SU1523284A1 - Method of pressure welding - Google Patents

Abstract

The invention relates to pressure welding and can be used in the aviation industry, energy and chemical engineering in the manufacture of critical structural components. The purpose of the invention is to improve the quality of welding by preventing intergranular cracking in the weld zone while ensuring process performance. The method of pressure welding with heating of dispersion-strengthened intermetallic nickel-based alloys includes the deformation of the materials being joined, their isometric annealing and cooling. Isothermal annealing is carried out at a temperature of 0.85 - 0.9 _Tmf , where _Tpl is the melting point. After isothermal annealing, with cooling, the temperature is reduced to 0.6 - 0.7 T _pl with an adjustable speed of 400-600 degrees / h. The speed reduction is carried out at a constant or variable controlled speed. 2 hp f-ly. 1 il. 2 tab.

Description

The invention relates to the field of pressure welding and can be used in the aviation industry, energy, chemical engineering in the manufacture of critical components of structures.

The aim of the invention is to improve the quality by preventing intergranular cracking in the weld zone while simultaneously ensuring the productivity of the process.

The drawing shows a scheme for the implementation of the method (a, b — the temperature at the initial stage of cooling is reduced at a constant rate a, and b — at a variable speed).

The essence of the method is that after isothermal annealing at 85–0.9 Tpl, the temperature is reduced to a level of 0.6–0.7 Gpls at a controlled rate not exceeding 400–600 deg / h, and this speed can be constant or variable.

The welding cycle includes four stages:

I - loading of the welded parts to the required degree of deformation;

H — load reduction and isothermal annealing at 0.85–0.9 Tpl;

III-cooling to 0.6-0.7 Gil with an adjustable speed not exceeding 400-600 degrees / h;

IV- final cooling.

The temperature range of the controlled cooling and the cooling rate can be explained as follows. The cooling in stage III (b, c) with an adjustable rate is carried out to a level of 0.6-0.7 Gpl, since in the temperature range below this boundary a high cooling rate no longer leads to cracking. With an increase in this temperature limit of controlled cooling, the probability of the occurrence of cracks greatly increases; with a decrease, the total time of the welding cycle increases unnecessarily. For dispersion-strengthened intermetallic alloys based on nickel in the specified temperature range

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In the zone of 0.6–0.9 Tpl, the cooling rate is 400–600 K / h, which is optimal, since an increase in the cooling rate leads to cracking and a decrease to a decrease in the productivity of the process.

The constancy of the cooling rate in a predetermined interval of 400-600 degrees / hour can be maintained by controlling this speed, which is as follows. Installations in which the samples are heated are equipped, along with other devices, with high-precision temperature control devices and devices for its registration. In order to maintain the required cooling rate, the following are determined in advance: temperature-time intervals for reducing the temperature of the sample in the first cooling stage. At the end of each time interval, the thermosetter is set to a subsequent lower start of the temperature range, etc., until the lower temperature limit of the controlled cooling is reached.

The regulation of the cooling rate also consists in a controlled change in its value during the first stage of cooling from the minimum value at the beginning of this stage to the maximum - at the end, but not exceeding 600 deg / h. For example, the initial cooling rate may be 360 degrees / h, then it may be increased to 480 degrees / h, and at the end of the first cooling stage it may be 600 degrees / h.

Such variable cooling rates are useful when the annealing temperature is high (on the order of 0.9 Tal and the probability of cracking during the initial cooling stage increases significantly.

Example. The method was tested when welding in vacuum 3, Pa of samples from a dispersion-strengthened intermetallic

VKNA alloy based on nickel. Mode: Gsv 1000 ° C; .ten-- . Cylindrical samples of sizes mm, mm were used. Loading according to the scheme of forced deformation. After the deformation was reached, the load was removed and the samples were annealed at Γ 1200 ° С for four hours. The temperature decrease after annealing was carried out at a speed of 400–600 K / h to 800–1000 ° C, and then the samples were cooled with a furnace or in air.

In tab. 1 and 2 shows the data characterizing the technological process

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compounds in accordance with the proposed method.

The sign “+ means the presence of cracks in the welded joint, the sign“ - their absence

In the experiments (Table 2), when the parts were cooled to a temperature of 0.55 Tpl and the cooling rate W. degrees / h was used, the presence or absence of cracks in the welded joints depended on the temperature range of application of this speed. If the cooling rate deg / h was used in the range of 0.55, 67ll cracks were absent in the welded joints, if the cooling rate deg / h was started to be used at temperatures of 67 ps cracks were observed in the welded joints.

An analysis of the data obtained suggests that when welding with pressure, dispersively strengthened intermetallic alloys based on Ni after high-temperature annealing (0.85–0.9 Gpl) to prevent cracking, it is advisable to limit the cooling rate (400 - 600 degrees / h)

The welding method allows controlling the formation of the structure and the redistribution of / grit between the grain boundary and the body in the heat-affected zone, which has a significant impact on the properties and quality of the welded joints of the dispersion-strengthened intermetallic alloys.

Claims (3)

1. Pressure welding method with heating of dispersion-strengthened nickel-based intermetallic alloys, in which, after the deformation process, isothermal annealing is performed at a temperature of 0.85-0.9 Gpl, and then cooling, characterized in that by preventing intergranular cracking in the welded joint zone while simultaneously ensuring the performance of the process, the temperature in the cooling process is reduced to 0.6-0.7 Tpl with an adjustable speed of 400-600 deg / h. 2. A method according to claim 1, characterized in that the temperature reduction is carried out at a constant rate. 3. A method according to claim 1, characterized in that the temperature reduction is carried out at a variable controlled rate. Table 1 Cooling rate, (constant) degree / h 0.55 0.60 0.70 0.75 0.55 0.60 0.70 0.75 0.55 0.60 0.70 0.75 0.55 0.60 0.70 0.75 0, 55 0,60 0,70 0,75 The presence of cracks in the welded joint + + + + + + + + + table 2 , 6-0.1Tnf ( Time