SU1794615A1 - Rod for termite welding - Google Patents

Description

The invention relates to fusion welding of metals, namely to thermite welding, and can be used for welding, surfacing of metals in everyday life, when repairing equipment in the field, and performing emergency rescue operations.

In various emergency and domestic situations, easy-to-use portable and reliable tools for the repair of machinery and equipment are needed. The greatest difficulties during repair arise when welding or surfacing of metal is required. The welding equipment currently used is not compact, its transportation requires special equipment, powerful sources of electric energy are needed, and special training is required.

A known method and device for thermite welding, which consists in the use of rods made from a thermite mixture, molded around

1794615 A1 about th wire of deposited metal. B. Liquid glass or resinous products are used as a binder for the rods.

A disadvantage of the known device is the low quality of the resulting compound.

This drawback is due to the fact that when the organic binder is burned out, intense gas evolution occurs, leading to dispersion of the burning termite, increased heat loss, contamination of the weld metal with combustion products. · (

A welding consumable electrode is known, consisting of individual elements with ** conical side surfaces. Elements are pressed sequentially one into another.

Closest to the proposed is a rod containing welding rods, the ignition of which creates the temperature necessary for welding, and the material for the formation of the weld.

Welding rods are made from a stoichiometric mixture of aluminum and iron oxide powders, and may contain ferrosilicon, ferromanganese, titanium, and tungsten as additives, which are sintered into rods at a temperature of 650-700 ° C. TSS is ignited as follows: the igniter head is screwed to the termite shaft, the front part of the head is coated with an igniter composition, on which a composition sensitive to friction or a small flame is applied.

The disadvantages of this device are;

- poor quality of the welded joint

- high risk of operation of the device.

These drawbacks are due to the fact that at the initial moment of welding a limited amount of heat is generated, determined by the diameter of the rod and going to heat the material being welded, therefore, when TCC combustion products come into contact with a cold surface, they crystallize quickly, which prevents the formation of a high-quality compound. In addition, the weld metal is contaminated with sulfur, phosphorus, lead, and barium compounds contained in the igniter head, which leads to a decrease in the quality of the welded joint. Composition. Serving for the manufacture of TSS, has a low (19 cells) sensitivity when exposed to impact, and high (7 cells) sensitivity to friction defined in accordance with GOST No. 13803-80. When assembling a rod on a thread, the composition is subjected to significant friction forces , which can lead to its ignition. The composition of the ignition head includes compositions with a very high (5 and 3 class), sensitivity to shock and friction, which significantly increases the risk of operation of the TSS.

The aim of this invention is to ensure safe operation and quality of the welded joint with flexible regulation over a wide range of rod lengths.

This goal is achieved by the fact that in the well-known pyrotechnic welding rod for thermite welding of metals, consisting of a set of welding elements in it, the welding elements are made in the form of stepped rods conjugated by a protrusion and a recess made in the form of a truncated cone.

the taper angle in the range from 3 ° to 5 °, the ratio of the height of the cone to the diameter of the base in the range from 0.8 to 1.2, and the ratio of the diameter of the base of the cone to the diameter of the rod in the range from 0.7 to 0.8.

When TCC ignites, a reaction of reduction of iron oxide with aluminum occurs. The reaction proceeds with a significant release of heat. The combustion products (aluminum oxide and iron) are heated to a temperature of about 3100 ° C. When the combustion products heated to a high temperature interact with the material being welded, it is melted and a welded joint is formed. At the same time, the combustion products spreading warm up the material being welded, preparing it for welding. Therefore, the most unfavorable conditions will be at the moment when the combustion products come into contact with a cold surface. Ensuring the quality of the welded joint is due to an increase in the heat flux to the material being welded at the beginning of welding.

The heat flux is defined as o = a_b.

m = p · S · U where p is the composition density

S - burning surface area

U is the linear burning rate q is the calorific value of the composition m is the mass rate of combustion of the composition is F is the contact area with the material. The initial combustion surface in the form of a truncated cone led to an increase in area by 1.5–2 times and, as a result, an increase in the mass flow rate and heat flow. Then, the combustion front is aligned and the tonne decreases. The conditions for the formation of a high-quality joint are ensured by preheating the welding zone with the spreading TCC combustion products. The quality of the welded joint was also ensured because the ignition of TSS is carried out using an external heat source (for example, thermal matches), which eliminates the possibility of contamination of the weld metal with compounds of sulfur, phosphorus, lead, barium, etc. The negative influence of the latter on the quality of the metal is known. In the proposed device, the stepped shape of the rods serves not only to ensure the quality of the connection in the initial mbment. but also for connecting elements together. To ensure a reliable connection of the elements to each other, the angle between the generatrix of the cone and the base should be in the range from 3 to 5 °, since at angles of less than 3 and more than 5 degrees the self-braking effect ceases to occur, ensuring a reliable connection of the rods to each other.

An increase in the Η / D and D / d ratios (H is the height of the cone, D is the diameter of the base of the cone, is the diameter of the rod), as indicated above, leads to cracks on the walls of the rods and to a loss in the strength of the assembly of the rods. A decrease in the Η / D and D / d ratios leads to a loss of mechanical strength, while the combustion surface decreases, and hence the heat flux to the weld zone, which leads to a decrease in the quality of the resulting welded joint. In addition, a thinner section compared to the core allows the thermite composition to be heated faster to the ignition temperature, providing easy and reliable ignition of the TCC.

Ensuring safety during the operation of the TSS occurred because:

in the described device when assembling the rods, there is no igniter head. The class and degree of danger for manual operation of the igniter head, determined in accordance with the requirements of GOST 13803-80 and GOST 13802-79, are:

to friction - grade 3, very high; to impact - grade 5, very high: the termite composition used for the manufacture of rods has a high sensitivity to friction - grade 7. The connection of the rods to each other on the thread implies significant friction of the composition on the composition. In the proposed device, the risk is reduced due to the implementation of the stepped form of the rods and the mating of the protrusion and recess, which dramatically reduces the friction path compared to the threaded connection.

The invention is illustrated in FIG. ! where a general view of the rods is shown, and FIG. 2 view of a single element.

TSS is made of individual elements 1, which are a pyrotechnic mixture pressed in the form of a stepped rod without a shell. The rods are inserted into each other with little effort.

The choice of the angle between the generatrix of the cone and the axis of symmetry of the cone was made in accordance with the purpose of the invention. The choice of the angle in the range from 3 to 5 degrees from the point of view of ensuring safety is due to the fact that the selected range ensures reliable adhesion of the elements to each other with a minimum friction path.

The protrusion or recess of one of the ends of the rod serve to increase the mass flow rate of the composition at the initial time and provide reliable ignition of the rod. They are made in the form of a truncated cone, and the ratio of the height of the cone to the diameter of the base Η / D is 1, and the ratio of the diameter of the base to the diameter of the rod D / d is 0.75.

When TCC ignites at the initial moment, due to the shape of the end face, an increased consumption of combustion products is ensured, during the interaction of which with the material being welded, a welded joint is formed.

The proposed device is tested in experimental design work, tested for performance in laboratory bench conditions.

TSS were made for testing, in which the composition according to Switzerland patent No. 383126, class. 496.35 / 01, dated 08/18/60.

Pyrotechnic elements of 0 to 15 mm were made by the method of press pressing at a specific pressure of 300 MPa.

For welding, 2 mm plates made of steel of the grade St.Z with dimensions 100x160x2 were used. Butt welding was carried out without cutting and edge preparation. To assess the quality of welding, samples with dimensions of 25x160 mm were cut from welded plates. which were tested in tension on a tensile testing machine ЦД-10.

The results obtained in comparison with the prototype are shown in the table.

To limit the weld zone and create a weld pool, refractory non-heat-conducting chamotte brick walls were used.

Samples for testing were taken from the initial section of the welded joint.

During the experimental testing of the pyrotechnic welding rod, when using welding elements with an angle of less than three and more than five degrees, cases of welding elements falling out during welding were observed, which leads to a significant increase in the risk of welding due to the uncontrolled position of the burning elements: a decrease in the quality of the resulting welded joint due to due to intermittent seam and the inability to adjust the welding speed.

1794615 8

Claims (1)

Claim A rod for thermite welding, consisting of termite elements interconnected, characterized in that, in order to increase safety during operation, the quality of the welded joint while allowing the regulation of the length of the rod over a wide range, the welding elements are made in the form of rods with a protrusion at one end and a hollow on the other, and the surface of the protrusion and the depression are made in the form of truncated cones with an angle between the generatrix of the cone and its axis 3-5 °, the ratio of height to diameter of the base in the range of 0.8-1.2 and the ratio iem base diameter of the cone to the diameter of the rod · within 0.7-0.8. No. ι / π D / d H / d Weld failure pattern CD-10 Tension welded joint., Kgf UM-5 Bend tested rod moment., CM The degree and class of danger. manual work under friction GOST 13803-80 1 0.5 0.5 Weld failure 2100 9.0 7 cl. high 2 0.7 0.8 Along the border of the material with a seam 2870 15.0 7 cl. high 3 0.75 1 By material 3100 16,4 n 4 0.8 1.2 By material 3050 18.0 η 5* 0.9 1.6 Along the border of the material with a seam. 1900 8 6 ** For welding 1980 3 cl. very high 5 * · there is a burn through of the welded plates. 6 ** - prototype, smooth end. Figure 1