Product Overview/产品概述:
The sizing nozzle is one of the refractory materials used in billet continuous casting, which plays a role in controlling the flow of molten steel. The molten steel flows into the crystallizer evenly and stably through the sizing nozzle, which is a necessary condition for ensuring the normal continuous casting. Therefore, the sizing nozzle must have good corrosion resistance and thermal stability, and clogging, falling off, cracking and expansion are not allowed during use.
Product Introduction/产品介绍:
According to its production process, the sizing nozzle can be divided into five types: full homogeneous sizing nozzle, direct composite sizing nozzle, vibration forming sizing nozzle, inlaid sizing nozzle and zirconium composite sizing nozzle.
1. Full homogeneous sizing nozzle Full homogeneous sizing nozzle is mainly made of zircon and zirconium oxide directly mixed in a certain proportion, and then formed, dried and sintered. The firing temperature is 1620-1650℃. Its characteristics are relatively uniform composition, performance and structure, good reliability and high cost.
2. Direct composite sizing nozzle In order to reduce costs, ordinary zirconium sizing nozzle can be made into a direct composite type. The nozzle body is made of zircon, and the working surface of the inner hole part of the nozzle sizing end is made of zircon and zirconium oxide composite. The zirconium oxide content of the composite part is 72%-78%. The body and the composite part are formed at the same time and fired at one time. The firing temperature is 1620℃-1650℃. The cost of this type of nozzle is much lower than that of a fully homogeneous sizing nozzle. Since the nozzle body and the composite part are formed and fired at the same time, the composite part will not fall off during use. However, since zirconium oxide undergoes martensitic phase transformation at 1100℃-1250℃ and is accompanied by volume change, it is easy to cause the nozzle to burst during use. Therefore, stable zirconium oxide must be used to produce this type of nozzle, and the content should not be too high. Since the thermal expansion coefficients of stable zirconium oxide and zircon are still inconsistent, the nozzle may also crack during use.
3. Vibration-formed sizing nozzle The vibration-formed sizing nozzle consists of a nozzle core, a nozzle body and an iron shell. The nozzle core is made of a composite of zircon and zirconium oxide, and the firing temperature is the same as that of the fully homogeneous nozzle. The nozzle body is made of high-aluminum material. The method of making this nozzle is to first make the nozzle core, and then form the nozzle core, high-aluminum material and iron shell together by vibration and pressure. The formed nozzle does not need to be sintered again, but only needs to be dried. This type of nozzle has the advantages of low cost and nozzle core that is not easy to fall off. The disadvantage is that it will leak steel due to the melting of the iron shell after long-term use.
4. Mosaic sizing nozzle The outer shell of the mosaic sizing nozzle body is made of high-aluminum material, and the nozzle core is made of zircon and zirconium oxide composite. The nozzle body and the nozzle core are made separately, and then the two are bonded together with refractory mud. Its characteristics are lower cost than the fully homogeneous nozzle and better thermal stability than the direct composite sizing nozzle. If the bonding is not good, the nozzle core will fall off after long-term use.
5. Performance of zirconium composite sizing nozzle Performance of the working surface of zirconium composite sizing nozzle: The advantages of zirconium composite sizing nozzle are low production cost and low price. It is more suitable when the continuous pouring time is less than 500min. However, this type of nozzle has obvious disadvantages, that is, when in use, zircon reacts with molten steel and inclusions in the molten steel to decompose, generating very fine zirconium oxide and multi-phase liquid, and the reaction products are easily washed away by the molten steel. Therefore, ordinary zirconium composite sizing nozzles have the problem of diameter expansion. Although increasing the zirconium oxide content in the nozzle can slow down the nozzle’s diameter expansion rate, it cannot fundamentally solve the problem.
