The loading of rock (hardness f = 12-14) in a mine is mainly completed by w-1001, w401 and km-602a excavators. The excavator adopts high manganese steel bucket teeth. Three combination group tests were organized to replace ordinary cast ductile iron bucket teeth. The practice of more than one year has proved that the quality of this bucket tooth is close to that of high manganese steel bucket tooth. The casting process is introduced as follows:
1、 Iron solution spheroidization treatment
The spheroidizing treatment adopts the ladle bottom hammering method. The rare earth magnesium master alloy accounting for 1.6% of the weight of molten iron is put into the pit at the bottom of the dam ladle. After being pounded tightly, it is covered with straw ash, and then pounded tightly. Soda powder is placed on it. The ratio of caustic soda and ferrosilicon is shown in Table 1 to promote the vulcanization and inoculation of molten iron. Place the ladle in front of the furnace and prepare for treatment. When tapping, do not let the molten iron directly rush on the alloy. Tap the iron to the required weight at one time. After the reaction, quickly remove the slag and cover the straw ash, that is, transport it to the sand mold for pouring.
| Iron return furnace | Pig iron place | Limestone | Fluorite | Layer carbon | Intermediate content | 75% ferrosilicon | Soda ash |
| 100 | 200 | 10 | 4 | 35 | 1.5-1.6 | 0.7-1 | 1 |
2、 Preparation of master alloy
The pit type orange vortex furnace is used for smelting. The ratio of 30 kg of molten alloy each time is shown in Table 2. When the alloy is in the molten state, stir it evenly with an iron rod, and discharge it quickly to minimize the oxidation of magnesium. It is poured in the iron mold, broken after cooling, and can be used.
| Material name | Magnesium | 1# rare earth | 25% ferrosilicon | Iron material | Total alloy |
| Proportion% | 8 | 30 | 28 | 23 | 30kg |
| Particle size (mm) | unlimited | 1-20 | 10-25 | 5-20 | 5-15 after crushing |
3、 Annealing process
The cast ductile iron bucket teeth are put into an electric furnace or oil furnace after sand cleaning, heated to 880 ° C-900 ° C, kept warm for 1.5-2 hours, cooled to 650 ° C with the furnace, kept warm for 1.5-2 hours, cooled to 650 ° C with the furnace, and then discharged. They can be used after air cooling.
4、 Existing problems
At present, nodular cast iron bucket teeth are used in our mine. The main problems are that some nodular cast iron bucket teeth are broken and not wear-resistant in use. We envisage the following improvements:
- Further reduce the brittleness of ductile iron bucket teeth: (1) Improve heat treatment process to solve tempering brittleness; (2) Strictly control the silicon content, which shall not be higher than 3.5%; (3) Strictly control the phosphorus content, which shall not be higher than 0.13%; (4) The former inoculation of nodular iron was improved to ladle inoculation to change the network structure of metallography.
- During modeling, place appropriate steel core at the part between bucket tooth handle and body to solve the problem of individual bucket tooth fracture.
- Select appropriate heat treatment process to make ductile iron bucket teeth tough and wear-resistant.