A method for glass sealing high-chromium ferritic stainless steel wire rod and a manufacturing method

Abstract

The present application relates to the technical field of metal smelting, and particularly relates to a glass-sealed high-chromium ferrite stainless steel wire rod, which comprises the following components in percentage by mass: C: 0.030%, Cr: 27.20-27.80%, Ni: 1.10-1.50%, Cu: 0.20%, Nb: 0.10-0.20%, Mn: 0.40-0.70%, Si: 0.20-0.50%, P: 0.010-0.020%, S: 0.005%, N: 0.040%, and the balance of Fe and inevitable impurities. The present application also relates to a preparation method of the stainless steel wire rod, which comprises the following steps: sequentially subjecting raw materials to electric arc furnace smelting, AOD smelting, LF smelting, continuous casting, hot delivery rolling, and solid solution process treatment, and finally obtaining a stainless steel wire rod product. Through optimization of the stainless steel component design and production process conditions, the material has good surface quality, excellent plasticity and toughness, fine grain size, and reasonable thermal expansion coefficient, and the manufacturing process is simple, and batch production can be carried out.

Description

Technical Field

[0001] This invention relates to the field of high-chromium ferritic stainless steel smelting and wire rod rolling technology, specifically a high-chromium ferritic stainless steel wire rod for glass sealing and its manufacturing method. Background Technology

[0002] 4J28 iron-chromium alloy is an expansion alloy with special thermal expansion properties. It is a common metallic material in vacuum electronic devices, used for mating and sealing with corresponding soft glass, and is an important sealing structural material in the vacuum electronic industry. This material is widely used in the electronics industry, precision measuring tools, precision instruments, cryogenic engineering, and other fields.

[0003] 4J28 stainless steel has a high ductile-brittle transition temperature, but it is relatively soft and lacks ductility and toughness at high temperatures, which brings production challenges to the smelting of billets and the rolling of wire rods. In industrial production, the material often needs to be cold-worked and stamped into various complex shapes of sealing parts, and the current material properties and production processes cannot meet the production requirements. Summary of the Invention

[0004] To address the problems mentioned in the background art, this invention provides a high-chromium ferritic stainless steel wire rod for glass sealing and its preparation method. By optimizing the stainless steel composition design and production process conditions, the material exhibits good surface quality, excellent ductility and toughness, fine grain size, and a reasonable coefficient of thermal expansion. At the same time, the manufacturing process is simple and can be mass-produced.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for manufacturing high-chromium ferritic stainless steel wire rod for glass sealing, comprising sequentially processing raw materials through electric arc furnace smelting, AOD smelting, LF smelting, continuous casting, hot rolling, and solution treatment to finally obtain the finished stainless steel wire rod; wherein,

[0006] In the electric arc furnace smelting process, the Si content of the tapped steel is controlled at 0.2~0.7%, and the P content is ≤0.015%.

[0007] In the AOD smelting process, argon gas is blown throughout the process to control the C content to ≤0.020%, while the tapping temperature is controlled to ≤1700℃.

[0008] In the LF smelting process, ferrochrome, electrolytic manganese, and ferroniobium are first added to fine-tune the composition, and then pure calcium wire is added and argon is blown softly for ≥10 minutes.

[0009] The chemical composition of the high-chromium ferritic stainless steel wire rod, by mass percentage, is: C≤0.030%, Cr: 27.20~27.80%, Ni: 1.10~1.50%, Cu≤0.20%, Nb: 0.10~0.20%, Mn: 0.40~0.70%, Si: 0.20~0.50%, P: 0.010~0.020%, S≤0.005%, N≤0.040%, with the balance being Fe and unavoidable impurities.

[0010] Preferably, in the electric arc furnace smelting process, the tapping temperature is controlled at the liquidus temperature of 50~100℃.

[0011] Preferably, the AOD smelting process includes a steelmaking period, a decarburization period, a reduction period, and a refining period. In the steelmaking period, cold lime is added, ferrochrome is added, and molten steel from an electric arc furnace is added, with oxygen supplied to raise the temperature. In the decarburization period, the temperature is controlled above 1650℃, and the carbon content is ensured by oxygen blowing to decarburize and retain chromium. In the reduction period, ferrosilicon, an appropriate amount of lime, and fluorite are added, stirred, and then the slag is removed. In the refining period, lime and fluorite are added to form slag for refining, and ferrochrome and electrolytic manganese are added according to the sampled spectral composition for fine-tuning of the composition, while simultaneously controlling the tapping temperature.

[0012] Preferably, in the continuous casting process, a crystallizer is used for production, the superheat is controlled at 25~40℃, the crystallizer water flow rate is 95±10m3 / h, the foot roller water flow rate is 4.0±1.0m3 / h, the secondary cooling water flow rate is 4.0±1.0m3 / h, the casting speed is controlled at 0.8~1.0m / min, and an external electromagnetic stirrer is used with a current intensity of 450~500A and a frequency of 2.5Hz.

[0013] Preferably, hot rolling is used during the continuous casting billet transfer process.

[0014] Preferably, during the continuous casting billet transfer process, the billet temperature upon entering the furnace is ≥350℃.

[0015] Preferably, in the hot rolling process, a heating furnace is used for production. The heating temperature of the heating furnace is 1100~1200℃, and the heating time is controlled within 180 minutes. At the same time, controlled rolling and controlled cooling are used for rolling, with a rolling temperature ≤950℃ and a wire drawing temperature ≤800℃.

[0016] Preferably, in the hot-rolling process, the Danieli wire rod high-speed twistless rolling mill is used for rolling, and the rolled material is cooled on the Steyrmo air-cooled roller conveyor.

[0017] Preferably, in the solution treatment process, the solution treatment temperature is 800~850℃ and the holding time is more than 3 hours.

[0018] The role of each chemical component in the high-chromium ferritic stainless steel wire rod of the present invention will be explained below.

[0019] C and N are strong austenite-forming elements, with their austenite-forming ability being approximately 30 times that of Ni. Excessive content of either element can cause ferritic stainless steel to develop a ferrite + martensite (austenite) duplex microstructure under certain heat treatment conditions, negatively impacting its ductility, toughness, corrosion resistance, and weldability. Furthermore, C and N have low solubility in ferritic stainless steel, easily leading to the precipitation of carbides and nitrides, which are the root cause of high-temperature brittleness and sensitization in ferritic stainless steel. Therefore, the content of both C and N elements is controlled below 0.040%.

[0020] Cr is a strong ferrite-forming element and the only irreplaceable alloying element in ferritic stainless steel. Within the specified Cr content range for ferritic stainless steel, higher Cr content increases strength, decreases toughness and ductility, significantly increases the ductile-brittle transition temperature, and improves corrosion resistance. Therefore, the Cr content is controlled between 27.2% and 27.8%.

[0021] Nitrogen (Nb) is a widely used stabilizing element in ferritic stainless steel. Because Nb has a much higher priority for forming carbonitrides than chromium (Cr), and because Nb (C, N) exhibits high-temperature stability, it can effectively pin grain boundaries, refine grains, and improve the material's corrosion resistance and cold-working properties. Therefore, an appropriate amount of Nb is added, with the content controlled between 0.10% and 0.20%.

[0022] Ni is an element that expands the austenite phase region. Its main role in ferritic stainless steel is to improve the strength of stainless steel, increase the toughness of stainless steel at room temperature, and reduce the ductile-brittle transition temperature of stainless steel. At the same time, Ni also promotes the susceptibility of stainless steel to stress corrosion, destroying the advantage of ferritic stainless steel to basically be immune to stress corrosion. Therefore, the Ni content is controlled at 1.00~2.00%.

[0023] P element usually exists in steel as an impurity, causing solid solution strengthening and affecting the plasticity of stainless steel. It also significantly increases the ductile-brittle transition temperature of stainless steel. Therefore, the P element content should be controlled as low as possible, so the P element content should be controlled at ≤0.020%.

[0024] Sulfur (S) tends to agglomerate at grain boundaries, reducing grain boundary bonding. It also forms sulfide inclusions in steel, thereby reducing the plasticity of stainless steel. Therefore, the content of sulfur is controlled at ≤0.005%.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] This invention mainly improves the ductility and toughness and hot working performance of stainless steel by controlling the C and N content to ≤0.040%; refines the grain size and improves corrosion resistance and cold working performance by adding Nb; and improves the room temperature ductility and toughness of stainless steel, lowers the ductile-brittle transition temperature of stainless steel, and improves corrosion resistance by adding Ni.

[0027] In the continuous casting-rolling billet transfer process, the present invention adopts a hot-rolling transfer method to ensure that the billet temperature entering the furnace is ≥350℃, thereby reducing the risk of billet cracking and brittle fracture.

[0028] In the wire rod rolling process of this invention, the entire rolling line channel, guide groove, and wire drawing tube should be carefully inspected before rolling, spare wire drawing tubes should be prepared, and sufficient empty steps should be reserved for loading into the furnace. At the same time, the heating temperature of the heating furnace should be controlled at 1160~1180℃, and the heating time should be controlled within 180 minutes. Meanwhile, a controlled rolling and controlled cooling method is adopted for rolling, with a rolling temperature ≤950℃ and a wire drawing temperature ≤800℃, so that the wire rod has good surface quality and fine grain size.

[0029] In the solution treatment process of this invention, the solution temperature of the wire rod shall not exceed 850°C to avoid grain growth of ferritic stainless steel wire rod. Attached Figure Description

[0030] Figure 1 A photograph showing the surface quality of the stainless steel wire rod of this invention;

[0031] Figure 2 The solid solution metallographic structure of the stainless steel wire rod of the present invention;

[0032] Figure 3 The measured value of the thermal expansion coefficient and the thermal expansion curve of the stainless steel wire rod of the present invention are shown. Implementation

[0033] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings, so that those skilled in the art can more clearly understand how to practice the present invention. Although the present invention has been described in conjunction with its preferred embodiments, these embodiments are merely illustrative and not intended to limit the scope of the invention.

[0034] The present application will be further described in detail below through specific embodiments.

[0035] A high-chromium ferritic stainless steel wire rod for glass sealing, wherein the chemical composition of the stainless steel wire rod, by mass percentage, comprises: C≤0.030%, Cr: 27.20~27.80%, Ni: 1.10~1.50%, Cu≤0.20%, Nb: 0.10~0.20%, Mn: 0.40~0.70%, Si: 0.20~0.50%, P: 0.010~0.020%, S≤0.005%, N≤0.040%, with the balance being Fe and unavoidable impurities.

[0036] A method for manufacturing high-chromium ferritic stainless steel wire rod for glass sealing includes sequentially processing the furnace charge through electric arc furnace smelting, AOD smelting, LF smelting, continuous casting, hot rolling, and solution treatment.

[0037] In the electric arc furnace smelting process, the furnace charge is melted and the molten steel is initially smelted through the electric arc furnace. The Si content of the tapped steel is controlled at 0.2~0.7%, the P content is ≤0.015%, and the tapping temperature is controlled at the liquidus temperature of 50~100℃.

[0038] In the AOD smelting process, argon gas is used throughout. During the steelmaking stage, chilled lime is added first, followed by ferrochrome, and then the molten steel from the electric arc furnace is added, with oxygen supplied to raise the temperature. Once the temperature reaches 1650℃, the decarburization stage begins, with oxygen blowing for decarburization and chromium retention, ensuring a carbon content ≤0.020%. During the reduction stage, ferrosilicon, appropriate amounts of lime and fluorite are added, stirred, and then the slag is skimmed off. During the refining stage, lime and fluorite are added for slag formation and refining, and ferrochrome and electrolytic manganese are added based on the sampled spectral composition to fine-tune the composition. The tapping temperature is 1666℃.

[0039] In the LF smelting process, ferrochrome, electrolytic manganese, and ferroniobium are added to fine-tune the composition, ensuring that the smelting composition meets the requirements. Pure calcium wire is added, and argon is blown softly for 12 minutes.

[0040] In the continuous casting process, a 180*180 crystallizer is used for production. The actual superheat is controlled at 30~40℃, the crystallizer water flow rate is 95~98m3 / h, the foot roller water flow rate is 3.0~3.5m3 / h, the secondary cooling water flow rate is 3.0~3.5m3 / h, the casting speed is 0.85m / min, and the electromagnetic stirring current intensity is 450A and the frequency is 2.5Hz.

[0041] The continuously cast billet undergoes hot-feed rolling. The billet temperature upon entering the furnace is ≥350℃. During the rolling process, the heating furnace temperature is controlled at 1160~1180℃, and the heating time is controlled within 180 minutes. Simultaneously, controlled rolling and controlled cooling are adopted, with a rolling temperature ≤950℃ and a wire ejection temperature ≤800℃. In the hot-feed rolling process, a Danieli high-speed twist-free wire rod mill is used for rolling, and the billet is cooled on a Steyrmo air-cooled roller conveyor after rolling. Before the hot-feed rolling process, the entire rolling line channel, guide groove, and wire ejection tube are carefully inspected, spare wire ejection tubes are prepared, and sufficient space is reserved for loading into the furnace to avoid rolling scratches.

[0042] In the solution treatment process, the solution temperature is controlled at 820~840℃ and the solution time is controlled at 3h.

[0043] The content of substances involved in the above steps is expressed as a percentage by mass.

[0044] The chemical composition of the steel was precisely controlled using electric arc furnace, AOD, and LF smelting. The chemical composition of the resulting stainless steel is shown in Table 1.

[0045]

[0046] Table 1

[0047] Processed stainless steel wire rods, such as Figure 1 As shown in the figure; the treated stainless steel wire rod was subjected to solution treatment, and metallographic structure, mechanical property comparison test, and thermal expansion coefficient test were performed. The test results are shown in the figure. Figure 2 Table 2 Figure 3 As shown, in the metallographic analysis, the grain size is grade 10; in the mechanical property comparison test, the elongation after fracture of the treated stainless steel wire rod is 37.0%~38.0%, and the reduction of area is 78.0%~80.0%; in the thermal expansion coefficient test, the stainless steel wire rod has a diameter of 7.5mm, and the test condition is: solution treatment at 1100℃ for 20min, the result is: thermal expansion coefficient of 10.9577 (unit: 10) at 20~530℃. -6 1 / K).

[0048]

[0049] Table 2

[0050] As can be seen from the above Example 1 and the finished product inspection results, the present invention, through component design and production process optimization, enables the material to have good surface quality, excellent grain size, plasticity and toughness and thermal expansion coefficient, which can meet the usage requirements. At the same time, the production process is simple and suitable for mass production. The present invention has broad market application prospects.

[0051] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for manufacturing high-chromium ferritic stainless steel wire rod for glass sealing, characterized in that: This includes processing raw materials sequentially through electric arc furnace smelting, AOD smelting, LF smelting, continuous casting, hot rolling, and solution treatment to ultimately produce finished stainless steel wire rods; among which, In the electric arc furnace smelting process, the Si content of the tapped steel is controlled at 0.2~0.7%, the P content is ≤0.015%, and the tapping temperature is controlled at the liquidus temperature of 50~100℃. In the AOD smelting process, argon gas is blown throughout to control the carbon content to ≤0.020%, while the tapping temperature is controlled to ≤1700℃. The AOD smelting process includes steelmaking, decarburization, reduction, and refining. In the steelmaking stage, cold lime is added, ferrochrome is added, and molten steel from the electric arc furnace is added, with oxygen supplied to raise the temperature. In the decarburization stage, the temperature is controlled above 1650℃, and the carbon content is ensured by oxygen blowing to decarburize and retain chromium. In the reduction stage, ferrosilicon, appropriate amounts of lime and fluorite are added, stirred, and then the slag is skimmed off. In the refining stage, lime and fluorite are added to form slag for refining, and ferrochrome and electrolytic manganese are added according to the sampled spectral composition for fine-tuning of the composition, while the tapping temperature is controlled. In the LF smelting process, ferrochrome, electrolytic manganese, and ferroniobium are first added to fine-tune the composition, and then pure calcium wire is added and argon is blown softly for ≥10 minutes. In the continuous casting process, a crystallizer is used for production, with the superheat controlled at 25~40℃ and the crystallizer water flow rate at 95±10m³. 3 / h, foot roller water flow rate 4.0±1.0m 3 / h, secondary cooling water flow rate 4.0±1.0m³ / h 3 / h, the pulling speed is controlled at 0.8~1.0m / min, an external electromagnetic stirrer is used, the current intensity is 450~500A and the frequency is 2.5Hz; In the hot rolling process, a heating furnace is used for production. The heating temperature of the heating furnace is 1100~1200℃, and the heating time is controlled within 180 minutes. At the same time, a controlled rolling and cooling method is used for rolling, with a rolling temperature ≤950℃ and a wire drawing temperature ≤800℃. The chemical composition of the high-chromium ferritic stainless steel wire rod, by mass percentage, is: C≤0.030%, Cr: 27.20~27.80%, Ni: 1.10~1.50%, Cu≤0.20%, Nb: 0.10~0.20%, Mn: 0.40~0.70%, Si: 0.20~0.50%, P: 0.010~0.020%, S≤0.005%, N≤0.040%, with the balance being Fe and unavoidable impurities.

2. The manufacturing method of a high-chromium ferritic stainless steel wire rod for glass sealing according to claim 1, characterized in that: During the continuous casting billet transfer process, hot rolling is used for transfer.

3. The method for manufacturing a high-chromium ferritic stainless steel wire rod for glass sealing according to claim 1, characterized in that: During the continuous casting billet transfer process, the billet temperature upon entering the furnace is ≥350℃.

4. The method for manufacturing a high-chromium ferritic stainless steel wire rod for glass sealing according to claim 1, characterized in that: In the hot-rolling process, the Danieli wire rod high-speed twistless rolling mill is used for rolling, and the rolled product is cooled on the Steyrmo air-cooled roller conveyor.

5. A method for manufacturing a high-chromium ferritic stainless steel wire rod for glass sealing according to claim 1, characterized in that: In the solution treatment process, the solution treatment temperature is 800~850℃ and the holding time is more than 3 hours.

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