A method of manufacturing a 410 ferritic stainless steel

Abstract

The application provides a 410 ferrite stainless steel manufacturing method, and the chemical composition of the 410 ferrite stainless steel is as follows: C: 0.03-0.07 wt%, Si: ≤0.60 wt%, Mn: ≤0.55 wt%, P: ≤0.040 wt%, S: ≤0.005 wt%, N: ≤0.050 wt%, Cu: ≤0.03 wt%, Cr: 11.50-13.50 wt%, and Ni: 0.40-0.60 wt%; the process route of the ferrite stainless steel is as follows: red soil nickel ore, sintering, initial smelting furnace smelting, AOD refining, LF refining, slab continuous casting, hot continuous rolling, annealing, inspection, packaging and warehousing. The steel contains 0.4-0.6% of nickel, the yield strength of the steel is high, and the steel can be used for general structural part purposes.

Description

[0001] This invention is a divisional application, parent application number: 2022104948474, title: 410 ferritic stainless steel, application date: May 7, 2022. Technical Field

[0002] This invention relates to the field of stainless steel production technology, and specifically to a method for manufacturing 410 ferritic stainless steel. Background Technology

[0003] Ferritic stainless steel is a type of stainless steel that is predominantly ferrite in its service state, with a chromium content of 11%-30% and a body-centered cubic crystal structure. This type of steel is characterized by high thermal conductivity, low coefficient of thermal expansion, good oxidation resistance, and excellent resistance to stress corrosion. In addition to its rust resistance and resistance to localized corrosion, ferritic stainless steel also exhibits excellent resistance to chloride stress corrosion, pitting corrosion, and crevice corrosion. It is a resource-saving and environmentally friendly type of stainless steel, widely used in the automotive, railway transportation, home appliance, and interior building decoration industries.

[0004] Most stainless steel companies typically use a two-step process of electric arc furnace-AOD (VOD) or primary furnace-hot metal pretreatment (converter)-AOD (VOD) to smelt ferritic stainless steel. Ferritic stainless steel obtained by the above process generally does not contain Ni, and the Ni content in the steel is almost zero. This type of stainless steel has lower hardness and yield strength, and the material is more suitable for stamping parts processing, but not for structural parts processing.

[0005] In summary, the existing technology has the following problems: the nickel-free ferritic stainless steel produced by the electric arc furnace or primary furnace-hot metal pretreatment (converter) process has low hardness and yield strength. Summary of the Invention

[0006] This invention provides a 410 ferritic stainless steel and its manufacturing method to solve the problem of low hardness and yield strength of nickel-free ferritic stainless steel.

[0007] The present invention also proposes a 410 ferritic stainless steel, wherein the chemical composition of the 410 ferritic stainless steel is as follows (weight percentage): C: 0.03-0.07 wt%, Si ≤ 0.60 wt%, Mn ≤ 0.55 wt%, P ≤ 0.040 wt%, S ≤ 0.005 wt%, N ≤ 0.050 wt%, Cu: ≤ 0.03 wt%, Cr: 11.50-13.50 wt%, Ni: 0.40-0.60 wt%.

[0008] Furthermore: the finished product thickness is 1.8-4mm.

[0009] Furthermore: the finished product thicknesses are 2.6mm, 3.0mm, and 3.2mm.

[0010] Further, the chemical composition of the 410 ferritic stainless steel by weight percentage is C: 0.062wt%, Si: 0.56wt%, Mn: 0.42wt%, P: 0.033wt%, S: 0.005wt%, N: 0.044wt%, Cu: 0.03wt%, Cr: 12.37wt%, Ni: 0.56wt%.

[0011] Further, the chemical composition of the 410 ferritic stainless steel by weight percentage is C: 0.047wt%, Si: 0.49wt%, Mn: 0.35wt%, P: 0.033wt%, S: 0.006wt%, N: 0.023wt%, Cu: 0.03wt%, Cr: 12.34wt%, Ni: 0.50wt%.

[0012] The 410 ferritic stainless steel is manufactured using the same method as 410 ferritic stainless steel.

[0013] The present invention also proposes a method for manufacturing 410 ferritic stainless steel, the method comprising:

[0014] The chemical composition of the 410 ferritic stainless steel is as follows (by weight): C: 0.03–0.07 wt%, Si ≤ 0.60 wt%, Mn ≤ 0.55 wt%, P ≤ 0.040 wt%, S ≤ 0.005 wt%, N ≤ 0.050 wt%, Cu: ≤ 0.03 wt%, Cr: 11.50–13.50 wt%, Ni: 0.40–0.60 wt%; the balance being Fe and unavoidable trace elements.

[0015] The manufacturing method of the ferritic stainless steel is as follows: laterite nickel ore, sintering, primary furnace smelting, AOD refining, LF refining, slab continuous casting, hot continuous rolling, annealing, inspection, packaging and warehousing.

[0016] In the AOD refining process: after molten iron is added into the AOD furnace, scrap steel and high-carbon ferrochrome are added in batches according to weight percentage, and ferrosilicon is added to heat up and melt the alloy furnace charge. After steelmaking is completed, the O2:Ar ratio is adjusted in stages to reduce the carbon content to the set composition range, and the tapping temperature is controlled at 1580℃~1610℃.

[0017] Further, LF refining: Molten steel undergoes slag formation and argon blowing in the LF furnace, with an argon blowing time of 8-12 minutes.

[0018] Furthermore, for slab continuous casting: the tundish pouring temperature is 1530–1550℃, an alkaline covering agent is used in the tundish, the superheat of the molten steel is controlled at 25–30℃, and the narrow-face flow rate of the crystallizer cooling water is 15–16 m³ / h. 3 / h; Wide-area flow rate 90-100m³3 / h, billet casting speed is 0.70~0.90m / min, straightening temperature ≥980℃.

[0019] Furthermore,

[0020] Hot continuous rolling: The billet heating temperature is controlled at 1130~1170℃, the soaking temperature is 1140~1160℃, and the billet time in the furnace is guaranteed to be ≥185min. Avoid excessive heating time, which would increase the amount of high-temperature ferrite phase. A four-stand roughing mill + nine-stand finishing mill hot continuous rolling mill is used. The final rolling temperature is controlled at 940~1000℃, and the coiling temperature is 680~720℃.

[0021] Further annealing: The hot-rolled coil is held at 720-740℃ for 20-24 hours and then slowly cooled.

[0022] This invention uses laterite nickel ore as raw material and employs appropriate component ratios and manufacturing processes to smelt and roll ferritic stainless steel 410. The material possesses suitable hardness, yield strength, and tensile strength, solving the problem that nickel-free molten iron must be obtained through an electric arc furnace or primary smelting furnace-converter process to produce ferritic stainless steel. The steel contains 0.4-0.6% nickel, exhibiting high yield strength, suitable for general structural applications. The ferritic stainless steel obtained by this invention has a yield strength ReL≥300MPa, tensile strength Rm≥500MPa, elongation A≥20%, Rockwell hardness HRB≤89, and a microstructure of ferrite + a very small amount of martensite + uniformly dispersed carbides, with a ferrite content ≥95%, reaching 95%, 96%, 97%, 98%, or 99%, and a grain size grade of 9.0-10.0. Furthermore, by employing suitable components and processes, the ferritic stainless steel obtained by this invention has a yield strength ReL of 340-390 MPa, a tensile strength Rm of 510-560 MPa, an elongation A of 25%-38%, and a Rockwell hardness HRB of 65-78. Attached Figure Description

[0023] Figure 1 This is a metallographic image of Embodiment 1 of the present invention;

[0024] Figure 2 This is a metallographic photograph of Embodiment 2 of the present invention;

[0025] Figure 3 This is a metallographic image of Embodiment 3 of the present invention. Detailed Implementation

[0026] To provide a clearer understanding of the technical features, objectives, and effects of this invention, the invention is now described.

[0027] The applicant discovered that ferritic stainless steel produced from low-nickel iron molten iron obtained by smelting laterite nickel ore in a primary smelting furnace contains residual Ni. In stainless steel, Ni is an element that expands the austenite region. The presence of Ni causes the (γ+α) / α phase boundary in the Fe-Cr binary phase diagram to shift towards higher Cr content, altering the single-phase temperature range of ferritic stainless steel at high temperatures. This leads to changes in the properties of ferritic stainless steel. Appropriate amounts of Ni can not only improve the strength of stainless steel but also maintain good plasticity and toughness, making the material more suitable for structural component processing. Therefore, ferritic stainless steel produced using the electric arc furnace-AOD (VOD) or primary smelting furnace-hot iron pretreatment (converter)-AOD (VOD) process routes has lower hardness and yield strength; while ferritic stainless steel produced based on the laterite nickel ore smelting low-nickel iron molten iron process route has better strength and toughness. Therefore, the applicant proposes a method for manufacturing 410 ferritic stainless steel:

[0028] 1) Technical solution adopted: A ferritic stainless steel, the chemical composition of which is C: 0.03~0.07wt%, Si≤0.60wt%, Mn≤0.55wt%, P≤0.040wt%, S≤0.005wt%, N≤0.050wt%, Cu:≤0.03wt%, Cr:11.50-13.50wt%, Ni:0.40-0.60wt%; the balance is Fe and unavoidable trace elements.

[0029] 2) In the AOD refining process: after the molten iron is added into the AOD furnace, scrap steel and high-carbon ferrochrome are added in batches according to the weight percentage, and ferrosilicon is added to heat up and melt the alloy furnace charge. After the steelmaking is completed, the O2:Ar ratio is adjusted in stages to blow the steel, and the carbon content is reduced to the set range of the composition. The tapping temperature is controlled at 1580℃~1610℃.

[0030] 3) Molten steel undergoes slag formation and argon blowing in the LF furnace, with an argon blowing time of 8-12 minutes;

[0031] 4) High-precision continuous casting control process: The continuous casting process adopts "weak cooling (secondary cooling water volume of 0.59L / Kg) + low superheat (superheat of 25-30℃) + constant casting speed (0.80m / min) + high straightening temperature (straightening temperature ≥980℃)" to reduce the generation of steel shrinkage billet cracks due to δ→γ phase transformation;

[0032] 5) In the hot continuous rolling process: the billet heating temperature is controlled at 1130~1170℃, the soaking temperature is 1140~1160℃, and the billet time in the furnace is guaranteed to be ≥185min. This avoids excessive heating time, which would increase the amount of high-temperature ferrite phase and reduce the problem of edge cracking. A four-stand roughing mill + nine-stand finishing mill hot continuous rolling mill is used, with the final rolling temperature controlled at 940~1000℃ and the coiling temperature at 680~720℃.

[0033] 6) In the annealing process described above: the hot-rolled coil is held at a temperature of 720-740℃ for 20-24 hours and then slowly cooled.

[0034] The production method of this ferritic stainless steel adopts the following component ratios and specific processes. Table 1 shows the composition (by weight percentage) of the steels in each embodiment and comparative example. Table 2 shows the rolling process parameters corresponding to the steels with the compositions described in Table 1. This invention pertains to the process before cold rolling; the above process parameters do not include cold rolling. Table 3 shows the mechanical properties after hot rolling and annealing corresponding to the steels with the compositions described in Table 1. The ferritic stainless steel obtained by this invention has a yield strength ReL of 340-390 MPa, a tensile strength Rm of 510-560 MPa, an elongation A of 25%-38%, and a Rockwell hardness HRB of 65-78. Figure 1 The metallographic structure of Example 1 is as follows: ferrite + a very small amount of martensite + uniformly dispersed carbides, wherein the ferrite content is ≥99% and the grain size is grade 9.5. Figure 2 The metallographic structure of Example 2 is as follows: ferrite + a very small amount of martensite + uniformly dispersed carbides, wherein the ferrite content is ≥99% and the grain size is grade 9.0. Figure 3 The metallographic structure of Example 3 is: ferrite + a very small amount of martensite + uniformly distributed carbides, wherein the ferrite content is ≥99% and the grain size is grade 9.0.

[0035] Table 1: Chemical Composition of the Product (wt%)

[0036] Example C Si Mn P S Ni Cr Cu N Example 1 0.062 0.56 0.42 0.033 0.005 0.56 12.37 0.03 0.044 Example 2 0.055 0.39 0.31 0.033 0.005 0.54 12.10 0.03 0.032 Example 3 0.047 0.49 0.35 0.033 0.006 0.50 12.34 0.03 0.023 Comparative Example 0.057 0.48 0.23 0.018 0.001 0.078 12.16 0 0.001

[0037] Table 2: Specific process parameters for each embodiment

[0038]

[0039] Table 3: Mechanical properties of ferritic stainless steel obtained in each embodiment

[0040] Example <![CDATA[R p0.2 / MPa]]> <![CDATA[R m / MPa]]> A / ％ Rockwell hardness HRB Example 1 345 518 36.0 70.0 Example 2 347 554 25.6 74.0 Example 3 374 552 29.2 74.0 Comparative Example 289 508 28.3 65.0

[0041] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. The various components of the present invention can be combined with each other without conflict. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for manufacturing 410 ferritic stainless steel, characterized in that, The method for manufacturing the 410 ferritic stainless steel includes: The chemical composition of the 410 ferritic stainless steel is as follows (by weight): C: 0.055 wt%, Si: 0.39 wt%, Mn: 0.31 wt%, P: 0.033 wt%, S: 0.005 wt%, N: 0.032 wt%, Cu: 0.03 wt%, Cr: 12.10 wt%, Ni: 0.54 wt%, with the balance being Fe and unavoidable trace elements. The manufacturing method of the ferritic stainless steel is as follows: laterite nickel ore, sintering, primary furnace smelting, AOD refining, LF refining, slab continuous casting, hot continuous rolling, annealing, inspection, packaging and warehousing. In the AOD refining process: after the molten iron is added into the AOD furnace, scrap steel and high-carbon ferrochrome are added in batches according to the weight percentage, and ferrosilicon is added to heat up and melt the alloy furnace charge. After the steelmaking is completed, the O2 and Ar ratios are adjusted in stages to reduce the carbon content to the set composition range, and the tapping temperature is controlled at 1580℃~1610℃. Slab continuous casting: The tundish pouring temperature is 1530-1550℃, an alkaline covering agent is used in the tundish, the superheat of the molten steel is controlled at 25-30℃, and the narrow flow rate of the cooling water in the crystallizer is 15-16 m³ / h. 3 / h; Wide-area flow rate 90-100m³ 3 / h, straightening temperature ≥980℃; The finished product thickness is 2.6mm; Hot-rolled coils are held at 720–740°C for 20–24 hours and then slowly cooled. Hot continuous rolling: The billet heating temperature is controlled at 1130~1170℃, the soaking temperature is 1140~1160℃, and the billet time in the furnace is guaranteed to be ≥185min. Avoid excessive heating time, which would increase the amount of high-temperature ferrite phase. A four-stand roughing mill + nine-stand finishing mill hot continuous rolling mill is used. The final rolling temperature is controlled at 940~1000℃, and the coiling temperature is 680~720℃. LF refining: Molten steel undergoes slag formation and argon blowing in the LF furnace, with an argon blowing time of 8-12 minutes; In slab continuous casting: the secondary cooling water volume is 0.59 L / Kg, and the casting speed is constant at 0.80 m / min.

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