DE2020984B2 - Joining lengths of steel piping - Google Patents

Abstract

Steel pipes made from steel strips coppered on both sides, rolled double and soldered over their whole opposed faces are axially joined by forming in each pipe end a press seating without increasing the external diam. A bush of coppered pipe is fitted into one pipe end so that it projects a predetermined amt. The other pipe end is then fitted over the projecting portion of the sleeve until the pipe ends are pressed together, and they are then soldered by heating above the melting point of copper in a protective gas.

Description

The invention relates to a method for endless axial connection from double-sided copper-plated, double-walled rolled and in its superimposed Layers of steel pipes made of brazed steel strip over the entire surface.

Such pipes, also called bundy pipes, are preferably used in the Refrigeration, e.g. B. as coolant lines, and in the automotive industry, e.g.

used as brake and fuel lines. You stand out in particular characterized by excellent bending properties.

These pipes can only be produced economically as a strand, that is in limited lengths. This is due to the manufacturing process. The rolling machines, on which the double-sided copper-plated steel strip rolled continuously to form a pipe can now be driven at speeds that depend on the pipe diameter are over 100 meters / minute. On the other hand, soldering the one on top of the other Layers in continuous ovens only with throughput speeds of around 3 meters / minute take place.

For the production of so-called wire liquefiers, e.g. B. for refrigerators, For reasons of cost, the industry wants to use systems with which the production process from bending the tubes to applying the wire layers largely fully automatically can be carried out. Such systems can only work economically, however, if the continuity of the production process can be guaranteed. The basic requirement which is to be met is that the tube to be used is endless, for. B.

in roles.

-It's been running since lap, g # e, r, time. Try to butt the pipe pieces to sneeze together. However, one of the important "t'e'n ~ assumptions; e'tz ,, ungen, which is to be observed in the manufacture of liquefiers, namely the flawless one Internal cleanliness of the pipe, not to be met. It is the same with brazing. This requires flux, which flows into the inside of the pipe during the soldering process and pollute this.

Attempts with retracted pipe ends also failed because on the one hand in the pipe outer wall notches at the drawn-in points do not appear can be avoided and because on the other hand the outer diameter does not cover the entire Pipe length is the same. This leads to the fact that individual wires or entire layers do not connect to the pipe jacket.

In addition, by pulling in the pipe ends, there is a strong reduction in cross-section ~ and thus a drop in performance of the condenser - inevitable.

Part of the procedures described above is in the »Manual the Löttec "hnik" from Dr.-Ing.

E. Lüder, Verlag Technik Berlin, 1952, shown on pages 185 and 186 and described.

The object of the invention is to find a method in which for the pipes to be connected are guaranteed to be perfectly clean can, in which the pipe outer wall remains unchanged in diameter and in which the inner cross-section is only slightly reduced or not at all.

According to the invention, this object is achieved in that by calibration on the inner surfaces of the pipe ends without enlarging the outer diameter knife of the pipes a press fit is formed that in the press fit of a pipe end from a solder socket copper-plated pipe is pressed in so far that it is a certain amount axially over the end of the pipe protrudes from the fact that the other was calibrated via this protruding solder socket The end of the pipe is pressed on until the machined pipe end surfaces lie against one another under pressure and that under protective gas at a temperature above the melting temperature of the copper is soldered.

This connection method has decisive advantages. First can keep the previous production process of double-walled rolled steel pipes will hold. This is valuable from an economic point of view. Furthermore all properties of this pipe remain, in particular the good flexibility and Gas tightness, fully preserved. The endless pipe is the same in all places Outside diameter and is practically seamlessly connected by appropriate selection of the calibration dimension (expansion of the inside diameter) and the dimensions of the soldering socket, the change in the internal cross-section of the connected pipe string very low, ideally even zero.

In addition, this method is very easy to perform and at the same time extremely economical.

This is because no additional solder is required. The solder joint is caused exclusively by the copper layers on the pipe and on the soldering socket. This is very important for a clean and flawless solder joint and a clean one Maintain inner surface in the pipe.

In the drawing, in one embodiment, there is one according to the method According to the invention produced connection of the pipe ends shown. On the basis of this The drawing is intended to describe the process in more detail below.

It should be noted that the drawing is the actual Cannot reproduce dimensional proportions for technical reasons in the drawing. she should serve only for clarification.

The #first process step in the process according to the invention is the calibration of the inner surfaces of two pipe ends 1 and 2 of double-walled 'rolled Steel pipes on a press fit 3 or 4. There is a stretching at the pipe ends of the material, the inner diameter depending on the requirements enlarged, but the outside diameter remains unchanged.

A soldering socket 5, most expediently one that is copper-plated on all sides, is then placed on it Steel pipe (possibly a double-walled rolled pipe) into one end of the pipe pressed in and the other end of the pipe under pressure over the soldering socket and with his Flat surface 6 out against the flat surface 7 of the first pipe end. Takes place under pressure Then the soldering under protective gas in an oven, taking to a temperature that is above the melting temperature of the copper, must be heated.

The copper layers come on the pipe ends and 'on the soldering socket flow and cause a uniform soldering also on the flat surfaces 6 and 7, because the doughy copper due to the pressing effect (press fit between the soldering socket and Pipe ends and the pressurized flat surfaces) in a capillary-like manner Effect reaches these places.

The connection point can depending on the requirements the Practice trained. The calibration can result in a strong increase in the inside diameter take place. Then the soldering socket can be relatively thick-walled. But it can only a small calibration can be made. Then it is to downsizing the To keep the cross-sectional area small, a thin-walled solder socket is required.

Claims (1)

Patent claim: Process for the endless axial connection of double-sided copper-plated, double-walled rolled and soldered over the entire surface in its superimposed layers Steel pipes made of steel band using a soldering socket, characterized in that that by calibrating the inner surfaces of the pipe ends without increasing the outer diameter A press fit is formed of the pipes that a soldering bushing is formed in the press fit of one pipe end is pressed so far from a copper-plated pipe that it is a certain amount axially over the pipe end protrudes that over this protruding solder socket the other calibrated pipe end is pressed on until the machined pipe end surfaces are below Pressure against each other and that under protective gas at a temperature above the melting temperature of the copper is soldered.