Study of factors contributing to decrease of carbide heterogeneity in bearing grades of steel

At present to meet requirement to the quality of bearing steels it is necessary of accomplish estimation of carbide heterogeneity by SEP 1520 and provide the level of carbide network, carbide liquation and streaking, not exceeding adjusted limits, required by customer. To estimate possibility to decrease carbide heterogeneity (segregation), factors influencing its value in the rolling production considered. Description of the process of long products of bearing steels production at the rolling mill 370/150 of the OJSC “BMZ - managing company of the holding “BMK” presented. Possibilities of the existing mill equipment considered for 804 accomplishing of technological operations aimed at decrease of carbide heterogeneity in the finished product. The factors studied, contributing to decrease of carbide heterogeneity under conditions of mill 370/150 operation. To determine the temperature modes effect on the level of carbide heterogeneity in bearing steels, in the process of three campaigns phased decrease of the temperature of end of rolling was accomplished. Results of data analysis obtained at the production of long products profiles of 34-50 diameter of bearing steel grades presented. Conclusion on rolled stock production of bearing steel grades with high requirements to carbide heterogeneity value was formed. It was shown that to obtain high-quality long products it is appropriate to accomplish the heating in the furnace before the rolling no less than 600 min at the temperature in the soaking zone 1150-1220°С followed by application of tech­nology of normalizing rolling and control of temperature of the end of rolling 750°С. For profiles with drawing less 25% it is rec­ommended to accomplish additional heat treatment of the finished profile - normalization. Long time heating of workpieces before the rolling at the temperature 1150-1220°С enables to decrease the carbide heterogeneity down to acceptable level (carbide liquation no more than 3 points and carbide streaking no more than 4 points). The value of carbide network is decreasing at decreasing of tem­perature of the end of the rolling and increasing deformation value in the last stands. A stable satisfactory result (CN no more than 5.4) was reached at the temperature of the end of rolling 750°С and drawing more than 25%. It was established that the higher the total drawing, the lower the point of carbide network and liquation in the finished profile, which is caused by crushing of nondissolved carbides to separate fragments.

The Optimization Solution of the Vertical Rolling Force by Using Unified Yield Criterion

Vertical rolling is an important technique to control the width of continuous casting slab in hot rolling field. Accurate prediction of vertical rolling force is a core point to maintain rolling mill equipment. Due to the limitation of the algorithm, the prediction accuracy of most vertical rolling force models based on the energy method can only reach more than 10%. Therefore, it is challenging to optimize the rolling force model to improve the prediction accuracy. This paper presents an innovative approach for optimizing the calculation of vertical rolling force with a unified yield criterion. Firstly, the maximal width of dog bone region is determined by the slip-line method and described the dog bone shape via sine function model. Furthermore, proposed velocity and corresponding strain rate fields satisfy kinematically admissible condition is used to calculate the total power. Finally, the analytical solution of the rolling force and dog bone shape model is obtained by repeatedly optimizing the weighted coefficient b of intermediate principal shear stress on the yield criterion. And the effectiveness of the proposed mechanical model is verified by measured data in strip hot rolling field and other models’ results. The results shows that the prediction accuracy of vertical rolling force model can be improved by optimizing the value of b. Then, the impacts of reduction rate, initial thickness and friction factor on dog-bone shape size and vertical rolling force are discussed.

BIO BRIKET CANGKANG ALEURITES MOLUCCANA MELALUI GELOMBANG ELEKTROMAGNETIK DENGAN VARIAN DAYA DAN DURASI WAKTU KARBONISASI

<span lang="EN-US">Bio briquette is a source of energy derived from biomass and can be used as a solid fuel instead of petroleum and other energy derived from fossils. Bio briquettes are one of the alternative solutions that are quite effective and efficient in dealing with the crisis of energy sources, one of which is by optimizing the pecan shell or shell of Aleurites moluccana as a bio briquette. Pecan shell is a waste that is very abundant in Indonesia and can be used as a solid fuel that is environmentally friendly and has a high calorific value. The purpose of this study was to determine the influence of microwave electromagnetic waves on the bio briquette quality of pecan shells through power variants and the duration of carbonization time. The stages are pecan shell cleaning, carbonization process with microwave electromagnetic waves at predetermined power and duration of time (0.5, 1, 1.5 and, 2 hours), the process of crushing into charcoal with disk mill equipment, mixing with adhesive material with a ratio between the mass of charcoal and adhesive material 80:20 (b/b), bio briquette printing and the last stage is drying with sunlight for 2 days. From the analysis obtained the most optimum results are at 440 watts of power for 1 hour with the following results: water content of 7.30%, ash content: 7.48%, Carbon Bound obtained: 73.31%, Volatile matter: 30.23% and, the calorific value of bio briquette is: 5706.24816 cal/gram</span>

Calculating Power Parameters of Rolling Mill Based on Model of Deformation Zone with Four-Roll Passes

Making “digital twins” for rolling processes and mill equipment should begin with the development of mathematical models of the deformation zone. The deformation zone of two-high flat mill rolling have been studied in detail, relevant models are available in many academic papers. However, the same cannot be said about the most complex deformation zones in stands with multi-roll gauge. Therefore, the task of their reliable mathematical description is of immediate interest. The development of mathematical models is necessary for the design of new wire mills and rolling-drawing units. The combination of rolling in stands with multi-roll gauge and drawing is a promising direction in the production of wire from difficult-to-form steels and alloys. Digital models for pressure-based metal treatment are also necessary for calculating the rolling-mill power parameters during the development of new assortments at the operating mills. The models of deformation zones present the basis for developing the multivariable control systems of process conditions of continuous mills. This research is devoted to the study of the deformation zone and the development of a procedure for calculating the power parameters of rolling in a stand with four-roll passes. The solution of these challenges is given using the example of an operating five-stand wire mill. The authors analysed the known analytical dependencies for calculating the rolling mill force and torque. A mathematical model of the deformation zone and a program for calculating the power parameters have been developed. The paper compares the results obtained from calculations based on analytical dependence and on modelling. A comparison with the experimental parameters obtained at the mill is given. The authors assess the feasibility of using the known formulas and analyse the impact of the front and rear tensions on the power parameters of rolling mill. The problem of developing an automatic tension control system for continuous mills with multi-roll groove is substantiated.

Electrical and Thermal Conductivity of Epoxy-Carbon Filler Composites Processed by Calendaring

Electrical and thermal conductivity of composites which contain carbon-based fillers in an epoxy matrix were investigated. The fillers were dispersed in the liquid matrix by using three roll mill equipment. The filler/matrix mixture was cast in a mold and then cured, thus obtaining composite specimens. Multiwall carbon nanotubes, graphene-like nanoplatelets, and graphite were used as fillers and their effect on conductivity was investigated. Electrical and thermal conductivity were measured at different filler loads. It was found that the formation of percolation paths greatly enhanced electrical conductivity, although they were not so effective in improving thermal conductivity. The behavior of composites containing each single filler was compared with that of hybrid composites containing combinations of two different fillers. Results show that fillers with different aspect ratios displayed a synergetic effect resulting in a noticeable improvement of electrical conductivity. However, only a small effect on thermal conductivity was observed.

Experience in CAD system introduction of rolling-mill machinery at Uralsmashzavod

A chronology and a sequence of works for more than 20 years in the development of different computer program packages which have formed a basis of a future CAD system of technologies and rolling-mill equipment at the enterprise of Uralsmashzavod are presented. The descriptions of the most efficient software packages are given to solve the optimization problems in different processes of blank deformation, parameters of mechanisms and their drives, design parameters of load-bearing parts and complex units from the point of view of strength and life obtaining.