High-strength 1.4589 stainless steel for power transmission hinges and method for producing same

Abstract

The present application belongs to the technical field of steel smelting, and particularly relates to a 1.4589 stainless steel for high-strength transmission hinge and a production method thereof, which comprises steelmaking, continuous casting, hot rolling, annealing, pickling and cold rolling, and is characterized in that the process flow of an electric furnace or a charge melting furnace + a converter + a vacuum furnace + a refining furnace + continuous casting is prepared, deep deoxidization before titanium addition is completed in the vacuum furnace to reduce the risk of billet inclusions, deep deoxidization is carried out in the vacuum furnace, air is extracted, and vacuum smelting is carried out under vacuum. The present application has the beneficial effects that the steelmaking process and the steel grade component design are optimized, the vacuum furnace process and the control of the A1 content of molten steel are optimized, the deep deoxidization effect is ensured before Ti is added in steelmaking, Ti oxidation is avoided, and the risk of billet inclusions is reduced. While improving the product quality, the present application overcomes the problems of nodule formation and leakage of martensite precipitation hardened stainless steel in the continuous casting process by controlling the superheat, pouring speed and weak cooling mode.

Description

Technical Field

[0001] This invention belongs to the field of steel smelting technology, and particularly relates to a high-strength transmission hinge made of 1.4589 stainless steel and its production method. Background Technology

[0002] Precipitation-hardening martensitic stainless steel achieves high strength and hardness through the precipitation strengthening effect of Nb, Cu, Al, and Ti elements. Because this type of martensitic stainless steel has a low carbon content and contains high levels of corrosion-resistant alloys, it has excellent corrosion resistance and weldability.

[0003] 1.4589 steel is a German grade steel, belonging to a type of martensitic precipitation hardening stainless steel, mainly used in petrochemical, chemical, pharmaceutical, food, and papermaking industries. Currently, few domestic steel mills produce this material, lacking mature production methods. The market is mainly based on imports, and it is generally used in large-scale transport chains and specialized special chains in manufacturing. The standard composition of 1.4589 steel, by weight percentage, is: C≤0.080%, Si≤1.00%, Mn≤1.00%, P≤0.04%, S≤0.015%, Ni 1.0~2.5%, Cr 13.50~15.50%, Mo 0.20~1.20%, Ti 0.30~0.50%, with the balance being iron.

[0004] Because titanium is a very reactive element, it is easily oxidized during the continuous casting process of steelmaking to form high-melting-point TiO2 inclusions. This oxide is very easy to react with CaO in the protective slag to form another high-melting-point inclusion, CaO.TiO2. During this process, a large amount of SiO2 component in the protective slag will be consumed, which will damage the fluidity of the protective slag and its ability to adsorb inclusions, resulting in inclusion entrapment during the casting process. Therefore, the yield of downstream processing can generally only reach about 95%. Summary of the Invention

[0005] The purpose of this invention is to provide a high-strength transmission hinge made of 1.4589 stainless steel and its production method, which overcomes the shortcomings of the prior art and solves the technical problems of unstable production and insufficient hardness and strength of this martensitic precipitation hardening stainless steel during continuous casting. The invention achieves a highly efficient and stable production process, produces finished products with good surface quality, and meets the requirements of various hinge transmission or similar hard plate products.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A high-strength transmission hinge made of 1.4589 stainless steel, characterized in that its chemical composition by weight percentage is as follows: C 0.060~0.080%; Si 0.40~0.80%; Mn 0.60~0.80%; P≤0.035%; S≤0.05%; Ni 1.4~1.6%; Cr 14.35~15.50%; Mo 0.26~0.60%; Cu≤0.5%; N≤0.015%; Al 0.020~0.050%; Ti 0.32~0.50%, with the balance being Fe and unavoidable impurities.

[0008] A method for producing 1.4589 stainless steel for high-strength transmission hinges includes steelmaking, continuous casting, hot rolling, annealing, pickling, and cold rolling. The method is characterized by preparation following a process of electric furnace or furnace charge melting furnace + converter + vacuum furnace + refining furnace + continuous casting. Deep deoxidation is performed in the vacuum furnace before adding titanium to reduce the risk of inclusions in the billet. Aluminum ingots are added at a ratio of 3-8 kg / ton for deep deoxidation in the vacuum furnace, followed by evacuation. Vacuum smelting is carried out at a vacuum degree <3 Pa. Before tapping, the composition is checked, and aluminum wire is added to ensure the Al content is within acceptable limits. After the aluminum wire is replenished, calcium wire is added at a rate of 0.2-0.4 tons, with micro-stirring for 5-10 minutes. Subsequently, titanium wire is injected at a rate of 1.0-1.5 tons, with micro-stirring for 5-10 minutes. Samples are taken for composition testing, and after the Ti content meets the standards, micro-stirring is performed before the steel is transferred to a turntable.

[0009] The continuous casting process adopts a weak cooling mode to promote the migration of impurities to the material surface. The superheat in the crystallizer is controlled to be ≤35℃, the pouring speed is 0.9~1.1m / min, the water volume of the wide mold is 3850±50L / min, and the water volume of the narrow mold is 380±50L / min. After the billet is continuously cast, it is slowly cooled to below 100℃ in the heat preservation pit before it can be removed from the pit.

[0010] The hot rolling process adopts the HSM hot rolling process, which controls the temperature of the hot-rolled coil at 670-730℃ with a temperature control accuracy of ±15℃, thereby improving the temperature control accuracy of the hot-rolled coil and reducing hot cracks.

[0011] The annealing process adopts the HAPL annealing pickling process, with an annealing temperature of 950±10℃ and an annealing speed of ≤18mpm. After annealing, various methods are used to remove inclusions on the material surface to reduce the impact of surface inclusions on the surface roughness of the final product.

[0012] The cold rolling process adopts the CRM reciprocating cold rolling process, and the surface roughness of the rolling rolls is controlled to be Ra0.3 to 0.4. The rolls are replaced in the first, fourth, sixth and seventh passes.

[0013] The O content after deep deoxygenation is 0.009%.

[0014] The slow cooling rate is 20–60 °C / h.

[0015] The final product has an HRC hardness of 25-30, a tensile strength of 780-920 MPa, and a yield strength of 780-920 MPa. The means for removing inclusions from the material surface include any one or a combination of two or more of sandblasting and rebrushing.

[0016] In this invention, carbon (C) is an effective element for strengthening steel. To maintain the necessary strength of the steel plate, the lower limit of C content is set at 0.06%. Excessive addition of C will increase the hardness of pipeline pipes, decrease their ductility, toughness, and weldability, and easily cause surface steel cracking (SSC). The development of microalloying technology allows steel plates to maintain high strength and toughness while reducing carbon content.

[0017] Si is a deoxidizing element in steel, and its deoxidizing effect is insufficient when the Si content is less than 0.05%. Therefore, the lower limit of Si content is set at 0.05%. On the other hand, when Si is added in excess, the toughness of the steel decreases.

[0018] Increasing the manganese (Mn) content can improve the overall properties of steel because Mn lowers the γ-α phase transformation temperature (lowering the decomposition temperature of austenite), thereby refining ferrite grains, reducing pearlite clusters, decreasing pearlite lamellar spacing, and thinning Fe3C lamellar thickness. All of these factors contribute to improved steel toughness. Appropriate amounts of manganese play a role in solid solution strengthening, grain refinement strengthening, phase transformation strengthening, improving toughness, and lowering the ductile-brittle transition temperature of steel. On the other hand, when Mn is added in excess, Mn segregation becomes significant, forming bainite and other hardening structures in the segregated areas, which can contribute to the formation of hardening structures like HIC (highly brittle fracture).

[0019] Sulfur (S) is an impurity element in steel that promotes segregation, increases the steel's susceptibility to cracking, and deteriorates its resistance to central segregation (HIC), resistance to surface cracking (SCC), and ductility and toughness. Steel plates typically require very low sulfur content to ensure good HIC resistance and other properties. Reducing the sulfur content in steel can effectively mitigate the degree of central segregation.

[0020] Phosphorus (P) is an impurity element in steel. It promotes center segregation, significantly reducing resistance to high brittle fracture (HIC), low-temperature toughness, and weldability. It also increases the brittle transition temperature of steel, causing cold brittleness in steel pipes. Therefore, it is best to keep the P content as low as possible.

[0021] Al is an essential element for deoxidizing steel. The combined effect of Al and Ca can reduce the size of TiN. Al is also a commonly used element in steel to refine grains, effectively improving the grain size and uniformity of ferrite. On the other hand, excessive addition of Al reduces the purity and toughness of the steel, easily leading to decreased castability and poor resistance to HIC.

[0022] One role of the microalloying element Ti is to inhibit austenite grain growth. When the titanium content is 0.04%, the grain coarsening temperature increases to approximately 1050℃. During slab heating, undissolved microalloyed carbides and amines significantly inhibit austenite grain coarsening through grain boundary pinning. Another role is to delay the recrystallization of γ during rolling. The strain-induced precipitation of microalloyed carbides during rolling significantly inhibits the recrystallization of deformation γ through grain boundary and subgrain boundary pinning, thereby achieving a fine phase transformation microstructure through the phase transformation caused by uncrystallized γ.

[0023] Nickel (Ni) and iron can be dissolved indefinitely. Nickel expands the austenite region of iron and is a major alloying element for the formation and stabilization of austenite. Nickel and carbon do not form carbides. It lowers the critical transformation temperature, reduces the diffusion rate of elements in steel, and improves hardenability. It reduces the carbon content of eutectoid pearlite, and its effect is second only to nitrogen and stronger than manganese. Its effect on lowering the martensitic transformation temperature is about half that of manganese.

[0024] Cr is an element in alloy steel. Adding Cr to steel significantly improves its oxidation resistance and increases its corrosion resistance. Chromium significantly increases the hardenability of steel, but it also increases its tendency for temper brittleness. Steels with high chromium content may also experience secondary hardening when tempered at 400–500℃ after quenching.

[0025] Cu can improve the resistance of steel to atmospheric corrosion. If the copper content in the steel is greater than 0.75%, precipitation strengthening can be achieved through solution treatment and aging, significantly increasing the strength of the steel.

[0026] Strengthening effect of nitrogen in steel: 1.1 Refine grain strengthening: Nitrogen removes excess oxygen from steel, forming fine and dispersed particles (Al). The presence of AlN particles promotes grain growth, resulting in fine-grained steel. Nitrogen forms pinning effects at austenite grain boundaries, inhibiting grain boundary migration. Simultaneously, it strongly hinders austenite grain growth.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] 1) This invention optimizes the steelmaking process and steel composition design, optimizes the vacuum furnace process and controls the Al content in the tapped steel, and ensures that deep deoxidation is completed before adding Ti in steelmaking, thereby avoiding Ti oxidation reaction and reducing the risk of inclusions in the billet.

[0029] 3) While improving product quality, this invention overcomes problems such as nodules, longitudinal cracks, and steel leakage that easily occur in cutting mold steel during continuous casting by controlling overheating, pouring speed, and weak cooling mode.

[0030] 3) The steel products produced by this invention have an HRC hardness of 25-30, a tensile strength of 780-920 MPa, a yield strength of 780-920 MPa, and can be bent at 60° without obvious cracks. They meet the performance standards of German 1.4589 steel and meet the strength requirements of stainless steel for transmission hinges.

[0031] 4) The surface roughness of the product of this invention meets the customer's requirement of ≤0.3μm, and the product surface quality is excellent with a 100% success rate. Detailed Implementation

[0032] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0033] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the specific embodiments used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the specific embodiments described below are some embodiments of the present invention. For those skilled in the art, other specific embodiments can be obtained based on these specific embodiments without creative effort.

[0034] The components of the embodiments of the invention described and shown in the specific embodiments herein can be arranged and designed in countless different configurations. Therefore, the following detailed description of the embodiments of the invention provided in the specific embodiments is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0035] This invention discloses a high-strength transmission hinge made of 1.4589 stainless steel, the chemical composition of which, by weight percentage, is as follows: C 0.060–0.080%; Si 0.40–0.80%; Mn 0.60–0.80%; P ≤0.035%; S ≤0.05%; Ni 1.4–1.6%; Cr 14.35–15.50%; Mo 0.26–0.60%; Cu ≤0.5%; N ≤0.015%; Al 0.020–0.050%; Ti 0.32–0.50%, with the balance being Fe and unavoidable impurities. The composition design of each embodiment is shown in Table 1.

[0036] Table 1

[0037] 1# 0.0746 0.5539 0.7051 0.0301 0.0013 1.4202 14.6491 0.3087 0.1090 0.0135 0.0526 0.3439 2# 0.0686 0.5789 0.6515 0.0240 0.0013 1.5747 14.5918 0.2852 0.1241 0.0124 0.0314 0.3337 3# 0.0668 0.5138 0.6837 0.0239 0.0007 1.4238 14.6558 0.2754 0.1053 0.0099 0.0306 0.3603 4# 0.0668 0.5118 0.6826 0.0247 0.0007 1.4238 14.6548 0.2753 0.1063 0.0114 0.0316 0.3612 5# 0.0668 0.5125 0.6877 0.0249 0.0006 1.4237 14.6555 0.2752 0.1058 0.0109 0.0308 0.3502 6# 0.0668 0.5228 0.6869 0.0259 0.0005 1.4239 14.6554 0.2757 0.1043 0.0106 0.0309 0.3635

[0038] This invention discloses a production method for high-strength transmission hinges using 1.4589 stainless steel, comprising steelmaking, continuous casting, hot rolling, annealing, pickling, and cold rolling. The process follows an electric furnace or furnace charge melting furnace + converter + vacuum furnace + refining furnace + continuous casting flow. In the electric furnace or furnace charge melting furnace, scrap steel or alloys are melted, and then added to the converter with high-carbon ferrochrome and ferrosilicon. Before the reduction period in the vacuum furnace, aluminum ingots are added for deep deoxidation of the molten steel. Simultaneously, vacuum smelting is performed by evacuation to reduce harmful elements and inclusions. Deep deoxidation before titanium addition is completed in the vacuum furnace, reducing... To reduce the risk of inclusions in the billet, aluminum ingots are added at a ratio of 3-8 kg / ton for deep deoxidation in a vacuum furnace. The furnace is then evacuated, and vacuum smelting is carried out at a vacuum level <3 Pa. Before tapping, the composition is checked, and aluminum wire is added to ensure the Al content is within acceptable limits. After the aluminum wire is replenished, calcium wire is added at a rate of 0.2-0.4 tons, with micro-stirring for 5-10 minutes. Subsequently, titanium wire is injected at a rate of 1.0-1.5 tons, and micro-stirring is performed for 5-10 minutes. Samples are then taken for composition testing. Once the Ti content meets the standard, micro-stirring is performed on the turntable. The O content after deep deoxidation is ≤0.010%. Vacuum smelting reduces the risk of central shrinkage cavities in the billet, avoids longitudinal cracks in the billet, and prevents nozzle nodules caused by high viscosity, poor fluidity, and low superheat in the molten steel. To reduce component segregation in the billet, the electromagnetic stirring current is set to 1500 A. The steelmaking process parameters for each embodiment are shown in Table 2.

[0039] Table 2

[0040] 1# <3Pa 2.2 kg / ton 0.400 tons 3min 1.3 tons 0.018％ 2# <3Pa 2.4 kg / ton 0.315 tons 3min 1.4 tons 0.014％ 3# <3Pa 2.5 kg / ton 0.200 tons 3min 1.1 tons 0.019％ 4# <3Pa 4.9 kg / ton 0.250 tons 3min 1.2 tons 0.007％ 5# <3Pa 5.0 kg / ton 0.290 tons 5min 1.4 tons 0.006％ 6# <3Pa 4.9 kg / ton 0.310 tons 4min 1.2 tons 0.007％

[0041] During continuous casting, a weak cooling mode is adopted to promote the migration of impurities to the material surface. The superheat in the crystallizer is controlled to be ≤35℃, the pouring speed is 0.9~1.1m / min, the water flow rate of the wide mold is 3850±50L / min, and the water flow rate of the narrow mold is 380±50L / min. After continuous casting, the billet is slowly cooled to below 100℃ in the heat preservation pit before being removed from the pit. After removal from the pit, the surface needs to be cold ground to ensure that there are no subcutaneous inclusions or cracks. The continuous casting process parameters of each embodiment are shown in Table 3.

[0042] Table 3

[0043]

[0044] Hot rolling employs the HSM hot rolling process, controlling the hot-rolled coil temperature at 670–730℃ with a temperature control accuracy of ±15℃. This improves the temperature control precision of the hot-rolled coil, reduces hot cracking, and ensures the coil temperature is slightly lower than the material's phase transformation temperature. This allows for an appropriate amount of carbide precipitation in the hot-rolled material. Subsequent continuous annealing, combined with the fact that the product itself contains Ti, enables maximum dispersion of precipitation, further enhancing the solid solution effect and increasing material strength. The hot rolling process achieves the ideal state for subsequent annealing and pickling pretreatment, ensuring good material properties and surface quality before rolling. The cold rolling effect meets the customer's sheet surface control requirements.

[0045] The hot rolling process parameters for each embodiment are shown in Table 4.

[0046] Table 4

[0047]

[0048] Annealing employs the HAPL annealing and pickling process. To ensure the material's solid solution properties while considering production stability (90° bending performance of the welded guide strip), the annealing temperature is 950±10℃, and the annealing speed is ≤18mpm. After annealing, various methods are used to remove surface inclusions, minimizing their impact on the final product's surface roughness. Methods for removing surface inclusions include sandblasting and re-brushing, or any combination of two or more of these methods.

[0049] The annealing process parameters for each embodiment are shown in Table 5.

[0050] Table 5

[0051]

[0052] The cold rolling process employs a CRM reciprocating cold rolling process, controlling the surface roughness of the rolling rolls to Ra 0.3–0.4, with roll replacement performed in the first, fourth, sixth, and seventh passes. The cold rolling process parameters and final product performance for each embodiment are shown in Table 6.

[0053] Table 6

[0054] 1# 7 23.9 819 793 No obvious cracks 2# 7 24.4 826 740 No obvious cracks 3# 7 24.7 813 742 No obvious cracks 4# 7 24.3 818 758 No obvious cracks 5# 7 26.6 891 865 No obvious cracks 6# 7 27.3 902 885 Cracks appeared

[0055] The technical solution of this invention solves the technical problem of unstable production in the continuous casting process of steelmaking. Before optimizing the vacuum furnace process and controlling the Al content of the steel, the liquid level curve and friction force curve of the continuous casting mold in steelmaking are prone to abnormal fluctuations, and there is a risk of steel leakage or nodule formation in continuous casting. After optimizing the process in the embodiment of this invention, the inclusion content of the molten steel decreases, and the liquid level curve and friction force curve of the continuous casting mold in steelmaking show normal performance.

[0056] The technical solution of this invention solves the technical problem of insufficient hardness and strength of materials after cold rolling. It mainly reduces the hot rolling coil temperature to slightly below the material phase transformation temperature, so that the hot-rolled material has an appropriate amount of carbide precipitation. After downstream pickling and appropriate annealing at 950±10℃, the product itself is a Ti-containing material, which can form the maximum degree of dispersion precipitation, further enhancing the solid solution effect, so that the material's performance before cold rolling is uniformly enhanced, and the corresponding material performance after cold rolling can be improved.

[0057] 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 high-strength transmission hinge made of 1.4589 stainless steel, characterized in that, Its chemical composition by weight percentage is as follows: C 0.060~0.080%; Si 0.40~0.80%; Mn 0.60~0.80%; P≤0.035%; S≤0.05%; Ni 1.4~1.6%; Cr 14.35~15.50%; Mo 0.26~0.60; Cu≤0.5%; N≤0.015%; Al 0.020~0.050%; Ti 0.32~0.50%, balance being Fe and unavoidable impurities; The production method of 1.4589 stainless steel for high-strength transmission hinges includes steelmaking, continuous casting, hot rolling, annealing, pickling and cold rolling. The process follows an electric furnace or furnace charge melting furnace + converter + vacuum furnace + refining furnace + continuous casting flow. Deep deoxidation is performed in the vacuum furnace before adding titanium to reduce the risk of inclusions in the billet. Aluminum ingots are added at a ratio of 3-8 kg / ton for deep deoxidation in the vacuum furnace. The furnace is then evacuated, and vacuum smelting is carried out at a vacuum degree <3 Pa. Before tapping, the composition is checked, and aluminum wire is added to ensure the Al content is within acceptable limits. After the aluminum wire is replenished, calcium wire is added at a rate of 0.2-0.4 tons, with micro-stirring for 5-10 minutes. Then, titanium wire is injected at a rate of 1.0-1.5 tons, and micro-stirring is performed for 5-10 minutes. Samples are taken to test the composition; once the Ti content meets the standard, micro-stirring is performed on the turntable. The continuous casting process adopts a weak cooling mode to promote the migration of impurities to the material surface, controls the superheat in the crystallizer to ≤35℃, the pouring speed to 0.9~1.1m / min, and the water flow rate of the narrow mold to 380±50L / min; after the billet is continuously cast, it is slowly cooled to below 100℃ in the heat preservation pit before it can be removed from the pit. The hot rolling process adopts the HSM hot rolling process, which controls the temperature of the hot rolled coil at 670~730℃ with a temperature control accuracy of ±15℃, thereby improving the temperature control accuracy of the hot rolled coil and reducing hot cracks. The annealing process adopts HAPL annealing and pickling process, with an annealing temperature of 950±10℃ and an annealing speed of ≤18mpm. After annealing, various methods are used to remove surface inclusions of the material to reduce the impact of surface inclusions on the surface roughness of the final product. The cold rolling process adopts the CRM reciprocating cold rolling process, and the surface roughness of the rolling rolls is controlled to be Ra0.3~0.

4. The rolls are replaced in the first, fourth, sixth and seventh passes. The O content after deep deoxygenation is ≤0.010%; The cooling rate of the slow cooling is 20~60℃ / h; The final product has an HRC hardness of 25-30, a tensile strength of 780-920MPa, a yield strength of 780-920MPa, can withstand a 60° bend without obvious cracks, and has a surface roughness of ≤0.3μm.

2. The high-strength transmission hinge made of 1.4589 stainless steel according to claim 1, characterized in that, The means of removing inclusions from the material surface include any one or two of sandblasting and rebrushing.

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