RU2096148C1 - Method of manufacture of long products from different metals - Google Patents

Abstract

FIELD: manufacture of long products from different metals. SUBSTANCE: the offered method provides for making oblique end face of blank from metal with low plasticity, fixing of the blank on press tool, location in press container of blank from metal with high plasticity, coaxial positioning of joined blanks and subsequent plastic deformation by application of axial load at which mutual oncoming motion of blanks material is accomplished along the surface of their contact due to plastic flow out of metal of high plasticity through hole in press tool or through gap between blank of low-plasticity metal and press tool. Oblique end face on blank from low-plasticity metal may be dihedral, or polyhedral angle, conical surface, etc. EFFECT: the offered method makes it possible, for a short period of time and at moderate loads, to produce long welded products from different metals having transverse location of joint zone with preset or arbitrary smooth change of properties on the transition from one metal to the other. 3 cl, 2 dwg

Description

 The invention relates to pressure welding of metals and can be used for the manufacture of dissimilar metals, significantly different in their properties, lengthy products with a transverse connection zone.

 Methods for producing long products from dissimilar metals, in which one of the metals is applied on top of the other along the entire length of the product, are known in metal pressing technology. There are also known processes for the manufacture of pipes and rods of large lengths from sequentially supplied individual billets. At the same time, the connection zones of previously separate workpieces are located across the lengthy product. However, such processes are used when joining workpieces from the same metal or from alloys on the same basis, or from dissimilar materials with similar mechanical properties and resistance to deformation.

 At the same time, in various fields of technology, for example, in cryogenic technology, there is a need for long products, the opposite ends of which are made of metals or alloys that differ significantly in properties. It is also desirable that in the zone of transition from one metal to another, the change in properties occurs gradually, including according to a given law.

 A known method of manufacturing long products from elements (preforms) made of dissimilar metals, which consists in the fact that the end surfaces of the elements to be joined are preformed by making them tapered (wedge-shaped), these elements are contacted along the end surfaces, the parts to be heated are heated to a temperature slightly exceeding the melting temperature of the eutectic alloy of the combined metals, and at the same time apply axial force (1). A liquid phase of the eutectic alloy is formed on the metal contact surface, which is partially extruded along the periphery of the end surfaces of the connected elements. After lowering the temperature, the liquid phase solidifies, forming a welded joint.

 The disadvantage of this method is the reduced strength of the weld / solid electric alloy / compared with the strength of each of the joined metals.

 There is also known a method of cold butt welding of pipes, in which the connected ends of the pipes are covered with matrices, the ends of the pipes are brought into contact with each other and create a load / 2 /. A known method of manufacturing long products from dissimilar metals with a transverse arrangement of the connection zone, including the coaxial arrangement of the connected workpieces, fixing the workpiece from a less ductile metal on a pressing tool and subsequent plastic deformation by applying axial load / 3 /. In this case, between the parts in contact, there is a strong one-piece connection without the formation of an intermediate crystalline phase in the weld zone. In most cases, in these methods the joined end surfaces are flat and oriented perpendicular to the common axis of the pipes, although there is also the option of connecting flanged pipes, in which the flanged sections take a conical shape and are welded along conical surfaces.

 To implement both of these methods, it is necessary to create and maintain very high loads for a sufficiently long time.

 The technical result achieved by the invention is that the method allows for a shorter time and when using conventional press equipment to obtain long welded products of uniform metals having a transverse arrangement of a zone / or several zones / joints with a given or arbitrary smooth change in mechanical properties on the transition from one metal to another.

 This is achieved by the fact that for the manufacture of long products of dissimilar metals in accordance with the invention, the end surface of the workpiece of less ductile metal is made beveled. Hereinafter, the term "beveled surface" means a surface that is not perpendicular to the axis of the workpiece or the axis of the long product as a whole and, as a rule, symmetrical about this axis. In specific cases, such a beveled end surface may be a dihedral angle / wedge /, a polyhedral angle, a conical surface, the surface of an ellipsoid, a paraboloid, and so on. In a more general form, the shape of the surface will be determined by the required nature of the change in certain properties of the material in the area of transition from one metal to another.

 A preform of less ductile metal is fixed on a pressing tool, for example, on a die; a preform of a more ductile metal is placed in a press container.

 The initial end surface of the workpiece of a more ductile metal can have almost any shape. To more reliably ensure alignment of the connected elements during welding, a centering hole can be made on it. However, coaxiality can be ensured only due to the appropriate location and design of the press and press tool.

 After the coaxial arrangement of the workpieces to be joined, an axial load is applied to at least one of them and the workpieces are reciprocally moved along the contact surface due to the plastic outflow of more ductile metal through openings in the pressing tool or through specially provided clearances.

 The connection of the workpieces is carried out at a temperature corresponding to the temperature of the technological plasticity of a softer metal. For lead and its alloys, the process can be carried out at room temperature. For aluminum alloys, elevated temperatures up to several hundred degrees are optimal. Under the influence of the axial load in the billet of a more ductile metal, a center of plastic deformation appears and this metal begins to flow along the surface of the element of a less ductile metal under conditions of significant shear deformations and high normal stresses on the contact surface. These conditions are achieved by extruding more ductile metal through the through holes in the die or in a press washer covering the workpiece of less ductile metal.

 Mutual displacement of the workpiece material in the axial direction should occur at a distance of not less than the length of the beveled portion of the workpiece from less plastic material, which ensures the displacement of contaminants and impurities from the contact zone.

 Shear deformation at the interface of metals ensures the renewal of this surface, and high normal stresses on the contact surface contribute to a strong connection of the workpieces.

 The diameter of a preform of a more ductile metal, at least from the side connected to another preform, may slightly exceed the diameter of a preform of a less ductile metal. After receiving the welded joint, excess metal extruded through the holes in the press washer. If necessary, align the entire length of the diameter (thickness) of the resulting lengthy product.

 To increase the strength of the connection on one or both of the joined surfaces of the workpieces, an intermediate layer of material, for example, matching the material of the connected workpieces, can be preliminarily applied by plasma spraying.

 The drawings show a schematic representation of devices for implementing the inventive method, while in FIG. 1 shows the connection of blanks using direct compression; in FIG. 2 back pressing. In the drawing, positions 1 indicate a blank of less ductile metal, positions 2 a blank of more ductile metal, 3 press container, 4 press washer, 5 die, 6 holes for the expiration of more ductile metal, 7 extruded metal. Arrow A shows the direction of movement of the press washer, arrow B indicates the direction of metal flow.

 The method is illustrated by the following specific example of its implementation.

A cylindrical rod 400 mm long was made of aluminum alloy, and the second of tool steel. The steel billet had a diameter of 30 mm, aluminum 50 mm. The press was carried out at a temperature of 450 ^o C. The steel billet was mounted on a matrix having round holes evenly spaced on a circle with a diameter of 40 mm. The end face of the steel billet in contact with aluminum was machined into a cone at a length of 70 mm. The press force was 600 tons with an exposure time of about 10 seconds. At the end of the process, excess aluminum alloy in the form of products squeezed out through the holes in the matrix was removed, and the resulting single rod was turned to a diameter of 25 mm.

 Tests of the obtained rod on a stretching machine showed that the destruction of the product occurs in aluminum alloy outside the zone of connection of dissimilar metals. The change in the mechanical properties in the joint zone occurs gradually, corresponding to a change in the proportion of the cross-sectional area of one of the metals to be joined in the total cross-sectional area.

Claims (3)

 1. A method of manufacturing long products from dissimilar metals with a transverse arrangement of the connection zone, including the coaxial arrangement of the workpieces to be joined, fixing the workpiece from a less ductile metal to a pressing tool and subsequent plastic deformation by applying axial load, characterized in that the workpiece from a more ductile metal is placed in a press container, on a workpiece made of less ductile metal, a beveled end surface is made and mutual counter movement of the mat rial workpieces along their contact surface due to plastic expiration of a ductile metal through the openings in the press tool or through the gap between the billet of ductile metal and at least a pressing tool.  2. The method according to claim 1, characterized in that the beveled end surface on the workpiece of less ductile metal is a dihedral or polyhedral angle or a conical surface.  3. The method according to claim 1, characterized in that the transverse size of the workpiece of more ductile metal, at least from the side connected to another workpiece, exceeds the transverse size of the workpiece of less ductile metal.

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