Hydrogen removal during out-of-furnace treatment of steel in an out-of-furnace refinement and degassing unit

The possibilities of hydrogen removal during degassing of both nondeoxidized and deoxidized metal and slag are demonstrated.     

Development and study of out-of-furnace treatment of steel using DC arc heating

The results of pilot studies performed to design dc ladle-furnace units are presented. The design, equipment composition, and technical characteristics of 15-t dc ladle-furnace units, which are intended for complex treatment of steel at atmospheric pressure and in vacuum and were designed by VNIIMETMASh, TsNIIChERMET, VNIIETO, and some other enterprises, are described.     

Improvement of the technology of the out-of-furnace treatment of wheel steel

Various versions of the deoxidation and out-of-furnace treatment of wheel steel under the OAO VMZ conditions are analyzed. The effective partial pressure of carbon monoxide over a melt in a 130-t ladle degasser is found to be 54 ± 9 kPa. Thermodynamic analysis of the deoxidation demonstrates that low oxygen concentrations in the melt of wheel steel can be achieved when it is deoxidized by aluminum, silicocalcium, aluminocalcium, or carbon in vacuum. Experiments and a thermodynamic calculation show that the vacuum-carbon deoxidation of a high-strength wheel steel provides oxygen concentrations in the metal that are comparable with the concentrations obtained by silicocalcium deoxidation (0.0023 ± 0.0005 wt %) and ensures the optimum morphology and concentration of oxide inclusions. The causes of the formation of the defects revealed by ultrasonic inspection in railway wheel templates are studied. The level of rejection controlled by these defects depends on the deoxidation method and is related to the number and morphology of the oxide inclusions that form during secondary oxidation.     

Rational technology for the deoxidation and out-of-furnace treatment of low-silicon steel

A rational technology is proposed for the deoxidation of low-silicon steel. It includes preliminary deoxidation by ferrosilicomanganese in metal tapping from a steel-melting unit and the introduction of aluminum ingots and aluminum rods during out-of-furnace treatment. As a result, the contamination of rolled roll sheets by nonmetallic inclusions decreases and the metal yield increases.     

Control and management of the out-of-furnace treatment of metal using ladle vibrations

A monitoring technique is proposed and subjected to laboratory and full-scale tests. The energy of a vibration signal in an informative frequency range is found to depend on the gas flow rate and blowing (bubble, jet) conditions. An experimental version of the process control system is tested under industrial conditions.     

Technology for out-of-furnace treatment of steel with the use of a new deoxidizer

A technology has been proposed for obtaining rolled plates with the use of calcium carbide instead of vacuum degassing. The technology makes it possible to obtain steel that is equivalent to vacuum-degassed steel with respect to the composition and quantity of nonmetallic inclusions and the quality of the finished plates. It is shown that the use of calcium carbide reduces the content of nonmetallic inclusions by a factor of roughly 1.5 compared to use of the standard technology without vacuum degassing. The percentage of hot-rolled plates rejected for defects detected in ultrasonic tests is also decreased.     

Intensification of out-of-furnace treatment of steel at an enhanced electric arc furnace capacity

The problems of intensifying the out-of-furnace treatment of steel in an LFU by decreasing the metal heating time and increasing the desulfurization rate are discussed.     

Effect of the out-of-furnace treatment technology on the contamination of steel by nonmetallic inclusions

Results are presented from studies and experiments conducted with the objective of reducing the overall contamination of steel by nonmetallic inclusions and changing their morphology. The article describes a new technology for deoxidizing steel and examines the main types of defects formed in steel’ the conditions under which they form’ and the mechanisms responsible for their formation.     

Physicochemical grounds for the substitution of nitrogen for argon during out-of-furnace treatment of high-carbon steel

Physicochemical grounds for the possibility of replacing of argon with nitrogen during blowing a metal in the course of degassing and in a ladle-furnace unit are obtained using a mathematical model of degassing steel for out-of-furnace treatment. According to the data of examining the model for adequacy, the calculation error does not exceed 1%. A numerical experiment demonstrates that the replacement of argon with nitrogen during degassing of steel does not lead to any increase in the nitrogen content in it. Blowing in a ladle-furnace unit can be performed using an argon-nitrogen mixture taken in the proportion (2–3): 1. The replacement of argon with nitrogen allows the cost of the out-of-furnace treatment of steel to be decreased.     

Status and prospects of out-of-furnace treatments of steel in Russia

Modern steelmaking practice requires treatment of the steel outside the furnace, and the results obtained from such treatment determine many of the economic and qualitative indices of the finished metal products. Forty three ladle-furnace units (LFU) have been introduced in Russia since 1991, these units having an aggregate capacity of roughly 30 million tons of steel a year. The number of ladle-furnace units operating in Russia is expected to increase in the future. Equipping open-hearth (OH) furnaces with an LFU not only improves the quality of the steels and increases the number of grades that can be made, but it also reduces product costs as a whole. An increasing number of two-stand LFU have recently been introduced, these units providing for electric-arc heating, top-blowing of the melt through a lance, and the injection of powdered materials into the steel. The demand for vacuum-degassed steel in Russia is slightly more than 21 million tons, but existing production facilities can supply only 16–17 million tons of this amount, i.e., there is a shortage of vacuum-degassing equipment in Russia. __________ Translated from Metallurg, No. 2, pp. 49–55, February, 2006.     

Current trends in the production of railroad wheels and the effect of out-of-furnace treatment of the steel on their properties

Current trends in the production of railroad wheels show the use of some promising techniques: a reduction in the carbon content of the finished steel; degassing the steel in a vacuum to decrease its hydrogen content; more efficient deoxidation and alloying of the steel. When used together, these measures are ensuring that the finished steel has the mechanical and service properties prescribed for wheel steel. Studies and factory testing of a new technology for making wheel steel have shown that the oxygen content of the steel can be reduced by its self-deoxidation during vacuum degassing. This approach also helps lower the steel’s hydrogen content while saving deoxidizers. Researchers have discovered certain laws that govern the relationship between the characteristics of wheel steel and its contents of sulfur and gases. The amount of sulfur and gases in this type of steel can be reduced by using efficient parameters for the treatment that is administered outside the steelmaking furnace. __________ Translated from Metallurg, No. 8, pp. 56–60, August, 2006.     

Multistage heat treatment

Multistage heat treatments have been used to clarify transformation mechanisms and to provide a basis for reducing heat treating time in commercial practice and/or obtaining improved properties. The influence of stepped transformation on the kinetics of the bainite reaction is examined and the results suggest means for improving the hardenability of medium alloy steels. The application of double aging treatments to age hardening systems also is examined. This paper is based on a presentation made at a symposium on Altering the Time Cycle of Heat Treatment, held at the Philadelphia meeting of The Metallurgical Society of AIME, October 14, 1969, under the sponsorship of the IMD Heat Treatment Committee.     

Phase transformation of Zn-4Al-3Cu alloy during heat treatment

The phase transformation in Zn-4 Al-3 Cu alloy employing various solution-treatment temperatures (230 °C to 325 °C) was studied by means of microhardness, scanning electron microscopy (SEM), electron probe microanalysis (EPMA), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The starting microstructure of the as-cast Zn-4Al-3Cu alloy consists of an α phase (aluminum-rich, fcc structure) in the η matrix (zinc-rich, h.c.p. structure) prior to solution-treatment. A platelike ε phase with 3-μm length and 0.5-μm thickness was found in the η phase matrix after solution-treating the as-cast material at 240 °C for 1 hour. The ε phase was then dissolved gradually back into the η matrix above that temperature. A four-phase transformation, α + ε → T′ + η, was observed from the temperature 250 °C to 310 °C, wherein the T′ phase formed at the interface of ε platelet and η phase matrix. This T′ phase was further identified as a rhombohedral structure. As the solution-treatment temperature was increased to above 310 °C, the ε phase was completely dissolved back into the η matrix and numerous β phase particles were distributed uniformly in the η matrix. The β phase subsequently decomposed at room temperature to a fine α phase embedded in the η matrix. For the materials solution-treated above 250 °C, the microhardness of the η matrix increased in 40 minutes during natural aging, which was associated with the formation of fine ε phase of 0.15-μm diameter. The orientation relationship between this fine ε phase and η phase was determined as .     

Cr3复合铸钢支承辊差温热处理过程

以Cr3复合铸钢支承辊为研究对象,采用差温热处理工艺制备满足性能要求的支承辊.研究了支承辊在差温热处理过程中的温度分布情况,分析了轧辊工作层的硬度和组织,运用已开发的淬火温度场模拟系统对支承辊油淬过程温度场进行模拟,并将模拟结果与实测结果进行了比较.结果表明:使用差温热处理工艺可使支承辊的辊芯和辊身在加热完成后得到不同的温度,从而使其在随后的淬火过程中得到不同的组织.支承辊经差温热处理工艺加热后,轧辊工作层内的硬度和组织均满足使用要求.运用已开发的淬火温度场模拟系统对支承辊油淬过程进行模拟,模拟结果与实验结果相吻合,证明该系统具有较高的可靠性,可用于热处理工艺优化,能够为实际生产提供定量的参考依据.