Joint of pipeline from stainless steel with vessel from titanium alloy and method of its realisation

FIELD: metallurgy.

SUBSTANCE: joint of a pipeline from stainless steel with a vessel from titanium alloy comprises an adapter made in the form of a bushing, the lower part of which is made according to a spherical shell shape and is connected to it by means of electronic beam welding. The upper part of the bushing is installed coaxially inside the pipeline and is connected with it by means of high-temperature vacuum soldering. The adapter is made from a niobium-based alloy alloyed with at least one of the metals selected from the following group: tantalum, molybdenum, vanadium, titanium. Electronic beam welding of the adapter with the vessel shell is carried out with beam displacement along the shell joint surface with the adapter towards the adapter.

EFFECT: invention provides for tightness and high strength of connection.

6 cl, 2 dwg, 1 tbl

 

The invention relates to metallurgy, in particular to welding and soldering of metals, and can be used for manufacturing various products in nuclear power and other industries.

The complexity of the compounds of titanium and its alloys, stainless steel is the incompatibility of these materials during the welding process. The reason for the incompatibility is their high chemical affinity, leading to the formation in the weld or heat-affected zone of brittle layers of chemical compounds, dramatically decreasing the strength of the weld, which can lead to destruction in these areas.

The best way to connect titanium and its alloys, stainless steel is the connection through the adapter.

A known method for joining titanium and its alloys, stainless steel, with which the adapter is used bimetallic adapter titanium + stainless steel obtained by mechanical cutting of the welded explosion of blanks, followed by welding with homogeneous materials: titanium+, titanium and stainless steel + stainless steel [Trykov P. and others "Composite adapter", Volgograd, Valgte, 2007].

However, this method can be applied to products in which the thickness of the bimetallic adaptor is not limited to specific dimensions, as in the fusion welding of titanium compounds + is atall + stainless steel unacceptable excess temperature-time conditions adjacent to the welded junction of the borders of the bimetal because of the educational opportunities it brittle intermetallics. This mode of heating is limited by the temperature of 850-900°C and the dwell time at these temperatures in the range 15-50 sec [Trykov P. and others, "the manufacturing Technology of titanium-steel adapter with pakowanie butt joints, "Welding production" No. 7, 2008].

A known method for joining titanium alloy with stainless steel through adapter niobium using TIG welding and brazing [CN application No. 101284336(A) 2008.10.15].

The disadvantage of this method is that the connection of titanium alloy adapter is TIG welding. In the manufacture of products, which include refractory metals such as niobium and its alloys, the connection must be carried out with the use of electron-beam welding, providing a high heat capacity, due to which the size of the weld is sharply reduced, which is especially important in the manufacture of products of small size. Another significant disadvantage is the use of the adapter niobium, compatible with the join materials, but has a sufficiently low mechanical properties; after annealing in the process of welding and soldering it σin=190-210 MPA, which is significantly lower mechanical properties of the joined materials.

The technical object of the present invention is developed the spacecraft design node connecting pipes made of stainless steel with a vessel of titanium alloy with a thickness of 0.8 to 5 mm, ensuring the integrity and durability of the connection.

Another technical object of the present invention to provide a method of manufacturing a node connecting the piping stainless steel vessel of titanium alloy with a thickness of 0.8 to 5 mm, ensuring tightness and durability of the connection.

To solve this task, the node connecting pipes made of stainless steel with a vessel of titanium alloy with a thickness of 0.8-5 mm is characterized by the fact that it uses an adapter made in the form of a sleeve, the lower part of which is made in the form of a spherical shell and connected to the electron-beam welding, and the upper part of the sleeve located coaxially inside a pipeline and connected by a high-temperature vacuum soldering, and the adapter is made from an alloy based on niobium-doped, at least one of the metals selected from the group of tantalum, molybdenum, vanadium, titanium, on the next the ratio of components,% by weight:

alloying element1-6
niobiumrest

In the private version of the lower part of the adapter when the Assembly is placed in the shell of the vessel and forms with it stegosauridae with parameters selected from the following formulas:

where a is the thickness of the shell,

b - height shelves castle,

C - width shelves of the castle.

Also for the technical solution of the method of manufacturing a node connecting the piping stainless steel vessel of titanium alloy with a thickness of 0.8-5 mm is characterized by the fact that the connection of the pipeline from the vessel passes through the adapter, with electron beam welding adapter with the shell of the vessel carried out with displacement of the beam on the surface of a joint of casing with the adapter in the direction of the adapter on the value of ddrug-dNR/2,

where ddrug- outer diameter of the adapter in the joint area;

dNR- inner diameter of the adapter in the joint area.

In the private case, the welding is carried out using electron beam across the joint with a frequency of 20-25 Hz and an amplitude of 0.2-0.3 mm

In another private version of soldering the top of the adapter with the pipeline is carried out with a gap of 0.03 to 0.04 mm

In another private embodiment, the solder pipe from the upper part of the adapter carry out soldering of the system copper - Nickel - manganese at a temperature of 1020-1050°C for 2 min, with the following ratio of components, solder, wt.%:

Nickel10-15
manganese25-35
copperrest

Figure 1 presents the design of the connection node of the pipeline from the vessel.

Figure 2 presents the cross-section area connection adapter with the shell of the vessel performed electrolicious welding (the dashed line denotes the boundary of the molten metal after welding, solid line - the location of input focus the electron beam on the surface of the adapter).

The connection node consists of a pipeline 1, the adapter 2, made in the form of a sleeve of the niobium alloy, the upper part of which is placed inside a pipeline, and the lower part is made in the form of a spherical shell surface of the vessel 3 and is connected with the shell by electron-beam welding of girth seam 4. The upper part of the adapter is connected to the pipeline using high-temperature vacuum brazing, forming a brazed seam 5.

Preparation of pipeline 1 to soldering is machined inner holes on the length of 5-7 mm in order to build it with the upper part of the adapter 2. Solder in the form of a ring placed on the surface of the adaptor in place of their connection. The solder elements are produced in a vacuum induction the mouth of the information by heating the soldering zone to the melting temperature of the solder, providing the wicking it into the gap with the formation of the soldered seam 5.

After soldering pipe with adapter assembling them with the shell of the vessel 3. Welded elements fixed to the rotator installation welding.

Electron-beam welding of the shell of the vessel with an adapter carried out in one pass. When this beam shift on the surface of a joint of casing with the adapter in the direction of the adapter on the distance of the inner diameter of the adapter in the joint area, evenly aplause the joined materials and forming a weld seam 4. To ensure full penetration of materials having a large difference in the temperature of their melting, and prevent sagging of the molten metal in the weld root welding is carried out with the required amplitude and frequency fluctuations across the joint.

As the material of the adapter used alloys of niobium, alloy, at least one of the metals selected from the group of TA, Mo, V, Ti in an amount of from 1 to 6 wt.%. This is the most optimal from the viewpoint of increasing the strength of the alloy by maintaining a sufficiently high degree of plasticity, which is very important for the manufacture of the adapter.

The table shows the mechanical properties of the alloys of niobium.

Alloying element Wt.%Mechanical properties
σInδ, %
In the initial stateAfter annealing at 1020°C, 2 minIn the initial stateAfter annealing at 1020°C, 2 min
Ti14402753951
54503806165
The13242986065
63463104649
V13743114951
642233 4648
Mo14273644560
44934174252

Used for soldering the solder Cu-Ni-Mn has high strength and ductility, which is especially important for connection of dissimilar materials having a difference in thermal coefficients of linear expansion (TCLE).

For the formation of the soldered seam of the compression stress during cooling of the product after soldering the niobium alloy is located in the inner part of the telescopic connection adapter - stainless steel. When this Assembly gap before soldering these materials should be 0,03-0,04 mm

An example of performing the method of manufacturing site

Testing of the proposed method of connection of dissimilar materials was carried out on model samples of titanium alloy VT-20 (washer type) with a spherical surface with a radius of 80 mm and a thickness of 1.5 mm, and the pipe from steel 12X18H10T ⌀ 3×1 mm and a length of 150 mm

The adapter is made in the form of a sleeve of the alloy Nb-4% Mo and had after mechanical is th processing in the lower part of the shape of a spherical shell with stegosaurus connection of its shell.

The upper part of the sleeve and the inner surface of the pipeline processed so that the gap when the Assembly was 0,03-0,04 mm the First operation carried out for the manufacture of the connecting host, was a high-temperature vacuum brazing of pipe with adapter. Before soldering joint surfaces were degreased, after which the pipeline was assembled with the adapter with the appropriate clearance. The solder composition of the Cu - 10 wt.% Ni - 35 wt.% Mn in the form of a ring ⌀drug=4.2 mm, ⌀NR=3.1 mm and a width of 0.6 mm was placed on the adapter in the connection zone.

Brazing was performed in a vacuum at a vacuum of 1.3·10-2PA using induction heating at a temperature 1020-1050°C with a holding time at the temperature for 2 minutes

Electron beam welding adapter with the shell of the vessel alloy W-20 was performed on installing SA-424 with accelerating voltage of 60 kV when the welding current 24 mA in one pass. Using system deflection and vibrations during welding was possible to obtain uniform penetration of heterogeneous materials with preservation of root required internal dimensions of the shell.

After carrying out the processes of welding and soldering joints were checked for tightness helium leak detector. The audit showed that all seams sealed. Conducted metallographic studies sworn the th and soldered joints. The incomplete fusion, cracks, pores, dry joints and other defects in the seams was not found.

To assess durable properties of compounds obtained from the model node cut samples for testing.

Performed mechanical tests on the gap showed high strength, which is determined by the strength of the material used and is not less than 400 MPa.

Thus, the proposed invention can be used for the manufacture of various products made of dissimilar materials to ensure the integrity and high strength, as in nuclear power and other fields.

1. The node connecting pipes made of stainless steel with a vessel of titanium alloy with a thickness of 0.8 to 5 mm, characterized in that it uses an adapter made in the form of a sleeve, the lower part of which is made in the form of a spherical shell of the vessel and connected to the electron-beam welding, and the upper part of the sleeve located coaxially inside a pipeline and connected by a high-temperature vacuum soldering, and the adapter is made from an alloy based on niobium-doped, at least one of the metals selected from the group of tantalum, molybdenum, vanadium, titanium in the following ratio of components, weight %:

alloying element 1-6
niobiumrest

2. The node according to claim 1, characterized in that the lower part of the adapter when the Assembly is placed in the shell of the vessel and forms with it stegosauridae connection with the parameters selected from the following ratios:


where a is the thickness of the shell;
b - height shelves lock;
C - width shelves of the castle.

3. A method of manufacturing a node connecting the piping stainless steel vessel of titanium alloy with a thickness of 0.8 to 5 mm, characterized in that the connection of the pipeline from the vessel passes through the adapter, with electron beam welding adapter with the shell of the vessel carried out with displacement of the beam on the surface of a joint of casing with the adapter in the direction of the adapter on the value of ddrug-dNR/2,
where ddrug- outer diameter of the adapter in the joint area;
dNR- inner diameter of the adapter in the joint area.

4. The method according to claim 3, characterized in that the welding is carried out using electron beam across the joint with a frequency of 20-25 Hz and an amplitude of 0.2-0.3 mm

5. The method according to claim 3, characterized in that the soldering of the upper part of the adapter with the pipeline is carried out with a gap of 0.03 to 0.04 mm

6. The method according to claim 3, characterized in that the soldering is Truboprovod with the upper part of the adapter carry out soldering of the system copper-Nickel-manganese at a temperature of 1020-1050°C for 2 min in the following ratio of components, solder, wt.%:

Nickel10-15
manganese25-35
copperrest



 

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