RU26991U1 - TUBULAR ADAPTER TITAN-STEEL - Google Patents

Description

2002120436

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TUBULAR ADAPTER TITAN-STEEL

The utility model relates to the field of joining with the ability to weld pipes from dissimilar materials that are not suited to traditional methods of fusion welding, and more particularly, to designs of tubular reducers titanium stainless steel - with which you can weld pipes from titanium alloys to stainless steel pipes by traditional methods fusion welding of homogeneous metals.

In modern machine building, titanium alloy pipes are used quite widely in combination with stainless alloy pipes, so there is always a need for their reliable connection by welding.

Titanium and stainless steel in a metallurgical plape are practically incompatible, since during their fusion welding in a welded joint a complex set of fragile iptermetallide compounds and liquid eutectics is formed.

Therefore, in industry, the main technological direction in the welding of titanium alloy pipes with stainless steel pipes was the use of bimetallic titanium-steel tube adapters, prefabricated by solid phase welding methods, when the heating temperature for welding does not exceed 0.7 the melting point of the easiest beige materials.

Tubular adapters of OT4 titanium alloy and X18H9T stainless steel are known, which were produced by solid phase welding by hot joint pressing of titanium and stainless steel blanks placed in a special sealed steel shell from which air was carefully removed (see L.G. Strizhevskaya et al. Welding dissimilar metals using bimetallic adapters, J. "Welding Production 1969, No. 8, p. 18-19).

Tubular adapters obtained by the hot co-pressing method have two main drawbacks: the first of these is the extremely high manufacturing cost, especially adapters with a diameter of more than 75 mm, since billets of titanium alloy and stainless steel for co-pressing must be made 4-5 times in diameter larger than the future adapter; the blanks are placed in a steel container, then it is closed with a lid, carefully vacuumized and sealed while maintaining a vacuum in the container; after that it is heated to a temperature of about 900 ° C and installed in a heated mold, through which a hot container is pressed through a point with a hydraulic press. For hot pressing of evacuated containers, designed even for adapters of relatively small diameter, a hydraulic press with a force of several thousand tons is required, which is not always available even in large plants.

The second disadvantage of tubular adapters made from welded billets obtained by joint hot pressing is the lack of reliable data on the strength of each diffusion joint in the lap area between the titanium alloy and stainless steel. If in a container with billets of NS titanium alloy and stainless steel

vacuum at all technological ethanes, including the initial moment of nressing, the diffusion welded joint in the form of a conical lining is highly durable.

If the welds on the container were made with micro-leaks or they appeared during the heating process before pressing, then the diffusion welded joint sharply loses its strength characteristics, and in practice it is practically impossible to detect micro-leak formation especially when the container is heated in the furnace to 900T.

For this reason, tubular adapters made from blanks welded by hot joint pressing. Have not been widely used in critical pipelines operating under conditions of constant vibration and frequent temperature fluctuations.

Also known are titanium-steel tube adapters made by solid phase welding by diffusion welding in vacuum using intermediate multilayer layers such as Y + Cu + STEEL + K1 and V + Cu + Ni, previously obtained by hot rolling in vacuum at temperatures of 800-900 S, (see Kazakov NF Diffusion welding of materials. M. Mshpinostroenie, 1976, p. 189).

Tubular adapters with a diameter of 60-70 mm and a length of up to 150 mm were made of VT5-1 titanium alloy and 12Kh18N10T stainless steel using intermediate multilayer gaskets installed between the welded ends of the bushings. Adapters were made by diffusion welding in vacuum when heated to 1000 T and squeezed with a force of 0.5 kgf / mm with an exposure time of at least 15 minutes.

The main disadvantage of these tubular adapters is the difficulty of evaluating both the adhesion strength between the layers of the multilayer gasket, and between the gasket and the ends of the bushings of titanium alloy and stainless steel, which also does not allow

use this design of adapters for welding critical pipelines made of titanium alloys with stainless steel pipelines operating in conditions of vibration and frequent temperature changes.

It is well known from the technique of pipe welding that tubular flanged welded joints are much more efficient in conditions of vibration of the pipeline than butt ones, since a tight telescopic fit of the pipes relieves the weld from bending moments arising from vibration of the pipeline.

Two experimental designs of titanium-steel tube adapters welded by lap diffusion welding are known: in the first design, the titanium splined cylindrical sleeve was located outside the stainless steel cylindrical sleeve, and in the second design, the lap joints were lapped on conical surfaces, while the stainless steel sleeve was made outside titanium bushings (see. N.F. Kazakov. Diffusion welding of materials. M. Mechanical Engineering, 1976, p. 189190).

The lapped design of the titanium-steel adapter, in which the stainless steel sleeve is installed inside the titanium alloy sleeve, has no prospects for industrial use, as during cooling after diffusion welding, the brittle diffusion layer, due to the twofold difference in the coefficients of thermal expansion between titanium and stainless steel, constantly works in tension and shear, which in the conditions of vibration and temperature fluctuations will inevitably lead to its destruction.

The closest to the claimed design of the adapter titanium steel for a combination of essential features is a tubular adapter titanium-stainless steel, made in the form of a sleeve of titanium alloy and a sleeve of stainless steel welded between

by diffusion lap welding on conical surfaces with the location of the stainless steel sleeve of the titanium alloy sleeve and with the formation of a diffusion layer between them (N.F. Kazakov. Diffusion welding of materials. M. Mechanical Engineering, 1976, p. 189).

This design of the tube adapter is also not very suitable for welding critical pipelines made of titanium and stainless steel, operating in conditions of vibration and frequent temperature changes, since in the axial direction the strength of the adapter is ensured only due to the strength of the diffusion layer formed as a result of diffusion sgfk and the presence of a conical surface in the lap joint only weakens the axial strength of the adapter.

The diffusion layer between the titanium alloy bushings and stainless steel, on which the strength and performance of the titanium-steel adapter, based on the known diffusion welding technology, is based, as a rule, has an extremely uneven thickness, both in the joint area and in its length, which is caused by properties of oxide films on the surfaces of titanium alloy and stainless steel, and, as a rule, this scatter in one lap joint can vary from the practical absence of a diffusion layer on the nyh areas to a thickness of several hundred microns. Moreover, in those areas where diffusion interaction has already begun, the growth of the diffusion layer occurs very intensively, and if the heating temperature in this place reaches the lower point of the eutectic between titanium and stainless steel, then the Liquid eutectic simply starts to flow out from the lap joint. In this regard, the known methods of diffusion welding in this design adapter is almost impossible to obtain

high-strength diffusion layer, the thickness of which will not exceed two microns, because only with these values provides high strength diffusion welded titanium-steel.

With large thicknesses of the brittle diffusion layer, tubular adapters do not withstand heat shock tests when heated to and lowering into water, because the brittle diffusion layer begins to crack and after several thermal shock the adapter loses its tightness.

This is explained by the fact that during cooling after diffusion welding, the diffusion layer experiences compression in the radial direction, and in the longitudinal it experiences shear stresses, which is associated with a thermal reduction in the diameter and length of the stainless steel sleeve relative to the titanium alloy sleeve.

Such an adapter under operating conditions in the composition of the pipeline, in addition to the stresses remaining after welding, will arise stresses in the diffusion layer from the pressure of the medium in the pipeline, fluctuations in its temperature, from thermal expansion of the pipeline and its vibrations. And all this in this design of the adapter is opposed only by a fragile diffusion layer, which is in no way suitable for critical pipelines operating in difficult operating conditions.

The problem to which the present utility model is directed is to design a tube adapter in the form of two bushings of titanium alloy and stainless steel, which are overlapped and welded by diffusion welding in a vacuum to form a brittle diffusion layer in a}) joint that would be It is efficient in critical high-temperature pipelines operating in conditions of vibration and temperature fluctuations in the pipeline.

The technical result obtained by the implementation of the claimed utility model consists in the fact that in the claimed design of the tube adapter, the brittle diffusion layer practically does not experience shear stresses that arise in the known titanium-steel tube adapters during cooling after diffusion welding, as well as during operation from the effects of the division of the medium flowing through the pipeline, as well as from vibration of the pipeline and fluctuations in the temperature of the medium.

The specified technical result is achieved by the fact that in the tubular adapter, titanium-stainless steel, made in the form of a sleeve of titanium alloy and a sleeve of stainless steel, welded together by diffusion welding overlap with the location of the sleeve of stainless steel on the outside of the sleeve of titanium alloy and with the formation between them diffusion layer,

- lap joint is made on cylindrical surfaces with mechanical engagement between them in the form of alternating annular protrusions and troughs of the threaded profile, while the thickness of the diffusion layer is not more than 20 microns;

In addition, the cylindrical surfaces of the bushings in the area of the lap joint have at least one cylindrical step;

-In addition, the place of thickening of the lap joint is made on the outside of the adapter:

- In addition, the site of thickening of the lap joint is made on the inside of the adapter.

welding between each other pipes of titanium alloys with pipes of stainless steel.

The high reliability of the claimed design of the titanium-steel tubular adapter is ensured by an overlap connection, which, in contrast to the prototype, is made on cylindrical surfaces, on which, in turn, mechanical engagement is made in the form of alternating annular protrusions and thread of the thread profile, which takes all the loads to which the diffusion layer is subjected both during the operation of the adapter, and from the twofold difference in the coefficients of thermal expansion between titanium and erzhaveyuschey steel. In addition to this, mechanical engagement in the form of annular protrusions and valleys creates a labyrinth seal in the lap joint, which can ensure tightness of the joint even if there is no diffusion layer, since in the process of cooling after diffusion welding, the stainless steel bushing, due to the difference in the thermal expansion coefficients, tightly compresses the titanium alloy bushing all the time.

In the claimed design of the adapter, the diffusion layer does not carry power loads, and only plays the role of ensuring the connection of the vacuum flotation, however, the thinner it is, the higher is its strength and corrosion characteristics, therefore its maximum thickness is limited in the claimed design of the adapter to the whole microns.

The lap joint of the adapter to reduce its radial dimensions can be multistage, which reduces the external strengthening of the wall thickness in the lap area to 0.5-3 mm, and in case of structural need

allows to MAKE an adapter without external amplification, replacing it with internal.

In addition, a stepwise lap joint allows one to reduce thermal and mechanical stresses in a brittle diffusion layer at the edges of the lap joint by making the ends of the bushings forming the lap joint as thin as possible, since thermal stresses, in addition to differences in thermal expansion coefficients, are determined by the rigidity of one of the welded walls, which directly proportional to its thickness.

The essence of the utility model is illustrated by drawings, where fng. 1 shows a titanium-steel pipe adapter designed for welding pipes from titanium alloys with stainless steel pipes, made in the form of two bushings of titanium alloy 1 and stainless steel 2, welded together by diffusion welding lap with mechanical engagement between them in the form of alternating annular protrusions and depressions of the threaded profile 3. In this case, the lap joint is made on a cylindrical surface with the location of the place thicker tions overlap the outside of the adapter.

In FIG. Figure 2 shows a similar titanium-steel tube adapter, in which the lap joint is multistage with the location of the minimum thickening of the lap outside the adapter.

In FIG. 3 shows a similar titanium-steel tube adapter,

whose lap joint is multi-stage

"The location of the minimum thickened lap inside

adapter.

Claims (4)

1. Tubular adapter titanium-stainless steel, made in the form of a sleeve of titanium alloy and a sleeve of stainless steel, welded together by diffusion lap welding with the location of the sleeve of stainless steel on the outside of the sleeve of titanium alloy and with the formation of a diffusion layer between them, characterized in that that the lap joint is made on cylindrical surfaces with mechanical engagement between them in the form of alternating annular protrusions and troughs of the threaded profile, while the thickness of the differential uzionnoy layer is not more than 20 microns.  2. The tubular adapter according to claim 1, characterized in that the cylindrical surfaces of the bushings in the area of the lap joint have at least one cylindrical step.  3. The tubular adapter according to claims 1 and 2, characterized in that the place of thickening of the lap joint is made on the outside of the adapter. 4. The tubular adapter according to claims 1 and 2, characterized in that the place of thickening of the lap joint is made on the inside of the adapter.