RU2568035C2 - Method of fusion welding of molybdenum with iron-nickel alloys - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to fusion welding of molybdenum article with iron-nickel alloy article to making of overlap joint. The groove is, first, made on molybdenum article surface, under the molten pool centre. Copper wire is fitted in said groove. Barrier layer and the weld are formed simultaneously by fusion of copper wire and iron-nickel alloy. Barrier layer thicker at the temperature peak point, under the molten pool, thicker than in periphery. That is, more efficient protection against intensive interaction of molybdenum with iron-nickel alloy is formed at the most critical point.

EFFECT: levelled temperature-time conditions of interaction of metals in welding.

3 dwg

Description

The invention relates to the field of fusion welding of dissimilar metals, and more particularly molybdenum with iron-nickel alloys.

The closest set of essential features to the invention is a method of fusion welding of molybdenum with iron-nickel alloys, in which an intermediate barrier layer of copper is created on the surface of molybdenum (RF patent No. 2049622, IPC V23K 9/23, publ. 10.12.1995).

In the known method, a barrier layer is created before welding, for this, a niobium gasket is soldered to a molybdenum product in a vacuum furnace by melting the copper foil. As a result, an intermediate barrier layer is obtained on the surface of molybdenum, consisting of a niobium layer and a copper layer, each of which has a certain thickness. Then, the molybdenum product with a barrier layer and the iron-nickel alloy product are assembled and assembled to produce welding with the melting of a more fusible metal.

The disadvantage of this method is that there is an interaction of metals with uneven intensity across the width of the weld pool. Under optimal temperature and time conditions at the periphery of the weld pool in its center, they are close to critical or go beyond the optimum. Moreover, these interaction conditions are difficult to control and if their values are exceeded above the optimum, they lead to the formation of a significant amount of intermetallic compounds, which reduces the strength properties of welded joints. In addition, the disadvantage of this method is that the technology of creating a barrier layer in the known method is very time-consuming and requires the manufacture of complex equipment for each size of the welded product.

The present invention is the creation of a technologically simplified method of fusion welding of molybdenum with iron-nickel alloys, which allows to obtain high-strength welded joints.

The technical result that is achieved using the present invention is to equalize the temperature-time conditions for the interaction of metals in the welding process over the area of the weld pool. A barrier layer of a greater thickness is formed under the weld pool at the temperature peak, than at the periphery, i.e. a more effective protection is formed from intensive interaction of molybdenum with an iron-nickel alloy in the most critical place.

The specified technical result is achieved by the fact that in the known method of fusion welding of molybdenum with iron-nickel alloys, in which an intermediate barrier layer of copper is created on the surface of the molybdenum, according to the claimed invention, the barrier layer is created during the welding process, using a copper wire, which is placed in the groove, having a depth not exceeding the diameter of the circular cross section or the height of the rectangular cross section of the wire, the groove being made in molybdenum under the center of formation of the weld pool.

The invention is illustrated by drawings, where figure 1 shows the assembly of products from molybdenum and an iron-nickel alloy before welding (general view, longitudinal section), figure 2 shows a groove with copper wire (type A), figure 3 shows a welded joint of products from molybdenum and an iron-nickel alloy (general view, longitudinal section).

The method is as follows.

To perform the lap joint of the article 1 of molybdenum and the article 2 of an iron-nickel alloy, for example of nimonik, a groove is made before the assembly of the articles 1 and 2 on the outer surface of the article of molybdenum 1 under the center of formation of the weld pool (location of the proposed heat source, for example, an electron beam) for placement of copper wire 3. The groove in the product 2 of nimonics is impractical because in this case, the interaction between the nimonic and the copper wire will occur at elevated temperatures, which will lead to the formation of structures that adversely affect the mechanical properties of the welded joint. The groove in the product 1 is performed with a depth equal to the diameter of the wire 3 (in the case of the use of round wire) or equal to the height of the wire cross-section (in the case of the use of rectangular wire).

толщины изделия из нимоника. Например, для толщины трубы 2 мм применяют проволоку диаметром 0,5 мм. После выполнения канавки, в которой располагают медную проволоку 1, осуществляют сборку изделий 1 и 2 сварного соединения внахлестку без зазора. Для этого на изделии из молибдена 1 сверху располагают изделие 2 из нимоника, при этом кромку изделия 1 оставляют выдвинутой за пределы центра канавки на величину, при которой происходит ее расплавление с образованием половины сварного шва по его ширине. Сварочный источник тепла, например электронный луч, наводят на место предполагаемого расположения медной проволоки 3. Процесс осуществляют с расплавлением только нимоника и медной проволоки. При этом молибден находится в твердом состоянии. Сварку осуществляют на минимально возможном режиме, чтобы исключить перегрев металлов в зоне их контакта. В процессе сварки при расплавлении проволоки 3 образующееся покрытие способствует смачиванию молибдена жидким металлом и создает медный барьерный слой, препятствующий интенсивному взаимодействию нимоника с молибденом. В центре сварочной ванны температура больше, чем на периферии, поэтому барьерный слой соответственно имеет большую толщину, что обеспечивает равномерный процесс взаимодействия металлов. Сварной шов 4, образующийся в процессе сварки, имеет механическое зацепление за счет затекания расплавленного металла в канавку, что также улучшает механические свойства сварного соединения.The wire is taken with a cross section of approximately 5-15% of the cross section of the weld, i.e. the diameter of the wire, for example, should be approximately $$\raisebox{1ex}{$\mathrm{one}$}\!\left/ \!\raisebox{-1ex}{$\mathrm{four}$}\right.$$

the thickness of the product from nimonika. For example, for a pipe thickness of 2 mm, a wire with a diameter of 0.5 mm is used. After completing the groove in which the copper wire 1 is located, assembling the products 1 and 2 of the welded lap joint is performed without a gap. To do this, on a molybdenum product 1, a nemonic product 2 is placed on top, while the edge of the product 1 is left extended beyond the center of the groove by the amount at which it melts to form half of the weld along its width. A welding heat source, such as an electron beam, is directed to the place of the intended location of the copper wire 3. The process is carried out with the melting of only nimonics and copper wire. In this case, molybdenum is in a solid state. Welding is carried out at the lowest possible mode to prevent overheating of metals in their contact zone. In the welding process during the melting of wire 3, the resulting coating promotes the wetting of molybdenum with liquid metal and creates a copper barrier layer that prevents the intensive interaction of nimonic with molybdenum. In the center of the weld pool, the temperature is greater than at the periphery; therefore, the barrier layer accordingly has a greater thickness, which ensures a uniform process of interaction of metals. The weld 4 formed during the welding process has mechanical engagement due to the flow of molten metal into the groove, which also improves the mechanical properties of the welded joint.

Claims (1)

A method of fusion welding of a molybdenum product with an iron-nickel alloy product, comprising forming an intermediate copper barrier layer on the surface of the molybdenum product and lap joint welding, characterized in that a groove is made on the surface of the molybdenum product under the center of formation of the weld pool, into which copper wire, and the formation of the barrier layer and the weld is carried out simultaneously by melting the copper wire and the iron-nickel alloy.

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