What Is a Casting Stand?

Castings are metal forming objects obtained by various casting methods, that is, smelted liquid metal is poured into a pre-prepared mold by pouring, injection molding, suction or other casting methods, and after cooling, grinding and other subsequent processing methods , The resulting object has a certain shape, size and performance.

Castings have a long history. Ancient people used castings and some household appliances. In modern times, castings are mainly used as rough parts of machine parts, and some precision castings can also be used directly as machine parts. Castings account for a large proportion of mechanical products. For example, in tractors, the weight of castings accounts for 50 to 70% of the weight of the whole machine, 40 to 70% in agricultural machinery, and 70 to 90% in machine tools and internal combustion engines. Among the various types of castings, there are the most variety of mechanical castings, the most complicated shapes, and the largest amount, which account for about 60% of the total output of castings. Followed by metallurgical ingot molds and engineering pipes, and some tools in life.

Castings are also closely related to daily life. Such as door handles, door locks,

There are many classification methods for castings: according to the metal materials used, they are divided into

During the casting process production of machine bed castings, the principles of high temperature and low temperature casting should be followed during pouring. Increasing the tapping temperature of the molten metal is conducive to the complete melting of the inclusions and the slag floating, which is convenient for slag removal and degassing, and reduces the slag inclusion and porosity defects of the machine tool castings. The lower pouring temperature is beneficial to reduce the The gas solubility, liquid shrinkage and high temperature metal liquid baking of the cavity surface can avoid defects such as pores, sticky sand and shrinkage. Therefore, under the premise of ensuring that the mold cavity is filled, the lower pouring temperature is used as much as possible. The process of pouring molten metal from a ladle into a mold is called pouring. Improper pouring operation can cause machine casting defects such as insufficient pouring, cold insulation, air holes, shrinkage holes and slag inclusion, and cause personal injury. ^[2]

It mainly includes appearance quality, intrinsic quality and use quality. Appearance quality refers to the surface roughness, surface defects, dimensional deviation, shape deviation, and weight deviation of the casting; intrinsic quality mainly refers to the chemical composition, physical properties, mechanical properties, metallographic structure, and holes, cracks, inclusions, Segregation and other conditions; the quality of use refers to the working durability of castings under different conditions, including wear resistance, corrosion resistance, cold and heat resistance, fatigue, shock absorption and other properties, as well as processability such as machinability and weldability.

The quality of castings has a great impact on the performance of mechanical products. For example, the wear resistance and dimensional stability of machine tool castings directly affect the accuracy and service life of machine tools; the sizes of various types of pump impellers, casings, and internal cavity of hydraulic parts, the accuracy of profile and surface roughness directly affect the pump And the development of hydraulic system's working efficiency, energy consumption and cavitation; the strength and resistance to chilling and heat resistance of the internal combustion engine cylinder block, cylinder head, cylinder liner, piston ring, exhaust pipe, etc., directly affect the engine's working life.

There are many factors that affect the quality of castings. The first is the design process of castings. When designing, in addition to determining the casting geometry and size according to the working conditions and metal material properties, the rationality of the design must be considered from the perspective of the casting alloy and casting process characteristics, that is, the obvious size effect and solidification and shrinkage , Stress and other problems to avoid or reduce the occurrence of defects such as segregation, deformation and cracking of castings. The second is to have a reasonable casting process. That is, according to the casting structure, weight and size, casting alloy characteristics and production conditions, the appropriate parting surface and shape, core making method are selected, and the casting ribs, cold irons, feeders, and pouring systems are reasonably set. To ensure the quality of castings. The third is the quality of the raw materials for casting. The quality of metal charge, refractory, fuel, flux, modifier, and foundry sand, molding sand binder, paint and other materials are not up to standard, which will cause defects such as pinholes, pinholes, slag inclusion, and sand sticking in the casting, affecting the appearance quality of the casting. And internal quality, casting will be scrapped in severe cases. The fourth is the process operation. It is necessary to formulate reasonable process operation procedures, improve the technical level of workers, and make the process procedures correctly implemented.

In casting production, the quality of castings should be controlled and inspected. First of all, it is necessary to formulate process codes and technical conditions from raw materials, auxiliary materials to the control and inspection of each specific product. Each process is strictly controlled and inspected in accordance with the process code and technical conditions. Finally, quality inspection is performed on the finished castings. Equipped with reasonable testing methods and suitable testing personnel. Generally speaking, the appearance and quality of castings can be judged by comparing the sample surface roughness; fine cracks on the surface can be inspected by coloring method and magnetic particle method. The internal quality of the casting can be checked and judged by audio, ultrasonic, eddy current, X-ray and gamma rays.

Sand casting casting defects include: cold insulation, insufficient pouring, porosity, sand sticking, sand trapping, trachoma, and swelling.

1) Insufficient cold-separation and insufficient pouring capacity of liquid metal or insufficient filling conditions. Before the cavity is filled, the metal liquid will stop flowing, which will cause castings to have insufficient pouring or cold-separation defects. When the casting is insufficient, the casting can not obtain the complete shape; although the casting can obtain a complete shape during cold insulation, the mechanical properties of the casting are seriously damaged due to the incompletely fused joints.

Prevent insufficient pouring and cold separation: increase pouring temperature and pouring speed.

1) Before work, check whether the furnace body, furnace door, trailer, wire rope pulley and blower are normal, and whether there are any unsafe factors such as collapse, breakage, cracking, etc. If so, it should be handled properly before the furnace can be turned on. Electric furnace annealing should carefully clean up the oxide scale and metal on or near the resistance wire.

2) When burning a fire, check the explosives in the coal carefully. During the wind stop, the coal seam must not be too thick to prevent gas explosion. Cinder removal should be handled at any time, and no backlog is allowed.

3) Before loading and unloading, check whether there are obstacles on the track groove and whether the tools such as hooks and chains are reliable.

4) When loading or unloading large castings or thin-walled workpieces, be sure to lay it flat and stable. Adequate gaps shall be left between adjacent ones, and the loading height shall not exceed the regulations.

5) Before being released from the furnace, the refractory bricks and refractory mud on the furnace door should be cleaned, and the pulling mechanism should be checked for good use.

6) When the furnace is released and moved, unrelated personnel must not be near the two sides of the flat car, so as to prevent the sand box or the workpiece from collapsing and hurting people. Do not rest or stack items around the furnace.

7) When the temperature of the work is higher than 400 , it is forbidden to use chain or wire rope to lift (or adopt heat insulation measures) to avoid breaking after annealing. When using cranes to lift working objects, the safe operating rules for cranes and hookers should be observed.

8) When using a gas stove, follow the gas ignition sequence: first blow out the remaining gas in the furnace with compressed air, close the compressed air valve, ignite the ignition rod, slightly open the gas nozzle valve, and adjust the compressed gas and gas flow after burning the nozzle To make it fully burnt. The order is reversed during a cease-fire.

9) When baking with an oil stove, the ignition sequence is: first close the damper, ignite the ignition stick, slightly open the throttle, after opening, adjust the air valve and throttle to make it fully burn, and prohibit "wind pressure oil".

10) When using a pulverized coal fuel furnace, it is prohibited to burn the furnace when the blower is defective or the pipe is cracked.

11) When repairing the electric furnace, the main switch must be cut off, a warning sign saying "Someone is overhauled, and no closing is allowed", or a person is required to monitor it. ^[2]

China is a large country in foundry production. There is a serious overproduction of domestic castings. However, China s severe overproduction of castings refers to the overcapacity of low-end castings in China. It is difficult to meet the needs of the market in the production of high-end castings. The demand of the casting industry transforms the low-end casting production capacity into high-end casting production capacity, and promotes the progress of China's casting industry.

In recent years, the vast and increasing demand at home and abroad has caused China's current casting industry, especially stainless steel hardware castings, to be favored. Industry experts summed up two major reasons: First, with the continuous improvement of China's economic status and the continuous development of China's casting industry, more and more hardware casting products are exported to other countries. The increase in overseas demand has directly driven China's casting manufacturing Increasing product output of enterprises. Second, high quality wins the world, and the improvement of the quality of domestic hardware casting products is also an important reason for its increased demand. China's hardware casting industry is booming.

Energy conservation and emission reduction will become the focus of China's policy for the production of castings: in order to cope with global warming and reduce consumption of fossil energy, the country attaches great importance to improving energy efficiency in the industrial sector and reducing greenhouse gas emissions. The process of improving energy efficiency is also the process of retrofitting or withdrawing backward energy production with high energy consumption and high emissions. China's casting industry as a whole is an industry with high energy consumption and high pollution, and the country is also paying close attention to energy conservation and emission reduction in the casting field. According to experts' predictions, in order to do a good job of energy conservation and emission reduction in the casting industry in the future, the state will formulate a combination of compulsory and incentive policies. The policies and measures may include: regulations and standards, fiscal policies, agreements and targets. In short, energy saving and emission reduction will become the focus of China's development of casting capacity policy. ^[2]