RU2404887C1 - Method of welding materials - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to the method of welding materials by high-power radiation sources, e.g. laser, plasma or electron beam, and can be used for welding thin-sheet and diverse materials in various industries. Prior to welding, material edges to be welded are pre-melted. Welding is performed with simultaneous addition of modifiers into melting zone, said modifiers being made up of nanopowders selected from refractory compounds, e.g. nitrides, carbonitrides and oxides. Concentration of nanopowders material makes less than 0.1% by weight of welding bath. Said nanopowders can represent suspensions.

EFFECT: welding of homogeneous and composite materials, higher quality of welded seams.

5 cl, 2 dwg

Description

The invention relates to the field of welding materials with high-energy radiation sources, for example, laser, plasma, or electron beam method, and can be used for laser welding of products for various purposes from sheet materials in the chemical, electronic and radio engineering industries, as well as in the production of pipes. It can be used to directly connect two homogeneous or dissimilar metals or alloys to each other.

The technical task of welding metals is to improve the quality of the welded joint and increase productivity. To achieve these results use, for example, filler materials or intermediate inserts that provide certain properties of the weld. The development of new technologies related to the impact aimed at forming the internal structure of materials and the properties of welded joints can contribute to a successful solution to this problem.

A known method of laser welding of metals with high thermal conductivity and high reflectivity, in which the surface of the metal being welded from the side of the laser beam is preliminarily coated with a layer of filler material with lower reflectivity and with a higher melting point / 1 /.

The main disadvantage of this method is the unregulated size of the filler material layer, as a result of which, in some welding modes, its efficiency is small and there may be a decrease in the welding efficiency (COP) and the appearance of defects in the weld.

A known method of welding stainless steel (X15H5D2T) with a titanium alloy OT4 using an intermediate insert, which is used as a vanadium alloy doped with tungsten / In the book: Lectures on welding dissimilar dissimilar metals. M .: MDNTP, 1973. P 46-51 /.

The disadvantage of this method is the need to control the composition of the weld metal and apply a welding technique that reliably provides welds of a given chemical composition, because The mechanical properties of such compounds are determined by the ratio of alloying elements in the weld metal.

The objective of the proposed method of welding materials is to improve the quality of welds and high-strength surface layers. When fulfilling the task, all requirements must be taken into account, such as the local nature of the thermal effect, minimal thermal deformation, a wide range of regulation of the energy characteristics of the beam, providing a rigid thermal regime with high heating and cooling rates.

A promising direction in the development of high-energy technologies for welding materials, for example, laser, is the combination of high-energy effects on the materials being welded with the saturation of their surface layer with alloying and modifying additives and the creation of a hardened modified layer by introducing, for example, refractory nanosized powder particles into the welding zone. Such modifying additives in metallurgy are called nanopowder innoculators (NPI).

The task is carried out due to the fact that the method of welding materials with high-energy radiation sources, such as laser, plasma or electron beam, by which prior to welding, preliminary melting of the materials to be welded is carried out, and welding is carried out with the addition of modifiers in the form of nanopowder materials selected from among refractory compounds, for example nitrides, carbonitrides, oxides, while the concentration of nanopowder material is less than 0.1% by weight of the weld pool. Nanopowder materials in the welding zone can be applied in the form of a suspension. The method allows welding of homogeneous materials or dissimilar materials with or without inserts, as well as composite materials with or without inserts.

The set of essential distinguishing features not identified from the existing level of technology, allows us to solve the problem, as well as to conclude that the claimed technical solution meets the criterion of "inventive step".

Figure 1 shows the microstructure of a weld of steel grade St 20: a) without the addition of nanopowder materials; b) with the addition of nanopowder materials TiN + Y ₂ O ₃ . Figure 2 - mechanical characteristics of the welded joint of VT5 alloy without additives NPI and with the addition of NPI refractory joints: a) elongation δ; b) tensile strength σ _b and c) yield strength σ _0.2 .

The method of welding materials is as follows.

Consider a laser welding method. First, weld surfaces are prepared. In the preparation of welded plates, a film of oxides is removed over a width of 20-25 mm along the entire length of the joint by etching in a NaOH solution (50 g per 1 L of H ₂ O), followed by clarification in a 30% HNO ₃ solution. After etching, parts are washed in hot water. Immediately before welding, the surfaces to be bonded are cleaned with a scraper to a shine. This will avoid welding defects and, first of all, porosity. As a protective medium for laser welding, helium is used as the most effective for achieving the greatest penetration effect, or helium is used to protect the upper surface of the weld pool, and the lower one is protected by argon. Moreover, the protection of both surfaces during laser welding of aluminum and titanium alloys is mandatory. Helium consumption is at least 7-8 l / min, argon - 5-6 l / min.

The mass flow rate of nanopowder material per unit length of the treated surface is M _p = pρdh, kg / m, where p is the mass fraction of powder; d is the width of the weld, h is the thickness of the plates, ρ is the density of the molten metal.

Example 1

Consider welding the material with the parameters: ρ = 7800 kg / m ³ , d = 0.004 m, h = 0.0015 m, then M _p = p7800 · 0.004 · 0.0015 = 0.0468 rub. We take the value of p similarly to the process of modifying alloys with nanopowder materials equal to 0.0005. As a result, we obtain m _p = 0.0468 · 0.0005 = 2.34 · 10 ^-5 kg / m = 0.0234 g / m. Since during the welding process it is possible to burn out nanopowder material, the value of this value can be established experimentally.

Example 2

Experimental studies have been conducted of the effect of refractory mechanically activated nanopowder materials on the quality of welded joints formed when laser is exposed to a metal. Samples from alloys based on aluminum, titanium, and iron were processed on a continuous CO ₂ laser in a helium atmosphere. The speed of beam movement on the treated surface varied in the range of (2-4) m / min, and the radiation power ranged from 2 to 3.5 kW. Specially prepared nanopowder materials and their compositions in the form of a suspension were applied to the pre-processed surface of the plates in an amount of less than 0.1% by weight of the weld pool (melted metal) based on refractory compounds. As nanopowder materials, various powder compositions with TiN, Y ₂ O ₃ , TiC nanoparticles clad with the corresponding metal (chromium, nickel, titanium, etc.) were used.

Figure 1 shows, by way of example, photographs of thin sections of a welded joint of steel plates that do not contain nanopowder additives and are modified with nanopowder material TiC _x N _y + St3.

It can be seen that the use of a modifier made of nanopowder material changed both the morphology of the weld and the microstructure of the joint. The crystal sizes of Widmanstätt ferrite in a weld without a modifier reach 100 ÷ 150 μm in length, while in a weld with modified additives they do not exceed 30 ÷ 40 μm.

It should be noted that the deposition of nanopowder materials into the welding zone in the form of a suspension significantly increases the absorption coefficient of radiation energy, which makes it possible to increase the welding speed of a part by 1.5–2 times with the same radiation power.

Example 3

A series of studies was carried out on the effect of modifiers in the form of nanopowder materials on the quality of the welded joint of VT5 titanium alloy. As nanopowder materials, refractory compounds were used: titanium nitride (TiN), as well as their mixture of titanium nitride (TiN) with yttrium oxide (Y ₂ O ₃ ), plated with chromium. The concentration of the modifying composition introduced into the weld pool was less than 0.1% by weight. The prepared composition was applied in the form of a suspension on the surface of the welded plates, the thickness of which was 2 mm; the laser beam power is 2.0 kW, and the welding speed is 2 m / min. It was found that the use of modifiers allows to increase the welding speed at the same beam power by increasing the absorption coefficient of the laser radiation intensity. This increased the quality of the connection (morphology and structure of the seam), significantly increased its mechanical characteristics (tensile strength, yield strength) when using the first and second modifying additives (see figure 2).

The experiments showed a positive effect of modifiers in the form of nanopowder materials selected from among refractory compounds on the macro- and microstructure of the metal and its mechanical properties in the high-energy impact zone. The absorption coefficient increases significantly, which allows one and a half to two times to increase the processing speed, the zone of thermal influence has decreased, the dispersion of the crystal structure and the density of the weld have increased.

Information sources

1. Patent RU No. 2133662, V23K 26/00, 1998

2. Book: Lectures on welding dissimilar dissimilar metals. M .: MDNTP, 1973, p. 46-51 - prototype.

Claims (5)

1. A method of welding materials, including welding materials with high-energy radiation sources, such as laser, plasma or electron beam, by which prior to welding, a preliminary melting of the material to be welded is carried out, characterized in that the welding is carried out with the addition of modifiers in the form of nanopowder materials in the welding zone selected from among refractory compounds, for example nitrides, carbonitrides, oxides, while the concentration of nanopowder material is less than 0.1% by Asse weld pool. 2. The method of welding materials according to claim 1, characterized in that the welding of materials is carried out in a protective helium environment of both surfaces. 3. The method of welding materials according to claim 1, characterized in that the nanopowder materials are applied to the welding zone in the form of a suspension. 4. The method of welding materials according to one of claim 1, 2, 3, characterized in that the welding of homogeneous materials with or without inserts. 5. The method of welding materials according to one of claims 1, 2, 3, characterized in that they carry out the welding of dissimilar materials with or without inserts.

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