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Vacuum Heat Treatment Furnace

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Vacuum Hardening of Alloy Steel

The so-called vacuum hardening is to heat the steel to 30-50°C above Ac3 (hypoeutectoid steel) or Ac1 (hypereutectoid steel) under vacuum conditions, and put it into various cooling media after heat preservation to obtain Martensitic steel. body tissue. The purpose of vacuum hardening is to transform supercooled austenite into martensite or bainite to obtain martensite or bainite structure, and then cooperate with tempering at different temperatures to greatly improve the strength, hardness, and durability of steel. Wear resistance, fatigue strength and toughness, etc., so as to meet the different requirements of various mechanical parts and tools. It can also meet the special physical and chemical properties of some special steel materials such as ferromagnetism and corrosion resistance through vacuum hardening.

In order to improve the mechanical, physical, chemical and technological properties of steel to meet the needs of use, a certain amount of elements such as chromium, nickel, tungsten, cobalt and rare earth are added to the steel. This kind of steel is called alloy steel. The more alloying element content, the greater the deformation resistance. The order of deformation resistance is high-speed steel, high-alloy tool steel and high-alloy austenitic stainless steel and heat-resistant steel, die steel and martensitic, ferritic martensitic stainless steel, alloy structural steel, spring steel, bearing steel. The types of alloy structural steel are divided into three categories according to their uses: structural steel for machines, structural steel for engineering, ultra-high-strength tough steel or ultra-high-strength steel.

Preparations before alloy steel vacuum hardening: Check the number, material and size of workpieces, and check whether there are cracks, bumps, sharp edges, sharp corners and rust on the workpieces that affect the quality of vacuum hardening. According to the drawings and process documents, specify the specific requirements for vacuum hardening, such as hardness, partial vacuum hardening range, etc. According to the requirements of vacuum hardening, choose suitable fixtures or carry out proper binding, and take appropriate protective measures in the parts prone to cracks, such as turning the blind holes of large forgings to see the light, wrapping and plugging holes with iron sheets or asbestos ropes, etc. . A large number of workpieces should be quenched for the first piece or a small batch, and mass production can only be carried out after approval, and random inspections are often carried out during the production process.

Vacuum hardening furnace loading: Workpieces of different sizes but with the same heating temperature are allowed to be loaded into the same furnace for heating (except for ultra-low carbon stainless steel). The workpieces entering the furnace should be dry, free of oil and other dirt. When workpieces with different cross-sectional sizes are loaded into the same furnace, the large workpieces should be placed in the furnace, and the holding time of large and small workpieces should be calculated separately. When loading the furnace, the workpiece must be placed on the furnace rack or the furnace floor, stacked with hooks and pliers, and the workpiece must not be thrown directly into the furnace, so as not to damage the workpiece or damage the equipment. When heating in a box furnace, it is generally arranged in a single layer, and the gap between the workpieces is 10-30mm. Small pieces are allowed to be stacked appropriately, but the holding time should be increased as appropriate. The slender workpiece is heated in the box furnace and should be placed as flat as possible.

Heating method: Carbon steel and low-alloy steel workpieces can generally be directly heated in a furnace with a vacuum hardening temperature or 20-30 degrees higher than the specified vacuum hardening temperature. High-carbon high-alloy steel and complex-shaped workpieces should be preheated , The heating temperature is determined by the process, the general workpiece takes the middle temperature, the large workpiece or the quenched and tempered part heated by the box furnace can take the upper limit temperature, and the complicated and easily deformed workpiece can take the lower limit temperature.

Vacuum heat treatment equipment adopts PL type programmable controller, and the intelligent temperature control instrument is combined with vacuum instrument, sensor and actuator to realize the automatic control of vacuum system, mechanism transmission, gas filling system and process parameters. Reliable operation, high precision temperature control.

Selection of vacuum hardening equipment: RVGQ vacuum hardening furnace produced by SIMUWU is a high-quality product for vacuum hardening process. Good temperature control accuracy and temperature control uniformity ensure the effective progress of vacuum hardening process. The equipment is easy to manage and maintain, greatly reducing maintenance costs.