RU1836201C - Method of monocrystal bodiesъ obtaining - Google Patents

Abstract

Usage: in the manufacture of parts and assemblies of various designs in instrumentation, power engineering, etc. Summary of the invention: the initial polycrystalline body of revolution is sequentially and continuously remelted by an electron beam. In this case, a bath of molten metal is reported to be displaced along a trajectory resulting from velocity vectors in two mutually perpendicular directions. The modules of these velocities are related by the ratio Vo / Vn t, rcD, with V0 being smaller than Vn and directed along the longitudinal axis of the body, where V0, Vn are the relative velocities of the concentrated heat source and the body being treated, mm / s; t is the displacement value of the weld metal bath, mm; D is the diameter of the treated body, mm The value of t is set in accordance with the expression t (0.1 -1.0) B / 4, where B is the width of the bath of molten metal, mm 2 ill.

Description

The invention relates to techniques for producing single-crystal billets with a single-sided surface from polycrystalline materials and can be used in the manufacture of parts and assemblies of various structures in instrumentation, power engineering, etc.

The proposed method allows to obtain single-crystal blanks with a monohedral surface of a given crystallographic orientation, which are used, in particular, in the production of TE-Pow.

The purpose of the invention is the development of such a method of obtaining a single crystal body with a monohedral surface that would allow to obtain single crystals with a monohedral surface, stable

by the surface structure of the same crystallographic orientation from polycrystalline materials, to simplify and reduce the cost of the technology for producing single-crystal blanks with a single-faceted surface, to reduce labor costs for manufacturing, and by obtaining a uniform single-crystal structure of a given crystallographic orientation, to improve the quality and increase the physicomechanical characteristics of products, increase the duration of their work in comparison with products obtained in a known manner.

In FIG. 1 shows a diagram of no method; in FIG. 2 is a view along arrow A.

The goal is achieved by a consistent and continuous locale00

00

about

YU

W

of remelting by a highly concentrated source of heating of the initial polycrystalline body of revolution with a diameter D and wall thickness I, and the predetermined path of motion of the molten metal bath is the result of the velocity vectors of its movement in two mutually perpendicular directions, the modules of which relate as:

Vo / Vn - t / (pi) D,

of which a smaller L / 0 is directed along the longitudinal axis of the body, and the offset value t of the seam of width B is set within the range of

t- (0.1-1.0) B / 4;

where VojVr, is the relative velocity of the electron beam and the body being processed, mm / s;

D is the diameter of the treated body, mm;

B - seam width, mm;

t is the amount of displacement of the seam, mm; s pi-coefficient (pi 3.14159.,.).

The proposed method is simple to implement and involves the use of standard equipment for ELS, in particular, single-crystal workpieces with a single-sided surface are obtained from polycrystalline niobium on serial equipment for electron beam welding, the U212M installation, equipped with a high-voltage power source (14 kW) and an axial welding gun type UL P9M. In welding, the vacuum in the welding chamber was 6.7 MPa. The main quality criterion was the state of the structure of the initial and obtained materials, which was determined by the X-ray method of back-taking by Lze. The results of x-ray studies confirm the advantages of the obtained single-crystal blanks with a monohedral surface. The goal is achieved in that a sequential and continuous remelting of the workpiece is carried out with a focused electron beam from the beginning to the end. In this way, it is possible to obtain tubular single crystals with a monohedral surface, the crystallographic orientation of the surface of which can be close to 100 or 110, which has high properties and structural stability at high temperatures. For example, the preparation of single-crystal cylindrical samples from cylindrical billets of polycrystalline niobium with a wall thickness of one millimeter was carried out using a tool placed in the welding chamber. The developed equipment allows you to rotate the workpiece at a given speed

around its axis, providing a given speed of relative displacement of the electron beam and the surface of the workpiece — Vn, and at the same time moving it along the axis also with a given speed Vo, and carry out a given displacement t The amount of fit t (seam axis) is fixed as the distance between the same (i.e., to the left if V0 is directed to the right

in, in the opposite direction, along the axis

bodies) with the fusion lines of an axisymmetric weld of width -B on the surface of the remelted body in the direction perpendicular (the axis of the weld) of the fusion line. The width of the seam and the amount of displacement are determined experimentally, and the parameters of the ELS modes are determined from the condition of obtaining through melting of the material with a thickness of H. The amount of displacement is chosen

from the condition t (0.1-1.0) B / 4, where B is the width of the seam. In practice, with ELS on constant (unchanged) parameters of the welding mode, it remains unchanged, then the value of t also does not change during the process, as does the value of ne

overlap the seam with its subsequent extension P B- (0.1-1.0) B / 4, mm. This interval of overlap or displacement due to the conditions for the formation of a single-crystal structure of the preform was found experimentally. If the displacement t is greater than B / 4 and P is less than the B- (B / 4) J single crystal structure does not form. If the displacement t is less than 0.1 V / 4 and the overlap P is greater than 1 V / 4, the process productivity is very low and it is not rational to conduct the process from this point of view,

We consider three cases for the values of the offset interval:

(1.0; 0.5; 0.1).

Example of parameters for remelting cylindrical niobium billets: Diameter D 18 mm Wall thickness H 1 mm a) Accelerating voltage Piece, 25 kV Beam current In. 67 mA

Linear speed Vn 5 mm / s

Joint width B 3.6 mm Displacement t 1.0 V / 4 3.6 / 4 -0.9) t 0.9 mm

G /

Vo / Vn t / (pi) D,

hence V0 t Vn / (pt) D 0.9 5 / 3.14159 18;

5, the linear velocity along the V0 axis is 0.08 mm / s.

b) displacement value t 0.5 V / 4 0.5 3.6 / 4-0.45 mm

therefore V0 0.45 5 / 3..14159 18- -0.04 mm / s

c) Displacement value t 0.1 V / 4 0.1 3.6 / 4 0.09 mm.

Therefore V0 0.09 5 / 3.14159 18 0.008 mm / s

and to reduce the value of t less than 0.45 mm in this case is irrational from the point of view of the productivity (speed) of the process.

X-ray diffraction analysis shows that the initial structure is polycrystalline, and the structure of the preform obtained by the proposed method is single-crystal with a monohedral surface 110. For cases a), c) a single-crystal structure was also confirmed by X-ray diffraction analysis according to Laue.

Using the proposed method for producing single-crystal billets from refractory metals provides the following advantages compared to existing methods: the ability to produce single-crystal billets with a polyhedral surface with a given crystallographic orientation, for example 110, from polycrystalline billets from polycrystalline billets; increasing the physicomechanical characteristics of products, reducing labor costs for manufacturing, saving initial expensive material, increasing the duration of the products.

The proposed method has significant economic efficiency.

In the proposed method, a preform from a pro-crystalline material is used. The entire surface of the workpiece after processing by the proposed method has, in the above example, crystallographic orientation 110. This allows to obtain high service characteristics of the product.

Annealing of the preforms obtained by the proposed method at temperatures up to 1500 ° C does not lead to noticeable changes in their structure. Test results for

high-temperature creep at temperatures of 0.57 Tm. and stresses of 5 MPa showed a decrease in creep rate by 3–10 times compared with products made from the starting material, with a test duration of 50 hours and by 15% –18% compared to products made according to the second embodiment, and the value of the high-temperature creep rate for this example, case b) is 2 10 7 cm 1,

at a test duration of more than 100 hours, and at stresses of 6 MPa, the high-temperature creep rate is 2.5 × 10 7 cm 1.

Claims (1)

The claims A method for producing single-crystal bodies, in which a concentrated heating source is used, characterized in that, in order to obtain single-crystal bodies of revolution from polycrystalline bodies of revolution, the initial polycrystalline body of revolution is melted sequentially and continuously, causing the molten metal bath to move along the path resulting from the vectors velocities in two mutually perpendicular directions, the modules of which are related by the relation vo / vn t-Tf D, and v0 Vn and is directed along along the single axis of the body, where VO, vn are the relative velocities of the concentrated heat source and the treated body, mm / s, t is the displacement of the molten metal bath. mm, D - diameter of the processed body, mm, and the value of t is set in accordance with the expression t- (0.1-1.0) iB / 4. where B is the width of the molten metal bath, mm. g KindA L Figure 1 FIG. 2