Production method of normalized H-shaped steel for ocean engineering

Abstract

The invention discloses a production method of normalized H-shaped steel for ocean engineering. The production method comprises the following steps: blast-furnace molten iron; pretreating molten iron; smelting in a converter; performing LF refining; continuously casting the special-shaped blank; feeding is conducted; a stepping heating furnace; dephosphorizing with high-pressure water; bD cogging is conducted; performing CCS universal rolling; hot sawing; cooling by a stepping cooling bed; straightening is conducted; saw cutting; the normalized H-shaped steel comprises chemical components in percentage by mass as follows: 0.08%-0.14% of C, 0.25%-0.35% of Si, 1.30%-1.50% of Mn, smaller than or equal to 0.02% of P, smaller than or equal to 0.010% of S, 0.05%-0.09% of V, 0.015%-0.035% of Nb and the balance of Fe and impurities, and the total mass fraction is 100%. According to the production method of the normalized H-shaped steel for ocean engineering, the cost is reduced, and meanwhile good performance is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of steel rolling, and in particular relates to a production method of normalized H-shaped steel for marine engineering. Background Art

[0002] Offshore platforms are landmark facilities in marine resource development projects and are super-large welded steel structures. Offshore platform steel, as an engineering structure steel, plays the most important role in ensuring the safety of marine facilities. Offshore platforms are used in severe marine working environments such as waves, tides, storms, and extremely cold drift ice to support drilling equipment with a total weight of more than hundreds of tons. These usage characteristics determine that offshore platform steel must have high strength, high toughness, good weldability and cold workability, and seawater corrosion resistance, which is of great significance for ensuring the safety of operators, improving the service life of offshore platform steel, and developing marine resources. At the same time, in order to improve the safety and mobility of offshore platform steel, the proportion of high-strength and high-toughness steel is increasing year by year.

[0003] Q355NE steel is a typical normalized low-temperature structural steel plate with good toughness, stability of organization and mechanical properties. It is the preferred structural material for these major engineering construction projects. However, the production technology of most of these high-performance steel plates that serve in low-temperature harsh environments is monopolized by foreign countries. It is urgent to develop normalized high-strength low-temperature structural steel plates with independent intellectual property rights. Therefore, it is necessary to propose a new component design concept, develop a short-process production process route based on microstructure control, and achieve the reduction of manufacturing volume and production costs of high-quality steel products. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a production method of normalized H-beam for marine engineering, which reduces the cost and has good performance.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The invention discloses a production method of normalized H-beam for marine engineering, comprising: blast furnace molten iron; molten iron pretreatment; converter smelting; LF refining; special-shaped blank continuous casting; feeding; walking beam heating furnace; high-pressure water dephosphorization; BD blanking; CCS universal rolling; hot sawing; walking beam cooling bed cooling; straightening; sawing; wherein:

[0007] The temperature of the preheating section is controlled at ≤1000℃, the temperature of the first heating section is controlled at ≤1200℃, the temperature of the second heating section is controlled at 1100-1330℃, the temperature of the soaking section is controlled at 1100-1330℃, and the total heating time of the ingot is controlled at 3-5h;

[0008] Before the ingot is put into BD1, it must be dephosphorized with high-pressure water to prevent the surface defects of the finished H-beam caused by the pressing of the iron oxide ingot. The ingot opening area does not carry out controlled rolling, the opening rolling temperature is controlled at 1170-1180℃, the final rolling temperature is controlled at 880-960℃, and close cooling is carried out;

[0009] The mass percentage of the chemical composition of the normalized H-beam steel includes: C 0.08%-0.14%, Si 0.25%-0.35%, Mn 1.30%-1.50%, P≤0.02%, S≤0.010%, V 0.05%-0.09%, Nb 0.015%-0.035%, and the rest is Fe and impurities, with a total mass fraction of 100%.

[0010] Furthermore, the mass percentage of the chemical composition of the normalized H-beam includes: C 0.08%, Si 0.30%, Mn 1.34%, P 0.0120%, S 0.015%, V 0.056%, Nb 0.018%, and the rest is Fe and impurities, with a total mass fraction of 100%.

[0011] Furthermore, the mass percentage of the chemical composition of the normalized H-beam includes: C 0.09%, Si 0.276%, Mn 1.31%, P 0.0117%, S 0.017%, V 0.059%, Nb 0.03%, and the rest is Fe and impurities, with a total mass fraction of 100%.

[0012] Furthermore, the mass percentage of the chemical composition of the normalized H-beam includes: C 0.10%, Si 0.254%, Mn 1.36%, P 0.0111%, S 0.015%, V 0.057%, Nb 0.023%, and the rest is Fe and impurities, with a total mass fraction of 100%.

[0013] Furthermore, the mass percentage of the chemical composition of the normalized H-beam includes: C 0.11%, Si 0.271%, Mn 1.45%, P 0.0090%, S 0.015%, V 0.063%, Nb 0.025%, and the rest is Fe and impurities, with a total mass fraction of 100%.

[0014] Furthermore, the starting rolling temperature is 1169°C and the final rolling temperature is 870°C.

[0015] Furthermore, the starting rolling temperature is 1174°C and the final rolling temperature is 890°C.

[0016] Furthermore, the starting rolling temperature is 1177°C and the final rolling temperature is 960°C.

[0017] Furthermore, the starting rolling temperature is 1183°C and the final rolling temperature is 920°C.

[0018] The main chemical components of the present invention are limited by the following reasons:

[0019] C: The C element is the most effective element for improving the strength of steel. The increase of C content can improve the tensile strength and yield strength of steel, but the elongation and impact toughness will decrease. In order to ensure that the low-temperature resistant normalizing rolled H-shaped steel obtains good comprehensive performance, the C element content of the steel of the present invention is designed to be 0.08-0.14%.

[0020] Mn: Mn is an important strengthening element with low cost. With the increase of manganese content, the strength of steel is significantly improved, the processing performance of steel is improved, and the ductile-brittle transition temperature hardly changes. However, if the manganese content is too high, it will inhibit the transformation of ferrite, affect the yield strength of steel, and be unfavorable for the control of yield strength ratio. The Mn element content of the steel of the present invention is designed to be 1.30-1.50%.

[0021] Si: Si can improve the strength of steel. By increasing the Si element, the strength of steel can be improved to a certain extent. However, as the mass percentage of Si further increases, martensite structure is easily generated in the steel. Therefore, the normalized H-beam for marine engineering and the production method thereof described in the present invention control the mass percentage of Si to 0.25-0.35%.

[0022] V: V can play the role of precipitation strengthening, grain refinement strengthening and grain boundary strengthening in steel, and can reduce the ductile-brittle transition temperature. V carbonitride can effectively refine ferrite grains. In low-temperature steel, a small amount of V can refine grains and increase toughness. The V element content of the steel of the present invention is designed to be 0.05% to 0.09%.

[0023] P: P has strong solid solution strengthening and cold working hardening effects in steel. Although P can improve the strength and hardness of steel by acting on ferrite, its biggest harm is that it causes serious segregation, increases temper brittleness, and significantly increases the plasticity and toughness of steel, causing the steel to be easily brittle during cold working, which is the so-called "cold brittle" phenomenon. Therefore, the P content of the steel of the present invention is designed to be ≤0.020%.

[0024] S: S is a hot brittleness and easy-to-cut machinability element. It is known that the machinability improves with the increase of the mass percentage of sulfur, but the hot workability deteriorates with the increase of the sulfur content. Therefore, the mass percentage of S in the preparation method of normalizing rolled low-alloy structural steel described in the present invention is limited to S≤0.015%.

[0025] Nb: Adding a trace amount of Nb alloying element to steel has a strong effect of preventing austenite grain growth and making it easy to obtain fine grain structure. Niobium will produce significant grain refinement and moderate precipitation strengthening during controlled rolling. The Nb element content of the steel of the present invention is designed to be 0.015% to 0.035%.

[0026] Compared with the prior art, the beneficial technical effects of the present invention are:

[0027] The H-shaped steel prepared by the present invention by reasonably controlling the contents of Nb and V elements has high strength and stable impact toughness, and the normalizing rolling process is adopted so that the product performance meets the requirements of normalized steel, thereby reducing the production cost. DETAILED DESCRIPTION

[0028] Table 1 is a table of chemical composition and content of steel grades in various embodiments, Table 2 is a table of starting rolling temperature and final rolling temperature control in various embodiments, Table 3 is a table of mechanical property test results in various embodiments, and Table 4 is a table of mechanical property test results after normalizing heat treatment in various embodiments

[0029] Table 1 Chemical composition of each example (mass percentage / %)

[0030]

[0031]

[0032] Table 2 The starting and final rolling temperature control of each embodiment

[0033] Example Rolling temperature (℃) Finishing rolling temperature(℃) Example 1 1169 870 Example 2 1174 890 Example 3 1177 960 Example 4 1183 920

[0034] Table 3 Mechanical properties of each embodiment

[0035]

[0036] Table 4 Mechanical properties of each example after normalizing heat treatment (900℃ for 30min, air cooling)

[0037]

[0038] It can be seen from the above embodiments that the H-beam has high strength and stable low temperature impact toughness, and after normalizing heat treatment, various properties can still meet the standard requirements of normalized steel. The low temperature resistant normalizing rolled H-beam of the present invention has simple chemical composition, and has the advantages of simple control, low manufacturing cost, strong operability, etc. for steel production.

[0039] 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 normalized H-beam for marine engineering, characterized in that: include: Hot metal from blast furnace; hot metal pretreatment; converter smelting; LF refining; continuous casting of special-shaped billets; feeding; walking beam heating furnace; high-pressure water dephosphorization; BD billet opening; CCS universal rolling; hot sawing; cooling of walking beam cooling bed; straightening; sawing; among which: The temperature of the preheating section is controlled at ≤1000℃, the temperature of the first heating section is controlled at ≤1200℃, the temperature of the second heating section is controlled at 1100-1330℃, the temperature of the soaking section is controlled at 1100-1330℃, and the total heating time of the ingot is controlled at 3-5h; Before the ingot is put into BD1, it must be dephosphorized with high-pressure water to prevent the surface defects of the finished H-beam caused by the pressing of the iron oxide ingot. The ingot opening area does not carry out controlled rolling, the opening rolling temperature is controlled at 1170-1180℃, the final rolling temperature is controlled at 880-960℃, and close cooling is carried out; The mass percentage of the chemical composition of the normalized H-beam steel includes: C 0.08%-0.14%, Si 0.25%-0.35%, Mn 1.30%-1.50%, P≤0.02%, S≤0.010%, V 0.05%-0.09%, Nb 0.015%-0.035%, and the rest is Fe and impurities, with a total mass fraction of 100%.

2. The method for producing normalized H-beam for marine engineering according to claim 1, characterized in that: The mass percentage of the chemical composition of the normalized H-beam steel includes: C 0.08%, Si 0.30%, Mn 1.34%, P 0.0120%, S0.015%, V 0.056%, Nb 0.018%, and the rest is Fe and impurities, with a total mass fraction of 100%.

3. The method for producing normalized H-beam for marine engineering according to claim 1, characterized in that: The mass percentage of the chemical composition of the normalized H-beam steel includes: C 0.09%, Si 0.276%, Mn 1.31%, P 0.0117%, S0.017%, V 0.059%, Nb 0.03%, and the rest is Fe and impurities, with a total mass fraction of 100%.

4. The method for producing normalized H-beam for marine engineering according to claim 1, characterized in that: The mass percentage of the chemical composition of the normalized H-beam steel includes: C 0.10%, Si 0.254%, Mn 1.36%, P 0.0111%, S0.015%, V 0.057%, Nb 0.023%, and the rest is Fe and impurities, with a total mass fraction of 100%.

5. The method for producing normalized H-beam for marine engineering according to claim 1, characterized in that: The mass percentage of the chemical composition of the normalized H-beam steel includes: C 0.11%, Si 0.271%, Mn 1.45%, P 0.0090%, S0.015%, V 0.063%, Nb 0.025%, and the rest is Fe and impurities, with a total mass fraction of 100%.

6. The method for producing normalized H-beam for marine engineering according to claim 2, characterized in that: The starting rolling temperature is 1169℃ and the final rolling temperature is 870℃.

7. The method for producing normalized H-beam for marine engineering according to claim 3, characterized in that: The starting rolling temperature is 1174℃ and the final rolling temperature is 890℃.

8. The method for producing normalized H-beam for marine engineering according to claim 4, characterized in that: The starting rolling temperature is 1177℃ and the final rolling temperature is 960℃.

9. The method for producing normalized H-beam for marine engineering according to claim 5, characterized in that: The starting rolling temperature is 1183℃ and the final rolling temperature is 920℃.

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