Pumping unit is a kind of mechanical equipment for oil extraction, which can make oil out of the well by pressurizing. The crank is the main force bearing part of the pumping unit, and it is the bearing and transmission part that transforms the high-speed motion into the low-speed motion. The crank of a certain type of pumping unit is the largest of the three types of pumping unit cranks manufactured by ZHY Casting, so it is also the largest of the three types of pumping unit cranks. The crank of the pumping unit is different in shape and structure from the conventional sand casting produced by our company, and is a new type of sand casting structure. Now take the crank of a pumping unit with the largest size and the largest stress as an example to study the process plan.
The product drawing material of a certain type of pumping unit crank is ZG270-500, and the sand casting complies with the standard requirements of GB/T 11352-2009 Carbon Steel Castings for General Engineering and JB/T 6402-2008 Technical Conditions for Large Low Alloy Steel Castings. According to the fact that ZG270-500 steel is not produced by the large ladle smelting of our company at the present stage, and the development stage of a certain type of pumping unit crank is still in a small amount of demand, after analysis, the conventional smelting steel of our company B+grade steel is selected to replace it, and the material properties of B+grade steel can fully meet the use requirements of the pumping unit crank products.
The maximum outline dimension of a certain type of pumping unit crank is 945 mm × 300 mm × 180 mm (as shown in the figure), which is a plate-shaped stress member. The overall wall thickness of the product is too thick, and most of the structural wall thickness is more than 95 mm. The key slot hole is the thickest and the highest, forming the largest hot spot, which leads to shrinkage cavity, shrinkage porosity and other sand mold casting defects.