Novel casting technique of semitrailer brake drum

Abstract

The invention relates to a novel casting technique of a semitrailer brake drum. The novel casting technique of the semitrailer brake drum comprises the following steps of: manufacturing an inner mold shell and a pouring cup; regulating the temperature of an iron mold, covering with sands, and modeling; checking by turning over a mold; assembling a shell mold; filling iron shots; pouring and cooling; turning over the mold, discharging elements, assembling the elements, and recovering; carrying out magnetic separation, and screening; dedusting and cleaning. No deformation of the brake drum is ensured fully; the steel shots are filled in an internal mold sand shell; poured steel liquids generate pressure inward; firstly, because of the 'arch bridge principle', the internal mold sand shell has great support force; and then the steel shots also can block the pressure by steel liquids, and the internal mold sand shell cannot be cracked or deformed absolutely. Before cast elements are condensed and contracted, the internal mold sand shell is scattered, the filled steel shots are at the scattered state, the deformability of the cast elements in contraction is ensured fully, so that free contraction instead of hindered contraction is formed; a bottom-pouring-type pouring mode is adopted, air is discharged smoothly; the cracking possibility at the crossed part is reduced; air holes of the cast elements caused by dampness of a sand mold are prevented; the novel casting technique of the semitrailer brake drum is an environment-friendly casting technique.

Description

technical field [0001] The invention belongs to the technical field of semi-trailer brake drum casting technology and relates to a novel casting process of a semi-trailer brake drum. Background technique [0002] The brake drum is an important part of the semi-trailer, which plays a vital role in the running of the vehicle, so it is very important to require the balance of the brake drum itself, and the mechanical properties of the cast brake drum must also fully meet the requirements of use scope. [0003] According to the survey data, there are several methods of casting brake drums in the world as follows: [0004] The first is clay sand molding casting, the second is lost foam molding casting, the third is all-iron sand-covered molding casting, the fourth is V-method binder-free vacuum casting, and the fifth is furan resin sand molding casting. [0005] The above casting methods all have inevitable process defects: [0006] 1. Clay sand molding: The sand mold has low ...

AI Technical Summary

Problems solved by technology

[0006]1. Clay sand molding: the sand mold is low in strength, which may easily cause local deformation of the brake drum, resulting in a lack of balance; clay is easily affected by the weather and absorbs air moisture. Excessive water content causes pores inside the casting, seriously affecting performance

[0007]2. Lost foam shape: the foam type itself is easily deformed, which seriously leads to the failure of balance; the foam and paint organic matter burn during pouring, resulting in carbon deposits and black Slag affects the internal structure of castings, resulting in substandard mechanical properties and seriously affecting performance

[0008]3. All-iron sand-covered molding casting: the outer mold and inner mold are made of iron mold sand-coated cavity that can be poured, but it is used for the molten iron of the brake drum Generally, it is alloy HT250 grade. During the cooling and forming process, the shrinkage rate is about 1%, that is, the circumference of the braking surface of the inner ring will become smaller, which will firmly lock the inner iron mold, making it difficult to remove the sand from the box. The important thing is that hindered shrinkage will increase a lot of internal stress, and it is difficult to find casting defects in ordinary times, but when the wheel rotates at high speed and brakes suddenly, its internal stress extends to the surface of the brake drum, which intensifies the surface tension and leads to cracking , Brake failure! The consequences of such phenomena are very serious, due to partial braking caused by brake drum rupture, causing the vehicle to roll over

[0009]4. V-method binderless vacuum casting: Because this process uses all dry sand vacuum molding, it is currently commonly known as green casting, but its disadvantages The outline of the cast brake drum is not clear, it is easy to make the balance of the brake drum not up to standard, and the wheel is unstable when running

In addition, a special plastic film should be laid before the three-dimensional compaction of the dry sand, and a refractory coating should be sprayed after the compaction. This kind of coating is easy to produce pores when the molten iron is poured into the cavity, which seriously affects the mechanical properties.

[0010]5. Furan resin sand molding casting: There are very few brake drums in this type of molding casting, because the molding sand consumption is relatively large, which is generally 3 times that of castings. The amount of furan resin added in the sand mixing is 1.5% of the molding sand, and the surface of the cavity must be coated with refractory paint, the molding cost is relatively high, and more equipment investment is required. If an assembly line is formed, the floor area will be large and the capital will be consumed More, generally not used

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