① Furan resin sand process
The average amount of resin added is 0.9%, the amount of curing agent added accounts for 35% of the resin, the price of resin is about 20000 yuan / ton, and the price of curing agent is 5500 yuan / ton (current market price). A single sand process is adopted. The recovery rate of sand is 90%, and the sand iron ratio is 4:1 (normal sand iron ratio). The following calculation is based on the cost per ton of sand castings:
Amount of new sand for sand mold casting: 1000kg × 10% × 4=400kg。
Cost of new sand for sand mold casting: 400 × 0.4 = 160 yuan (the price of sand is 0.4 yuan / kg).
Dosage of recycled sand: 1000kg × 90% × 4=3600k。
Reclaimed sand cost: 3600 × 0.15 = 540 yuan (the cost of recycled sand is 0.15 yuan / kg).
The resin dosage is generally 0.9% of the total sand amount, and the resin addition is 4000 × 0.9%=36kg。
Resin cost: 36 × 20 = 720 yuan (resin price: 20 yuan / kg).
The curing agent is 35% of the resin, i.e. 36% × 35% = 12.25kg, curing agent cost: 12.25 × 5.5 = 67 yuan (the price of curing agent is 5.5 yuan / kg).
The furan resin sand process is adopted, and the molding material cost per ton of sand casting is 160 + 720 + 67 + 540 = 1487 yuan.
② Alkaline phenolic resin sand process
The average amount of resin added is 1.6%. The amount of curing agent accounts for 23% of the resin. The price of resin is about 9000 yuan / ton, and the curing agent is 16000 yuan / ton (current market price). The process of 25% new sand + 75% recycled sand is adopted, and the sand iron ratio is 4:1 (normal sand iron ratio). The following calculation is based on the cost per ton of sand castings:
Dosage of new sand: 4000kg × 25=1000kg。 New sand cost 1000 × 0.4 = 400 yuan (the price of sand is calculated according to 0.4 yuan / kg)
Dosage of recycled sand: 4000kg × 75=3000kg。 Cost of reclaimed sand: 3000kgx0 18 = 540 yuan (the cost of recycled sand is 0.18 yuan / kg)
Resin dosage: 1.6%: 4000 × 1.6%=64kg, 64 × 9 = 576 yuan (resin price: 9 yuan / kg).
The curing agent is 23% of the resin, i.e. 64% × 23%=14.72Kg. fourteen point seven two × 16 = 236 yuan (the price of curing agent is 16 yuan / kg).
The cost of molding materials for ton sand mold castings using alkaline phenolic resin sand is 400 + 540 + 576 + 236 = 1752 yuan.
③ The cost comparison of molding materials between alkaline phenolic resin sand process and furan resin sand process for producing steel castings of motor shell per ton is shown in the table. It can be seen from the table that the molding material cost of alkaline phenolic resin sand process is 265 yuan / ton more than that of furan resin sand process. Raw sand is the main item causing the cost difference of molding materials.
| Project | Process cost of alkaline phenolic resin sand (yuan / ton) | Process cost of furan resin sand (yuan / ton) | Cost difference (yuan / ton) |
| Resin and curing agent | 812 | 787 | 25 |
| Raw sand | 940 | 700 | 240 |
| Total | 1752 | 1487 | 265 |