RU2243871C1 - Explosion welding method - Google Patents

Abstract

FIELD: mechanical engineering; welding.

SUBSTANCE: invention can be used for connecting two or several metal parts. Facing (throw) plate is installed with clearance over base plate and charge of explosive arranged over facing plate is initiated. Preliminarily surfaces of plates to be welded are machines to roughness R_z=8.0-12.0 mcm. Welding is done by pressure of detonation products. Time of action of said products. Time of action of said products exceeds time of cooling of surface layers of plates melted to depth exceeding 2 mcm.

EFFECT: provision of multilayer material featuring high processing and operating characteristic with any combination of metals and alloys.

2 tbl, 3 dwg

Description

The invention relates to the processing of metals by explosion and can be used to connect two or more metal surfaces.

The term "explosion welding" refers to the phenomenon of the connection of metal plates that occurred during their collision as a result of throwing detonation products of explosives. The first work on explosion welding was carried out in the USA and the USSR and belong to the period 1958-63, the first patent was obtained by J. Pearson in 1960 (US Pat. No. 3024526).

A number of technical solutions are known related to the field of explosion welding. The nomenclature of materials welded by explosion is large and amounts to several hundred combinations of various metals and alloys. In almost all technical solutions, the process of welding metals in the solid phase involves the sequential creation of a physical contact of two materials, in which, as a result of plastic deformation of the contacting surfaces, their joints may be strong, and the speed of the contact point should be less than the speed of sound in the plates being welded. The joining of metals is possible only when applying loads in excess of the yield strength of materials. The main elements of explosion welding, as a rule, are a fixed part; a throwing plate located at an angle or parallel to the part and at a certain distance H from it; explosive sheet charge with a thickness of HB; detonator: a rigid support on which the described device is mounted; a set of anti-unloading and anti-school devices that ensure the safety of welded parts when exposed to an explosion. Explosion welding can be carried out either with direct contact of the explosive with a missile plate, or through a buffer gasket, which protects the surface of the plate from the direct action of the explosion products.

A technical solution is known according to the patent of the Russian Federation No. 2024374, IPC 5 V 23 K 20/08 “Method of explosion welding of amorphous metal foils”, which consists in installing with a gap above the clad foil part with placing a damping pad, auxiliary plate, explosive charge above it, its initiation and throwing foil by explosion products pressure. Current leads are connected to the foil, heated by a current pulse with a heating rate of more than 10 ° C, and charge is blown after the foil temperature exceeds the glass transition temperature of the alloy.

Known technical solution for A.S. No. 1503185, IPC 4 V 23 K 20/08 “Explosion welding method”, according to which, to improve the quality of the welded joint, the initial clearance between the plates being welded is set by applying a pulsed magnetic field (IMP) to the plate being thrown. The force impact of the UHF raises the missile plate by the desired value, and then the initiation of the explosive charge follows. and the raised plate is thrown on a motionless one. Explosion welding occurs. In this case, an additional heating of the missile plate by eddy currents occurs.

A technical solution is known according to the patent of the Russian Federation No. 2056987 IPC 6, 23 K 20/08 “Method of welding metals by explosion”, which consists in placing an explosive charge on the surface of the welded part, which, when undermined, provides an oblique collision of the welded part with the surface of the stationary part. The gap between the parts is determined by the ratio Δ≤2h · V / D, where h is the thickness of the welded part; D is the speed of the shock wave in this part: V is the metal speed of the welded part behind the front of the shock wave, and the number of explosives is taken based on the constancy of D and V at a thickness h.

A technical solution is known for US patent No. 3137937, which consists in the mutual arrangement of the welded plates on top of each other with a gap of 0.5 ÷ 15 mm, placement of the explosive charge on the upper plate, installation of the entire structure on a rigid base, initiation of the explosive charge and subsequent machining of the lack of penetration zones.

This description of the explosion welding process, as the closest in technical essence and the achieved result, is selected as a prototype.

Signs of a prototype common with the claimed method;

- installation of welded parts (plates) on a rigid support;

- placement of the welded parts (plates) with a gap between them;

- placement of explosive charge above the upper part (plate);

- initiation of explosive charge.

The specified prototype has the following disadvantages:

- high consumption of explosives (determined by the thickness of the missile plate):

- the presence of significant plastic deformations of the metal and, as a result, the presence of additional operations in the technological process - the installation of protective devices, or the manufacture of blanks with allowances for deformation with subsequent mechanical processing of the finished product;

- the presence of a lack of penetration zone (start of welding) and, as a result, the presence of additional operations in the technological process — installation of an insert made of metal or an additional charge. It should be noted that there is practically no reliable way to completely eliminate lack of fusion at the initiation point:

- the limitation of the field of application of explosion welding is the hardness of materials, in particular, to date, it has not been possible to obtain strong joints of high hard steels;

- the limitation of the scope of explosive compositions that ensure the speed of the contact point of the surfaces is less than the speed of sound in the materials being welded.

The technical result to which the claimed invention is directed is to obtain, by explosion welding, bimetallic and multilayer materials with high technical and operational characteristics with any combination of metals and alloys.

In contrast to the known method (US Pat. 3137937, MKI ³ V 23 k 29/00), which consists in the mutual arrangement of the welded plates on top of each other with a gap of 0.5-15 mm, placement on the top plate, the explosive charge, the installation of the entire structure on a rigid the base, initiating the explosive charge and subsequent machining of the lack of penetration zones, in the proposed method, the surfaces of the welded plates are pre-machined to roughnesses Rz = 8.0-12.0, welding is carried out by the pressure of the detonation products, while in the gap between the connected plates an air wave is created, the energy of which preheats and melts the surface layer of the welded plates. The duration of the detonation products exceeds the cooling time of the molten surfaces. The process is carried out at a penetration depth of welded surfaces of more than 3 microns.

Analogues with signs similar to the claimed solution was not found, therefore, we can assume that the claimed method is new and has a sufficient inventive step.

The proposed method due to the preliminary development of the welded surfaces to a roughness of R _Z = 8.0 ÷ 12.0 allows for preheating and melting of the surface layers of the welded plates, which in turn affects the reduction of the gap and the height of the explosive charge, thereby reducing the collision velocity surfaces to be welded and the effect of an explosion, which leads to a decrease in the consumption of explosives, a decrease in plastic deformations while expanding the scope of the proposed method of explosion welding. Using the proposed method allows welding at a surface contact speed exceeding the speed of sound in the materials being welded.

The essence of the proposed solution is illustrated in the drawing, where Fig. 1a shows a device that implements the inventive method of welding by explosion of plates by a heat flow of shock-compressed air.

Figure 2 shows a diagram of the heat flux q from shock-compressed air in the gap from the gap H / R _Z between the plates to be welded for different explosive detonation velocities.

Figure 3 shows a diagram of the penetration depth of surface roughness versus time t of the action of an airborne hydrocarbon.

The proposed method is implemented as follows. Preliminary, the welded surfaces of the plates 1 and 2 are worked out to a roughness of Rz = 8.0 ÷ 12.0, then the welded plates 1 and 2 are mounted on a steel support 3 to ensure the safety of the finished product. Between the plates set the gap H (figa), necessary to create conditions for the occurrence of an air shock wave. The charge BB 4 is installed on the horizontal surface of the missile plate 2. The thickness of the charge HBB is selected from the conditions for providing a pressure action time sufficient to cool the molten layers.

The basic principles of the proposed method of explosion welding are as follows (see figb): the shock wave 5 generated by throwing the plate 2, separated by a gap from the plate 1, forms a high-temperature flow of shock-compressed air in the gap, which leads to heating of the surface layer of the plates to the melting temperature, providing subsequent contact welding of the plates between themselves. For high-quality welding, it is necessary to create conditions for the contact of the plate melts, followed by cooling to a temperature below the melting temperature until rarefaction waves arrive. The heat flux coming from gas to metal is determined by the equation:

S_t, M - числа Стантона и Маха; Т. Ср, ρ - температура, теплоемкость и плотность воздуха соответственно; Тс - температура металла; γ - показатель адиабаты воздуха; U - массовая скорость воздуха; σ - постоянная Стефана-Больцмана.Where

S _t , M are the numbers of Stanton and Mach; T. Ср, ρ - temperature, heat capacity and air density, respectively; Tc - metal temperature; γ is the adiabatic index of air; U is the mass velocity of air; σ is the Stefan-Boltzmann constant.

If a turbulent mode of movement is realized in the gap, then the Stanton number will be equal to:

where H is the gap between the plates, R _Z is the height of the profile irregularities (roughness). The level of heat fluxes coming from the plasma into the metal depends on the detonation velocity. Rz and the gap values are in the range 1.3 · 10 ⁹ to 3.1 · 10 ¹⁰ J / m ² s (see figure 2).

By the magnitude of the flow, one can estimate the temperature and the depth of heating of the metals being welded. The heating depth h of the metal will generally depend on the detonation velocity and the duration of the air shock wave (see figure 3).

For high-quality welding, it is necessary that the thickness of the melt zone exceeds 2–3 μm, and the roughness size in this case lies in the range: 8.0 <R _Z > 12.0 μm.

The ability to achieve the desired technical result when using the claimed invention is confirmed by experiments:

Experiment 1. Base - steel 110G13L. hardness 500 units HB.

Weld-in plate - 50HFA steel, hardness 350 units. HB.

Weld plate thickness, mm Classic way (prototype) The inventive method The mass of explosives, kg per 1 m ² The area of lack of penetration, mm The mass of explosives, kg per 1 m ² The area of lack of penetration, mm 2 twenty 40 fifteen <5 3 thirty fifty 17 <5 4 40 no welding 19 <5

Experiment 2. Base - sheet steel 10.

Weld-in plates - stainless steel, copper, aluminum, titanium.

Weld Plate Material Weld plate thickness The mass of explosives, kg per 1 m ² The area of lack of penetration, mm Peel strength, MPa The strength of the clad metal, MPa Steel 12X18H10T 2 fifteen <5 500 550 Copper Ml 2 fifteen <5 90 220 Aluminum AMG-16 2 fifteen <5 100 110 Titanium VT 1-1 2 fifteen <5 250 450

Experiment 3. The manufacture of bearings for bearings:

Bimetal: St08KP - alloy AO-20. The thickness of the main material (St08KP) is 6 mm, the thickness of the antifriction coating (AO-20 alloy) is 1.5 mm. Explosive consumption: 6 kg / m ² . The quality of welding corresponds to TU 48-21-840-89.

Explosion welding in examples 1-3 was carried out by an explosive with a detonation velocity lower than the speed of sound in the welded metals.

Experiment 4. Explosion welding in supersonic mode:

Base - steel 3, thickness 10 mm.

The welded plate is steel 12X18H10T, thickness 0.2 mm.

VV - EG-85 with a thickness of 4.5 mm, detonation velocity of 7.8 km / s.

A strong connection is obtained over the entire surface.

The main advantage of the invention is to reduce the level of stress required to accelerate the plate being thrown (there is no need to provide a high impact speed necessary to exceed the yield strength of the material) while improving the quality of the parts being manufactured, due to the reduction or complete absence of deformation of the plates being welded and the reduction or exclusion of zones lack of penetration.

Claims (1)

Explosion welding method, based on the installation with a gap of the projectile plate over the fixed plate and the initiation of an explosive charge located above the projectile plate, characterized in that the surfaces of the welded plates are pre-treated to a roughness of Rz = 8.0 ÷ 12.0 μm, and welding is carried out pressure of detonation products, the duration of which exceeds the cooling time of the surface layers of the plates melted to a depth of more than 2 microns.

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