Vol 46, No 3 (2016)

No standard methods exist for determining the wear and abrasive properties of coke corresponding to its motion on conveyers or in the furnace shaft. A test method is proposed for determining the wear and abrasion of foundry coke, on a vibrational system; the effective total vibrational amplitude is 1.6 mm. For the tests, samples of size classes 40–60 and 60–80 mm are taken from four different batches of foundry coke. In the tests, the vibrator, equipped with a special attachment in the form of a chamber with an aluminum plate at the bottom, transmits vibrations to the coke sample. The test time is 30 min. The relative mass loss of the coke sample indicates its wear, while the relative mass loss of the aluminum plate indicates the abrasive properties of the coke. The test results correspond to coke strength M₄₀. Coke of the 60–80 mm class is more abrasive than coke of the 40–60 mm class. With increase in strength of the foundry coke, its wear is reduced by 22% for the 40–60 mm class and by 41% for the 60–80 mm class. The coke’s abrasive action is increased by a factor of 7.6 and 2.3, respectively

Strength tests of sinter associated with the optimization of sinter production have certain deficiencies, whose analysis calls for models of sinter failure. The theory of melt mixing in sintering and structure formation in the sinter cake is reviewed. A model for the failure of metallurgical sinter is proposed on the basis of a model of the stress state of the solid inclusions in the matrix and a failure model based on the Rittinger law. The load in the sinter pieces in the test drum is determined, and a method is proposed for adapting the model of sinter failure by means of granulometric data regarding the test products. The adaptation employs the probability distributions of the model parameters. The dependence of these parameters on the sinter basicity, the carbon content in the batch, and the size of the limestone pieces is determined.

The laminar development of damage in thick 10Г2С1 steel sheet during cold plastic deformation by cyclic flexure is investigated. The steel is subjected to pure flexure in a symmetric cycle, with strain of amplitude 5.5%. The variation in steel strength indicates the damage kinetics in the plastic deformation. In the region of reversible damage, the rate of change in the strength increases to a maximum and then declines. In the region of irreversible damage there is no further change in strength of steel before failure occurs. An upper limit is proposed for the damage of the steel: 20–30% of N_f, where N_f is the number of cycles to failure in cyclic extension–compression. In structural terms, the upper limit of reversible damage is assumed to correspond to the transformation of cellular dislocation structure to band structure.

To determine the best heat treatment of steel, thermokinetic diagrams of austenite decomposition are required. Experimental determination of those diagrams is extremely difficult. In the present work, a model of the phase transitions is proposed; the model takes account of the structure of powder steel. A method is developed for computer experiments with steel cooling. The proposed model permits the determination of the kinetic parameters of austenite decomposition on the basis of isothermal diagrams for two values of the steel porosity. By that means, the transformation kinetics in this steel may be predicted for other values of the porosity, both in isothermal conditions and in continuous cooling. The model is verified for У8 and ПК80 steel with different porosity, by means of published experimental data.

Magnetites form the main component of the iron-ore concentrates produced at the Central (Ukraine) and Lebedinsk (Russia) enrichment facilities. The influence of the chemical composition and physical characteristics of the magnetites and the methods used in their enrichment on the metallurgical characteristics of the unfluxed roasted pellets produced is investigated.

Vacuum treatment of pipe steel and the maintenance of superlow sulfur concentration (0.002%) are not enough to ensure high corrosion resistance. Hydrogen cracking of pipe steel may be prevented by if complex modifiers are used to maintain certain proportions of the active elements Al, Ca, rare-earth metals, and sulfur.

The influence of deformation and heat treatment on the hardness at the inner and outer surfaces of cold-rolled pipe made from ПХ23Ю5 ferritic powder steel is assessed.