Method for producing mounting seat steel casting based on precoated sand shell mold process

Abstract

The invention relates to a method for producing a mounting seat steel casting based on a precoated sand shell mold process. Upper and lower box molding is adopted. The method comprises the following steps: (1) precoated sand core manufacturing; (2) molding; (3) core falling and box closing; (4) smelting and pouring; (5) box opening and sand falling; (6) casting head cutting; (7) normalizing heat treatment; (8) rough machining; (9) flaw detection, welding repair and polishing; (10) quenched-tempered heat treatment; (11) magnetic powder inspection and appearance examination; and (12) finish machining. According to the method, the core manufacturing procedure is simplified, the production efficiency can be improved by 20%, the product size precision is high, the machining allowance can be properly reduced by 4-8 mm, and the machining time of castings can be shortened to a certain extent. A casting is formed by a precoated sand shell mold and a shell core, the casting defects of air holes, sand washing, sand inclusion, sand burning, cracks and the like of the castings are effectively prevented, and the percent of pass of the casting is increased by 30% or above. The precoated sand has excellent collapsibility, the sand cleaning difficulty and workload of castings are greatly reduced, and the casting cleaning production efficiency is improved.

Description

technical field [0001] The invention relates to a method for producing a steel casting of a mounting seat, in particular to a method for producing a steel casting of a mounting seat based on a coated sand shell molding process. Background technique [0002] At present, there are mainly three molding sand processes in the production of steel castings in my country: ordinary CO 2 Hardened water glass sand process, ester hardened water glass sand process and resin sand process, wherein resin sand includes alkali phenolic, pep-set, furan and Bonney resin sand process. [0003] Ordinary CO 2 Problems existing in the hardened water glass sand process: the old sand has extremely poor collapsibility and is difficult to regenerate and reuse, a large amount of waste sand discharge causes serious environmental pollution problems, and the appearance quality of castings is poor. It is difficult for enterprises using this process to pass the foundry industry. system, the process will so...

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Problems solved by technology

[0003] Ordinary CO 2 Problems existing in the hardened water glass sand process: the old sand has extremely poor collapsibility and is difficult to regenerate and reuse, a large amount of waste sand discharge causes serious environmental pollution problems, and the appearance quality of castings is poor. It is difficult for enterprises using this process to pass the foundry industry. system, the process will soon be phased out

[0004] Problems in the process of ester hardened water glass sand: the modified water glass commonly used by cast steel enterprises currently has some problems in the selection and content of modifiers. Water glass cannot achieve the purpose of ideal modification, so water glass is added The amount cannot be reduced, the regeneration index of old sand is poor, the reuse rate is low, and defects such as low strength of molding sand and creep sinking often occur in production, and pores often appear in castings. These have brought a lot of trouble to the production organization, resulting in some cast steel Enterprises have always been wary of this process during transformation and upgrading, and dare not adopt it rashly

[0005] Problems existing in the resin sand process: ① For steel castings with uneven wall thickness and complex structure, there is still a tendency to crack; ② Alkali phenolic resin film has good toughness, it is difficult to regenerate old sand, and the recycling rate can only reach about 75%; ③ Emitting irritating and toxic gases, causing personal health hazards and air pollution problems; ④The price of resin fluctuates greatly, and there is a problem of high cost of molding sand

In the actual production process, water glass sand is greatly affected by environmental factors, the addition of water glass and organic ester is difficult to control, the sand mold is easy to absorb moisture, and creep will cause casting defects such as casting pores, which will affect the dimensional accuracy of castings

At the same time, the water glass sand sand mold has poor yield, more loose sand on the surface, more crack defects in the casting cavity, more serious problems of sand sticking, sand washing, and sand inclusion in the casting, poor collapsibility of the molding sand, and greater difficulty in cleaning the casting.

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