Surgical instruments stainless steel vacuum heat treatment

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Cr13 stainless steel is a commonly used martensitic stainless steel. There are 5 kinds of steel grades. It is named after the single-phase martensitic structure obtained in the quenched state. It is widely used in surgical instruments. The purpose of heat treatment is not only to obtain certain mechanical properties, but also to improve its corrosion resistance.

The level of heat treatment technology has always been one of the indicators to measure the final quality of products. For decades, surgical instruments have long relied on salt bath heat treatment, which has many problems. With the progress of the times, uncoated products and precision specialty products will become the development trend of surgical instruments, therefore, advanced heat treatment methods are required to match them.In recent years, through the transformation of process technology, the transition from traditional salt bath heat treatment to bright heat treatment has been completed, and the heat treatment process has gradually moved towards the goal of green environmental protection, showing a good development prospect.

Surgical instruments are special commodities with unique uses and performance requirements, which are related to personal health and safety. In order to give full play to the function of stainless steel and learn from the technical information of developed countries, the bright heat treatment process is gradually adopted for heat treatment and quenching. The currently implemented schemes mainly include two types: vacuum heat treatment and protective atmosphere heat treatment.

The application of domestic vacuum heat treatment to surgical instrument products began in the 1980s. The first is to introduce vacuum heat treatment equipment from abroad, and on the basis of successful application, gradually expand the scope of application. At present, a production line consisting of multiple vacuum quenching and tempering furnaces that can choose a variety of quenching methods has been formed.

The advantages of vacuum heat treatment workpieces such as no oxidation, no decarburization, degassing, degreasing, good surface quality and small deformation have long been recognized. After vacuum heat treatment of martensitic stainless steel, it can effectively overcome the damage to the surface of the product by the original process, which is beneficial to improve the mechanical properties and final corrosion resistance of the product.

The application of domestic vacuum heat treatment has become more and more popular, and the process method has become more and more perfect. Regarding the heating method of the vacuum furnace, convection is the main method at low temperature, and radiation and conduction are the main methods at high temperature. The actual temperature of the workpiece in the furnace lags far behind the instrument display value. This situation should be fully considered when determining the process, otherwise the workpiece will be heated unevenly, which will ultimately affect the quenching hardness and its uniformity. At present, the relevant data have different expressions on the preheating and heat preservation of vacuum heat treatment. It seems that it is difficult to have a unified standard, which should be determined according to the specific workpiece. It is impossible to use the same calculation formula for large molds and small parts. Surgical instruments are mostly for small workpieces, considering the poor thermal conductivity of martensitic stainless steel, two-stage preheating at 400°C and 800°C is performed during the heating process. In addition to the effective thickness of the workpiece, the holding time should also consider the number of loading factors. Quenching and heat preservation reference calculation formula t=K×D+T, in which, t is the quenching and heat preservation time (min), K is the heat preservation time coefficient, D is the effective thickness of the workpiece (mm), T is the time margin (min), according to the furnace load Size adjustment. At present, the vacuum quenching furnaces that are widely used in China mainly include high-pressure gas quenching furnaces and gas and oil double-chamber quenching furnaces. Vacuum air quenching or oil quenching can be used for martensitic stainless steel workpieces. Oil quenching has high production efficiency, but it involves degreasing and cleaning of workpieces after quenching and environmental protection issues. The vacuum air-quenched workpiece has the best surface quality, no pollution to the environment, and is more and more widely used.

4Cr13 steel medical scissors originally used salt bath furnace plus application example

Thermal quenching, large deformation, surface oxidation, large machining allowance; surface corrosion, affecting subsequent processing. After switching to vacuum air quenching, the appearance is basically free of oxidation, the hardness is above 53HRC, and the deformation is very small. In response to this feature, the manufacturing process of the product has been adjusted accordingly, and the calibration process has been advanced before quenching, which has effectively improved the qualified rate of the product.

Equipment selection: The VOGQ series vacuum heat treatment furnace produced by SIMUWU is a high-quality product for the vacuum heat treatment process of tooling and molds. Good temperature control accuracy and temperature control uniformity ensure the effective progress of the vacuum heat treatment process. SIMUWU specializes in the manufacture of vacuum furnaces, has more than ten years of relevant experience, and has a good reputation in the field of vacuum furnace manufacturing. The product line includes vacuum air quenching furnace, vacuum oil quenching furnace, vacuum brazing furnace, etc., which are widely sold in developed and developing countries.