RU2847204C1 - Method of ingot-less rolling-pressing of bars and device for its implementation - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, in particular to methods and devices for combined processes using continuous casting, rolling and pressing operations. Technical result is achieved by the AD31 alloy bars ingot-less rolling-pressing method, which includes the metal rolling in the working gage and the workpiece pressing in the matrix with the gaps formation between the rolls working surfaces and the matrix working surfaces, in which metal is extruded with formation of metal clad layer on surfaces of rolls. Wherein melt of AD31 alloy secondary wastes is used. Melt is poured into rotary rolls to crystallize-deform the alloy in water-cooled rolls at controlled temperature of processed alloy.

EFFECT: increasing the efficiency of manufacturing hot-pressed bars by reducing the number of technological stages and labour intensity of production.

2 cl, 2 dwg, 1 tbl

Description

The invention relates to metallurgy, specifically metal forming, and more specifically to methods and devices for combined processes involving continuous casting, rolling, and pressing. The invention is intended for producing rods from molten secondary non-ferrous alloy waste using a direct rolling-press method.

An analogue of the invention is the method of direct rolling-pressing [Sidelnikov S.B., Lopatina E.S., Dovzhenko N.N., Drozdova T.N. et al. Features of structure formation and properties of metal during high-speed crystallization-deformation and modification of aluminum alloys: monograph. Krasnoyarsk: Siberian Federal University, 2015. 180 p.] and a device for its implementation [RU No. 2724758, published 06/25/2020]. A device for direct rolling and pressing metal, comprising a mixing furnace, a grooved roll, and a lugged roll, each with cooled cavities that form a box-type working pass. A die holder with a water-cooled die is installed at the outlet of the die. The die outlet contains a tube with external ribs located in longitudinal slots of the die. The die face is distinguished by a quick-change insert made of iron-graphite composite with a working channel of a predetermined shape and a calibrating belt, having a rectangular cross-section and dimensions necessary to cover the pass before it opens. This device design eliminates the disadvantages associated with the need to produce a cast blank in a rotary crystallizer, thereby reducing labor intensity and production costs. However, the assignment of design parameters for the rolling and pressing tools (the dimensions of the roll caliber and the matrix) requires certain geometric relationships between these parameters, since if they are chosen incorrectly, the process of direct rolling-pressing on this installation may not be feasible.

A method for the combined continuous casting, rolling, and pressing of a metal blank and a device for implementing it [RU No. 2639203, published 20.12.2017] were selected as a prototype. The method includes forming a continuous cast blank in a rotary crystallizer, regulating the temperature of the cast blank, rolling the cast blank at a predetermined temperature in a working pass formed by two rolls, and pressing the blank in a die. The rolling of the metal blank is characterized by the formation of gaps between the working surfaces of the rolls and the working surfaces of the die. When the cast blank is fed into the working pass, the metal of the cast blank is extruded into these gaps, forming a cladding layer of metal on the surfaces of the rolls. This method and device for implementing it can significantly increase the productivity of the rod manufacturing process and reduce its energy consumption compared to traditional methods of direct pressing on hydraulic presses. However, this method involves a technological process associated with obtaining a blank in a rotary crystallizer, which increases the labor intensity of production and reduces the yield of usable metal.

The technical objective of the invention is to obtain rods from secondary waste of non-ferrous metal alloys by using the method of direct rolling-pressing with an increased level of mechanical properties.

The technical result consists in increasing the efficiency of the hot-pressed rod manufacturing process by reducing the number of process stages and labor intensity of production.

The stated objective is achieved by the fact that in the method of ingot-free rolling-pressing of rods, including rolling of metal in a working caliber and pressing of a workpiece in a matrix with the formation between the working surfaces of the rolls and the working surfaces of the matrix of gaps into which the metal is extruded with the formation of a cladding layer of metal on the surfaces of the rolls, sequentially obtaining a metal melt from secondary waste of non-ferrous metal alloys at a given temperature, pouring the metal melt into rotating rolls and carrying out crystallization-deformation of the metal in water-cooled rolls at a controlled temperature of the alloy being processed. To implement this method in a device for ingot-free rolling-pressing, containing a furnace-mixer, a pouring device, a roll with a groove and a roll with a projection, having cooled cavities and forming a working caliber of a box type, at the exit of which a die holder with a water-cooled die is installed, the width of the channel of the pouring device h ₀ and the minimum gap between the rolls h ₁ are selected from the ratio h ₀ /h ₁ ≥ 2, and the height of the die h _m is found from the ratio h _m /h ₁ ≤ 4.

Unlike the prototype, the claimed invention uses molten metal from secondary non-ferrous alloy waste to produce rods. The melt must be at a temperature that ensures subsequent crystallization of the blank in water-cooled rolls, and cooling of the rolls should reduce the temperature of the crystallized blank to the deformation temperature of the alloy used.

During simultaneous crystallization-deformation of metal, an important condition for the stable process is the ratio of the channel width of the pouring device h ₀ and the minimum gap between the rolls h ₁ . It is known [S. B. Sidelnikov, N. N. Dovzhenko, N. N. Zagirov. Combined and combined methods of processing non-ferrous metals and alloys: monograph - M.: MAX Press, 2005. - 344 p.] that the process of combined rolling-pressing is stably implemented at rolling reduction values of 50% and higher. Based on these recommendations, the ratio of the channel width of the pouring device h ₀ and the minimum gap between the rolls h ₁ is selected from the ratio h ₀ /h ₁ ≥ 2. At ratios h ₀ /h ₁ <2, the rolling reduction and the feasibility of the rolling-pressing process are sharply reduced, since the caliber in this case is not completely filled and the magnitude of the active friction forces supplied by the rolls is reduced.

At h _m /h ₁ >4, the matrix is located behind the plane of opening of the roll caliber, which leads to uncontrolled deformation, penetration of metal into the gap between the matrix and the rolls and stopping of the process.

The invention is illustrated graphically below.

Fig. 1 shows a general view of the claimed device for direct rolling and pressing of rods. Fig. 2 shows a view of the secondary waste used in the form of trimmings from pressed profiles.

The device for the direct rolling and pressing of rods (Fig. 1) includes a casting device 1, water-cooled rolls with a projection 2 and a groove 3, forming a closed caliber, covered at the exit by a water-cooled matrix 4. The matrix is located on a matrix holder 5 and is pressed through a slide 6 to the rolls by a hydraulic clamp 7.

The device operates as follows. Molten metal is fed into casting device 1 and captured by rollers 2 and 3. Crystallization of the metal begins on the surfaces of water-cooled rollers 2 and 3. The metal, now crystallized as a rectangular blank, is then compressed in a closed gauge, depressed, and extruded through the calibrating hole of die 4, forming a pressed product (rod) of the specified shape and dimensions. As the rollers rotate, hydraulic clamp 7, via die holder 5 and slide 6, presses die 4 tightly against the surfaces of rollers 2 and 3, ensuring a constant gap between the rollers and the die. Slide 6 changes the direction of the rod's exit with diameter d and removes it from the device.

As an example of the practical application of the proposed method and its implementation device, experimental results are presented. Using an SPP-400 installation with 385 mm rolling diameters, a direct rolling-pressing method was simulated to produce 9 mm diameter rods from factory-pressed section scraps (Fig. 2) made of AD31 alloy.

The technological parameters of the BPP process were as follows:

- melt temperature 760±10°С;

- instrument temperature 20°C;

- roll rotation frequency 5 rpm;

- degree of deformation during rolling 50%;

- pressing elongation 9.7.

The casting width and die height were determined from the stated ratios. Thus, with a minimum roll gap of 9 mm, the casting width h ₀ was 20 mm, and the die surface height h _m was assumed to be 27.4 mm.

After conducting experimental studies, pilot batches of rods from secondary waste of AD31 alloy with a diameter of 9 mm were obtained, the average values of mechanical properties of which are presented in the table.

Table - Mechanical properties of rods with a diameter of 9 mm, obtained by the proposed method and according to GOST 21488-97.

Characteristic The proposed method Prototype GOST 21488-97 Yield strength, MPa 86 78 60 Tensile strength, MPa 127 107 90 Relative elongation, % 35 17 15

An analysis of the mechanical properties of rods from AD31 alloy recycled waste produced by the proposed method showed that their hot-pressed properties meet the requirements of the existing standard. Furthermore, the ductility of the rods produced by this method is superior to that of the prototype, exceeding the standard requirements by more than two times.

Thus, the proposed method and the device for its implementation make it possible to increase the efficiency of the process of manufacturing hot-pressed rods by reducing the number of technological stages and labor intensity of production and to obtain pressed products with an increased level of mechanical properties.

Claims (2)

1. A method for the direct rolling and pressing of rods made of AD31 alloy, which includes rolling the metal in a working gauge and pressing the blank in a die with the formation of gaps between the working surfaces of the rolls and the working surfaces of the die, into which the metal is extruded with the formation of a cladding layer of metal on the surfaces of the rolls, characterized in that a melt from secondary waste of AD31 alloy is used, the melt is poured into rotating rolls and crystallization-deformation of the alloy is carried out in water-cooled rolls at a controlled temperature of the alloy being processed. 2. A device for the direct rolling and pressing of rods made of AD31 alloy, comprising a mixer furnace, a pouring device, a roll with a groove and a roll with a projection, having cooled cavities and forming a box-type working caliber, at the outlet of which a die holder with a water-cooled die is installed, characterized in that the width of the channel of the pouring device h ₀ and the minimum gap between the rolls h ₁ are selected from the ratio h ₀ /h ₁ ≥ 2, and the height of the die mirror h _m is found from the ratio h _m /h ₁ ≤ 4, wherein the device is intended to implement the method according to paragraph 1 of the formula.