KR800001183Y1 - High temperature welding backup strip - Google Patents

Abstract

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Description

Rear Support Tape for High Temperature Welding

1 is a cross-sectional view showing two butted metal pieces welded, showing that a tape of one embodiment of the present invention spans a butt line.

2 is a cross-sectional view of another embodiment of the present invention.

3 is a cross-sectional view similar to the first diagram showing a metal plate to be welded as yet another embodiment of the present invention used in connection with a rear support rod.

The present invention relates to a novel backing support used for welding, and in particular, to a novel press-fit adhesive tape for use in backing up of a butted metal base when welding.

In making large tanks, ships, etc., steel plates are usually joined by welding their edges together. Although not absolutely necessary, it is highly desirable to perform welding by completely penetrating the bottom from the surface of the welding material. It is common to use metal backing rods for welding from one side of the butted iron plate, which is surface-treated with fiberglass or other refractory material to prevent inadvertent bonding of the backing rods to the weld. It is good to be.

In recent years, it has also been common to use heat resistant tapes such as glass fiber tapes alone or in combination with backing supports such as metal or ceramic plates.

Another very common welding backing support tape has a flexible support coated with an adhesive and a flexible refractory strip is attached to the center of the coating side of the support, the tape being welded directly adjacent to the joint surface. It is attached to the iron plate parts.

Rear support rods and flexible back support tapes have been used effectively but in some welding situations annoy welders.

For example, the parts to be joined have irregular edges, so that local overheating is likely to occur when the spacing is irregular or the current flowing in the arc welder fluctuates. In such cases, it is often the case that the refractory material is completely dissolved and the molten weld metal flows into it. If a rear support rod is used, the occurrence of the support rod itself can be welded to the joint, making it inconvenient and costly and time consuming to separate it. On the other hand, when a flexible back support tape is used, irregular welds are formed by burn through to the support, and the irregular welds must be removed after welding is completed, and this process is also very inconvenient and expensive. .

The welding state of the above-described form is particularly common when large steel plates or other parts are welded together, and can be seen in the construction of large storage tanks, ship equipment, and the like. Since such devices are very expensive and operate under severe conditions, it is important to weld them uniformly and structurally. However, prior to the present invention, no means for achieving this purpose have been proposed.

The present invention provides a very simple solution to the problem of obtaining a structurally robust and uniform weld when the welding temperature is locally very high.

The present invention utilizes a novel arrangement for back support of a butt line welded, to provide a conventional technique for supporting a refractory material in direct contact with the molten weld material with a back support member such as a flexible sheet or a rigid back support rod. It is an improvement.

According to the present invention, a carbon fabric is inserted between the refractory material and the rear support member to prevent the molten welding material from flowing. That is, part of the refractory material melts to block the pores of the carbon fabric and thus prevent the flow of molten weld material. Also, the molten weld material does not wet the carbon fabric and therefore does not pass easily past the carbon fabric.

Although the high temperature resistance of carbon fabrics is known, such fabrics have not been used in the welding process. Because welds occupy a relatively small portion of the workpiece, they tend to form martensite that quickly cools and is brittle. When using a carbon electrode in welding, the formation of martensite is promoted by the high carbon content, so that carbon enters the welding material and makes the weld vulnerable. Conventional attempts to use carbon blocks to support weld backs also have poor brittle results and have not been used continuously. In fact, a back support tape for welding which uses refractory particles in an organic adhesive for bonding to the weld surface generally includes a carbon trap to prevent the weld from breaking due to the presence of a small amount of organic material. It turns out that it is essential.

In a simple form, the present invention provides a support formed of a carbon fabric by coating a refractory layer such as glass fiber fabric, refractory particles, etc. on one surface to form a surface to which the weld metal contacts. For many purposes, a further layer of glass fiber fabric layer, crepe paper or metal foil support, or combinations of such components that impart additional strength in addition to the carbon fabric (to dissolve and prevent carbon fabric pores). It is believed that complex backing supports are preferred.

If a metal back support is used, good results have been obtained by attaching a carbon fabric to the support and overlaying a layer of glass fabric or other refractory material in direct contact with the weld surface. The refractory is replaced after every weld and the carbon fabric is reused for subsequent welding.

The present invention is described in more detail below with reference to the true drawing.

1 shows a relatively simple form of the present invention. The press-fit welding back support tape 10 comprises a backing 11 formed of carbon fabric. The term "carbon fabric" as used herein refers to a structure containing 55% to about 100% of carbon, which is usually formed by saturating with salts of nitrogen and then heating the polymerized rayon fabric. See 3,235,323 and 3,484,183.) On one side of the support 11, an adhesive layer 12 which is usually tacky and pressure-bonded is coated. Although it has been found advantageous to use silicone substrate adhesives that are resistant to very high temperatures, the specific properties of the adhesives are not particularly important. A narrow fire resistant layer 13 is arranged in the middle along the pressure bonding layer 12. The fire resistant layer 13 is a glass fiber fabric in the example shown in FIG. Tape 10 is shown attached in place along the butt line between workpieces 14 and 15 to be butt welded.

2 shows a more complicated form of tape made in accordance with the present invention. In this figure, the tape 20 comprises a support 21 in three separate layers laminated on each other, and the support 21 comprises a metal foil 22 having a generally sticky and press-coated coating material 23 attached to an upper surface thereof. A carbon fabric 24 is disposed in the center along the metal foil 22, and an adhesive layer 25 is attached to the upper surface of the fabric 24, and a glass fiber layer 26 is bonded to the adhesive layer 25. An adhesive layer 27 is coated on the upper surface of the glass fiber layer 26, and a fireproof layer 28 is bonded to the adhesive layer 27. In this example, the refractory layer 28 consists of refractory particles such as aluminum oxide, glass, or mixtures thereof mixed with a small amount of adhesive sufficient to hold the layer. The press-fit coating 23 is protected by a liner 29, which is removed before the tape is attached to the joint to be welded. Tape 20 is used in the same way as tape 10, and more reliably prevents "melting."

If the work is repeated, the welder may find it more convenient to use a rear support rod. 3 shows the means of using the present invention in such an application. The metal weld back support rod 31 has a channel 82 extending longitudinally in the central portion of the upper surface. A carbon fabric 35 is placed in the center above the rear support rod 31 (if there is channel 32) and the carbon fabric is bonded to the central portion of the rear support rod 31 by adhesive 36. A glass fiber fabric layer, a refractory layer of the type shown in FIG. 2, or a combination thereof may also be used, but in this example a refractory material 37 of aluminum oxide fibers is placed on the carbon fabric 35. The rear support rod 31 is firmly fixed to the butt line between the metal workpieces 33 and 34 to be welded. This arrangement allows welding while the molten weld is in contact with the base of the channel 32, preventing the work wool 33 and 34 from being accidentally welded to the rear support rod 31.

Preferred embodiments are described for easy understanding of the present invention. This embodiment is for illustration only and does not limit the present invention thereto.

Example 1

A viscose artificial silk fabric of plain weave of about 8.7 inclinations and 9.4 wefts per centimeter, about 0.6-0.7 mm thick and about 240 g / m2 in weight, was treated with an aqueous solution of nitride salts and dried. Heated to about 230 ° -275 ° C. for 12-15 minutes. The resulting fabric was tough, flexible, elastic, black, had a carbon content of about 55%, and tensile strengths of about 8 kg / cm and 4.5 kg / cm, respectively, in warp and weft directions.

As described in US Pat. No. 3,235,323, one side of the carbon fabric was coated with a polyvinylchloride suspension. Next, the opposite surface of the carbon fabric was coated with a tacky and pressure-sensitive silicone adhesive as described, for example, in US Pat. No. 3,372,852.

A pressure-sensitive adhesive formed from a mixture of styrenebutadiene rubber and isooctylacrylate: acrylic acid copolymer of 95.5: 4.5 was coated with a remarkable aluminum foil having a thickness of about 75 microns to form an aluminum foil support tape. Next, a 2.5 cm wide adhesive coated carbon fabric was placed along the middle of the aluminum foil about 5 cm wide with the adhesive side facing outward. Next, a glass fiber fabric tape was attached on the exposed adhesive coated surface of the carbon fabric. A pressure-sensitive adhesive is applied to the exposed outer surface of the fiberglass fabric tape. Next, an extruded refractory strip having a thickness of about 10 mm and a width of about 2.5 cm was attached to the exposed pressure-sensitive adhesive on the glass fiber fabric.

This refractory strip consisted of glass shavings of similar size to about 400 micron particles of dissolved aluminum oxide, bonded with a polyisobutylene adhesive (about 10% of the total strip weight) and contained ammonium nitride as carbon trapping agent. . Fire resistant layers of this type are described in detail in US Pat. No. 3,494,020. Until the backing tape is actually used, the removable liner strip is preferably attached over the exposed adhesive adhesive coating along the aluminum foil backing. When the liner strip is removed and the tape of this example is attached in place along the butted edge of the workpiece to be welded, no "melt" occurs even if the edge is extremely irregular or the welding current changes significantly.

While it is convenient to use adhesive, pressure-adhesive adhesives in preparing various layers of support material, thermoplastic or solvent-activated adhesives can likewise be used. In fact, it is entirely possible to combine composite support layers by suture or staple fastening along the edge to minimize manufacturing costs.

It is also possible to use thin asbestos plates instead of fiberglass fabrics. Similarly, paper formed alone or in combination with magnesite, gypsum, alumina-silica fibers or other refractory materials such as powder, asbestos, rock wool and the like can be used. Likewise, although slightly larger in volume, mats such as fiberglass or granite may be used.

In addition, instead of the glass fiber fabric used in the present invention, conventional abrasive structures in which silicon carbide particles having an effective diameter in the range of 100-500 microns are bonded to a suitable backing paper may be used.

Claims (1)

A layer of refractory material disposed on the line facing each other between two adjacent welded pieces is joined to one surface and is a narrow, long, flexible plate-like support held in place to support the welding material during welding, and rolls around the iron core. A back support tape for welding, which may be wound in a) form, wherein a carbon fiber fabric is attached to at least a portion of the support, such that the tape can withstand ultra-high welding temperatures without burn-through to the support. Rear support tape for welding, characterized in that.