Non-magnetic alloy with high product of strength and elongation and heat treatment process thereof

Abstract

The non-magnetic alloy comprises the following chemical components in percentage by weight: less than or equal to 0.03% of C, less than or equal to 0.15% of Si, less than or equal to 0.15% of Mn, 39.00%-41.00% of Cr, 3.50%-6.00% of Al, less than or equal to 0.80% of Ti and the balance of Ni and inevitable impurities. The heat treatment process comprises the steps of preheating, hot charging and high-temperature solid solution treatment and double-gradient overaging treatment, the excellent comprehensive performance of the non-magnetic alloy can be achieved, the tensile strength ranges from 2209 MPa to 2350 MPa, the ductility ranges from 23.2% to 26.3%, the average grain size ranges from 10.87 micrometers to 18.56 micrometers, and the product of strength and ductility ranges from 51.98 GPa% to 60.84 GPa%.

Description

Technical Field

[0001] The invention belongs to the technical field of heat treatment of metal materials, and in particular relates to a high-strength plasticity non-magnetic alloy and a heat treatment process thereof. Background Art

[0002] Bearings, known as the "joints" of mechanical equipment, carry a variety of complex alternating loads. As a major player in the global research and development and production of bearing materials, my country currently possesses a diverse range of bearing material families, including high-carbon chromium bearing steel, carburized bearing steel, high-temperature bearing steel, medium-carbon bearing steel, and non-magnetic bearing steel. Non-magnetic bearing steel, in particular, is a critical component in this field and plays a vital role in industries such as aerospace, defense, and military. Furthermore, with technological advancements, the application of non-magnetic bearing steel in civilian applications such as medical devices continues to expand.

[0003] 00Cr40Ni55Al3 is a nickel-based non-magnetic alloy that combines non-magnetic, wear-resistant, corrosion-resistant, and high-temperature resistant properties. It exhibits excellent processability under solid solution conditions. After aging treatment, due to the precipitation hardening effect of the γ´ and α-Cr phases in the microstructure, the surface hardness reaches as high as 62HRC, meeting the performance requirements of bearing materials for non-magnetic, vacuum, and self-lubricating service conditions in high-temperature environments of 300°C to 500°C. However, due to the excessively high surface hardness and poor plasticity after aging, the alloy cannot meet the quality requirements of critical aerospace non-magnetic bearings in actual service. Achieving a balance between the strength and plasticity of non-magnetic alloys is key to further improving the material's service life.

[0004] Traditional methods for achieving strength and plasticity balance in bearing steel mainly include: (1) Microstructure refinement: According to the Hall-Petch formula, by maximizing the refinement of grain size and secondary phases such as carbides, high strength, good plasticity, and toughness of the material can be achieved simultaneously. Some typical technical methods to achieve this goal include cyclic quenching, recrystallization annealing, and multi-directional forging.

[0005] (2) Surface strengthening: By reducing the carbon content in the steel matrix, its plasticity is improved, and then the surface structure is made to obtain a higher strengthening element than the core material through surface carburizing, nitriding, carbonitriding, etc., and the surface structure with high strength and high hardness and the core structure with high plasticity are obtained through quenching and tempering; typical representatives are M50NiL, CSS-42L, etc. (3) Induction quenching: Through the skin effect of high-frequency induction heating, the surface area of the steel is fully quenched and strengthened compared to the core area. The strength decreases from the surface to the core, and the plasticity increases from the surface to the core.

[0006] The above-mentioned typical technical means of balancing strength and toughness of bearing steel can all achieve a significant improvement in the overall performance of the steel. However, since the 00Cr40Ni55Al3 non-magnetic alloy is a nickel-based alloy, its strengthening mechanism is different from that of traditional bearing steel. It mainly relies on the precipitation strengthening of intermetallic compounds and second phases such as α-Cr, and there is no solid-state matrix phase transformation. It is impossible to achieve microstructure refinement through phase transformation, nor can it achieve martensitic transformation through quenching. Therefore, it is impossible to improve the fatigue strength of the 00Cr40Ni55Al3 non-magnetic alloy simply by using traditional technical means. Therefore, it is urgent to adopt innovative technical means to achieve a good balance between strength and plasticity of the non-magnetic alloy 00Cr40Ni55Al3. Summary of the Invention

[0007] The purpose of the present invention is to provide a high-strength-ductility non-magnetic alloy and its heat treatment process, to obtain a gradient microstructure consisting of micron-level α-Cr, nanometer-level γ' and austenite grains with an average size of 10.87μm~18.56μm, and to achieve a higher strength-ductility.

[0008] To achieve the above object, the technical solution adopted by the present invention is: A high-strength and high-plasticity non-magnetic alloy, wherein the chemical elements and mass fractions of the non-magnetic alloy meet the following requirements: C≤0.03%, Si≤0.15%, Mn≤0.15%, Cr: 39.00%-41.00%, Al: 3.50%-6.00%, Ti≤0.80%, and the balance is Ni and unavoidable impurities.

[0009] A heat treatment process for a strong-plastic non-magnetic alloy comprises the following steps: S1. Preheating: keep the alloy at 500℃~600℃; S2. Hot charging and high temperature solution: the preheated alloy is directly placed in a heating furnace at 1180℃~1250℃ for heat preservation. After the heat preservation is completed, it is immediately placed in a water pool to cool to room temperature; S3. Double gradient overaging: The alloy after hot-charging and high-temperature solid solution is heated from room temperature to 750℃~850℃ and kept warm, then cooled to 650℃~700℃ at a cooling rate of no more than 30℃ / hour and kept warm, and then naturally cooled to room temperature in air to obtain a non-magnetic alloy.

[0010] Preferably, the holding time in S1 is 2 hours to 3 hours.

[0011] Preferably, the holding time in S2 is 1 hour to 2 hours.

[0012] Preferably, the water temperature in the water pool in S2 is 20-28°C.

[0013] Preferably, the time for heating from room temperature to 750° C. to 850° C. in S3 is 2 hours to 3 hours.

[0014] Preferably, the holding time at 750° C. to 850° C. in S3 is 18 hours to 24 hours.

[0015] Preferably, the cooling to 650° C. to 700° C. and holding time in S3 is 18 hours to 24 hours.

[0016] Preferably, the alloy described in S1 and the non-magnetic alloy described in S3 have the same chemical elements and mass fractions.

[0017] Preferably, the non-magnetic alloy has a tensile strength of 2209 MPa to 2350 MPa, an elongation of 23.2% to 26.3%, an average grain size of 10.87 μm to 18.56 μm, and a strength-ductility product of 51.98 GPa% to 60.84 GPa%.

[0018] Furthermore, the non-magnetic alloy is prepared into hot-rolled bars through vacuum induction melting, vacuum consumable remelting, forging, rolling and other processes.

[0019] The room temperature of the present invention is 4-39°C.

[0020] The beneficial effects of the technical solution of the present invention are: The present invention adds the intermetallic compound strengthening element Ti on the basis of the chemical composition of the 00Cr40Ni55Al3 non-magnetic alloy and increases the Al element content to achieve the stabilization and refinement of the grain structure. At the same time, the size distribution of the second phase precipitates is effectively controlled by means of gradient aging treatment.

[0021] The present invention scientifically optimizes the chemical composition of existing non-magnetic alloys and combines them with double-gradient aging treatment to obtain a gradient microstructure consisting of micron-level α-Cr, nanometer-level γ' and austenite grains with an average size of 10.87μm to 18.56μm, thereby achieving an alloy with a high strength-ductility product. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a temperature-time curve diagram of the heat treatment process of the present invention.

[0023] Figure 2 This is a scanning electron microscope photo of the non-magnetic alloy in Example 1. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below with reference to the embodiments. Example 1

[0025] The hot-rolled bars were prepared by the processes of forging, hot rolling and other processes with a φ300mm×700mm ingot smelted by "vacuum induction + vacuum consumable" and the chemical composition was C: 0.03%, Si: 0.10%, Mn: 0.15%, Cr: 39.00%, Al: 3.50%, Ti: 0.80%, Ni: 56.41%. The non-magnetic alloy bars were preheated, hot-charged, high-temperature solid solution treated and double-gradient overaging treated in sequence. The specific operations are as follows: (1) Preheating: Keep the alloy at 500℃ for 2 hours; (2) Hot charging and high temperature solution: the preheated alloy is directly placed in a heating furnace at 1180℃ for 1 hour, and then quickly placed in a 20℃ water pool to cool to room temperature; (3) Double gradient overaging: The solution-treated alloy was heated from room temperature to 750°C within 2 hours and kept at this temperature for 18 hours. It was then cooled to 650°C at a cooling rate of 30°C / hour and kept at this temperature for 18 hours. It was then naturally cooled to room temperature in air. Figure 2 , the temperature-time curve of heat treatment process is shown in Figure 1 .

[0026] The tensile strength, elongation, strength-ductility product and average grain size of the non-magnetic alloy of this embodiment are shown in Table 1. Example 2

[0027] The hot-rolled bars were prepared by the processes of forging, hot rolling and other processes with a φ300mm×700mm ingot smelted by "vacuum induction + vacuum consumable" method. The chemical composition is C: 0.02%, Si: 0.10%, Mn: 0.15%, Cr: 40.00%, Al: 4.2%, Ti: 0.64%, Ni: 54.88%. The non-magnetic alloy bars were preheated, hot-charged, high-temperature solid solution treated and double-gradient overaging treated in sequence. The specific operations are as follows: (1) Preheating: Keep the alloy at 550℃ for 3 hours; (2) Hot charging and high temperature solution: the preheated alloy is directly placed in a heating furnace at 1200℃ for 2 hours, and then quickly placed in a 28℃ water pool to cool to room temperature; (3) Double gradient overaging: The solution-treated alloy was heated from room temperature to 800 °C within 3 hours and kept at this temperature for 20 hours. It was then cooled to 700 °C at a cooling rate of 30 °C / hour and kept at this temperature for 20 hours. It was then naturally cooled to room temperature in air.

[0028] The tensile strength, elongation, strength-ductility product and average grain size of the non-magnetic alloy of this embodiment are shown in Table 1. Example 3

[0029] The hot-rolled bars were prepared by the processes of forging, hot rolling and other processes with a φ300mm×700mm ingot smelted by "vacuum induction + vacuum consumable" smelting. The chemical composition is C: 0.03%, Si: 0.15%, Mn: 0.15%, Cr: 41.00%, Al: 5.00%, Ti: 0.80%, Ni: 52.86%. The non-magnetic alloy bars were preheated, hot-charged, high-temperature solid solution treated and double-gradient overaging treated in sequence. The specific operations are as follows: (1) Preheating: Keep the alloy at 600℃ for 3 hours; (2) Hot charging and high temperature solution: the preheated alloy is directly placed in a heating furnace at 1250℃ and kept warm for 2 hours, and then quickly placed in a 25℃ water pool to cool to room temperature; (3) Double gradient overaging: The solution-treated alloy was heated from room temperature to 850 °C within 3 hours and kept at this temperature for 24 hours. It was then cooled to 700 °C at a cooling rate of 30 °C / hour and kept at this temperature for 24 hours. It was then naturally cooled to room temperature in air.

[0030] The tensile strength, elongation, strength-ductility product and average grain size of the non-magnetic alloy of this embodiment are shown in Table 1. Example 4

[0031] The hot-rolled bars were prepared by the processes of forging, hot rolling and other processes with a φ300mm×700mm ingot smelted by "vacuum induction + vacuum consumable" and the chemical composition was C: 0.01%, Si: 0.10%, Mn: 0.10%, Cr: 40%, Al: 6.00%, Ti: 0.70%, and Ni: 53.08%. The non-magnetic alloy bars were preheated, hot-charged, and subjected to high-temperature solid solution and double-gradient overaging treatments in sequence. The specific operations are as follows: (1) Preheating: Keep the alloy at 550℃ for 2.5 hours; (2) Hot charging and high temperature solution: the preheated alloy is directly placed in a heating furnace at 1190℃ for 1.5 hours, and then quickly placed in a 26℃ water pool to cool to room temperature; (3) Double gradient overaging: The solution-treated alloy was heated from room temperature to 800 °C within 2.5 hours and kept at this temperature for 24 hours. It was then cooled to 700 °C at a cooling rate of 30 °C / hour and kept at this temperature for 24 hours. It was then naturally cooled to room temperature in air.

[0032] The tensile strength, elongation, strength-ductility product and average grain size of the non-magnetic alloy of this embodiment are shown in Table 1. Example 5

[0033] The hot-rolled bars were prepared by the processes of forging, hot rolling and other processes with a φ300mm×700mm ingot smelted by "vacuum induction + vacuum consumable" method. The chemical composition is C: 0.03%, Si: 0.15%, Mn: 0.15%, Cr: 41.00%, Al: 5.50%, Ti: 0.80%, Ni: 52.36%. The non-magnetic alloy bars were preheated, hot-charged, high-temperature solid solution treated and double-gradient overaging treated in sequence. The specific operations are as follows: (1) Preheating: Keep the alloy at 500℃ for 3 hours; (2) Hot charging and high temperature solution: the preheated alloy is placed directly into a heating furnace at 1200°C for 1 hour, and then quickly placed in a 26°C water pool to cool to room temperature; (3) Double gradient overaging: The solution-treated alloy was heated from room temperature to 850 °C within 2.5 hours and kept at this temperature for 20 hours. It was then cooled to 650 °C at a cooling rate of 30 °C / hour and kept at this temperature for 20 hours. It was then naturally cooled to room temperature in air.

[0034] The tensile strength, elongation, strength-ductility product and average grain size of the non-magnetic alloy of this embodiment are shown in Table 1. Example 6

[0035] The hot-rolled bars were prepared by the processes of forging, hot rolling and other processes with a φ300mm×700mm ingot smelted by "vacuum induction + vacuum consumable" and the chemical composition was C: 0.03%, Si: 0.15%, Mn: 0.15%, Cr: 40.00%, Al: 3.50%, Ti: 0.50%, Ni: 55.66. The non-magnetic alloy bars were preheated, hot-charged, high-temperature solid solution treated and double-gradient overaging treated in sequence. The specific operations are as follows: (1) Preheating: keep the alloy at 550℃ for 2 hours; (2) Hot charging and high temperature solution: the preheated alloy is directly placed in a heating furnace at 1180℃ for 2 hours, and then quickly placed in a 27℃ water pool to cool to room temperature; (3) Double gradient overaging: The solution-treated alloy was heated from room temperature to 750 °C within 3 hours and kept at this temperature for 24 hours. It was then cooled to 650 °C at a cooling rate of 30 °C / hour and kept at this temperature for 24 hours. It was then naturally cooled to room temperature in air.

[0036] The tensile strength, elongation, strength-ductility product and average grain size of the non-magnetic alloy of this embodiment are shown in Table 1.

[0037] Table 1 Properties of non-magnetic bearing alloys in various embodiments

[0038] The scanning electron microscope photo of the microstructure of Example 1 is shown in Figure 2 The microstructure scanning electron microscope photos of the other examples are similar to Figure 2 Similar, no more repetition.

[0039] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A high-strength, high-plasticity, non-magnetic alloy, characterized in that: The chemical elements and mass fractions of the non-magnetic alloy meet the following requirements: C≤0.03%, Si≤0.15%, Mn≤0.15%, Cr: 39.00%-41.00%, Al: 3.50%-6.00%, Ti≤0.80%, and the remainder is Ni and unavoidable impurities.

2. The heat treatment process of a strong plastic non-magnetic alloy according to claim 1, characterized in that: The following steps are involved: S1. Preheating: keep the alloy at 500℃~600℃; S2. Hot charging and high temperature solution: the preheated alloy is directly placed in a heating furnace at 1180℃~1250℃ for heat preservation. After the heat preservation is completed, it is immediately placed in a water pool to cool to room temperature; S3. Double gradient overaging: The alloy after hot-charging and high-temperature solid solution is heated from room temperature to 750℃~850℃ and kept warm, then cooled to 650℃~700℃ at a cooling rate of no more than 30℃ / hour and kept warm, and then naturally cooled to room temperature in air to obtain a non-magnetic alloy.

3. The heat treatment process of a high-strength-plastic-product non-magnetic alloy according to claim 1, characterized in that: The holding time in S1 is 2 to 3 hours.

4. The heat treatment process of a high-strength-plastic-product non-magnetic alloy according to claim 1, characterized in that: The holding time in S2 is 1 to 2 hours.

5. The heat treatment process of a high-strength-plastic-product non-magnetic alloy according to claim 1, characterized in that: The water temperature in the pool in S2 is 20~28℃.

6. The heat treatment process of a high-strength-plastic-product non-magnetic alloy according to claim 1, characterized in that: The time for heating from room temperature to 750° C. to 850° C. in S3 is 2 to 3 hours.

7. The heat treatment process of a high-strength-plastic-product non-magnetic alloy according to claim 1, characterized in that: The holding time at 750℃~850℃ in S3 is 18 hours~24 hours.

8. The heat treatment process of a high-strength-plasticity non-magnetic alloy according to claim 1, characterized in that: In S3, the temperature is cooled to 650°C~700°C and the holding time is 18 hours~24 hours.

9. The heat treatment process of a high-strength-plasticity non-magnetic alloy according to claim 1, characterized in that: The alloy described in S1 and the non-magnetic alloy described in S3 have the same chemical elements and mass fractions.

10. The heat treatment process of a high-strength-plasticity non-magnetic alloy according to claim 1, characterized in that: The non-magnetic alloy has a tensile strength of 2209 MPa to 2350 MPa, an elongation of 23.2% to 26.3%, an average grain size of 10.87 μm to 18.56 μm, and a strength-ductility product of 51.98 GPa% to 60.84 GPa%.

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