- Pattern making
The pattern is a wooden scraper with a thickness of 25 mm, which is simple, practical, fast and low cost.
The casting shrinkage is 2%; The machining allowance is 10 mm. Therefore, the outer diameter of the cavity is calculated as the radius of the drawing ×（ 1 + shrinkage 2%) + machining allowance 10 mm; The inner diameter of the cavity is the radius of the drawing ×（ 1 + shrinkage 2%) – machining allowance 10 mm; The height of the cavity is the height of the drawing ×（ 1 + shrinkage 2%) + machining allowance 20 mm. The upper and lower centers respectively play the role of fixing the scraper. When installing and manufacturing, the upper and lower centers must be concentric, and the diameter of the upper and lower centers is ϕ 8 mm round steel rolled and welded in thickness（ δ） It is 15 mm in diameter ϕ On 80 mm steel plate ϕ Drill 4 holes with diameter of ϕ Through hole of 6 mm, and spot facer depth of 7 mm at the position of welding center, so as to install the fastening wood screw, so as to connect the upper and lower centers with the support shaft.
- Modeling
When molding, the scraper is used to make the lower box. Firstly, the center positioning steel shaft of the scraper is fixed with an iron frame, which should be firm without deflection. Then, the levelness of the scraper is checked with a level ruler. When it meets the requirements, the scraper is stacked at the position of the insulation riser according to the process requirements ϕ 70 mm three way straight gate porcelain pipe (the position is consistent with the upper box) and inner gate ϕ 40 mm porcelain pipe, and finally put sand to scrape out the lower flange box.
Scraping process of top plate lower box:
(1) Scrape the groove with scraper;
(2) After pressing out the position and shape of 8 ribs with wood strips equal to the width of the ribs, the depth of the ribs is dug out with a pressure spoon;
(3) After pressing out the position and shape of the two domes with a wooden disc with the same diameter as the cone, the depth of the cone is dug out with a pressure spoon;
(4) Smooth the surface of sand box with pressure spoon.
The upper box is made on the platform, and the insulation riser is placed and stacked in advance according to the process requirements ϕ The 70 mm straight gate porcelain pipe (the position is the same as the lower box) is evenly rolled out in the upper sand mold ϕ 10 mm vent. When molding, there should be enough and even compactness. When putting molding sand, attention should be paid to the straight gate and inner gate porcelain pipes not to be washed down or run away.
- Packing
After stacking the lower box, clean up the falling sand and floating sand in the mold cavity, and press asbestos rope on the parting surface of the upper and lower boxes. The refractory brick pipe of the gate cup is added on the top of the gate of the upper box, and the sand is cultivated and solidified. When closing the box, ensure that the tilt height is within 500 ~ 1 000 mm, strictly prevent the wrong box, ensure that the upper and lower boxes are positioned accurately and the position of the sprue is aligned, and fasten the upper and lower boxes with bolts to prevent the fire when lifting the box.
- Melting and pouring
The melting equipment is a 15 t electric arc furnace. The total weight of casting blank including riser is 7.45 T. two castings are poured in one furnace. The pouring temperature is 1580 ℃. Deoxidation of liquid steel must be clean and thorough to prevent porosity. When pouring, heat preservation agent should be added in time after one third of the height of the liquid steel in the exposed riser, until the pouring is full. There is no need to point the riser for feeding, so that the liquid steel consumption is less, the feeding efficiency is high, and the chemical composition of the casting is kept unchanged.
- Casting cleaning
After pouring, the casting shall be kept in the sand box for at least 24 hours. After unpacking, the outer surface of the casting shall be cleaned, and then the pouring riser shall be cut off. After aging annealing heat treatment (eliminating internal stress) and surface shot peening, the surface of the casting shall be polished.
- Production verification
After machining, the top plate produced by this process is inspected by magnetic particle inspection, and there are no casting defects such as shrinkage cavity or shrinkage porosity, cracks and air holes inside the casting. The internal and external quality of the casting products meet the technical requirements of users.
The top plate castings were produced by adopting the casting process of gate through insulating riser, strengthening feeding and inclined pouring. It not only eliminates the shrinkage porosity and cracks in the casting, but also saves the liquid steel and reduces the production cost.