Distribution Characteristics of Inclusions in Continuous Casting Slabs

The Distribution Characteristics of Inclusion in Continuous Cast Slab

Continuous casting is a common process for producing steel products. The continuous cast slab is in meltonic state and the inclusion characteristics of the slabs are extremely important for the properties, properties, performance and applications of the products. This paper aims to analyze the major types and distribution characteristics of inclusions in continuous cast slab.

First of all, the inclusions found in the continuous cast slab are mainly divided into non-metallic inclusions, slag inclusions, gas inclusions and floating inclusion. Due to their differences in appearance, size and distribution, they have different effects and influences on the properties of the steel products.

Non-metallic inclusions are composed of oxide, sulfide, nitride and carbide components, including silicates, aluminates, and spinels. They are stable inclusions, solid particles, and the size of their individual particles varies from a few μm to hundreds of μm. Non-metallic inclusions are mainly derived from the liquid steel in two forms: (1) formed during the oxidation of the liquid steel at the slag-liquid interface; (2) formed by the decomposition of alloying elements and deoxidation products in liquid steel. Non-metallic inclusions exhibit a great impact on the performance of the steel products.

Slag inclusions are mainly produced due to the oxygen pick-up and reactions effect between oxygen and components in the steel during continuous casting to form various oxides. The particles of the slag inclusions vary in size and shape. The slag inclusion particles are typically elongated and the size is generally larger than that of the non-metallic inclusions. Slag inclusions affect the mechanical properties, thermal properties and fatigue properties of the steel.

Gas inclusions generally refer to micro-bubbles composed of variety of gas. Its diameter can vary from several microns to hundreds of microns. The gas inclusions in continuous cast slab are mainly produced from the gasification of alloying elements, deoxidation products, and other soluble matter in the liquid steel. The gas inclusion has extremely low solid particle density, so the paper form its considerable influence on mechanical properties.

The floating inclusion refers to the inclusion composed of complex oxides, hydroxides and chlorides which are not completely dissolved and float in the slab surface. The floating inclusions, which are generally a few millimeters in size, are mostly caused by the poor protection of the liquid steel and the poor release of hydrogen. Floating inclusions can result in defects in the steel products such as hairline cracks.

In conclusion, the properties, properties, performance and applications of steel products are significantly impacted by the inclusions found in the continuous cast slab. It is important to select the appropriate control measures in order to keep the inclusions at an acceptable level in order to ensure the quality of the steel products.

Continuous casting slab impurity distribution characteristics are usually divided into five modes. The first mode is the distribution of the impurity which is equal with the alloy content. The second mode is densely distributed inside the mixed impurities, resulting in local segregation. The third mode is also densely distributed, but mixed with a large number of impurity particles, resulting in macroscopic segregation. The fourth mode is the uniform distribution of mixed impurities, and the fifth mode is the mixed adjacency.

The first four modes are not the best cast products, while the fifth mode is the most suitable pattern for the distribution of impurities. It is related to the quality, performance and cost of the ingot. For example, when a large number of elongated particles (such as clusters) are present in a ingot, the ingot surface structure and properties are not good, and it is difficult to satisfy the scales in the slab flatness test and steel performance. Therefore, the appropriateness of impurity distribution is an important factor to ensure the quality of the mechanical.

In order to ensure the uniformity of impurity distribution in the continuous casting slab, it is necessary to pay attention to the pure slag and pure alloy smelting process. At the same time, in the roller compacting technology, the tundish ladle pouring distance, the slag amount and the regulations on the ladle’s motion orbit and pouring time should be strict to reduce the small particles aggregation. In addition, the proportion of slag in the tundish mud should not be too high to prevent impurities from entering the ingot. Therefore, reasonable impurity distribution is a necessary condition for improving continuous casting slab quality.