index I of the corrosion-resistant steel is ≥ 6.0; wherein,

[0037] I=26.01(%Cu)+3.88(%Ni)+1.20(%Cr)+1.49(%Si)+17.28(%P)-7.29(%Cu)(%Ni)-9.10(%Ni)(%P)-33.39(%Cu) 2 .

[0038] In a second aspect, the present invention provides a method for preparing corrosion-resistant steel, which comprises: converter smelting, LF furnace refining, continuous casting, heating, descaling, rolling, controlled cooling and coiling.

[0039] In a preferred embodiment of the present invention, the converter smelting includes: adding scrap steel, copper blocks and nickel plates into a converter for smelting, the C content in the obtained molten steel is 0.04-0.08wt%, the P content is ≤0.018wt%, and deoxidizer, alloy and lime are added during steel tapping.

[0040] In a preferred embodiment of the present invention, the LF furnace refining includes: the inlet temperature of the molten steel is ≥1530°C, the refining cycle is 35-40min, the soft blowing time is ≥15min, lime and slag-reducing agent are added to adjust the white slag, and finally silicon carbide and carbon powder are added for deoxidation.

[0041] In a preferred embodiment of the present invention, 100-200m of pure calcium wire is fed before the soft blowing.

[0042] In a preferred embodiment of the present invention, appropriate crystallizer and continuous casting cooling process parameters are selected to control superheat and reduce cracks in the ingot. The continuous casting conditions include: the target superheat of the tundish is 20-30°C, the cooling water volume is 115m 3 / h, the secondary cooling water ratio is 0.70L / kg, and the basicity of the protective slag is 0.75-1.15; the protective slag with a higher melting point and viscosity is designed to control the uniform heat transfer of the meniscus and reduce the cracks of the ingot. The viscosity of the protective slag is 1.65-2.25 and the melting point of the protective slag is 1200-1300℃.

[0043] In a preferred embodiment of the present invention, in order to reduce the precipitation embrittlement of Cu grain boundaries in steel after heating, the heating temperature should not be too high, and a suitable rolling start temperature should be selected. At the same time, it is necessary to control the furnace time, adopt a heating technology with low residual oxygen, low air-coal ratio in the soaking section and appropriately reduced temperature in the high temperature section, and improve the descaling property of Ni-containing steel. The heating conditions include: furnace time <150min, maximum temperature in the soaking section <1080°C, air-coal ratio in the soaking section 0.55-0.6:1, and residual oxygen content <2%.

[0044] In a preferred embodiment of the present invention, the phosphorus removal method is high-pressure water phosphorus removal.

[0045] In a preferred embodiment of the present invention, in order to ensure the surface quality of the finished product, the rolling temperature and the spinning temperature are controlled, and the rolling conditions include: the rolling temperature is 1000-1020°C, and the spinning temperature is 880-910°C.

[0046] In a preferred embodiment of the present invention, in order to ensure the surface quality of the finished product and optimize the air cooling line controlled cooling process, the controlled cooling method is to delay the slow cooling by opening the first three groups of insulation covers of the Stelmore air cooling line after rolling.

[0047] In a third aspect, the present invention provides a corrosion-resistant steel prepared by the preparation method described in the second aspect.

[0048] In a fourth aspect, the present invention provides a use of the corrosion-resistant steel described in the first aspect or the third aspect in the preparation of corrosion-resistant special-shaped bolts.

[0049] The present invention will be described in detail below through examples. In the following examples, the drugs and pharmaceutical agents are all conventional commercial products.

[0050] Table 1 shows the production process parameters for preparing corrosion-resistant steel in Example 1 and Comparative Examples 1-2.

[0051]

[0052]

[0053] Among them, the cooling control method described in Comparative Example 2 is to delay slow cooling after opening the first group of insulation covers of the Stelmore air cooling line after rolling, and other technical conditions are the same as those of the embodiment.

[0054] Table 2 shows the performance parameters of the corrosion-resistant steel prepared in Example 1 and Comparative Examples 1-2

[0055]

[0056] Depend on Figure 1-2 It can be seen that the corrosion-resistant steel prepared in Example 1 of the present invention has no obvious cracks on the surface of the ingot after pickling, while the corrosion-resistant steel prepared in Comparative Example 1 has obvious cracks on the corners of the surface of the ingot after pickling;

[0057] Depend on Figure 3-4 It can be seen that the pickled surface of the finished corrosion-resistant steel product prepared in Example 1 of the present invention has no obvious defects, while the pickled surface of the finished corrosion-resistant steel product prepared in Comparative Example 1 has cracks;

[0058] Depend on Figure 5-6 It can be seen that the water descaling quality of the corrosion-resistant steel prepared in Example 1 of the present invention before rolling is good, while the water descaling quality of the corrosion-resistant steel prepared in Comparative Example 2 before rolling is poor;

[0059] Depend on Figure 7-8 It can be seen that the thickness of the oxide scale of the corrosion-resistant steel product prepared in Example 1 of the present invention is 13-25.8 μm, while the thickness of the oxide scale of the corrosion-resistant steel product prepared in Comparative Example 2 is 16-28.5 μm.

[0060] From the above content combined with the data in Table 1-2, it can be seen that the present invention optimizes the chemical composition ratio to ensure that the atmospheric corrosion resistance index of the steel meets the corrosion resistance requirements under a specific use environment and has excellent corrosion resistance. Furthermore, the corrosion-resistant steel prepared by the composition ratio and preparation method of the present invention has better surface quality of the ingot and finished pickling quality than that of Comparative Example 1. Compared with Comparative Example 2, the morphology and thickness of the finished oxide scale after rolling are better, indicating that the surface quality of the corrosion-resistant steel prepared in Example 1 of the present invention is excellent. In addition, the composition ratio and heating process design of the present invention alleviate the hot rolling forming problem caused by the precipitation of Cu element grain boundaries and the adhesion of Ni element oxide scale after the ingot is heated. Compared with Comparative Example 2, the corrosion-resistant steel of Example 1 of the present invention has better descaling effect and hot rolling plasticity of the rolled ingot, and has better processing performance.

[0061] At the same time, it can be seen from the corrosion-resistant steel performance data in Table 2 that the corrosion-resistant steel of the present invention not only meets the requirements of corrosion resistance and processing performance, but also ensures that the mechanical properties of the steel are high and improves the overall quality of the product. Compared with the corrosion-resistant steel of Comparative Example 2, the finished product implemented by the present invention has better mechanical performance indicators.

[0062] In addition to the above-mentioned key technical points which must be implemented as required, the present invention requires that other production processes be implemented in a conventional manner.

[0063] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0064] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0065] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A corrosion-resistant steel, characterized in that: The corrosion-resistant steel contains C, Si, Mn, P, S, Cr, Ni, Cu and Fe; wherein: The contents of the elements in the corrosion-resistant steel are as follows by weight percentage: C content is 0.15-0.20%, Si content is 0.18-0.28%, Mn content is 0.75-0.85%, P content is ≤0.020%, S content is ≤0.010%, Cr content is 0.85-0.95%, Ni content is 0.26-0.32%, Cu content is 0.20-0.36%, and Cr content + Ni content + Cu content>1.25%; The type of the corrosion-resistant steel is 15CrNiCu.

2. The corrosion-resistant steel according to claim 1, characterized in that: The atmospheric corrosion resistance index I of the corrosion-resistant steel is ≥ 6.0; wherein, I=26.01(%Cu)+3.88(%Ni)+1.20(%Cr)+1.49(%Si)+17.28(%P)-7.29(%Cu)(%Ni)-9.10(%Ni)(%P)-33.39(%Cu) 2 。 3. A method for preparing corrosion-resistant steel, characterized in that: The preparation method comprises: converter smelting, LF furnace refining, continuous casting, heating, descaling, rolling, controlled cooling and coiling.

4. The preparation method according to claim 3, characterized in that: The converter smelting comprises: adding scrap steel, copper block and nickel plate into the converter for smelting, wherein the C content in the obtained molten steel is 0.04-0.08wt%, the P content is ≤0.018wt%, and deoxidizer, alloy and lime are added during steel tapping.

5. The preparation method according to claim 3 or 4, characterized in that: The LF furnace refining includes: the inlet temperature of the molten steel is ≥1530°C, the refining cycle is 35-40min, the soft blowing time is ≥15min, lime and slag-reducing agent are added to adjust the slag, and finally silicon carbide and carbon powder are added for deoxidation; Preferably, 100-200m of pure calcium wire is fed before the soft blowing.

6. A preparation method according to any one of claims 3 to 5, characterized in that: The continuous casting conditions include: the target superheat of the tundish is 20-30°C, the cooling water volume is 115m 3 / h, the secondary cooling water ratio is 0.70L / kg, the basicity of the protective slag is 0.75-1.15, the viscosity of the protective slag is 1.65-2.25, and the melting point of the protective slag is 1200-1300℃.

7. A preparation method according to any one of claims 3 to 6, characterized in that: The heating conditions include: furnace time <150 min, maximum temperature of soaking section <1080° C., air-to-coal ratio of soaking section 0.55-0.6:1, and residual oxygen content <2%.

8. A preparation method according to any one of claims 3 to 7, characterized in that: The phosphorus removal method is high-pressure water phosphorus removal; Preferably, the rolling conditions include: the rolling start temperature is 1000-1020°C, the spinning temperature is 880-910°C; More preferably, the cooling control method is to delay the cooling by opening the first three groups of heat preservation covers of the Stelmore air cooling line after the rolling.

9. A corrosion-resistant steel prepared according to the preparation method according to any one of claims 3 to 8.

10. Use of the corrosion-resistant steel according to claim 1 or 2 and the corrosion-resistant steel according to any one of claim 9 in the preparation of corrosion-resistant special-shaped bolts.

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