RU2432220C1 - Method of producing bimetal rod and wire articles - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: proposed method comprises performing grippers with sharpened and conical sections on rod or wire article and bench drawing. Strength of bond between core and shell is ensured by drawing with relation between temperatures of core and shell defined by mathematical relation that allows for core and shell temperatures, core radius, shell outer radius and other parameters.

EFFECT: higher quality of drawn bimetal articles.

1 ex

Description

The invention relates to the processing of metals by pressure and is intended for the production of bimetallic bar and wire products by drawing.

It is known that bimetallic rods and wire are produced mainly by rolling or pressing followed by drawing of a bimetallic billet (Perlin I.L., Yermanok M.Z. Theory of drawing. - M.: Metallurgy, 1971. - p. 50).

Closest to the claimed invention is a method of drawing products (A.S. USSR No. 1245375, class B21C 1/100, 1986), including pre-forming on the product grips with pointed and conical sections and subsequent drawing through a monolithic fiber.

The reason that impedes the obtaining of a technical result, which is ensured by the claimed invention, is that when drawing bimetallic products in a known manner, deformation heating of both the core and the shell having different thermophysical and mechanical characteristics is not taken into account, which can lead to delamination of the shell (outer layer of bimetal ) from the core (the central part of the bimetallic billet).

Signs of the prototype, coinciding with the essential features of the proposed solution, is the preliminary formation on the product grips with pointed and conical sections and subsequent drawing through a monolithic die.

The objective of the invention is to improve the quality of the bimetallic product.

The technical result is to prevent possible detachment of the shell of the bimetallic billet from the core during plastic deformation.

The problem was solved due to the fact that in the known method, including the preliminary formation on the product grips with pointed and conical sections with subsequent drawing through a monolithic die, the drawing of products is carried out with the following ratio of core and shell temperatures:

where T _c - core temperature, degrees;

T _about - shell temperature, degrees;

r _c is the radius of the core, mm;

r _o is the outer radius of the shell of the bimetallic billet, mm;

α _about - coefficient of thermal expansion of the shell material, 1 / deg;

α _c - coefficient of thermal expansion of the core material, 1 / deg;

ν _o - Poisson's ratio of the shell material;

ν _with - Poisson's ratio of the core material.

The features of the proposed method, distinctive from the prototype, the drawing of products is carried out at a temperature ratio of the core and shell:

Taking into account the temperature regime during drawing is especially important for repeated drawing, since the shell and core during the deformation have different temperatures of deformation heating, as well as different cooling conditions between passes. With multiple drawing between passes, the drawn product is cooled on the drums of the drawing machine by the influence of a cooling medium, the role of which is either air (air cooling) or process lubrication (oils, emulsions). In this case, the cooling of the outer surface of the shell occurs more intensively, which leads to different temperature conditions of the shell and core.

The thermoelastic deformations of the core and shell are taken into account using the thermoelasticity apparatus. So, the differential equation for radial displacements of the axisymmetric theory of thermoelasticity is as follows (Timoshenko S.P., Goodyear J. Theory of elasticity. - M .: Nauka, 1975):

- градиент температуры в радиальном направлении;Where

- temperature gradient in the radial direction;

u - radial thermoelastic displacements, mm;

ν is the Poisson's ratio of the material;

α is the coefficient of thermal expansion, 1 / deg.

Equation (2) is applied separately for a core having a temperature averaged over the cross section T _c , and for a shell having

temperature averaged over the thickness of the shell T _o The temperatures T _c and T _{о are} determined from the conditions of deformation in the technological tool and cooling of the workpiece between the passes during repeated drawing, while the ratio of T _c and Т _о can be different depending on the thermophysical and mechanical properties of the components of the bimetallic workpiece .

From the solution of equation (2) we obtain the radial movement of the core at the core-shell interface (r = r _c )

where ν _c is the Poisson's ratio of the core material.

Accordingly, for the shell at the shell-core interface, we obtain the displacement

where ν _about - Poisson's ratio of the shell material.

With the equality of displacements u _c = u _о in the bimetallic billet, contact between the shell and the core is maintained. When u _about > u _c there is a gap, which is unacceptable. It is necessary to provide u _c > u _о , at the same time compressive stresses appear on the contact, which ensure the continuity of the bimetallic workpiece, and also increase the plastic properties of the core metal during deformation at subsequent transitions of drawing. Thus, from the standpoint of the thermoelastic state of the bimetallic billet, it is necessary to fulfill the temperature ratio of the core and shell:

An example of a specific implementation of the method

, для меди

. Соотношение r_о/r_c=2. Из формулы (5) следует, что для обеспечения прочного соединения оболочки и сердечника необходимо обеспечить соотношение T_c/T_o>3,4. Из данного условия должен быть построен технологический процесс получения качественного сверхпроводника на основе ниобия и меди.In the production of superconducting materials, a composite bimetallic billet consisting of a core comprising a large number of niobium fibers and a current-stabilizing shell of ultra-pure copper is subjected to multiple drawing. For this combination of bimetal components, ν _c ≈ν _о , for niobium the coefficient

for copper

. The ratio r _o / r _c = 2. From the formula (5) it follows that to ensure a strong connection between the shell and the core, it is necessary to provide a ratio of T _c / T _o > 3.4. From this condition, a technological process should be built to obtain a high-quality superconductor based on niobium and copper.

Claims (1)

A method for the production of bimetallic bar and wire products, including the preliminary formation on the product grips with pointed and conical sections and subsequent drawing through a monolithic fiber, characterized in that the drawing of the products is carried out at the following ratio of core and shell temperatures:

where T _with - core temperature, degrees;
T _about - shell temperature, degrees;
r _c is the radius of the core, mm;
r _o is the outer radius of the shell of the bimetallic billet, mm;
α _about - coefficient of thermal expansion of the shell material, 1 / deg;
α _c - coefficient of thermal expansion of the core material, 1 / deg;
ν _o - Poisson's ratio of the shell material;
ν _c - Poisson's ratio of the core material.