A bearing bush and a process for making the same

Abstract

The application relates to the field of metal materials and metallurgical processing technology, in particular to a bearing bush and a preparation process thereof. The bearing bush is used for sliding support of roll system equipment such as sinking rolls and stabilizing rolls in a cold-rolled hot-galvanizing production line, is made of a zinc liquid corrosion-resistant wear-resistant alloy, and contains the following components in percentage by mass: C: 0.08-0.28%, Cr: 16.00-21.00%, Ni: 8.00-14.00%, Mo: 2.00-4.50%, Nb: 0.20-1.80%, Ti: 0.03-0.60%, V: 0.03-0.80%, Mn: 0.30-2.00%, Si: 0.20-1.20%, N: 0.02-0.20%, P<=0.035%, S<=0.020%, and the balance of Fe and inevitable impurities. The preparation process comprises raw material batching, smelting and refining, modification and purification, casting forming, solid solution treatment, aging treatment and mechanical processing. The application introduces carbonide forming elements such as niobium, titanium and vanadium into the austenitic corrosion-resistant alloy system, and cooperates with controlled smelting and heat treatment processes, so that a uniform and dispersed hard second phase particle is formed in the bearing bush matrix, the hardness, wear resistance and dimensional stability are improved while the high-temperature zinc liquid corrosion resistance is maintained, and the bearing bush is suitable for severe working conditions of high temperature, molten zinc liquid corrosion and abrasive wear.

Description

Technical Field

[0001] This invention relates to the field of metal materials and metallurgical processing technology, and more particularly to a bearing bush and its manufacturing process. More specifically, this invention relates to a high-temperature zinc melt corrosion resistant and wear-resistant bearing bush suitable for submerged rolls, stabilizing rolls, and other roll systems in cold-rolled hot-dip galvanizing production lines, as well as the alloy composition design, smelting and casting, heat treatment, and machining processes used to manufacture this bearing bush. Background Technology

[0002] In cold-rolled hot-dip galvanizing production lines, strip steel typically undergoes annealing, enters a zinc bath, and passes through submerged rolls and stabilizing rolls to complete the galvanizing process. Submerged rolls and stabilizing rolls operate continuously in a high-temperature molten zinc environment, requiring sliding support at their journals via bearings or bushings. As key components in the roll system that bear radial loads and maintain rotational stability, the performance of bearings directly affects the operating accuracy, service life, and continuous operation capability of the submerged rolls and stabilizing rolls.

[0003] Compared to sliding bearings in ordinary mechanical equipment, bearing bushes in hot-dip galvanizing production lines face more complex and demanding service conditions. First, bearing bushes need to be exposed to high-temperature environments for extended periods; the strength, hardness, and structural stability of the material at these temperatures directly affect its load-bearing capacity. Second, the external environment of the bearing bush contains molten zinc, and the zinc slag and oxide particles it carries cause corrosion, erosion, and abrasive wear on the bearing bush surface. Third, there is relative sliding between the inner arc working surface of the bearing bush and the journal of the submerged or stabilizing roller; under the combined effects of load and high temperature, adhesive wear, scratches, localized seizing, and fatigue spalling are prone to occur. These factors collectively lead to frequent replacement of traditional bearing bushes in the production line, increasing spare parts consumption and causing downtime for maintenance and repair.

[0004] In existing technologies, common bearing materials include austenitic stainless steel, high-chromium cast iron, cobalt-based alloys, and surface-strengthened steel-based materials. Among these, austenitic stainless steels such as 316L have good corrosion resistance and machinability, but their low hardness results in insufficient wear resistance under the combined effects of high-temperature molten zinc, zinc slag, and journal friction, easily leading to accelerated wear and increased clearance. While high-hardness materials such as high-chromium cast iron offer improved wear resistance, their brittleness makes them prone to cracking under assembly impact, thermal cycling, or localized loads. Furthermore, their resistance to molten zinc corrosion is insufficient for long-term use. Cobalt-based alloys offer good high-temperature wear resistance, but their high cost and processing difficulty hinder large-scale adoption.

[0005] Some technologies attempt to strengthen the surface of the bearing bush through thermal spraying, welding, nitriding, and boronizing. While surface coatings or hardened layers can improve local surface hardness, the bond strength between the coating and the substrate can easily become weak under the combined effects of thermal cycling, high-temperature zinc corrosion, and mechanical loads. Once the coating cracks, peels off, or suffers localized damage, molten zinc and abrasive particles will further erode the substrate along the damaged area, leading to rapid bearing bush failure. Furthermore, the surface treatment layer has a limited thickness, making it difficult to withstand long-term severe wear conditions, and the dimensional stability of the parts after surface treatment and the consistency of subsequent processing also require additional control.

[0006] Therefore, it is necessary to develop a bearing material and its manufacturing process that can simultaneously achieve resistance to high-temperature zinc liquid corrosion, high hardness, wear resistance, toughness, and dimensional stability, making it suitable for key equipment such as submerged rolls and stabilizing rolls in cold-rolled hot-dip galvanizing production lines that are exposed to high-temperature, corrosive, and abrasive environments for extended periods. Summary of the Invention

[0007] The technical problem to be solved by this invention is to provide a bearing and its manufacturing process, addressing the issues of low hardness, poor wear resistance, insufficient resistance to zinc liquid corrosion, easy peeling of coating, short service life, and high overall maintenance costs in traditional bearing bushes produced in cold-rolled hot-dip galvanized production lines.

[0008] The technical approach of this invention does not rely solely on surface coatings or post-treatment strengthening. Instead, it addresses the issue through a synergistic approach involving alloy composition, casting microstructure, precipitate control, and heat treatment processes. It introduces elements such as niobium, titanium, and vanadium, which can form stable hard second phases, into the corrosion-resistant austenitic alloy system, enabling the bearing bush material to possess both a corrosion-resistant matrix and a dispersed strengthening phase. Through smelting and refining, modification and purification, controlled casting, solution treatment, and aging treatment, a uniform and refined microstructure is formed within the bearing bush material, reducing component segregation and coarse network carbides, thereby improving the wear resistance and stability of the bearing bush in high-temperature molten zinc.

[0009] To address the aforementioned technical problems, this invention provides a bearing bush for sliding support in the roller system of a cold-rolled hot-dip galvanized production line. The bearing bush includes a bearing body having an inner arc working surface for mating with the roller journal and an outer support surface for mating with a bearing housing. The roller system can be a submerged roller, a stabilizing roller, a straightening roller, or other rollers that need to rotate in a high-temperature molten zinc environment.

[0010] The bearing body is made of a zinc liquid corrosion resistant and wear-resistant alloy, which, by mass percentage, comprises the following components: C: 0.08%-0.28%, Cr: 16.00%-21.00%, Ni: 8.00%-14.00%, Mo: 2.00%-4.50%, Nb: 0.20%-1.80%, Ti: 0.03%-0.60%, V: 0.03%-0.80%, Mn: 0.30%-2.00%, Si: 0.20%-1.20%, N: 0.02%-0.20%, P≤0.035%, S≤0.020%, with the balance being Fe and unavoidable impurities.

[0011] Among them, Cr is an important element for forming corrosion resistance, which can improve the corrosion resistance of alloys in high-temperature zinc liquid and oxidizing environments; Ni is used to stabilize the austenite structure, improve the toughness and thermal fatigue resistance of materials; Mo can improve corrosion resistance, especially the resistance to localized corrosion, and has a positive effect on high-temperature strength; C combines with Nb, Ti, V and other elements to form hard carbides, nitrides or carbonitrides, which can improve the hardness and wear resistance of materials; Nb can form stable NbC or Nb(C,N), which is beneficial to refine grains and improve wear resistance; Ti can form fine precipitates with C and N, and also has a certain effect on controlling the morphology of inclusions; V can further improve the precipitation strengthening effect and improve the resistance to abrasive wear; N is beneficial to improve the stability and strength of austenite, but too high a content will increase the risk of porosity and nitride coarsening, so it needs to be controlled within an appropriate range. Mn and Si are deoxidizing and microstructure regulating elements, and should be controlled within a reasonable range to avoid excessive amounts leading to microstructure segregation or increased inclusions. P and S are harmful impurities and should be minimized to improve the material's hot working properties, toughness, and crack resistance.

[0012] Preferably, the zinc liquid corrosion resistant and wear-resistant alloy comprises, by mass percentage, the following components: C: 0.12%-0.22%, Cr: 17.00%-19.50%, Ni: 9.00%-12.50%, Mo: 2.50%-3.80%, Nb: 0.50%-1.30%, Ti: 0.08%-0.35%, V: 0.10%-0.50%, Mn: 0.60%-1.50%, Si: 0.35%-0.90%, N: 0.04%-0.14%, P≤0.030%, S≤0.015%, with the balance being Fe and unavoidable impurities. This preferred range achieves a good balance between corrosion resistance, hardness, toughness, and casting process stability.

[0013] Furthermore, the microstructure of the zinc liquid corrosion resistant and wear-resistant alloy comprises an austenitic matrix and hard second-phase particles dispersed within the austenitic matrix. The hard second-phase particles comprise carbides, nitrides, or carbonitrides formed from at least one element selected from Nb, Ti, and V. Preferably, the average particle size of the hard second-phase particles is 0.2 μm-8 μm. If the particle size of the hard second-phase particles is too large, it easily leads to localized stress concentration and reduces toughness; if the particle size is too small and the quantity is insufficient, the improvement in resistance to abrasive wear and adhesive wear is limited. Therefore, controlling the composition and heat treatment to make the hard second-phase particles small and dispersed is beneficial to improving the overall wear resistance of the bearing.

[0014] Furthermore, the bearing body is a semi-circular bearing, a fan-shaped bearing, or a full-circular bushing. For equipment such as submerged rollers and stabilizing rollers, semi-circular or fan-shaped bearings are easy to assemble and replace; for specific bearing housing structures, full-circular bushings can also be prepared using the materials and processes of this invention. At least one of the following structures can be provided on the inner arc working surface: a chip storage groove, a flow guide groove, or a positioning lip. The chip storage groove is used to accommodate a small amount of grinding debris or zinc slag particles, reducing the probability of continuous scratching between the inner arc working surface and the journal by hard particles; the flow guide groove is used to improve the flow state of zinc liquid or medium near the working surface, reducing local accumulation; the positioning lip is used to improve the assembly stability of the bearing in the bearing housing.

[0015] Furthermore, the bearing bush can also be a bimetallic composite bearing bush. The bearing bush body includes a support base and a wear-resistant layer composited inside the support base. The wear-resistant layer is made of the zinc liquid corrosion resistant and wear-resistant alloy described in this invention and forms an inner arc working surface. The support base can be made of a steel-based material with good toughness, and the wear-resistant layer bears the main functions of friction and wear resistance and zinc liquid corrosion resistance. This composite structure can reduce the overall alloy usage while ensuring the performance of the working surface, thus improving economy.

[0016] The present invention also provides a process for manufacturing bearing bushes, comprising the following steps.

[0017] S1. Raw Material Batching. Weigh out the iron-containing raw materials, chromium-containing raw materials, nickel-containing raw materials, molybdenum-containing raw materials, and alloying raw materials containing at least one element selected from Nb, Ti, and V according to the composition ratio of the zinc liquid corrosion-resistant and wear-resistant alloy. The iron-containing raw materials can be low-phosphorus and low-sulfur scrap steel, industrial pure iron, or stainless steel recycled materials; the chromium-containing raw materials can be metallic chromium or low-carbon ferrochrome; the nickel-containing raw materials can be electrolytic nickel or ferronickel; the molybdenum-containing raw materials can be ferromolybdenum; and the alloying raw materials containing Nb, Ti, and V can be ferroniobium, ferrotitanium, ferrovanadium, or corresponding intermediate alloys, respectively. Before batching, the raw materials should be dried, derusted, and their composition retested to prevent moisture, oil, and high-impurity raw materials from entering the smelting process.

[0018] S2. Melting and Refining. The weighed raw materials are added to a melting furnace and melted to obtain an alloy melt. The alloy melt is then subjected to deoxidation, desulfurization, and inclusion removal treatments. The melting furnace can be a medium-frequency induction furnace, an electric arc furnace, or a vacuum induction furnace. The melting temperature can be controlled between 1540℃ and 1660℃. Argon or vacuum protection is preferably used during the melting process to reduce abnormal fluctuations in the content of gases such as oxygen, hydrogen, and nitrogen. For alloy melts requiring higher purity, AOD, VOD, or ladle refining treatments can be performed after melting to reduce the oxygen content and inclusion content in the alloy melt.

[0019] S3. Modification and Purification. A modification and purification agent or inoculant is added to the molten alloy to cause inclusions to float and refine the solidification structure. The modification and purification agent can be rare earth ferrosilicon, calcium-silicon alloy, aluminum-based deoxidizer, or a composite agent. The purpose of modification and purification is to improve the morphology of inclusions, promote their floating, reduce the adverse effects of large inclusions on the fatigue performance and wear resistance of the bearing, and refine the solidification structure, providing a foundation for obtaining a uniform microstructure in subsequent heat treatment.

[0020] S4. Casting and Molding. The refined alloy molten metal is poured into a mold, and after cooling and solidification, a bearing blank is obtained. The mold can be a sand mold, metal mold, or centrifugal casting mold. The pouring temperature can be controlled between 1480℃ and 1580℃. If the pouring temperature is too low, the alloy molten metal will lack fluidity, easily resulting in cold shuts, slag inclusions, and incomplete pouring; if the pouring temperature is too high, it will easily cause coarse grains, element loss, and increased segregation. Therefore, an appropriate pouring temperature should be selected according to the casting size, mold material, and pouring method. After pouring, the cooling rate should be controlled to avoid the formation of continuous network carbides or severe dendritic segregation.

[0021] S5. Solution Treatment. Heat the bearing blank to 1040℃-1160℃, hold for a period, and then rapidly cool. Solution treatment allows some alloying elements to re-dissolve into the austenite matrix, mitigating the adverse effects of as-cast segregation and coarse precipitation on performance, and improving subsequent aging precipitation conditions. The holding time can be determined based on the thickness of the bearing blank, generally controlled at 0.5h-1.5h per 25mm of effective thickness. Rapid cooling can be achieved using water cooling, oil cooling, or forced air cooling; preferably, the cooling rate should be sufficient to suppress the continuous precipitation of unfavorable brittle phases.

[0022] S6. Aging Treatment. The solution-treated bearing blank is heated to 650℃-850℃, held at that temperature, and then cooled to precipitate hard second-phase particles formed by at least one of Nb, Ti, and V. The aging treatment temperature and time have a significant impact on the particle size, quantity, and distribution of the hard second phase. If the aging temperature is too low, precipitation is insufficient, and the hardness improvement is limited; if the aging temperature is too high or the holding time is too long, the second-phase particles are prone to growth, reducing the strengthening effect and potentially affecting toughness. Through proper aging treatment, the bearing material can achieve higher hardness and better wear resistance.

[0023] S7. Machining. The heat-treated bearing blank undergoes roughing, semi-finishing, and finishing to obtain a finished bearing with an inner arc working surface and an outer support surface. Machining includes turning, milling, boring, grinding, honing, or scraping. The inner arc working surface is a critical working surface of the bearing, and its dimensional accuracy, roundness, and surface roughness should be controlled. Preferably, the surface roughness Ra of the inner arc working surface after finishing is 0.4μm-1.6μm. After finishing, a low-temperature stress relief treatment can be performed to reduce residual machining stress and improve dimensional stability.

[0024] By adopting the above technical solution, the present invention has at least the following beneficial effects: 1. By introducing strong carbide-forming elements such as Nb, Ti, and V into the corrosion-resistant austenitic alloy system, and through the appropriate combination of C and N content, dispersed hard second-phase particles are formed in the bearing material. This structure can significantly improve the hardness and abrasive wear resistance of the bearing material, addressing the problems of low hardness and insufficient wear resistance in traditional 316L-type materials.

[0025] 2. By constructing a high-temperature zinc molten metal corrosion-resistant matrix using elements such as Cr, Ni, and Mo, the bearing material retains good corrosion resistance even in the high-temperature molten zinc environment. Compared to simply using high-hardness cast iron or brittle alloys, the material of this invention combines corrosion resistance and toughness, and is less prone to premature failure due to pitting corrosion, intergranular corrosion, or brittle fracture.

[0026] 3. By reducing gas, inclusions, and severe component segregation through smelting refining, modification purification, and controlled casting, the internal quality of the bearing billet is improved. This process can reduce the probability of shrinkage cavities, slag inclusions, coarse inclusions, and continuous network carbides, thereby improving the reliability of the bearing under alternating loads and high-temperature service environments. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of a bearing bush according to the present invention; Figure 2 This is a schematic diagram of the inner arc working surface of the bearing bush in this invention; Figure 3 This is a schematic diagram of the cross-sectional structure of the bimetallic composite bearing in this invention; Figure 4 This is a schematic flowchart of a bearing manufacturing process according to the present invention.

[0028] Explanation of reference numerals in the attached figures: 1. Bearing body; 11. Inner arc working surface; 12. Outer support surface; 13. End face; 14. Chip storage groove; 15. Guide groove; 16. Positioning lip; 2. Support base; 3. Wear-resistant layer; 4. Roller journal; 5. Bearing seat. Detailed Implementation

[0029] The present invention will be further described below with reference to embodiments. It should be understood that the following embodiments are used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Where there is no conflict, the technical features of the various embodiments can be combined with each other. Example

[0030] This embodiment provides an integral zinc liquid corrosion resistant and wear-resistant bearing and its manufacturing process. This bearing is used for the journal support position of the submerged roller in a cold-rolled hot-dip galvanized production line. The bearing body 1 is a semi-circular bearing structure, having an inner arc working surface 11, an outer support surface 12, and end faces 13 located at both axial ends of the bearing body 1. The inner arc working surface 11 is used to cooperate with the roller journal 4 of the submerged roller to form a sliding friction pair, and the outer support surface 12 is used to cooperate with the bearing seat 5 and is provided with radial support by the bearing seat 5. In this embodiment, the bearing body 1 is made of a zinc liquid corrosion resistant and wear-resistant alloy. The alloy composition by mass percentage is: C: 0.16%, Cr: 18.20%, Ni: 10.50%, Mo: 3.10%, Nb: 0.85%, Ti: 0.18%, V: 0.22%, Mn: 0.95%, Si: 0.55%, N: 0.08%, P: 0.020%, S: 0.008%, with the balance being Fe and unavoidable impurities.

[0031] In this composition, Cr, Ni, and Mo together constitute the main alloying system of the corrosion-resistant austenitic matrix. Cr enhances the material's corrosion resistance in high-temperature zinc bath and oxidizing atmospheres; Ni stabilizes the austenitic structure and improves toughness; and Mo improves resistance to localized corrosion and high-temperature strength. C and N, in combination with Nb, Ti, and V, form fine, dispersed carbides, nitrides, or carbonitrides, enhancing the material's wear resistance. Because the C content is higher than that of conventional 316L stainless steel, without the addition of strong carbide-forming elements and controlled heat treatment, coarse grain boundary carbides can easily form, reducing corrosion resistance. This embodiment, through controlled Nb, Ti, and V ratios and subsequent solution treatment and aging, ensures that carbon and nitrogen preferentially form stable second-phase particles with Nb, Ti, and V, minimizing the adverse effects on the matrix's corrosion resistance.

[0032] The bearing manufacturing process in this embodiment is as follows.

[0033] First, raw material preparation and batching are carried out. Low-phosphorus, low-sulfur scrap steel, electrolytic nickel, low-carbon ferrochrome, ferromolybdenum, ferroniobium, ferrotitanium, ferrovanadium, electrolytic manganese, and industrial silicon are selected as the main raw materials. Before batching, each raw material is surface-cleaned and dried to remove oil, moisture, and loose rust. The materials are weighed according to the target composition, and the addition amount is adjusted based on the content of the main elements and the burn-off rate in each ferroalloy. For elements such as Nb, Ti, and V, which are prone to forming inclusions or burn-off, a certain amount is reserved for process adjustment and added in the later stages of smelting.

[0034] Then, smelting and refining are carried out. Iron-containing raw materials, low-carbon ferrochrome, electrolytic nickel, and a portion of ferromolybdenum are added to a medium-frequency induction furnace for melting. During smelting, the furnace temperature is controlled at 1580℃-1620℃. After the furnace charge is completely melted, surface slag is removed, and a deoxidizer is added for pre-deoxidation. Subsequently, the remaining ferromolybdenum, ferroniobium, and ferrovanadium are added, ensuring they are fully dissolved and evenly diffused. Ferrotitanium is added before tapping to reduce Ti burn-off and oxidation inclusions. Argon gas is used for protection during smelting to reduce gas absorption and oxidation of the alloy melt. Before tapping, samples are taken for rapid composition analysis, and appropriate alloys are added based on the analysis results to bring the composition within the target range.

[0035] Subsequent purification and modification are carried out. A small amount of rare earth ferrosilicon and calcium-silicon composite purifying agent is added to the alloy melt and allowed to stand for a short time to allow deoxidation products and inclusions to float to the surface. This step can improve the morphology of inclusions, reduce the adverse effects of coarse inclusions on the working surface of the bearing, and also help refine the as-cast grains. After purification treatment, slag is removed again to ensure that the surface of the alloy melt is clean before casting.

[0036] Then, casting is performed. The molten alloy is poured into a preheated resin sand mold at 1520℃-1550℃. The sand mold has cavities corresponding to the semi-circular bearing blank, and feeding risers and venting structures are installed in thicker areas to reduce shrinkage cavities and porosity defects. During pouring, the filling process is kept stable to avoid air entrapment and secondary oxidation inclusions. After pouring, the casting is allowed to cool slowly in the sand mold to a suitable temperature before being opened. The risers and gating gates are cleaned, and the surface is shot-peened to obtain the bearing blank.

[0037] Solution treatment is then performed. The bearing blank is heated to 1100℃, held for 2 hours, and then rapidly water-cooled. Solution treatment allows some of the as-cast segregated structures and unfavorable precipitates to re-dissolve, improving matrix homogeneity and providing conditions for the subsequent precipitation of fine second phases during aging. After solution treatment, the surface of the bearing blank should be inspected; there should be no obvious cracks, deformation, or oxide spalling.

[0038] Aging treatment was then performed. The solution-treated bearing blank was heated to 760℃, held for 4 hours, and then air-cooled. During aging, Nb, Ti, and V formed fine, dispersed carbide, nitride, or carbonitride particles with C and N. These hard second-phase particles are distributed in the austenitic matrix and provide wear-resistant support when the inner arc working surface of the bearing is subjected to cutting by zinc slag particles and sliding friction of the journal. The aging temperature and holding time were controlled to avoid excessive coarsening of the second-phase particles.

[0039] Finally, machining is performed. First, the cast billet is rough turned and rough milled to remove casting allowances; then, semi-finishing is performed to form the inner arc working surface 11, outer support surface 12, and end face 13 of the bearing body 1; subsequently, the inner arc working surface 11 is precision bored, precision ground, and honed to meet the designed arc dimensions and surface roughness requirements. In this embodiment, the surface roughness of the inner arc working surface 11 is controlled to Ra 0.8μm-1.2μm. After machining, a low-temperature stress relief treatment is performed at 280℃, held for 2 hours, and then cooled in the furnace to reduce machining stress and improve dimensional stability after assembly.

[0040] The bearing bush produced by the above process has an austenitic matrix with dispersed hard second-phase particles in its microstructure. Compared with traditional 316L type bearing bushes, the bearing bush of this embodiment has significantly improved hardness and wear resistance, and can better resist wear caused by the relative sliding of hard particles in molten zinc and journal; at the same time, since the Cr, Ni and Mo contents are kept within the range of corrosion-resistant alloys, the bearing bush still has good corrosion resistance in the high-temperature molten zinc environment. Example

[0041] This embodiment provides a bearing suitable for stabilizing the support position of a roller journal and its manufacturing process. The difference between this embodiment and Embodiment 1 is that this embodiment further increases the Mo and Nb content to enhance resistance to localized corrosion and precipitation strengthening effect, and uses metal mold casting to improve the density of the cast billet structure. In this embodiment, the bearing body 1 is a fan-shaped bearing structure. Two axially extending chip storage grooves 14 are provided on the inner arc working surface 11 of the bearing body 1, located in the non-main load-bearing area of ​​the inner arc working surface 11. The chip storage grooves 14 can accommodate a small amount of grinding debris, zinc slag particles, or oxide particles, reducing the probability of repeated scratches from hard particles between the inner arc working surface 11 and the roller journal 4. A positioning lip 16 is also provided on one end of the bearing body 1. The positioning lip 16 is used to cooperate with the limiting groove on the bearing seat 5 to prevent circumferential movement of the bearing during operation. By mass percentage, the zinc liquid corrosion resistant and wear-resistant alloy composition of this embodiment is: C: 0.20%, Cr: 18.80%, Ni: 11.20%, Mo: 3.60%, Nb: 1.15%, Ti: 0.12%, V: 0.35%, Mn: 1.10%, Si: 0.60%, N: 0.10%, P: 0.018%, S: 0.006%, with the balance being Fe and unavoidable impurities.

[0042] The preparation process in this embodiment includes the following steps.

[0043] First, raw material preparation. Low-sulfur and low-phosphorus raw materials are selected based on the target composition, with priority given to the use of electrolytic nickel, ferromolybdenum, ferroniobium, and ferrovanadium with stable compositions to reduce compositional fluctuations caused by recycled materials. All raw materials are preheated and dried before being added to the smelting furnace.

[0044] Second, vacuum induction melting. The raw materials are added to a vacuum induction furnace and melted under vacuum conditions. After the melt is cleared, high-purity argon gas is introduced for protection, and the furnace temperature is adjusted to approximately 1600℃. Vacuum induction melting reduces the gas content and oxide inclusion content, improving the purity of the alloy melt. Nb and V are added in the later stages of melting, while Ti is added before tapping to ensure effective yield.

[0045] Third, composite deoxidation and purification. An aluminum-based deoxidizer is added to the alloy melt for initial deoxidation, followed by the addition of a calcium-silicon alloy for inclusion modification treatment, transforming sharp inclusions into relatively rounded and easily floating inclusions. After treatment, the mixture is allowed to stand for 5-8 minutes, and slag is removed.

[0046] Fourth, metal mold casting. The molten alloy is poured at 1500℃-1530℃ into a metal mold preheated to 250℃-350℃ to obtain the bearing blank. Metal molds have a faster cooling rate than sand molds, which is beneficial for refining the as-cast microstructure and reducing coarse dendrites and segregation areas. For thick-walled bearing blanks, a heat-insulating and feeding zone can be set on the outside of the metal mold to ensure the compactness of the blank.

[0047] Fifth, a two-stage heat treatment. First, the bearing billet is heated to 1120℃, held for 2.5 hours, and then water-cooled to complete the solution treatment. Then, a first-stage aging treatment is performed, holding at 720℃ for 3 hours followed by air cooling, allowing the fine second phase to initially precipitate. A second-stage aging treatment is then performed, holding at 680℃ for 5 hours followed by air cooling, further stabilizing the second-phase particles. This two-stage aging treatment results in a more uniform distribution of the hard second phase and reduces particle coarsening caused by prolonged high-temperature aging alone.

[0048] Sixth, machining and surface treatment. The heat-treated billet is first rough-machined, leaving room for finishing; then the chip storage groove 14, positioning lip 16, inner arc working surface 11, and outer support surface 12 are machined. The surface roughness of the inner arc working surface 11 is controlled to Ra 0.6μm-1.0μm after precision grinding. The edges of the chip storage groove 14 are rounded to avoid stress concentration or scratching of the journal at sharp corners.

[0049] This embodiment enhances resistance to zinc bath corrosion through a higher Mo content, improves precipitation strengthening and resistance to abrasive wear through higher Nb and V content, and improves microstructure uniformity through metal mold casting and two-stage aging treatment. This scheme is suitable for stable roller bearing locations with high loads and significant zinc slag particle erosion. Example

[0050] This embodiment provides a bimetallic composite bearing and its manufacturing process. This embodiment is suitable for applications where material cost is a concern, but the inner arc working surface 11 still needs to possess high wear resistance and resistance to zinc liquid corrosion. In this embodiment, the bearing body 1 includes a support substrate 2 and a wear-resistant layer 3 composited on the inner side of the support substrate 2. The support substrate 2 is made of a steel-based material with good toughness, used to bear the overall support and assembly load of the bearing; the wear-resistant layer 3 is made of the zinc liquid corrosion resistant and wear-resistant alloy described in this invention, and forms the inner arc working surface 11 of the bearing. The thickness of the wear-resistant layer 3 can be 3mm-15mm, preferably 5mm-10mm. Too small a thickness of the wear-resistant layer 3 will reduce the wear allowance, while too large a thickness will increase the amount of alloy material used and the difficulty of composite bonding.

[0051] By mass percentage, the zinc liquid corrosion resistant wear-resistant alloy composition used in the wear-resistant layer 3 in this embodiment is as follows: C: 0.14%, Cr: 17.60%, Ni: 10.00%, Mo: 2.80%, Nb: 0.70%, Ti: 0.20%, V: 0.18%, Mn: 0.85%, Si: 0.50%, N: 0.06%, P: 0.020%, S: 0.008%, with the balance being Fe and unavoidable impurities.

[0052] The manufacturing process of the bimetallic composite bearing in this embodiment is as follows.

[0053] First, the support substrate 2 is prepared. The steel-based support substrate 2 is machined according to the bearing bush's external dimensions. The inner composite surface of the support substrate 2 is then roughened by turning or sandblasting to give the composite surface a certain roughness, thereby improving the mechanical bonding force between the wear-resistant layer 3 and the support substrate 2. Before lamination, the support substrate 2 undergoes degreasing, rust removal, and preheating treatment at a temperature of 250℃-450℃.

[0054] Next, the wear-resistant layer alloy melt is prepared. The materials are batched and smelted according to the aforementioned three components of the wear-resistant layer, with the smelting temperature controlled between 1560℃ and 1640℃. After smelting, deoxidation, purification, and composition adjustment are performed to ensure the alloy melt meets the target composition requirements. Before tapping, the temperature of the alloy melt is controlled to make it suitable for composite casting.

[0055] Then, composite molding is performed. The preheated support substrate 2 is fixed in the composite casting mold, with its inner composite surface facing the cavity. The wear-resistant layer alloy molten material is poured into the inner side of the support substrate 2, allowing the alloy molten material to metallurgically bond with the surface of the support substrate 2, or a combination of metallurgical bonding and mechanical interlocking. After pouring, the cooling rate is controlled to prevent cracking and severe segregation of the wear-resistant layer 3. For a fully circular bushing structure, centrifugal casting can also be used to ensure that the wear-resistant layer alloy molten material is evenly spread on the inner surface of the support substrate.

[0056] The composite billet is then subjected to heat treatment. It is heated to 1060℃-1100℃ for solution treatment, held at that temperature, and then rapidly cooled. Next, it undergoes aging treatment at 700℃-780℃ to form dispersed hard second-phase particles in the wear-resistant layer 3. Considering the difference in thermal expansion between the supporting substrate 2 and the wear-resistant layer 3, rapid temperature changes should be avoided during the heating and cooling processes to reduce interfacial thermal stress.

[0057] Finally, machining is performed. The outer support surface 12, end face 13, and inner arc working surface 11 of the composite blank are machined. During machining, it should be ensured that the wear-resistant layer 3 has a continuous thickness in the area of ​​the inner arc working surface 11, and the wear-resistant layer 3 should not be machined through. After finishing, the inner arc working surface 11 is honed to meet the journal fit requirements.

[0058] This embodiment employs a composite structure of the support substrate 2 and the wear-resistant layer 3, enabling the working surface of the bearing bush to possess the wear and corrosion resistance properties of the alloy of this invention, while simultaneously reducing the overall amount of high-alloy materials used. This solution is suitable for bearing bush products with larger specifications and higher cost control requirements. Example

[0059] This embodiment provides a fully circular bushing with a guide groove and its manufacturing process. This fully circular bushing can be used in bearing support parts of some roller systems that require integral assembly. In this embodiment, the bearing body 1 is a fully circular bushing structure, the inner arc working surface 11 is a complete cylindrical inner hole surface, and the outer support surface 12 is a cylindrical outer surface that mates with the bearing seat 5. A spiral guide groove 15 is provided on the inner arc working surface 11. The guide groove 15 extends spirally along the bushing axis to improve the flow state of molten zinc or trace amounts of lubricating medium in the working area and to provide temporary storage space for small amounts of wear debris. The bottom of the guide groove 15 adopts a rounded transition to reduce stress concentration.

[0060] By mass percentage, the zinc liquid corrosion resistant and wear-resistant alloy composition of this embodiment is: C: 0.18%, Cr: 19.20%, Ni: 12.00%, Mo: 3.30%, Nb: 0.95%, Ti: 0.10%, V: 0.28%, Mn: 1.20%, Si: 0.65%, N: 0.09%, P: 0.022%, S: 0.009%, with the balance being Fe and unavoidable impurities.

[0061] This embodiment uses centrifugal casting to prepare a fully circular bushing billet. The melting and refining processes are basically the same as in Embodiment 1. During casting, the alloy molten liquid is poured into a rotating metal mold at 1510℃-1550℃. Centrifugal force causes the alloy molten liquid to adhere to the inner wall of the mold and solidify to form a cylindrical billet. Centrifugal casting can improve the density of the bushing billet, causing inclusions and porosity to tend to concentrate inward, facilitating their removal in subsequent processing. After cooling, the billet undergoes solution treatment and aging treatment. The solution treatment temperature is 1110℃, held for 2 hours, and then water-cooled; the aging treatment temperature is 740℃, held for 4 hours, and then air-cooled.

[0062] During machining, the outer support surface 12 and end face 13 are machined first, then the inner hole is machined to form the inner arc working surface 11. Finally, a special tool or grinding tool is used to machine the spiral guide groove 15. After the guide groove 15 is machined, the groove opening is chamfered or rounded to prevent the sharp edge of the groove from scratching the roller journal 4. The final surface roughness of the inner arc working surface 11 is controlled to Ra 0.8μm-1.6μm.

[0063] The fully circular bushing of this embodiment is suitable for scenarios where the bearing housing structure allows for integral installation. Centrifugal casting improves the density of the cast billet, and the guide groove 15 improves the medium flow and particle containment capacity near the inner arc working surface 11, which is beneficial to improving the stable operation of the bushing in the high-temperature zinc liquid environment.

[0064] The bearing bush and its manufacturing process described in this invention are applicable to key equipment such as submerged rolls and stabilizing rolls in cold-rolled hot-dip galvanizing production lines. They can also be used in other mechanical support components subjected to high temperatures, liquid metal corrosion, abrasive wear, and sliding friction. By adjusting the bearing bush structure, wear-resistant layer thickness, and the arrangement of the chip storage groove or guide groove, this invention can be adapted to different bearing housings and roller journal structures, demonstrating significant industrial application value. The above description is merely a preferred embodiment of this invention and is not intended to limit the invention. All equivalent substitutions, adjustments, and improvements made within the scope of the invention's concept and principles to the alloy composition range, smelting equipment, casting method, heat treatment regime, bearing bush structure, and processing method should be included within the protection scope of this invention.

Claims

1. A bearing bush, characterized in that, The bearing bush is used as a sliding support for the roller system equipment in a cold-rolled hot-dip galvanized production line. The bearing bush includes a bearing bush body, which has an inner arc working surface for cooperating with the roller journal and an outer support surface for cooperating with the bearing seat. The bearing body is made of a zinc-water corrosion-resistant and wear-resistant alloy, which comprises the following components by mass percentage: C: 0.08%-0.28%, Cr: 16.00%-21.00%, Ni: 8.00%-14.00%, Mo: 2.00%-4.50%, Nb: 0.20%-1.80%, Ti: 0.03%-0.60%, V: 0.03%-0.80%, Mn: 0.30%-2.00%, Si: 0.20%-1.20%, N: 0.02%-0.20%, P≤0.035%, S≤0.020%, with the balance being Fe and unavoidable impurities.

2. The bearing bush according to claim 1, characterized in that, The zinc liquid corrosion resistant and wear-resistant alloy comprises the following components by weight percentage: C: 0.12%-0.22%, Cr: 17.00%-19.50%, Ni: 9.00%-12.50%, Mo: 2.50%-3.80%, Nb: 0.50%-1.30%, Ti: 0.08%-0.35%, V: 0.10%-0.50%, Mn: 0.60%-1.50%, Si: 0.35%-0.90%, N: 0.04%-0.14%, P≤0.030%, S≤0.015%, with the balance being Fe and unavoidable impurities.

3. A bearing bush according to claim 1 or 2, characterized in that, The microstructure of the zinc liquid corrosion resistant and wear-resistant alloy includes an austenitic matrix and hard second-phase particles dispersed in the austenitic matrix. The hard second-phase particles include carbides, nitrides or carbonitrides formed by at least one of Nb, Ti and V.

4. A bearing bush according to claim 3, characterized in that, The hard second phase particles have an average particle size of 0.2μm-8μm and are dispersed in the austenitic matrix; the surface roughness Ra of the inner arc working surface of the bearing body after precision machining is 0.4μm-1.6μm.

5. A bearing bush according to claim 1, characterized in that, The bearing body is a semi-circular bearing, a fan-shaped bearing, or a full-circular bushing; the inner arc working surface is provided with at least one of the following structures: a chip storage groove, a flow guide groove, or a positioning lip, and the chip storage groove or flow guide groove extends along the axial, circumferential, or inclined direction of the bearing body.

6. A bearing bush according to claim 1, characterized in that, The bearing bush is a bimetallic composite bearing bush. The bearing bush body includes a support base and a wear-resistant layer composited inside the support base. The wear-resistant layer is made of the zinc liquid corrosion resistant wear-resistant alloy and forms the inner arc working surface.

7. A manufacturing process for the bearing bush as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Raw material preparation: Weigh iron-containing raw materials, chromium-containing raw materials, nickel-containing raw materials, molybdenum-containing raw materials, and alloying raw materials containing at least one element among Nb, Ti, and V according to the composition ratio of the zinc liquid corrosion resistant and wear-resistant alloy. S2. Melting and refining: The raw materials are added to a melting furnace to melt them, and the alloy melt is then subjected to deoxidation, desulfurization and inclusion removal treatment. S3, Modification and Purification: Add a modification and purification agent or inoculant to the alloy melt to make the inclusions in the alloy melt float to the surface and refine the solidification structure; S4. Casting and molding: The refined alloy molten liquid is poured into the mold and cooled and solidified to obtain the bearing blank; S5. Solution treatment: Heat the bearing blank to 1040℃-1160℃, hold it at that temperature, and then cool it rapidly. S6. Aging treatment: Heat the solution-treated bearing billet to 650℃-850℃, hold it at that temperature and then cool it to allow hard second-phase particles formed by at least one of Nb, Ti and V to precipitate out. S7. Machining: Rough machining, semi-finishing and finishing are performed on the heat-treated bearing blank to obtain the finished bearing with an inner arc working surface and an outer support surface.

8. The manufacturing process of a bearing bush according to claim 7, characterized in that, In step S2, the melting furnace is a medium-frequency induction furnace, an electric arc furnace, or a vacuum induction furnace; the melting temperature is 1540℃-1660℃; argon gas protection or vacuum protection is used during the melting process; and the oxygen content in the alloy melt is controlled to be no higher than 80ppm before tapping.

9. The manufacturing process of a bearing bush according to claim 7, characterized in that, In step S4, the mold is a sand mold, a metal mold, or a centrifugal casting mold, and the pouring temperature is 1480℃-1580℃; after pouring, the cooling rate is controlled so that continuous network carbides do not form in the bearing blank.

10. The manufacturing process of a bearing bush according to claim 7, characterized in that, In step S7, after finishing, the inner arc working surface is subjected to stress relief treatment, fine grinding or honing treatment so that the dimensional accuracy and surface roughness of the inner arc working surface meet the assembly requirements of the submerged roller or stabilizing roller journal.

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