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The ingot die of the vermicular graphite cast iron has a higher service life than the gray cast iron ingot die, that is, the consumption of the steel die is low, which was recognized ten years ago, but it has not been widely used due to various reasons. The most important reason is that the stability of the creeping effect in large-scale production process is difficult to control. Today, this problem has been re-proposed. The special steel of the Great Wall Special Steel Plant has higher requirements on the ingot mold, and the surface quality of the steel ingot directly affects After the rolling, the quality of the sheet and the consumption of steel per ton are high. Therefore, the factory intends to use part of the creeping iron ingot mold. We immediately started the research and test work after receiving this topic.
2 Test plan and result test For 1t ingot mold and 4t ingot mold Because the ingot mold is thick and large section casting, for 4t ingot mold, the light casting will take about 7min, until the end of solidification is nearly 1h, so the choice of creeping agent We must consider the problem of anti-swelling decay. Here we choose Xt30 rare earth ferrosilicon alloy as the main supplement with a certain trace element as the homemade creeping agent, and the rare earth producing area is Sichuan Suining. The advantage of rare earth ferrosilicon as a creeping agent is that the amount of the creeping agent can be fluctuated within a range of fluctuations, and the anti-recession ability is strong; the disadvantages are also prominent, such as no self-gripping ability, white mouth tends to be large. But for large castings such as steel ingots, we believe that these shortcomings can be overcome.
In order to accurately grasp the fluctuation range of the amount of creeping agent added, the composition and temperature of the cupola molten iron in the plant were simulated in the laboratory, and a series of tests on the graphite form and matrix structure corresponding to the amount of the addition agent and the change of the inoculant amount were made. . The test results are: for the original molten iron with a sulfur content of Q05%~0.075%, when the amount of the creeping agent is changed from 1.3% to 1.7%, the satisfactory vermicular iron structure can be obtained. This is in line with our previous experience, namely Sichuan. The smelting ability of the rare earth element in the cast iron is 0. 10%~0.13%. At the time of graphite, the shape of graphite is still dominated by worms; while in the treatment of rare earth in Baotou, the residual amount exceeds 0.10%, and the graphite is completely globalized. It can be made into a single rare earth ductile iron. It can be said that a single rare earth can not produce qualified ductile iron. However, it is a good osmotic agent. If the dosage is too much, the hot metal white mouth tends to increase, and it can be easily solved by increasing the amount of gestation.
3 The creeping process and industrial production results In the production test, we adopted the easiest and most easy to master the creeping process. Taking into account the fluctuation of the sulfur content of molten iron, the fluctuation of the amount of molten iron, and the deterioration of the creeping, etc., it is determined that the amount of the creeping agent added is 1.%. First, 20% of the alloy is scattered at the bottom of the 4t package, and the rest is in the tapping. The trough is slowly added with the molten iron. Generally, after the molten iron is filled with 2/3 of the tapping amount, the surface of the molten iron is pushed with the steel crucible for 1 min to ensure that the alloy wrapped by the slag is fully dissolved in the molten iron. After the slag is slag, 0.8% of the ferrosilicon alloy for fertilization is added to the surface of the molten iron, and the scorpion is slightly pushed to make it into a molten state, and then the ash is covered with the ash, and then the pouring is obvious. At this time, the distribution of the alloy in the molten iron is uneven. The alloy content on the surface will be slightly higher than the middle and lower parts. However, in the case of dumping, as in the principle of floating silicon inoculation, the composition of molten iron poured into the mold tends to be uniform. Although there is a slight difference between the composition of the molten iron that is poured first and the composition of the molten iron that is poured afterwards, this has little effect on thick and large parts such as ingot molds. In fact, we are: 1999-11-25