In the great progress of counterweight iron industry since the 20th century, inoculation and chemical hardening of gray cast iron sand mold have special significance. These two inventions broke through the traditional methods that lasted for thousands of years, opened up a new field for the processing of counterweight iron, and had a great impact on improving the competitiveness of castings. Generally speaking, the counterweight iron is classified according to the modeling method, and it is customarily divided into ordinary sand mould counterweight iron and special counterweight iron. Ordinary sand mold counterweight iron includes three types: wet sand mold, dry sand mold and chemically hardened sand mold. According to the different molding materials, special counterweight iron can be divided into two categories: one is natural ore and gravel as the main molding materials, such as investment counterweight iron, shell counterweight iron, negative pressure counterweight iron, clay counterweight iron, solid counterweight iron and ceramic counterweight iron; A kind of metal as the main mold material, such as metal type counterweight iron, centrifugal counterweight iron, continuous counterweight iron, pressure counterweight iron and low pressure counterweight iron. The process of counterweight iron can be divided into three basic parts, namely, preparation of counterweight iron metal, preparation of mold and casting treatment. The metal of counterweight iron refers to the metal material used for casting when producing counterweight iron. It is an alloy with a metallic element as the main component and other metallic or nonmetallic elements. Traditionally known as counterweight ferroalloy, it mainly includes cast iron, cast steel and non-ferrous alloy of counterweight iron.

Due to special requirements, some castings need post-treatment, such as heat treatment, shaping, rust prevention, rough machining and so on. Counterweight iron is an economical blank forming method, which can better reflect its economy for parts with complex shapes. Such as cylinder block and cylinder head of automobile engine, propeller of ship and exquisite works of art. Some difficult-to-cut parts, such as nickel-based alloy parts of gas turbines, cannot be molded without counterweight iron. In addition, the size and weight of counterweight iron parts are widely applicable, and the types of metals are almost unlimited; Parts not only have general mechanical properties, but also have comprehensive properties such as wear resistance, corrosion resistance and shock absorption, which cannot be achieved by forging, rolling, welding, stamping and other metal forming methods. Therefore, the number and tonnage of blank parts produced by counterweight iron method in machinery manufacturing industry are still the most. The materials commonly used in the production of counterweight iron are various metals, coke, wood, plastics, gas and liquid fuels, molding materials and so on. The required equipment includes various furnaces for smelting metals, sand mixers for mixing sand, molding machines for making cores, core-making machines, sand mixers for cleaning castings and shot blasting machines. There are also machines and equipment for special counterweight iron and many transportation and material handling equipment. The production of counterweight iron is different from other processes, which mainly includes wide adaptability, more materials and equipment needed and great environmental pollution. The production of counterweight iron will produce dust, harmful gas and noise pollution to the environment, which is more serious than other mechanical manufacturing processes and needs to be controlled by measures.

The development trend of counterweight iron products is to require better comprehensive performance, higher precision, less allowance and smoother surface of castings. In addition, the demand for energy conservation and the call for social restoration of the natural environment are getting higher and higher. In order to meet these requirements, new counterweight ferroalloys will be developed, and new smelting processes and new equipment will also appear accordingly. With the continuous improvement of mechanization and automation of counterweight iron production, it will develop more into flexible production to expand its adaptability to different batches and varieties of production. Give priority to the development of new technologies that save energy and raw materials, and give priority to the development of new technologies and equipment that are less polluting or pollution-free. Quality control technology will make new progress in detection, nondestructive testing and stress determination of each process. With the development of electronic technology and detection means, the counterweight iron workers will make a deeper exploration on the theory of metal crystallization and solidification and sand compaction, so as to study the effective ways to improve the performance and internal quality of castings. Robots and computers will be widely used in the production and management of counterweight iron.

Metal melting is not only a simple melting, but also a melting process, which makes the metal poured into the mold meet the expected requirements in temperature, chemical composition and purity. Therefore, in the process of smelting, all kinds of inspections and tests aimed at quality control should be carried out, and liquid metal can only be poured after reaching various specified indexes. Sometimes, in order to meet higher requirements, molten metal must be treated outside the furnace, such as desulfurization, vacuum degassing, refining outside the furnace, inoculation or deterioration. Commonly used metal smelting equipment includes cupola, electric arc furnace, induction furnace, resistance furnace and reverberatory furnace. Different methods of counterweight iron have different modeling contents. Taking sand mold counterweight iron, which is widely used, as an example, mold preparation includes two major tasks: molding material preparation and molding core making. All kinds of raw materials used for modeling and core-making in sand mold counterweight iron, such as counterweight iron sand, sand binder and other auxiliary materials, as well as molding sand, core sand and coatings prepared from them, are collectively called modeling materials. The task of preparing molding materials is to select suitable raw sand, binder and auxiliary materials according to the requirements of castings and the properties of metals, and then mix them into molding sand and core sand with certain properties according to a certain proportion. Commonly used sand mixing equipment includes drum mixer, counter-current mixer and blade slot mixer. The latter is specially designed for mixed chemical self-hardening sand, with continuous stirring and high speed. Modeling and core-making is based on the technological requirements of counterweight iron, on the basis of determining modeling methods and preparing modeling materials.

The precision of castings and the economic effect of the whole production process mainly depend on this process. In many modern counterweight iron workshops, modeling and core-making have been mechanized or automated. Commonly used sand mold core-making equipment includes high, medium and low pressure molding machine, sand throwing machine, boxless injection molding machine, core shooting machine, cold and hot core box machine and so on. After the casting is taken out of the pouring cooling mold, there are gates, risers and metal burrs, and the sand mold counterweight iron casting still adheres to sand, which must be cleaned. The equipment for this kind of work includes shot blasting machine, gate and riser cutting machine, etc. Sand removal and cleaning of sand castings is a process with harsh working conditions, so when choosing the molding method, we should try our best to create convenient conditions for sand removal and cleaning.