Introduction to the Process of Valve Hot Casting

With the advancement of technology and the flourishing development of the casting industry, different casting methods have different mold preparation contents. Taking the most widely used sand casting as an example, mold preparation includes two major tasks: material preparation and core making. The various raw materials used for molding and core making in sand casting, such as casting sand, sand binders, and other auxiliary materials, as well as the sand, core sand, coatings, etc. prepared from them, are collectively referred to as molding materials. The task of preparing molding materials is to select appropriate raw sand, binders, and auxiliary materials according to the requirements of the casting and the properties of the metal, and then mix them in a certain proportion to form molding sand and core sand with certain properties. The commonly used sand mixing equipment includes roller type sand mixer, counter flow sand mixer, and blade groove type sand mixer. The latter is designed specifically for mixed chemical self hardening sand, with continuous mixing and fast speed.

Core shaping is carried out based on the requirements of casting technology, after determining the shaping method and preparing the shaping materials. The accuracy of castings and the economic benefits of the entire production process mainly depend on this process. In many modern casting workshops, molding and core making have been mechanized or automated. The commonly used sand molding and core making equipment includes high, medium, and low pressure molding machines, sand throwing machines, box less injection molding machines, core shooting machines, cold and hot core box machines, etc.

After the castings are taken out of the self poured and cooled mold, there are gates, risers, metal burrs, burrs, and mold lines. The castings cast by sand molds also adhere to sand, so they must go through a cleaning process. The equipment used for this work includes polishing machines, shot blasting machines, sprue and riser cutting machines, etc. Sand cleaning of sand castings is a process with poor working conditions, so when choosing a molding method, it is important to consider creating convenient conditions for sand cleaning. Some castings require post-treatment due to special requirements, such as heat treatment, shaping, rust prevention treatment, rough machining, etc.

Characteristics of the Foundry Industry

Casting is a relatively economical method of rough forming, which can better demonstrate its economy for parts with complex shapes. Such as the cylinder block and cylinder head of car engines, ship propellers, and exquisite artworks. Some difficult to cut parts, such as nickel based alloy parts of gas turbines, cannot be formed without casting methods.

In addition, the size and weight of the cast parts have a wide range of adaptability, and the types of metals are almost unrestricted; Parts not only have general mechanical properties, but also comprehensive properties such as wear resistance, corrosion resistance, and shock absorption, which cannot be achieved by other metal forming methods such as forging, rolling, welding, and punching. Therefore, in the machine manufacturing industry, the number and tonnage of raw parts produced by casting methods are still the largest to date.

The materials commonly used in casting production include various metals, coke, wood, plastics, gas and liquid fuels, molding materials, etc. The required equipment includes various furnaces for smelting metals, various sand mixers for sand mixing, various molding and core making machines for shaping and core making, as well as sand blowers and shot blasting machines for cleaning castings. There are also machines and equipment for special casting, as well as many transportation and material handling equipment.

Casting production has different characteristics from other processes, mainly including wide adaptability, requiring a large number of materials and equipment, and polluting the environment. Casting production produces dust, harmful gases, and noise that pollute the environment,