Under the rapid development of the current society, users are increasingly demanding the quality of steel. This requires steelmaking to continuously improve the quality of molten steel. At the same time, high-purity magnesia bricks must continuously reduce various consumption in steelmaking production, reducing costs and increasing efficiency. The practical application of tapping slag technology in converter steelmaking is a good way to reduce raw materials.

The tapping slag is to leave the slag in the furnace to a maximum extent by some method to reduce the high oxidizing final slag of the converter flowing into the ladle during the tapping process. Reducing the amount of slag discharged from the converter is an important aspect to improve the quality of molten steel. The process of slag blocking operation in the tapping process of the converter not only stabilizes the chemical composition of the molten steel, but also reduces the inclusions in the steel, improves the cleanliness of the molten steel, and can reduce the slag of the ladle and prolong the service life of the ladle. At the same time, it can also reduce the refractory material, correspondingly improve the service life of the refractory material of the taphole of the converter, and provide good conditions for refining of molten steel.

The earliest slag blocking method used in China is the slag ball slag blocking method invented in Japan in 1970. It is widely used at present. From the development trend of slag blocking technology, foreign countries are gradually moving from the tangible slag method to the invisible slag blocking method. development of. Since the slag blocking material such as the slag ball is used to block the slag, the material consumption is high, and the slag effect is not ideal. Many foreign steel mills have adopted the invisible slag blocking method and are equipped with a slag detection device to implement automatic control of slag blocking. Such as pneumatic slag method, electromagnetic interference method, etc. In addition to better slag blocking effect, these methods also increase the yield of molten steel, and the cost of slag blocking is also reduced. In particular, the pneumatic slag slag method has obvious advantages in slag blocking effect, reliability and cost, and has been adopted in large converters of many steel mills abroad. However, the technical requirements are relatively high, so at present, the physical slag blocking method is basically adopted in China.

Since the invention of the steel slag slag method, various countries have invented more than a dozen slag blocking methods for improving the slag blocking technology, such as: slag ball method, slag blocking method, slag blocking method, slag sluice method, skateboard method, Pneumatic slag method, electromagnetic slag method, steel outlet vortex method, rotating cantilever method, slag bar method, slag slag slag method, steel outlet slag method, tundish method, slag tray Method, slag cap method, slag cover method, vacuum slag method, siphon tapping method, etc. However, at present, the slag ball and slag blocking method are widely used in China, so this paper mainly introduces the application of these two methods in converter steelmaking.

1 slag ball slag method

This method is a slag ball tapping slag method invented by Nippon Steel Corporation in 1970. The principle is to use the slag ball density between steel and slag, and block the taphole at the end of tapping to block The slag is poured into the ladle. The shape of the slag ball is spherical, and its structure is generally divided into two parts: a core portion and a casing. There are two kinds of production processes. Most of the cores are made of raw iron chip pressing blocks, cast iron blocks, small waste steel billets and other materials. The outer cladding is made of refractory mud, which is made of high-aluminum refractory concrete and refractory brick powder. High alumina bauxite refractory concrete or magnesia refractory mud, another shell is cast iron, leaving a hole, the core can be filled with sand refractory mud, such as sand, the hole needs to be sealed with refractory mud, this The method is simple to make, low in cost, and can meet the needs of slag blocking, so it is widely used.

The principle of slag ball slag blocking work is that when there is molten steel in the furnace, the slag blocking ball should be in a floating state, so that the molten steel flows out from the tapping port, and once the molten steel is cleaned, the slag blocking ball should sink into the bottom of the slag. The taphole is blocked in time, and the position of the slag ball is not affected by the movement of the slag. Therefore, the specific gravity of the slag ball should be between the molten steel and the slag specific gravity. The specific gravity of the molten steel is about 7.15 gcm3, and the specific gravity of the slag is about 3.0 to 3.5 gcm3. According to experience, the specific gravity of the slag ball is generally 3.7 to 4.2 gcm3. The diameter of the slag ball is suitable for the diameter of the taphole of the converter. It has been proved by practice that the ratio of the diameter of the steel port to the diameter of the slag ball is 2:3.

At present, the slag blocking operation of the converter slag ball is mostly mechanically thrown, and the direct casting rate is low, and most of them are cast around the tapping port. Moreover, when tapping, the power of the vortex vortex formed at the tapping port is moved to the taphole. The pitching time is generally appropriate when tapping 2 3 .

The advantage of using the slag ball to block the slag operation is that the cost is low and the operation is simple and easy. The shortcoming is that the pitching rate is low, and the slag ball usually arrives at the taphole in a wave-by-flow manner. However, due to the high viscosity of the steel slag, the slag ball sometimes cannot reach the taphole smoothly, or cannot effectively flow when the molten steel will flow. Block the taphole. In addition, since the circular slag ball completely falls on the taphole, the probability of premature sealing of the taphole is significantly increased, and the yield of molten steel is lowered. Its slag blocking effect is general. When smelting ordinary steel grades, the requirements for phosphorus are not high. Because of its low cost and simple operation, domestic steel mills smelt mostly ordinary steel, so it is widely used, and is high quality in smelting. Most steel manufacturers use the slag plug method.

2 slag plug slag method

This method was developed in 1987 by michaeldlabate to summarize the experience of the German slag bar used in the UK, inventing a slag plug with a dual function of slag blocking and vortex suppression. The device has a gyro shape, with 2 to 4 grooves at the thick end and 4 to 8 corners (the groove can be adjusted according to the size of the taphole), which can destroy the molten steel vortex and reduce the eddy current slag. slightly)

Its specific gravity slag ball is slightly larger, between 4.2 and 4.8gcm3. At present, some manufacturers make it simpler. The whole gyro body is made of refractory material except for the core. Only small scrap steel and cast iron are added to the refractory material. Blocks, etc., in order to achieve a proper specific gravity, reduce costs, and make production easier.

The gyro-shaped slag plug addition time is also added when the tapping amount reaches 2 3, and the delivery vehicle, because the lower part is the guide rod, automatically and accurately reaches the predetermined position, because the groove on the body is realized. The eddy current is suppressed, and when the slag plug body blocks the tap hole, the residual steel can still flow into the ladle through the groove, thereby increasing the yield of the molten steel. At the same time, the success rate of slag blocking can reach about 98%, which is the slag blocking method adopted by many domestic enterprises.

The slag blocking method has the advantages of accurate delivery and high slag blocking success rate, so it is widely used in refining high quality steel.