Precision casting sand casting knowledge

(1) a wide range of adaptation. Casting method is almost not limited by the size, thickness and complexity of the shape of the casting, casting wall thickness up to 0.3 ~ 1000mm, length from a few millimeters to more than a dozen meters, the mass from a few grams to more than 300t. Suitable for the production of complex shapes, especially the internal cavity of complex parts, such as complex boxes, valve bodies, impellers, engine blocks, propellers, etc..

2) casting method can be used in a wide range of materials, almost any alloy material can be melted into the liquid state can be used for casting. Such as cast steel, cast iron, fly a variety of aluminum alloys, copper alloys, renewed alloys, iron alloys and mantle alloys and other castings. For poor plasticity of brittle alloy materials (such as ordinary cast iron, etc.), casting is the only viable forming process, in industrial production to cast iron parts are widely used, accounting for about 70% of the total output of castings.

3) castings have a certain degree of dimensional accuracy. In general, more accurate than ordinary forgings, welded parts forming size.

4) Low cost, good overall economic performance, energy, material consumption and cost of other metal forming methods are inferior.

Castings in the general machine accounts for 40% ~ 80% of the total mass, and the cost of manufacturing only 25% ~ 30% of the total cost of the machine, the reason for the low cost is: ① flexible production methods, mass production can be organized mechanized production. ②The large amount of scrap and used metal materials and renewable resources can be used. ③Compared with forging, its power consumption is small. ④ have a certain degree of dimensional accuracy, so that the machining allowance is small, saving processing time and metal materials. Casting is the main supplier of blanks and parts for the machinery manufacturing industry, occupies an extremely important position in the national economy. Castings in mechanical products, products accounted for a large proportion, such as internal combustion engine key parts (eight or nine kinds) are castings, accounting for 70% to 90% of the total quality, the quality of automotive castings accounted for 19% (cars) ~ 23% (trucks); beds, tractors, hydraulic pumps, valves and general machinery in the quality of castings accounted for 65% to 80%; agricultural machinery castings. Quality accounted for 40% ~ 70% of the mining and metallurgy (steel, iron, non-ferrous alloys), energy (fire, water, nuclear power, etc.), marine and aerospace industries such as heavy, large, difficult equipment in the castings are a large proportion and play an important role.

Liquid metal solidification forming method mainly refers to the process of casting forming, it is the first to create a shape, size and the required parts corresponding to the casting cavity, and then the liquid metal filled into the cavity, to be cooled after solidification, and obtain parts (called castings) method.

Solidification of many methods of forming, according to the different methods of filling metal into the mold can be divided into gravity casting (liquid metal by its own gravity filling the cavity), low-pressure casting, extrusion casting, pressure casting (liquid metal under a certain pressure filling the cavity) and so on. According to the formation of different casting materials, can be divided into primary casting (such as sand casting, ceramic casting, shell casting) and permanent type (such as metal casting). For sand casting, according to the different sand binder, there are clay sand, resin sand, water glass sand, etc. O according to the different molding methods are hand molding and mechanical molding. In addition, for some special solidified parts, continuous casting (equal cross-sectional long casting), centrifugal casting (cylindrical casting), solid casting, investment casting and other methods.