Experience of production of hollow tubular ingots by electroslag melting

New Possibilities of ESR for Modern Machine Engineering

“…Mechanical properties of ESR-cast billets which are smelted with used low-frequency AC (used for the main circulation line and made out of ASTM A508 grade 3) at standard and raised temperatures exceeded respective properties of metal in forged blanks produced in a conventional way [6,17,18]. Ferrite grain score of cast metal is 7-10 by GOST 5639 scale, it is as good as the requirements set to the deformed metal whilst the ductile-to-brittle transition temperature Т 50 of ESR metal is lower by 30-40 0 С.…”

“…Fourth example demonstrates the findings of ESR metal obtained with using low-frequency AC at the management of thermophysical processes in ESR. JSC "RPA "CNIITMASH" research works [6,12,16] established that reduction of power frequency makes it possible to effectively control the melting rate and bath formation coefficient, extension of two-phase area, characteristics of dendritic structure: distance between dendrite arms and parameters of impurity distribution; a possibility was also shown to obtain actually homogeneous dimensional characteristic for the cast structure -mean primary dendrite arm spacing. Due to applied low-frequency AC (2 Hz instead of 50 Hz) it was possible to reduce dendrite inhomogeneity in the pipe billet wall up to 3-4 times.…”

“…An analysis of the effect of the electric current frequency on the nature and intensity of thermal processes in ESR of hollow ingots is presented in [12]. Shown that as the frequency of the current decreases, the maximum temperature of the electrode surface (𝑡𝑡 м , К) and the heating time (𝜏𝜏 0 , s) constant decrease according to the square root law and at other equal conditions the mass melting rate of the consumable electrode decreases:…”

“…ESR, as a method of controlling the crystallization of a metal (like any technical solution), has its limitations. It is impossible to completely separate the supply of energy required for the melting of the consumable electrode and the amount of metal to be melted [2][3][4]. There is no possibility to control the completeness of oxidation-reduction processes objectively and operatively.…”

“…There is no possibility to control the completeness of oxidation-reduction processes objectively and operatively. Analysis of economic efficiency for metallurgic processes conducted by JSC "RPA "CNIITMASH" [5,6] in this context demonstrated that improvement of product consumer properties is an important competitive advantage of ESR metal implemented in the finished product. Such distant benefit, however, does not arouse too much enthusiasm from metal consumers, hence the cost reduction for ESR metal items has become a challenging task.…”