Corrosion-active Nonmetallic Inclusions Research Articles

Mastering the Production of Rolled Products and Tubes of Steel 20-KSKh Guaranteed to Be Free of Corrosion-Active Nonmetallic Inclusions

Results obtained from comprehensive corrosion tests have established that in addition to limiting the content of corrosion-active nonmetallic inclusions in steel to make it resistant to corrosion, it is also desirable to restrict the steel's contents of sulfur, manganese, and silicon. The new specifications for steels 20-KS (corrosion-resistant) and 20-KSKh (corrosion- and cold-resistant) were therefore developed based on steel 20sp, which is distinguished by its relatively low contents of manganese and silicon. These steels also have a limited sulfur content, and they are microalloyed with niobium or vanadium to obtain a fine-grained structure. All the other indices of the steels meet the requirements of SNiP. Mastering the production of welded tubes made of steel 20-KSKh is an important step toward the goal of improving the durability of oil-field tubing in Western Siberia. Such tubes are the first type of tubular metal product that has been guaranteed to be clean with respect to corrosion-active nonmetallic inclusions, and guarantees of this kind are a prerequisite to ensuring that pipelines have satisfactory corrosion resistance and last for their normal service life.

Methods of Evaluating the Corrosion Resistance of Low-Alloy and Carbon Tube Steels under the Service Conditions of Oil and Gas Pipelines

At present, determining the content of corrosion-active nonmetallic inclusions in tube steels is the best way to evaluate these steels' resistance to local corrosion under the service conditions of oil-field tubing in Western Siberia. However, the method needs to be refined or supplemented. Field tests of tube steels are an important means of gauging the corrosion resistance of these materials and pipes when certain conditions are observed. Laboratory corrosion tests should be performed under conditions identical to the corrosion conditions encountered in the field. The rates of the main corrosion processes that take place during the problem-free operation of pipelines may turn out to be significantly higher in the laboratory than in field tests.

Development of Recommendations on Making Tube Steels Produced at the Severstal’ Combine Cleaner with Respect to Corrosion-Active Nonmetallic Inclusions

Recommendations are given on out-of-furnace treatments which will allow the production of steel that is clean in terms of its content of corrosion-active nonmetallic inclusions.

The Role of Nonmetallic Inclusions in Accelerating the Local Corrosion of Metal Products Made of Plain-Carbon and Low-Alloy Steels

Using the principles of physicochemical modeling to describe the deoxidation and desulfurization of steel in the ladle and interactions between the metallic and slag phases with allowance for features of the equipment in use at specific plants, the paper shows that it is possible to quickly optimize the parameters of out-of-furnace treatments of the steel without losing productivity. The optimum parameters make it possible to fully realize all of the main advantages of such treatments: further refining of the steel, modification of the nonmetallic inclusions, guaranteeing that the steel will be clean in terms of the presence of corrosion-active nonmetallic inclusions, and, thus, ensuring that the steel will be resistant to local corrosion.