Casting steel ingot operation site

A comprehensive guide to ensuring quality and efficiency when pouring steel ingots

In the steel production process, ingot casting is an extremely critical link. Its quality and efficiency are directly related to the smooth progress of subsequent forging, rolling and other processes as well as the performance of the product. When casting ingots, it is necessary to ensure that the internal structure of the ingot is uniform and defect-free, and to improve production efficiency as much as possible and shorten the production cycle. The following will introduce in detail how to ensure quality and efficiency when casting ingots from multiple dimensions.

1. Adequate preparation before pouring

1. Raw material quality control

The quality of steel ingots is based on raw materials. First of all, the scrap steel, ferroalloys and other raw materials required for steelmaking must be strictly screened to ensure that their chemical composition meets the standard requirements. For scrap steel, its source must be carefully checked to avoid mixing with scrap steel containing harmful elements (such as lead, zinc, etc.), which are difficult to remove in molten steel and will seriously affect the quality of steel ingots. At the same time, there are strict requirements for the purity and particle size of ferroalloys. Different types of ferroalloys must be added in precise proportions to ensure the uniformity of the composition and mechanical properties of the steel ingots. For example, when producing high-strength alloy steel ingots, the accuracy of the content of alloying elements is extremely high, and a slight deviation may result in substandard performance of the steel ingots.

2. Ingot mold preparation

The quality and state of the ingot mold have an important impact on the forming and quality of the ingot. Before pouring, the ingot mold needs to be fully inspected to check whether the mold wall is smooth and flat, and whether there are defects such as cracks and sand holes. If there are defects, it may cause the surface of the ingot to be uneven, and even cracks may be generated due to stress concentration during the cooling process. At the same time, the ingot mold should be cleaned to remove impurities such as oxide scale and oil stains remaining in the mold to prevent these impurities from mixing into the molten steel. In addition, it is necessary to apply a suitable coating on the inner wall of the ingot mold. The coating can not only play a lubricating role to facilitate the demolding of the ingot, but also isolate the molten steel from the mold wall to a certain extent, reducing the occurrence of surface defects on the ingot.

3. Equipment debugging and inspection

Pouring steel ingots involves a series of equipment, such as steelmaking furnaces, steel ladles, pouring equipment, etc. Before pouring, these equipment must be fully debugged and inspected. The steelmaking furnace must ensure that its heating and temperature control systems operate normally and can stably heat the molten steel to the appropriate pouring temperature. The steel ladles must be checked for erosion of refractory materials to avoid steel leakage during transportation and pouring. The operating accuracy of the pouring equipment is also crucial. It must ensure that it can accurately control the flow rate and pouring speed of the molten steel to ensure the molding quality of the steel ingot. At the same time, related auxiliary equipment, such as lifting equipment and temperature measuring equipment, must also be inspected to ensure their reliable operation and provide protection for the pouring process.

2. Precise control of the pouring process

1. Molten steel temperature control

The temperature of molten steel is a key factor affecting the quality of steel ingots and the efficiency of casting. If the temperature is too high, the molten steel will easily produce a large amount of oxidation and air absorption during the casting process, resulting in defects such as pores and inclusions inside the steel ingot; if the temperature is too low, the fluidity of the molten steel will deteriorate, which may cause problems such as insufficient casting and cold shut of the steel ingot. Therefore, in the steelmaking process, the tapping temperature of the molten steel must be strictly controlled, and the temperature of the molten steel must be monitored in real time during the casting process. According to the different types of steel, the casting temperature should be adjusted reasonably. For example, for some high-alloy steels, the casting temperature may need to be controlled in a relatively high range to ensure its fluidity; while for ordinary carbon steel, the casting temperature can be appropriately lowered. At the same time, the time from tapping to casting of the molten steel should be shortened as much as possible to reduce the temperature drop of the molten steel.

2. Pouring speed and height control

The pouring speed and height have a significant impact on the quality of the steel ingot. If the pouring speed is too fast, the molten steel is prone to splashing, resulting in an uneven surface of the steel ingot, and may also involve air and form pores; if the pouring speed is too slow, it will extend the pouring time and reduce production efficiency. It may also cause the molten steel to solidify prematurely during the pouring process, resulting in insufficient pouring and other problems. Reasonable pouring speed should be adjusted according to factors such as the size and shape of the steel ingot and the temperature of the molten steel. The pouring height is also important. Too high a pouring height will cause the molten steel to impact the bottom of the mold, causing turbulence, resulting in inclusions and pores inside the steel ingot; while too low a pouring height may affect the filling effect of the molten steel. Generally speaking, the pouring height should be controlled within an appropriate range to ensure that the molten steel flows smoothly into the ingot mold.

3. Preventing and protecting molten steel from contamination

During the pouring process, effective measures should be taken to prevent molten steel from being contaminated. On the one hand, it is necessary to avoid long-term contact between molten steel and air to reduce oxidation and air inhalation. Protective pouring technology can be used, such as using long nozzles and protective slag to isolate molten steel from air. The long nozzle can guide the molten steel to flow smoothly into the ingot mold, reducing the splashing and oxidation of the molten steel; the protective slag forms a covering layer on the surface of the molten steel, which plays a role in heat preservation, air isolation and absorption of inclusions. On the other hand, it is necessary to prevent impurities in equipment such as steel ladle and ingot mold from mixing into the molten steel, and regularly clean and maintain the equipment to ensure its cleanliness.

3. Timely treatment after pouring

1. Cooling control of steel ingots

After casting, the cooling process of the steel ingot also has an important impact on its quality. If the cooling speed is too fast, it will cause greater thermal stress inside the steel ingot, leading to cracks; if the cooling speed is too slow, it will extend the production cycle and reduce production efficiency. Ingots of different materials require different cooling methods and cooling speeds. For ordinary carbon steel, air cooling can be used to allow the steel ingot to cool naturally in the air; for some high-alloy steels or large steel ingots, slow cooling or annealing may be required to control the cooling speed, eliminate the thermal stress inside the steel ingot, refine the grains, and improve the quality of the steel ingot.

2. Quality inspection and defect handling

After the steel ingot has cooled to a certain degree, it is necessary to conduct quality inspection in time. The quality of the steel ingot is comprehensively evaluated through appearance inspection, non-destructive testing (such as ultrasonic testing, magnetic particle testing, etc.) and physical and chemical performance testing. Once the steel ingot is found to have surface cracks, internal inclusions, pores and other defects, it must be dealt with in time. For surface defects, grinding, repair welding and other methods can be used to repair them; for steel ingots with serious internal defects, they may need to be scrapped to prevent them from flowing into subsequent processing procedures and causing greater losses.

When pouring steel ingots, only by making full preparations before pouring, accurately controlling the pouring process, and handling it in time after pouring, can we ensure the quality of the steel ingots while improving production efficiency, lay a good foundation for the subsequent processes of steel production, and achieve high-quality development of the enterprise.