As a key piece of equipment for metal heat treatment, the vacuum oil quenching furnace regulates the microstructure of materials through precise heating in a vacuum environment and rapid cooling in an oil medium, thereby significantly altering the mechanical properties and application characteristics of the materials. In the research and development of vacuum oil quenching furnaces, Taicang Huarui Vacuum Furnace Industry Co., Ltd. has deeply integrated material science with heat treatment processes. By optimizing heating curves, cooling rates, and vacuum degree parameters, it enables different materials to fully exert their performance potential after treatment, providing high-performance material solutions for industrial production.
The improvement of the hardness and strength of materials
Hardness and strength are the core mechanical properties of metallic materials. Vacuum oil quenching furnaces significantly enhance the hardness and strength of materials by promoting martensitic transformation, and this enhancement shows a uniform and stable characteristic. During the vacuum heating stage, the material undergoes austenitizing in an oxidization-free environment, with carbides fully dissolved and evenly distributed, laying a foundation for the subsequent quenching transformation. Compared with traditional air heating, the vacuum environment avoids decarburization, keeps the carbon content on the material surface at its original level, and ensures that the surface hardness after quenching is consistent with that of the core. For instance, after Cr12MoV die steel is treated by Huarui vacuum oil quenching furnace, the hardness difference between the surface and the core can be controlled within 1HRC, while the difference in traditional salt bath quenching often reaches 3-4HRC. The characteristics of the oil medium during the cooling stage determine the sufficiency of martensitic transformation. The quenching oil of Huarui vacuum oil quenching furnace features high flash point and low viscosity. It can provide a cooling rate of 50-80℃/s within the temperature range of 60-120℃, ensuring that the material can quickly pass through the "nose tip" temperature zone (the sensitive zone for pearlite transformation) from the austenitizing temperature and minimizing the formation of pearlite or bainite to the greatest extent. After treatment, the hardness of high-speed steel W6Mo5Cr4V2 can reach HRC63-65, which is significantly higher than that of air-cooled box furnaces (HRC55-58), meeting the high hardness requirements of cutting tools. The enhancement of material strength stems from the strengthening effect of martensite. Martensite is a supersaturated solid solution of carbon in α-Fe, and the distortion of its crystal structure generates intense solid solution strengthening and dislocation strengthening effects. For instance, after vacuum oil quenching and tempering, the tensile strength of 40CrNiMo steel increases from 800MPa to over 1200MPa, and the yield strength rises by 40%. This high-strength characteristic enables it to be competent for heavy-load components such as automotive drive shafts. Taicang Huarui Vacuum Furnace Industry Co., Ltd. ensures a consistent martensite transformation rate on the material cross-section by controlling the uniformity of the cooling rate, thus avoiding strength fluctuations caused by uneven cooling in traditional quenching.
Optimization of the toughness and plasticity of materials
The vacuum oil quenching furnace not only enhances the hardness of materials but also achieves a balance between hardness and toughness by controlling the morphology and distribution of martensite, thus avoiding the drawback of being "hard and brittle" in traditional quenching. The fine structure of martensite directly affects the toughness of the material. The Huarui vacuum oil quenching furnace controls the cooling rate in sections, enabling the material to cool rapidly in the high-temperature zone (600-400℃) and form fine plate-like martensite. In the low-temperature zone (400-200℃), appropriately slow down the cooling rate to reduce the volume stress during martensitic transformation. This control has raised the impact toughness of Cr12MoV die steel to over 15J/cm², which is 30% higher than that of ordinary oil quenching treatment. As a result, the die is less likely to break during use. The reasonable retention of residual austenite is another key to toughness optimization. The isothermal residence process of the vacuum oil quenching furnace (holding above the Ms point for 10-15 minutes) can stably retain some austenite. When these residual austenites are impacted, they will transform into martensite, absorbing the impact energy and playing a "buffering" role. For instance, after the bearing steel GCr15 is treated in the Huarui vacuum oil quenching furnace, the residual austenite content is controlled at 5%-8%, which not only ensures the hardness of HRC62-64 but also increases the impact toughness to 20J/cm², extending the service life of the bearing to 1.5 times the original. The plasticity of the material has also been improved. Non-oxidizing heating in a vacuum environment reduces the microcracks inside the material. The tempering process after oil quenching further eliminates quenching stress, thereby increasing the elongation and reduction of area of the material. For instance, after vacuum oil quenching and tempering at 500℃, the elongation of 30CrMnSi steel increases from 10% to 15%. It is less prone to breakage when subjected to complex loads and is suitable for manufacturing high-strength bolts and other connecting parts.
Improvement of the wear resistance and fatigue performance of materials
Wear resistance and fatigue performance are important indicators of materials in dynamic service environments. Vacuum oil quenching furnaces significantly enhance these two properties by optimizing the surface structure and internal structure of materials, thereby extending the service life of parts. The improvement of the material's wear resistance stems from the uniformly distributed carbides and the high-hardness surface layer. During the vacuum oil quenching process, the carbide particles in the material redissolve and precipitate at high temperatures, forming fine and uniform secondary carbides. These carbides have a hardness as high as HV1200-1500 and can effectively resist wear. For instance, after the high-speed steel W18Cr4V is treated in the Huarui vacuum oil quenching furnace, the surface carbide size is controlled at 1-2μm, the distribution density is 20% higher than that of traditional quenching, and the cutting life of the tool is extended by more than 50%. The improvement of surface integrity also enhances wear resistance. Vacuum oil quenching avoids the surface oxidation and decarburization of traditional quenching, maintaining uniform hardness and smoothness on the material surface and reducing the generation of "abrasive particles" during the wear process. After vacuum oil quenching treatment of 42CrMo steel, the surface roughness of the track pins of a certain construction machinery enterprise was reduced from Ra3.2μm to Ra1.6μm, the friction coefficient with the track plate was decreased by 15%, and the wear amount was reduced by 30%. The improvement of fatigue performance is related to the elimination of internal stress and the uniformity of the microstructure. The vacuum heating and staged cooling process of Huarui vacuum oil quenching furnace reduces the residual stress inside the material by more than 60%, avoiding the initiation of fatigue cracks caused by stress concentration. Meanwhile, the uniform martensitic structure reduces the number of fatigue sources, significantly increasing the fatigue limit of the material. For instance, after vacuum oil quenching and medium-temperature tempering of automotive spring steel 50CrVA, the bending fatigue limit is increased from 600MPa to 750MPa, and the cycle life of the spring is extended from 500,000 times to 800,000 times, meeting the usage requirements of heavy-duty vehicles. For contact fatigue performance, materials treated with vacuum oil quenching perform even better. After treatment, the rolling contact fatigue life L10 (the life of 90% of bearings without failure) of bearing steel is more than twice that of traditional quenching. This is attributed to the uniform hardness distribution and pure material surface layer, which reduces the surface spalling phenomenon under contact stress.
The influence on the corrosion resistance and oxidation resistance of materials
The improvement of corrosion resistance and oxidation resistance of materials by vacuum oil quenching furnaces mainly results from the enhancement of surface quality and the uniform distribution of alloying elements, especially for materials such as stainless steel and heat-resistant steel, with remarkable effects. During the vacuum oil quenching process of stainless steel, the vacuum environment avoids intergranular oxidation during heating. Meanwhile, the tempering process after oil quenching promotes the uniform distribution of carbon and reduces the precipitation of chromium carbide. For instance, after 304 stainless steel is treated in a Huarui vacuum oil quenching furnace (vacuum heating at 1050℃ and tempering at 450℃ after oil quenching), the chromium content near the grain boundaries remains above 18%, preventing intergranular corrosion. The time for rusting in salt spray tests is extended from 24 hours to 72 hours, making it suitable for medical devices and food equipment. The oxidation resistance of heat-resistant steel is enhanced through vacuum oil quenching. Vacuum heating reduces the volatilization of alloying elements in steel, such as chromium, aluminum and silicon. These elements form a continuous oxide film on the surface, preventing further oxygen penetration. The heat-resistant steel furnace bottom plate of a certain industrial furnace manufacturing enterprise is made of 310S steel and treated with vacuum oil quenching. After that, the oxidation rate at 1000℃ is reduced by 40%, and the service life is extended from 6 months to 10 months, reducing the equipment maintenance cost. For common carbon steel, surface passivation treatment (such as phosphating) after vacuum oil quenching ensures a stronger bond. As there is no oxide scale on the surface, the adhesion of the passivation film increases by 30%, and the corrosion resistance is indirectly improved. For instance, after vacuum oil quenching and phosphating of 45 steel used for agricultural machinery parts, the rust prevention period in a humid environment has been extended from one month to three months, reducing the rust loss during storage.
The effect on the dimensional stability and processing performance of materials
The dimensional stability and processing performance of materials directly affect the manufacturing accuracy and subsequent processing costs of parts. Vacuum oil quenching furnaces significantly improve these two characteristics by controlling thermal deformation and microstructure transformation. The improvement of dimensional stability stems from the reduction of residual stress and the stabilization of the structure. The Huarui vacuum oil quenching furnace adopts the "step heating + isothermal quenching" process, which reduces the thermal stress of materials caused by temperature gradients. Meanwhile, during the tempering process, multiple holding times (such as 200℃×2h+300℃×2h) promote the decomposition of martensite and the precipitation of carbides, making the microstructure tend to stabilize. For instance, after vacuum oil quenching and low-temperature tempering of the die steel Cr12, the residual stress was reduced from 300MPa to below 80MPa. During the subsequent grinding process, the dimensional change was controlled within 0.01mm/m, meeting the assembly requirements of precision molds. The thermal stability of the material also improves accordingly. In high-temperature service environments, materials treated with vacuum oil quenching have an enhanced resistance to tempering softening due to the uniform distribution of carbides. For instance, after high-speed steel cutting tools are vacuum oil quenched and held at 500℃ for one hour, the hardness decrease is no more than 2HRC, while the hardness of traditionally quenched tools drops by 4-5HRC. This makes vacuum oil quenched tools more suitable for high-speed cutting (the temperature in the cutting zone often reaches 400-500℃). The improvement of processing performance is reflected in the reduction of cutting force and the extension of tool life. The material structure after vacuum oil quenching is uniform, with small hardness fluctuations. During the cutting process, the force on the cutting tool is stable, and it is less likely to cause chipping. For instance, after vacuum oil quenching and tempering at + 200℃, the hardness of 40Cr steel is controlled at HRC30-32, which is easier to machine than the traditional quenched HRC35-38. The tool life during milling is extended by 50%, and the processing efficiency is increased by 20%. For parts that need to be ground, the uniform surface hardness ensures an even distribution of grinding force, reducing the wear of grinding wheels and the burning of parts.
Case Analysis of the Influence on the Properties of Different Materials
Due to the differences in chemical composition and microstructure, the performance changes of different materials after vacuum oil quenching furnace treatment present different characteristics. The following typical cases further illustrate the influence rules. Die steel (Cr12MoV) : After being treated in the Huarui vacuum oil quenching furnace (vacuum heating at 980℃, oil quenching at 80℃, and tempering at 200℃), the hardness is HRC58-60, and the impact toughness is 18J/cm², which is increased by 2HRC and 5J/cm² respectively compared with salt bath quenching. The dimensional accuracy of the mold cavity reaches IT7 grade, and the service life has been increased from 50,000 times to 80,000 times. It is particularly suitable for precision molds for stamping stainless steel thin plates. High-speed steel (W6Mo5Cr4V2) By vacuum heating at 1200℃ (with a vacuum degree of 5×10⁻²Pa), oil quenching at 60℃, and three tempering processes at 560℃, the hardness reaches HRC63-65, and the red hardness (600℃×4h) remains above HRC60. The tool life when cutting titanium alloys is 1.5 times that of traditional quenching, making it suitable for precision machining in the aerospace field. Structural steel (40CrNiMoA) After vacuum oil quenching (heating at 850℃ and oil quenching at 100℃) and tempering at 550℃, the tensile strength is 1100MPa, the elongation is 16%, and the impact toughness is 80J/cm². The uniformity deviation of all performance indicators is ≤5%, meeting the requirements of heavy-duty components such as automotive drive shafts. The failure rate in installation tests is reduced by 40%. Stainless steel (3Cr13) : After vacuum oil quenching (heating at 1050℃ and oil quenching) + tempering at 200℃, the hardness is HRC48-50, and it can withstand salt spray for 72 hours without rust. Its corrosion resistance is 50% higher than that of ordinary air quenching. It is suitable for manufacturing parts such as surgical knives and valves that require both hardness and corrosion resistance. The influence of vacuum oil quenching furnaces on material properties is multi-dimensional, ranging from mechanical properties to service performance, from macroscopic characteristics to microscopic structure, forming a complete performance optimization system.
Taicang Huarui Vacuum Furnace Industry Co., Ltd. makes the improvement of material performance repeatable and stable by precisely controlling every link of vacuum oil quenching - from the stable maintenance of vacuum degree to the precise adjustment of oil temperature, from the optimization of heating curves to the matching of tempering processes. This precise control over material properties has enabled vacuum oil quenching furnaces to occupy a significant position in fields such as mold manufacturing, automotive parts, and aerospace, providing reliable heat treatment guarantees for the application of high-performance materials and promoting the development of industrial products towards high precision and long service life.
