SU1260568A1 - Method of making interference joint of components - Google Patents

Description

This invention relates to mechanical engineering technology and is intended to connect parts with tension.

The aim of the invention is to increase the reliability of the connection.

FIG. 1.2 shows matrices with annular and rod parts; in fig. 3 is a plot of strain versus time.

The method is carried out as follows.

The female parts 1 are pressed onto the rods of the matrix 2 by the inner diameter, and the covered parts 3 are pressed into the holes of the matrix 4. At the same time, the material of the rods of the matrix 2 should have approximately the same or more significant coefficient of thermal expansion with respect to the pressed parts. The temperature expansion coefficient of the metal must be less than or equal to that of the parts.

The tensioning pressure, when pressing in, both covering and covering parts, must be within the limits of

 - | -e; B to 1 ,, which is achieved by ensuring the dimensions of the matching diameters of the holes and rods in the matrices 4.2 and the corresponding, to the dimensions of the parts 3.1.

Value of pre nat

impractical to take less --- B | D

since at values of tension less than the specified value, the part pressed into the matrix is in an elastic stress-strain state, which leads to a significant decrease in the rate of previously induced creep and, therefore, to obtain the desired effect, it requires many times more time for lagging the part in the heat treatment process.

It is impractical to use the value of tension on hectares over 1.8 10

l

So

or rod, In the case when M, 1.8 10 D, increasing pressing force can lead to an influence of the zone of plastic deformations on the end face

5 of the pressed-in part, which distorts its shape and makes it impossible to press it.

After pressing, parts with dies are placed in electric ovens

10 and is heated to a temperature of 0.35-0.40 from the melting point of the material of the part.

A decrease in the heating temperature below the limit of 0.35 leads to a decrease in the productivity of the method, since it significantly reduces the intensity of the preliminary creep, which will require a longer durability of the part with the matrix in the heated state. An increase in temperature above the limit of 0.40 may lead to an uncontrolled change in the initial structure of the material of the part.

25 At a given temperature, parts with matrices can withstand 80–200 h. Increasing the holding time with 200 h is impractical because the creep rate decreases with time, and at holding more than 200 h, the use of preliminary creep becomes ineffective. In addition, increasing the exposure time leads to a decrease in

35 of the productivity of the technological process and an increase in the cost of manufacturing parts.

Reducing the exposure time less than WH is not recommended for the reason

40 then even for metals with high ductility (aluminum, copper alloys), during this period there is no transition of the creep process to the steady state, i.e. artificially caused by pre-creep does not yet exhaust its possibilities. It is advisable in the manufacture of parts of the interface of more ductile metals time

as when pressing parts into the matrix 50 ““ reduce and increase it with decreasing plasticity of the material of the matched parts.

kind of press there is a significant increase in the pressing force, and the stresses in the parts that cause the preliminary creep of its material, while practically not increasing, i.e. there is a cut of the tension value per ha, exceeding the value of 1.8 10 O, when pressing on the edge of the hole board

It should be taken into account that the greatest weakening of the contact pressure occurs in the initial stage of the creep process of the material of the matched parts. Therefore, in order to reduce the effect of the creep process on the rod being reliably, In the case of M, 1.8 10 D, increasing the force of the press can result in a plastic deformation zone at the end.

pressed-in parts that distorts its shape and makes it impossible to press-fit.

After pressing, parts with dies are placed in electric ovens

and heated to a temperature of 0.35-0.40 on the melting point of the material of the part.

A decrease in the heating temperature below the limit of 0.35 leads to a decrease in the productivity of the method, since this significantly reduces the intensity of the preliminary creep, which will require a longer retention of the part with the matrix in the furnaces in the heated state. An increase in temperature above the limit of 0.40 may lead to an uncontrolled change in the initial structure of the material of the part.

At a given temperature, parts with matrices can withstand 80-200 hours. Increasing the holding time of 200 hours is impractical because the creep rate decreases with time, and at more than 200 hours, the use of preliminary creep becomes ineffective. In addition, an increase in the exposure time leads to a decrease in

the performance of the process and increase the cost of manufacturing parts.

Reducing the exposure time less than WH is not recommended because

even for metals with high ductility (aluminum, copper alloys), during this period there is no transition of the creep process to the steady state, i.e. Artificially caused pre-creep does not exhaust its possibilities yet. It is advisable in the manufacture of parts made of more ductile metals. The time taken into account. It should be noted that the greatest weakening of the contact pressure occurs in the initial stage of the creep process of the material of the parts being mated. Therefore, in order to reduce the effect of the creep process on the reliability of the connection with tension, it is advisable to ensure that the creep process proceeds preliminarily in the parts from which the connections with the tension will be formed. The tension connection, assembled from parts previously hardened by thermomechanical machining, has an increased reliability, since the strength of the joint under the action of the creep process decreases less intensively in time. This is due to the fact that the most intense part of the creep of the metal of the parts connected to the tension under the action of stresses occurs not in the joint itself, but during the thermomechanical treatment of the joint details.

The conditions for the creep process in the parts are created according to the proposed method by thermomechanical processing of the parts in accordance with the indicated modes.

At the end of the exposure, the matrix with the parts is removed from the furnaces and cooled in air. Parts are removed from the dies by pressing out under a press, after which they are finished. At the covered parts 1 remove the allowance at the inner diameter, and at the covered 3 - at the outside. The machined parts are monitored by the obtained dimensions, so ... l.

sets are assembled of male and female parts and assembled by pressing under pressure and by cooling the male part 3 with dry ice or liquid nitrogen or by heating the female part in an oil bath or electric furnaces.

After carrying out heat treatment for 120 hours, the parts are cut out from the dies, the mating surfaces are finished with fine turning, and the seam allowance of 0.4 mm is removed.

A compound with a tension in the range of 75–80 nmq is formed from the parts obtained. After this, the compounds were kept for 5,000 hours to verify their reliability. To force them by time, the compounds were tested at 100 ° C. As an indicator of reliability, shear strength of joints is determined, the results of which are also shown in the table.

From the results presented in the table, it follows that when a compound is formed using the method described, its strength after 5000 hours (tested at 100 ° C) is 1.25-2.0 times greater than with a normal compound.

F1 / g, Z

Bi

t (tfoc)

Editor M, Kelemesh

Compiled by V. Belinsky

Tehred M. Khodanich Proofreader L. Pilipenko

Order 5205/30. Circulation 777 Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, st. Project, 4

3

Claims (1)

METHOD FOR CONNECTING PARTS WITH TENSION, ^ including assembling them by pressing one part into another, characterized in that, in order to increase the reliability of the connection, FIG. 1, before assembling the part, it is subjected to heat treatment at a temperature of 0.35-0.40 of the melting temperature of the materials to be joined for 80-200 hours in an elastoplastic state with an interference fit N „ranging from N _n ⁼ 2 £; TD Д ° 1 »8 * r10 ' ² D, where Nn is the preload preload · 8j _r is the relative deformation corresponding to the yield strength of the material of the part; 17 - the outer diameter of the part. and sg £