DE2061560A1 - Small diameter double walled tubing - made from one sided solder coated strip - Google Patents

Abstract

Superimposed layers of rolled strip are soldered together on heating, only one side of the strip being coated with solder, this side being the one which on progressive rolling is destined to become the inner plane i.e. the planes which solder together. After rolling, the unsoldered tube is wound into coils, which are then heated to a temp. which is above the m.p. of the solder. Pref. Cu is used as solder. The process ensures that there is no dnger that the tubes are joinded together on heating and permits the making of long continuous lengths of tubing lending themselves to further continuous processing steps.

Description

"Process for the production of double-walled rolled tubes small Diameter "The invention relates to a method for manufacturing from with a Solder pad provided double-walled rolled and in its superimposed Layers of pipes of small diameter formed over the entire surface of soldered steel tape.

The basic principle of such a pipe production has been known for a long time and is referred to in the literature as the so-called "BUNDY" method (see e.g. B. "Dubbels-Taschenbuch riir den Maschinenbau" 12th edition 1963, page 537). That "BUNDY" method is for example in German patents 518 709, 620 371 and 751 170 and is used for pipe diameters up to about 15 mm.

In lines 34 to 41 of DPS 518 709 it is indicated that the pipe preformed to the steel strip directly in the connection. to the rolling process continuously is passed through a heating device, but in it at a temperature is heated, which brings the Lotrnittcl to melt. In practice, however, it has has shown that this process cannot be carried out economically.

If, for example, copper is used as solder on the steel strip, the heating device must be used a constant temperature of approx. 11000 C and a certain exposure time for this Temperature on da '; Rolled tape enable so besides the pure fusing The copper layers also cause diffusion of the copper into the outer steel layers take place can. At this temperature, however, the tensile strength or dimensional stability is the tubular core made of steel is greatly reduced, so that it is torn off or deformed of the tube to avoid only a relatively limited length of the tube in the heated State can be maintained.

The required exposure time also results in that continuous heating devices with optimal design only with speeds operated from about one fortieth of the rolling speed of the rolling devices can be (max. rolling speeds at approx. 140 m / min, max through the heating device 4 m / min).

This has led to the fact that the pipes are rolled into unsoldered tubes Steel strips ir lengths between 25 and 35 meters and cut the pipe strings Corresponding continuous heating devices in which several strands run in parallel transported to each other in guide tubes through annealing furnaces equipped with heating coils will.

If the pipes manufactured in this way are to undergo surface post-treatment (e.g. by electroplating), the strands for the Pass through an appropriate system together again - mostly acid-tight - get connected. For many consumers or processors, too, it would be desirable the pipes manufactured according to the "BUNDY" process in practically endless lengths to get delivered. For the production of so-called wire condensers, e.g. for refrigerators, the industry wants to use systems with which the production process from bending the tubes to applying the wire lay largely can be carried out fully automatically. Such systems can only be economical work when the continuity of the production process can be guaranteed. The basic requirement that has to be met is that the one to be used The tube is endless, e.g. in bundles.

This could be achieved, for example, through appropriate connection procedures will. All connection methods have the disadvantage that they are one in production Require great economic outlay and also the uniformity of the inner pipe or. Affect the outer diameter in any way.

The pipe cannot easily be bent at the connection points either will.

The object of the invention was now to find a method that with an economical production of double-walled rolled and full-surface soldered Rohr supplies practically endless lengths of pipe.

According to the invention, this object is achieved in that only one Side of the steel strip is provided with a solder coating, namely the one that the inside or the one to be soldered as the tape is gradually rolled transversely superimposed surfaces of the front tube that forms the rolled tape Formed pre-pipe after the rolling process in any length unsoldered to bundles is wound up and that these collars for soldering the front pipe to the pipe on a heated above the melting temperature of the solder.

Using the previous knowledge from the "BUNDY" pipe manufacturing process it is particularly advantageous to use a copper layer as a one-sided solder coating to be provided.

The heating of the front pipe collar can be done in a cycle furnace, whereby several bundles can be carried out at the same time.

The particular advantages of this method are that the the double-walled, rolled front pipe with a soldering pad on one side Immediately after the end of the rolling process, wound into coils can be.

The length of the pre-pipes or pipes coiled into bundles is practical only limited by the tape length of the starting material.

The one-sided and the inner side when the tape is rolled The result of solder overlay is that the outer surface of the tube is solder-free. That's why the pre-pipe, which is heated in the round, cannot stick to the outside.

The process is much more economical than the one previously used Procedure. The length of the separation process is saved. But this also does not apply a pipe waste piece of approx. 20 cm length, which results from the fact that the rolled pipe through the cutting device is squeezed when severing suddenly. At a roll speed of 140 m / min and a strand length of 30 n can be achieved with the method according to the invention by the elimination of the cutting processes on a single rolling machine pipe waste of approx. 112 meters per hour can be saved.

In addition, with the method according to the invention, a further, filr tlic improvement in the qual.nt of the pipe a decisive advantage can be achieved. When soldering the pipe strings, the disadvantages already described at the beginning is due to the relatively fast turnaround time through the continuous heating devices and the limited length of these devices an undesirable entanglement effect a. In the case of a cycle furnace, as can be used in connection with the invention, the annealing time can be extended so that a soft annealing of the tube coil is achieved will. This allows the technological values of a manufactured according to the invention Tube can be significantly improved compared to the manufacturing processes that have been customary up to now manufactured pipes. Measurements on pipes manufactured according to the invention have shown that e.g. the elongation at break can be increased by approximately 100 t (from 22 z to 40 83. The initial value of the steel strip is almost reached.

- patent claims -

Claims (3)

P A T E N T A N S P R Ü C H E 1. Method for producing from double-walled rolled with a solder layer and in its superimposed Layers of small tubes formed by heating the entire surface of the soldered steel band Diameter, characterized in that only one side of the steel strip with one Solder pad is provided, namely the one as the cross-scrolling progresses of the tape forms the inside or the surfaces lying on top of each other for soldering, that the Vorröhr formed from the rolled tape after the rolling process in any Length is wound into bundles unsoldered and that these bundles for soldering the Pre-pipe to the pipe to a temperature above the melting temperature of the soldering mole be heated. 2. The method according to claim 1, characterized in that the one-sided Solder pad e £ nt copper layer is. 3. The method according to claim 1, characterized in that the heating several bundles are carried out at the same time in a cycle oven.