Causes of Air Bubbles in Seamless Steel Tubes

The analysis indicates that seamless steel tubes must have three conditions because the gas in the melt is precipitated as bubbles: one is that the dissolved gas is in a supersaturated state; the other is that the sum of the partial pressures of various gases in the bubble is greater than the external pressure acting on the bubble; Third, there are bubble nuclei larger than the critical. Under actual casting conditions, non-spontaneous bubble nuclei in the melt are easily formed because there are always a large number of non-metallic inclusions, aggregates, and bubbles that do not escape during refining. In addition, although the hydrogen content of the melt after the refining is lower than the equilibrium concentration, the gas concentration during the solidification process is redistributed, which causes the local hydrogen content in the liquid at the front of the crystal to be supersaturated. Bubbles create favorable conditions. When the partial pressure of hydrogen in the crystallization front liquid increases above the external pressure, bubbles may form. However, the buoyancy of the formed bubbles is less than the adhesion force of the solid surface to the bubbles,
or the floating speed of the bubbles is less than the crystallization speed of the ingot.The bubbles stay in the ingot and become pores.

The stomatal criterion number indicates the multiple of the concentration of the gas in the liquid phase at the crystal interface compared with the original concentration of the liquid when the metal or alloy crystallized. Therefore, the greater the V of the seamless steel pipe, the greater the degree of gas supersaturation in the liquid phase at the crystalline interface, and the easier it is to form pores. According to relevant data, among common metals, the 7 value of aluminum is the largest, so aluminum and aluminum alloys form pores when solidified.

The short-term adjustment of seamless steel tube prices is mainly due to the impact of nickel. Due to the decline in the price of imported raw materials, the price of seamless steel pipes also declined, but the margin was small. Iron and steel enterprises are facing tepid situations. According to the survey, 50% of steel company personnel expressed dissatisfaction with the future development of steel. On the other hand, due to the influence of the property market, seamless steel pipe enterprises have also been affected to some extent. The impact on the steel market is still very large, and this impact may continue for some time.