RU2106230C1 - Method for manufacture of soldered telescopic construction - Google Patents

Abstract

FIELD: power engineering. SUBSTANCE: method involves making outer shell of construction from two members 1 and 2 welded along joint 3; assembling outer and inner shells and positioning them on thermal compensator having ring 6 and truncated cone 7. Ring 6 is made from material with thermal expansion coefficient equal to that of material of shell 4. Truncated cone 7 is made from material with thermal expansion coefficient exceeding that of material of member 1. Auxiliary thermal compensator 8 positioned on member 1 has thermal expansion coefficient equal to that of material of member 2. Method further involves heating, soldering and cooling assembled unit. Method allows joint free of cracks to be obtained. EFFECT: increased efficiency, simplified method and improved parameters of construction. 1 dwg

Description

 The invention relates to the field of welding and soldering, in particular to methods for manufacturing a soldered telescopic structure, and can find application in power engineering and other industries.

 A known method of manufacturing a soldered telescopic structure, consisting of dissimilar materials, in which a ring with a coefficient of thermal expansion close to the coefficient of thermal expansion of the material of the inner shell is installed inside the assembled structure, all this is placed on a mandrel made in the form of a truncated cone of material, the coefficient of thermal expansion of which equal to or greater than the coefficient of thermal expansion of the material of the outer shell. After assembly, heating is carried out, while the soldered parts are lowered under the action of their own weight or additional load on the cone, expanding in a smaller section. After soldering, the structure together with the mandrel is cooled.

 However, this method does not allow high-quality soldering of telescopic structures of complex configuration when, for example, the outer shell contains two elements of dissimilar materials. The reason is the appearance of cracks in the metal of the outer shell due to the simultaneous exposure to it of molten solder and tensile stresses arising during the welding of two elements.

 The objective of the invention is to obtain a high-quality telescopic structure without cracks in the base metal at the border with the soldered seam.

 To this end, in a method of manufacturing a soldered telescopic structure, consisting of a thick-walled outer and thin-walled inner shells made of dissimilar materials, including assembly under soldering by placing the structure on a temperature compensator made in the form of a truncated cone with a ring made of material with a coefficient of thermal expansion equal to the coefficient thermal expansion of the material of the inner shell, heating, soldering and cooling, the outer shell is made of two elements of heterogeneous materials materials that are welded together, placing one of them outside the soldering zone, and the element located outside the soldering zone is made of material with a thermal expansion coefficient less than the thermal expansion coefficient of the material of the element located in the soldering zone, the truncated cone thermal compensator is made of material with a coefficient of thermal expansion equal to or greater than the coefficient of thermal expansion of the material of the element of the outer shell located in the soldering zone, and during assembly under yku placed on the outer shell with the possibility of contacting it with its elements and an additional weld thermal compensator made of a material with a thermal expansion coefficient equal to the coefficient of thermal expansion element arranged outside the soldering area.

 The drawing shows a schematic illustration of the housing in the form of a telescopic structure, welded in accordance with the proposed technology.

 The method in accordance with the invention is as follows.

 The housing is assembled in the form of a telescopic structure containing a thick-walled outer shell and a thin-walled inner shell 4. The thick-walled outer shell is welded and contains elements 1 and 2 of dissimilar materials, and the coefficient of thermal expansion of the material of element 2 is less than the coefficient of thermal expansion of the material of element 1. Previously, elements 1 and 2 outer shells are welded together with the formation of a thick weld 3. The weld 3 is performed using a welding wire, chemical the composition of which is close to the chemical composition of the outer shell element 2, in order to obtain a weld strength of at least 0.85 of the strength of the base metal. A solder 5 is arranged between the element 1 and the inner shell 4. On its inner side, a thermal compensator is installed, made in the form of a ring 6 of material with a coefficient of thermal expansion equal to the coefficient of thermal expansion of the inner shell 4 and a truncated cone 7 of material with a coefficient of thermal expansion equal to or large coefficient of thermal expansion of the material of the element 1. On the outer diameter of the element 1 place an additional temperature compensator 8 so that it borders on the element 2 and weld seam 3. An additional temperature compensator 8 is made of a material whose thermal expansion coefficient is equal to the thermal expansion coefficient of the material of element 2, and therefore less than the coefficient of thermal expansion of the material of element 1 of the outer shell of the casing located in the soldering zone. The need to comply with this condition is due to the following considerations. Elements 1 and 2 are interconnected by a thick weld seam 3 bordering an additional temperature compensator 8. Since the chemical composition and physicomechanical properties of the material of the weld seam 3 are similar to the properties of the material of element 2, in the process of soldering, the weld seam 3 is a transmission link from the action of element 2 . In the case of non-compliance with the conditions for the uniformity of the materials of element 2 and the additional temperature compensator 8, tensile stresses from the action of elements 1, 2 and weld 3 will appear in the latter during the soldering process, which will lead to eravnomernoy deformation additional thermal compensator 8, and as a consequence to nespayu and occurrence of cracks in the solder joint.

где δ_к - толщина стенки компенсатора,
δ_нар.об. - толщина элемента 1 наружной оболочки,
E_нар.об. - модуль упругости материала элемента 1 наружной оболочки,
α_нар.об. - коэффициент термического расширения материала элемента 1 наружной оболочки,
E_к - модуль упругости материала компенсатора,
α_к - коэффициент термического расширения материала компенсатора.In the manufacture of an additional temperature compensator 8, the preliminary wall thickness is calculated depending on the thickness of the outer shell element 1 and the properties of the selected materials. The wall thickness should be such that during brazing, the additional thermal compensator 8 absorbs the tensile forces in element 1 from the action of the weld and element 2. The wall thickness of the additional thermal compensator is determined from the ratio:

where δ _to - the wall thickness of the compensator,
δ _nar.ob. - the thickness of the element 1 of the outer shell,
E _nar.ob. - the elastic modulus of the material of the element 1 of the outer shell,
α _nar.ob. - coefficient of thermal expansion of the material of the element 1 of the outer shell,
E _to - the modulus of elasticity of the material of the compensator,
α _to - coefficient of thermal expansion of the material of the compensator.

The heating and soldering processes are carried out in a furnace in a shielding gas - argon atmosphere under a pressure of 0.1 - 0.3 kgf / cm ² . The soldering temperature is selected depending on the material of the brazed shells. In the process of cooling the structure from the soldering temperature in the interval of solder crystallization, the tight contact between the element 1 of the outer shell and the inner shell 4 is maintained due to the action of the temperature compensator 7.

 Analysis of soldered joints of the structure showed the absence of defects such as cracks and joints. The elimination of defects is due to the absence of deformation of the element 1 located in the soldering zone. The prevention of the formation of defects in element 1 was achieved by using an additional thermal compensator 8, the coefficient of thermal expansion of the material of which is less than the coefficient of thermal expansion of the material of element 1 and is identical to the coefficient of thermal expansion of the material of element 2 of the outer shell and the material of the weld 3. This ensured an increase in the process of soldering size to a lesser extent compared with element 1 and equally with element 2 and weld 3.

 The application of this method provided 100% yield by increasing the tightness of soldered joints.

An example implementation of the proposed method. A housing was assembled containing an outer shell of element EI-435 nickel alloy 1 and the element 2 made of high-alloy steel VNS-25 welded together. The shell thickness is 30 mm. The weld is multilayer: from the inside using electron beam welding, from the outside - argon-arc in a shielding gas environment. Welding was carried out using an iron-based welding wire with the addition of chromium and nickel and a chemical composition similar to the material of element 2 of the outer shell of the body. Its inner shell is made of silver alloy. Between it and the element 1 of the outer shell located in the soldering zone, there was a silver based solder. A temperature compensator 7 was installed on the inner side of the shell, and an additional temperature compensator 8, made of VNS-25 steel, was installed on the outer shell. Its wall thickness is calculated taking into account the obtained experimental data and is equal to 34 mm. The calculation was carried out by choosing the characteristics of the VNS-25 steel and the nickel alloy EI-435 at a temperature of 600 ^o C, because starting from this temperature, their coefficients of thermal expansion differ as much as possible. The gap between the walls of the element 1 and the additional temperature compensator 8 was 0.1 mm. The soldering was carried out in a furnace in an argon atmosphere at a temperature of 770 ± 5 ^o C with holding it for 3-5 minutes.

 Metallographic studies of soldered joints showed the absence of defects: cracks and joints. Hydrotest did not detect leaks in soldered structures.

Claims (1)

 A method of manufacturing a soldered telescopic structure consisting of a thick-walled outer and thin-walled inner shells of dissimilar materials, including assembling for soldering the structure by placing it on a temperature compensator made in the form of a truncated cone with a ring made of material with a coefficient of thermal expansion equal to the coefficient of thermal expansion inner shell, soldering and cooling, characterized in that the outer shell is made of two elements from dissimilar materials s, which are welded together, placing one of them outside the soldering zone, and the element located outside the soldering zone is made of material with a coefficient of thermal expansion less than the coefficient of thermal expansion of the material of the element located in the soldering zone, the temperature compensator in the form of a truncated cone is made of material with a coefficient of thermal expansion equal to or greater than the coefficient of thermal expansion of the material of the element of the outer shell located in the soldering zone, and during assembly under soldering an outer shell disposed to come into contact with its elements and an additional weld thermal compensator made of a material with a thermal expansion coefficient equal to the coefficient of thermal expansion element arranged outside the soldering area.