METALLURGICAL TECHNOLOGIES
Pipe rolling plants (PRP) with three-high screw rolling mills are used to produce hot-rolled seamless pipes. In Russia, two such rolling units are used: PRP 160 at Pervouralsk Novotrubny Plant and PRP 200 at Volzhsky Pipe Plant. Recently, the most acute issue is increasing their technological capabilities. There is a need of expanding size and grade mix, as well as non-traditional use of gauge and rolling mill for screw rolling. The paper presents results of experimental study of the process of reduction or un-adjusting rolling of pipes on three-high screw rolling mills with an increase in reduction of diameter up to 25 %. The results of computer finite element modeling in QFORM program are provided. The aim of this work was to study effect of rolling process with increased reduction in diameter on change of metal form in deformation zone and changes in geometrical dimensions at reduction of cups with different wall thickness on the pilot mill. Important role in process of metal forming during screw rolling (especially when rolling hollow products and pipes) plays cupped blank ovality that is equal to the ratio of the roll radius when the metal comes in contact with the roller to the radius under the roller in the cross section of deformation zone. Ovality characterizes stability of change in geometric dimensions of pipes and their resistance to deformation in inter-roll space. The reduction of thin-wall cupped blank is accompanied by large va lues of ovality, deformation process is less stable, and as a result, form defects (faceting) and end defects occur during plug rolling. Ovality at plug rolling increases more intensely in comparison with plugless rolling. Presence of plug limits displacement of metal in axial direction and contributes to displacement of metal in gaps between rollers. At plugged rolling, it is necessary to use rolls with collars allowing main reduction along the wall, thereby localizing reduction zone on the plug, and reducing ovality of cupped blanks.
The paper states urgency of the problem of determining stressstrain state of metals of the cladding layer and the main strip in production of three-layer bimetal: alloyed steel-constructional steelalloyed steel. Temperature field of the main strip and cladding layer is given to calculate stress-strain state of metals of three-layer bimetallic strip. Initial data for calculating this stress-strain state are given. To assess the effect of coefficient of friction between cladding layer s and the main strip on stress-strain state of metals in deformation zone, three values of it are taken. Geometric model is described for calculating stress-strain state and metal flow in deformation center of cladding layer. Characteristic lines and points of calculation are provided. Technique for solving the problem of determining stresses and flows in deformation focus is described by finite element method using ANSYS app. Regularities of flow of cladding layer’s metal along the length of deformation center and movement of the main strip of bimetallic ingot are given. Values of mutual displacement of layers of bimetallic strip are determined as a function of deformation degree of the cladding layer. And the recommendations are given on this degree to improve quali ty of a three-layer bimetal. Regularities of distribution of axial and tangential stresses in deformation center are presented for production of steel three-layer bimetallic strips in the unit of combined continuous casting and deformation. Stress state of the cladding layer’s metal in focus of cyclic deformation was estimated from the position of improving quality of three-layer bimetallic strips produced in such unit.
RESOURCE SAVING IN FERROUS METALLURGY
MATERIAL SCIENCE
INNOVATIONS IN METALLURGICAL INDUSTRIAL AND LABORATORY EQUIPMENT, TECHNOLOGIES AND MATERIALS
Increasing performance of steelmaking units is possible with changing methods of steel production. Such variances entail serio us changes in the subsequent redistributions: in metals processing by pressure and in thermal treatment of finished metal products. It is known that these two metallurgical processes are equipped with a large number of heating and thermal furnaces, and their thermal work does not always meet increased requirements for products quali ty. Issues of improving thermal performance of furnaces are also relevant in mechanical engineering. High technological requirements are associa ted with very strict environmental ones. Therefore, a new concept is needed for the design and construction of modern highly automated industrial heating furnaces. In order to improve the design and technical and economic indicators, technical obsolescence and the construction of new industrial furnaces are carried out. In design and construction of furnaces, fuel-burning devices of new designs and modern materials are used. In turn, this necessitates the use of new approaches to working space and heating system design of the furnace, taking into account arrangement of heated products charge. Such events are carried out, as a rule, in operating workshops, that causes certain difficulties due to limited space provided for placement of new furnaces and equipment for their operation and maintenance. A complex study was made of the design and thermal performance of a block of three chamber thermal furnaces. They were built in a limited space of the workshop with specific loading and delivery of heated thin sheet.
SCIENCE APPLICATION
Rolling process is carried out due to power supplied to the center of deformation using contact friction forces. Rolling takes place in two stages – the capture stage and the steady-state process. The capture stage determines possibility of deformation in rolls. During this period, retracting forces of friction are used with maximum efficiency. The main stage of rolling is the steady-state stage of the process, where contact friction capabilities are not fully used and reserve of friction forces is created, which can increase efficiency of rolling process. To balance excessive friction forces on contact surface in deformation zone during the steady-state process, zones of advance and adhesion appear. Their length characterize amount of excessive friction forces. Theoretical dependences for determining slip and adhesion zones are given taking into account variety of rolling factors. Estimation indicator of abilities of friction forces reserve at the steady-state stage is offered as well as dependence for its definition. It is analytically established that in steady-state stage of rolling on smooth rolls with ratio α/μз = 1 it is possible to supply 1.7 – 2 times greater energy due to exis ting reserve of friction force than at the stage of capture at a lower ratio α/μз ; these numbers are even higher for rolling on grooved rolls. Dependence which determines amount of additional power provided by friction forces reserve is given. Promising directions of using friction forces reserve at the steady- state stage of rolling are provided to improve its efficiency. On the example of rolling in drive – non-drive stand, an increase in efficiency (Efficiency Ratio) of the main line of rolling mill is established with more efficient use of friction forces at the steady-state stage of rolling process. Theoretical dependences are given to determine Efficiency Ratio at usual rolling process and at more full use of friction forces reserve.
ISSN 2410-2091 (Online)