Rocker arm shell is one of the important parts of shearer. The rocker arm shell of the shearer is a large box type steel casting, the structural shape is shown in the figure, and the outline dimension is 4130 mm × 1 924 mm × 1050mm, with main wall thickness of 70 ~ 80 mm and local thickness greater than 200 mm. The net weight of the casting is 11045 kg and the gross weight is 13550 kg. The overall structure of the part is complex and irregular, and the internal structure of the cavity is complex; Because the transmission system is installed inside the cavity, the center dimension accuracy of each hole is required to be high. From the point of view ofprocess, the shell has many hot spots and is prone to shrinkage, porosity and cracks. In addition, due to the high pouring temperature of molten steel, it is easy to produce defects such as sand sticking in sand casting.
|Mass fraction /%||0.25||0.5||1.2||≤0.025||≤0.025||0.35|
By comparing the comprehensive mechanical properties of zg30crnimo and ZG25MnNi test bars made of two different materials after normalizing and quenching and tempering heat treatment, it is determined that ZG25MnNi is used as the material of 3050 shearer rocker arm shell. Its chemical composition is shown in Table 1, and its mechanical properties are shown in Table 2.
|Mechanical property||σb/MPa||σ0.2/MPa||δ/%||Ψ/%||Hardness HB|
Using computer simulation software to optimize the sandscheme, the sand casting defects such as shrinkage cavity and porosity in the casting are eliminated, the casting quality is improved, the sand casting production cycle is shortened, and the production cost is saved.