Rolling Of Billets Research Articles

Influence of thermal state of the end area of multiple continuous-cast billet on cracking of the ends of hot-rolled breakdown at rolling

The authors have made an analysis of problems arising in the rolling of continuous-cast billets in the modern mini-metallurgical and rerolling plants. It is shown that the use of trio stands in rolling mills of these plants makes it necessary to obtain billets of multiple lengths from bars (most often of 12-meter length) produced in the rolling shop. The subsequent rolling of such multiple billets has revealed increased cracking of the front edge and, as a result, increased metal consumption. Analysis of the causes of these cracks has been made. It was indicated that this defect can appear as a result of a certain stress-strain state formed at the end of hot-rolled breakdown. It is caused by the presence of an uneven temperature field due to more intensive end cooling, to reduction mode in the trio stand and to the presence of axial defects in the continuous-cast billet. The study was conducted on the industrial medium-grade mill 500/370, as well as using mathematical modeling by finite element method. The influence of a set of technological factors, such as temperature of the billets heating before rolling, the time interval of their transportation on the site “heating furnace – first stand of the rolling mill” and parameters of the macrostructure of axial area of the metal were investigated. Calculations by the developed mathematical model have indicated the need to take into account the presence of a scale layer on the heated continuous-cast billet. It is shown that depending on the heating temperature and transport time, the temperature difference at the billet’s end compared to the heating temperature can be from 45 to 100 °C. It will lead to an uneven distribution of deformation resistance and unfavorable stress-strain state at the billet’s end. In addition, the presence of an axial defect can affect the cracking because of its shape and its transformation during reduction. Obtained experimental data allowed hypothesizing the mechanism of transformation of discontinuity defects into cracks at the billet’s end due to the conditions of continuous casting and cutting of billets during rolling in the reduction stand.

Development and scientific justification of the longitudinal rolling method of high billets under severe plastic deformation conditions

Abstract The paper presents the results of the study of innovative technology of longitudinal rolling of high billets under severe plastic deformation. It was found that the implementation of the proposed method will help to reduce the coefficient of variation and create conditions for the intensification of plastic deformation in the deformation center during the billet rolling in two passes, which will provide a satisfactory penetration of deformation in the axial zone of the ingot and a uniform distribution of the strain in the volume of the billet with minimal changes in its size.

Investigation of the Process of Screw Rolling in a Four-Roll Stand by Simulation

We designed and produced a working model of new four-roll mill with the use of additive technologies. The model has two driven working rolls and two driven auxiliary rolls for screw rolling of round billets. Plasticine billets were rolled in the model mill to show that the four-roll screw rolling is possible. The experimental rolling was simulated by using the QForm software. The accuracy of computer simulations was estimated by comparing the dimensions of the billets obtained after rolling and as a result of computer simulations. We simulated the procedure of rolling of a round billet of alloyed steel both in a four-roll mill and in a three-roll mill with radial-shear rolling. According to the results of computer simulations, it was shown that the variations of the diameter along the length of the billet and the total work required to realize shape-forming are lower for the four-roll mill.

О ВЫБОРЕ РЕЖИМОВ ИЗГИБА ПРИ ВАЛЬЦОВКЕ ЗАГОТОВОК

О ВЫБОРЕ РЕЖИМОВ ИЗГИБА ПРИ ВАЛЬЦОВКЕ ЗАГОТОВОК

DEVELOPING MODES TO OBTAIN DEFORMED SEMI-FINISHED PRODUCTS FROM EXPERIMENTAL SCANDIUM CONTAINING ALUMINUM ALLOY AND STUDYING THEIR MECHANICAL PROPERTIES

The paper demonstrates the urgency of studies focused on creating new Al-Mg alloys doped with scandium and featuring by an advantageous combination of operational and mechanical properties such as weldability, corrosion resistance and sufficient strength. In production conditions, 560×1360×4520 mm flat ingots were obtained from an experimental scandium-containing alloy. They were cut into billets with a maximum thickness of 40 mm and then heat treatment and sheet rolling modes were developed for them and tested. The DUO 330 mill with smooth rolls having an initial diameter of 330 mm and a barrel width of 540 mm was used as rolling equipment. Experimental studies consisting in blank preparation for rolling (homogenization annealing and face milling), hot rolling at 450 °C, cold rolling to a thickness of 3 mm and annealing of cold-deformed semi-finished products at 350 °C for 3 hours allowed making deformed semi-finished products by various drafting patterns at rolling that were subjected to heat treatment. The maximum total degree of deformation during billet rolling to the 3 mm thickness was 92,5 %, and the draw ratio per pass changed from 1,04 to 1,2. The LFM400 400 kN universal test machine as per GOST 1497-84 was used to determine mechanical properties of deformed and annealed semi-finished products of various thicknesses made of an experimental alloy and identify regularities of their changes depending on the total degree of deformation during rolling. It was found that when rolling strips of an experimental scandiumcontaining aluminum alloy the ultimate tensile strength and yield strength of the metal grow, and the percentage elongation decreases with an increase in the total degree of deformation. This corresponds to the general ideas of metal forming theory. The mechanical analysis of semi-finished products showed that the level of strength and plastic properties is quite high, wherein the ultimate tensile strength reaches 453–481 MPa, yield strength – 429–457 MPa, and percentage elongation – 3,8-5,0 % for cold-deformed samples. Annealing made it possible to increase percentage elongation values to 14–16 % at sufficiently high yield strength (up to 277 MPa). The results of the conducted studies were used to develop casting, rolling and annealing modes for making semi-finished products of the Al–Mg alloy sparingly doped with scandium within 0,10–0,14 % that will be used when mastering machining technologies in production.

Prediction of the Fracture of Metal in the Process of Screw Rolling in a Two-Roll Mill

We study the process of two-roll screw rolling of billets made of stainless steel in order to estimate the influence of the feed angle on the plasticity of the metal of rolling billets. Pilot rollings were simulated by using the DEFORM software. In the computer simulation, the normalized Cockroft–Latham fracture criterion is used to predict the so-called Mannesmann effect (axial fracture of a billet). The comparison of the results of pilot rollings with the data of computer simulations showed that this fracture criterion is an efficient tool for the investigation of screw rolling. A procedure is proposed for the prediction of fracture of the metal subjected to screw rolling.

Studying the Nonstationary Stages of Screw Rolling of Billets with Profiled Ends

The rolling of VT-6 alloy billets with profiled ends in a screw rolling mill is studied to determine the geometry of the end sections minimizing the funnel depth after rolling. The rolling experiment conducted is of 23 factorial design. The nonstationary stages of the process are simulated using Deform-3D software. The results of the simulation are used to find the shape and dimensions of the end sections of the billet that minimize the funnel depth.

Computer Simulation of Porous Material Plastic Deformation

This paper reports on a computer simulation of plastic deformation of refractory material porous billets when rolling in four-roll-pass mills. This model allows calculating the geometrical, kinematic, and energy parameters of the rolling process accounting for the preset law of porous billet compacting in the deformation zone. The theoretical study of porous billet rolling process using the mathematical model has proved the decrease of billet elongation compared with that of non-porous ones. The computer analysis has shown that in the process of rolling falling of creep value, the rolling force and rolling moment take place. The experimental test of the computer simulation results has shown a good correspondence of main rolling process parameters.

3D modeling of large steel-copper billet rolling for electrolyzer cathode rods

3D modeling of large steel-copper billet rolling for electrolyzer cathode rods

Increasing Hot Rolling Mass of Steel Sheet Products

The article exposes contemporary materials and structures for metallurgy. Feasible increase of dynamic forces on the rolling machinery during rolling of billets with masses up to 20 t (Stand No.1 of CWM 1700 HR, «U.S. Steel Košice», Košice, Slovakia, and PJSC «Illich MMPP», Mariupol, Ukraine) is discussed. It is proved that weight of billet, velocities of metal delivery to working rolls and rolling significantly influence the dynamic loads during metal biting. The technical solutions are suggested which would allow the steady rolling process of billets with masses up to 20 t and prevent accidental failures of frame parts, chocks and main lines.

Effect of Annealing on Mechanical Properties and Formability of Cold Rolled Thin Sheets of Fe-P P/M Alloys

Phosphorus in steel is known to increase strength and hardness and decrease ductility. Higher phosphorus content (more than 0.05%), however, promotes brittle behavior due to segregation of Fe3P along the grain boundaries which makes further mechanical working of these alloys difficult. In this work, thin sheets of Fe-P alloys (with phosphorus in range of 0.1–0.35%) have been developed through processing by powder metallurgy followed by hot rolling and cold rolling. The effect of phosphorus content and annealing parameters (temperature and time) on microstructure, mechanical properties, formability in biaxial stretching and fracture behavior of the cold rolled and annealed sheets has been studied. A comparison has also been made between the properties of the sheets made through P/M route and the conventional cast route with similar phosphorus content. It has been shown that thin sheets of Fe-P alloys with phosphorous up to 0.35% possessing a good combination of strength and formability can be produced through rolling of billets of these alloys made through powder metallurgy technique without the problem of segregation.

丸鋼片の軸芯欠陥閉塞挙動に及ぼす孔型の影響

丸鋼片の軸芯欠陥閉塞挙動に及ぼす孔型の影響

Effect of Groove Shape on Closure of Center Defects in Symmetric Rolling of Round Billets

Effect of Groove Shape on Closure of Center Defects in Symmetric Rolling of Round Billets

Effect of Mn/S Ratio on the Hot Ductility of Eco-friendly Bi-S based Free Cutting Steel

AbstractThe hot ductility of eco-friendly Bi-S based free cutting steels with different Mn/S ratios was studied using a Gleeble-1500 thermal–mechanical simulator. The hot ductility of the steel was found to depend on the Mn/S ratio, and the Mn/S ratio of the steel should be greater than 3.5 for hot rolling of billets without crack development. The low Mn/S ratio would inhibit the occurrence of the dynamic recrystallization and cause the formation of the low melting point sulfide Fe-rich (Fe,Mn)S as secondary phases, which could obviously reduce the strength of the grain boundary and resulted in the formation of cracks along the grain boundary. The higher the Mn/S ratio in the steel, the lower the Fe content in the Fe-rich (Fe,Mn)S phases. When the Mn/S ratio in the steel was high enough, the sulfide phases in the steel were mainly MnS as primary inclusions and the low melting point sulfide phases could be effectively avoided forming. While the Mn/S ratio could influence the hot ductility of the steel over the whole temperature range of 900–1200 °C, the segregation of bismuth along grain boundary could be harmful to the hot ductility in addition to the lower Mn/S ratio for the temperature was no more than 1050 °C.

Effect of Stress Field on Closure of Center Defects in Symmetric Rolling and Asymmetric Rolling of Round Billets

Although the closure of defects at the center of billets on rolling such billets is an important subject, a method of quantity evaluation for such closure has not yet been clarified. Therefore, to establish a method for such quantity evaluation, we study such defects using experiments and finite element analysis including asymmetric rolling, especially with respect to the integration of the hydrostatic stress Gm. The results showed that stress was widely distributed, as determined in the experiment and in the FEM analysis of rolling at the edge around an artificial central hole in which defects were simulated. Therefore, it was suggested that, to evaluate the behavior of defect closure, the size of defects and the shape of the grooved roll used should be taken into account. [doi:10.2320/matertrans.P-M2014837]

Deformation action of screw rolling on a cast wheel billet

Results are presented for an experimental study of the effect of screw rolling of solid billets on mechanical properties and macrostructure of T grade wheel steel. It is shown that piercing of continuous billets with a drawing factor λ = 1.6 makes it possible to work a cast structure, improve ductility properties, and impact load resistance.

Analysis of Square Billet Cross Wedge Rolling Process Using Finite Element Method

The aim of this paper is to determine whether the train axle cross wedge rolling(CWR) using square billet as blank is available or not. Based on numerical simulation software DEFORM-3D, we built the finite element model. And the whole forming process was simulated successfully. The stress and strain distributions of workpiece in the process were analyzed. The effect of forming angle, stretching angle and billet size on rolling force was investigated, then determined the proper process parameters. The differences between the round billet rolling and the square billet rolling were obtained by comparing the tangential, axial and radial forces during the rolling process. The studied results show the availability of using square billet as blank in train axle CWR and provide important realistic meaning and application value.

Formation Mechanisms of Cracks Formed During Hot Rolling of Free-Machining Steel Billets

In this study, cracks formed in the edge side of Bi-S–based free-machining steel billets during hot rolling were analyzed in detail, and their formation mechanisms were clarified in relation with microstructure. Particular emphasis was placed on roles of bands of pearlites or C- and Mn-rich regions and complex iron oxides present in the edge side. Pearlite bands in the cracked region were considerably bent to the surface, while those in the noncracked region were parallel to the surface. This was because the alignment direction of pearlite bands was irregularly deviated up to 45 deg from the normal direction parallel to the surface, while the billet was rolled and rotated at 90 deg in the same direction between rolling passes. On the edge side, where pearlite bands were bent, iron oxides intruded deeply into the interior along pearlite bands, which worked as stress concentration sites during hot rolling and, consequently, main causes of the crack initiation in the rolled billet. On the surface of the wire rod rolled from the cracked billet, a few scabs were found when some protrusions were folded during hot rolling. In order to prevent the cracking in billets and scab formation in wire rods, (1) the increase of rolling passes and the decrease of reduction ratio for homogeneous rolling of billets and (2) the reduction in sulfur content for minimizing the formation and intrusion of complex iron oxides were suggested.

Rational controlled rolling on a 5000 pipe-blank mill at reduced temperature

Effective controlled billet rolling on the OAO MMK 5000 mill permits the production of pipe for underground pipelines (diameter 1220 mm; wall thickness 22 mm) from steel of strength category X80. The slab temperature before rolling may be reduced to 1100°C, with corresponding adjustment in the rolling energy and with the required solubility of carbonitrides of the microcomponents, so as to ensure the required strength.

鋼材表面疵近傍におけるサブスケール層内の粒状酸化物の生成機構

Since there are many generation factors for surface cracks on steel products manufactured by the processes of continuous casting through billet rolling, it is important for their prevention to identify the process where the surface cracks are generated. In this study, the formation mechanism of the oxide particles in the subscale layer around surface cracks of steel products was investigated towards establishing an estimation method of crack generation temperature. It was found that, the average radius leveled off corresponding with its exposed temperature after enough holding time. The average radiuses were 0.2 μm and 0.3 μm for 1473K and 1573K, respectively. Those oxide particles were consisted of MnO·SiO2 and MnO·Cr2O3 phases. Their formation and growth mechanism was as follows: Firstly, MnO·SiO2 precipitates at the internal oxidation reaction front. Then, MnO·Cr2O3 forms on the MnO·SiO2 particles. The existence of these two phases played an important role to determine the terminal value of the average radius.