FR2759309A1 - METAL TUBES AND METHOD AND INSTALLATION FOR MAKING SAME - Google Patents

Abstract

This installation for manufacturing metal tubes comprises a reservoir (12), the bottom of which comprises an opening in which a mandrel (14) is engaged, an ingot mold (13) surrounding the mandrel, an electromagnetic stirring ring (15), a ring of cooling (16) and an extraction system (18).

Description

Metallic tubes and process and installation for manufacturing them

  present invention relates to metal tubes and their

  manufacturing processes and facilities.

  The traditional method of manufacturing seamless copper alloy tubes combines the hot spinning of blanks with the hot spinning of blanks

  hollow then cold drawing of these blanks followed by heat treatments.

  The eccentricity, that is to say the variation of the thickness measured at different points of a circumference of the tube, is large and commonly reaches%. 1o The invention overcomes this drawback by making it possible to obtain a batch of metal tubes in which, for all the tubes in the batch and at any point of a tube whatsoever, the ratio of the difference between the thickness of the wall of the tube at this point and the average thickness of the wall of the tubes at the average thickness of the wall of the tubes is less than 7% and commonly reaches

only 5%.

  This is achieved by a method of manufacturing metal tubes which consists of continuously or semi-continuously casting by gravity a blank.

  tubular, cold drawing the blank and cutting the drawn blank into a tube.

  By pouring a tubular blank, we obtain a surface state free of defects, a crystallographic structure not sensitive to decohesion and

  a very constant wall thickness.

  As metal tubes, use may be made in particular of copper alloy tubes. As copper alloy, there may be mentioned cupronickel with nickel content varying from 5 to 35%, cupro-tin with tin content

  varying from 5 to 9%, special alloys such as cupro-nickel silicon, cupro-

  beryllium and beryllium cupro-cobalt. The percentages are expressed by weight.

  The invention also relates to an installation for manufacturing metal tubes, characterized in that it comprises a) a tool for casting tubular blanks consisting of, - a liquid metal tank, the bottom of which has an opening in which is engaged a mandrel, - an ingot mold surrounding the part of the mandrel leaving the reservoir at a distance, so that the liquid metal leaving the reservoir solidifies in a transition zone between the mandrel and the ingot mold, - an electromagnetic stirring ring surrounding the ingot mold approximately at the level of the transition zone,

  - a cooling ring surrounding the ingot mold in-

  below the stirring ring, and - an extraction system intended to draw the blanks from

casting tools.

  s 5b) a set of cold drawing and heat treatment consisting of a shrinking machine, - a drawing bench, and

- an annealing oven.

  In the accompanying drawing, given solely by way of example: FIG. 1 illustrates a method of manufacturing tubes according to the invention, FIG. 2 is a sectional view of a casting tool for the installation according to the invention, and Figure 3 is a sectional view of the bench to stretch the installation of

  manufacture of metal tubes according to the invention.

  The process illustrated in FIG. 1 consists in melting, in a first stage, metal 1 in a tank 2. In a second stage, this metal 1 is poured into a casting machine 3 so as to obtain a tubular blank 4 under the shape of a hollow billet. In the next stage of the process, the hollow billet 4 is stretched in a drawing bench 5 so as to stretch the tube 6 when cold. The tube 6 can then be treated if desired in an oven 7 of

heat treatment.

  The installation according to the invention is shown in Figures 2 and 3. It consists of a casting tool, shown in Figure 2, and a

  set of cold drawing and heat treatment, shown in Figure 3.

  The casting tools consist of a liquid metal reservoir 12 called the holding furnace in which the liquid metal 11 previously melted and then put in the shade is

  maintained at a casting temperature.

  a graphite tube called an ingot mold 13 which is fitted into two superimposed elements: - electromagnetic stirring ring 15 enabling the temperature of the metal in the transition zone from liquid to solid to be controlled,

- cooling ring 16.

  A graphite core called a mandrel 14 which is engaged in the opening of the bottom of the reservoir 12. The liquid metal is gradually solidified between the ingot mold 13 and the mandrel 14 in the transition zone T. An extraction system 18 ensures the draft 17 draft through

Casting tools.

  An electronic assembly allows the adjustment of the draft parameters.

  The whole cold drawing and heat treatment consists, on the one hand, of a shrinking machine which allows a reduction of

  end of the blank, on the other hand, of a bench or drawing press.

  The blank 17 is mounted on an internal shape 21 called a ball or mandrel.

  The constricted end of the blank extended by an extension 23 or false-

  silk is introduced into a die 22, the protruding false silk 23 is hooked by a jaw system 24 on a carriage 25. The carriage 25 driven by a chain or a piston 26 pulls the blank between the die 22 and the

ball 21.

  An annealing furnace or cell allows annealing after the drawing operation

  recrystallization of the blank 17.

  The shrinking machine - cold drawing - annealing cycle is repeated from

  3o two to n times, depending on the dimensions to be achieved.

  Production example Casting - Cupro-nickel alloy Cuni10 FelMn produced in a medium frequency induction melting furnace with: Ni = 10.2% Fe = 1.6% Mn = 0.8% Impurities <0.10% Copper = rest

  s T C = 1400 C when tilting the oven into a pocket.

  - Metal cast at 1330 C in a furnace to maintain a vertical continuous casting machine: casting tools with outside diameter 258 mm with inside diameter 232 mm the drawing parameters are: * average speed 11 m / h * pulling movement go -stop (descent-stop) * descent = 3 seconds * stop 1.2s * instantaneous speed = 15.4 m / h the cooling parameters are: * water flow = 2.5 m3 / h * T inlet = 23 C * T outlet = 52 C At the brewing parameters * before filling the oven 20 KW * after and during casting 100 KW frequency = 2600 HZ The blanks obtained have a temperature at the outlet of the ingot mold of 990 C. Their length is 2200 mm. They are free from defects,

their ovalization is <0.5%.

  Drawing - Heat treatment - Cold drawing on a rough blank, with a first pass allowing a blank to be obtained outside diameter = 241.8 mm inside diameter = 224.5 mm length = 3020 mm annealing treatment at 780 C - 1 hour - Cold drawing of a last pass on an annealed blank to obtain a tube with an outside diameter = 218.7 mm inside diameter = 210.8 mm

  This is subjected to annealing at 780 C for 1 hour to give a tube of 6000 mm length after the two ends have been dropped.

  After the standardized checks (hydraulic pressure, surface appearance, etc.), the tubes are free from surface defects and the metal has the required mechanical characteristics. A welding test demonstrates the ability to weld the tubes. The thickness measurement (E) gives the following results

  Theoretical tube e mini e maxi% excen-

  (mm) (mm) (mm) tration i 4 4.06 4.25 4.6%

2 4 4.07 4.23 4%

3 4 4.04 4.23 4.8%

Claims (3)

  1. Lot of metal tubes, in particular of copper alloys, characterized in that, for all the tubes in the lot and at any point of a tube whatsoever, the ratio of the difference between the thickness of the wall of the tube in this point and the average thickness of the wall of the tubes at the average thickness   of the wall of the tubes is less than 7%.   2. Method for manufacturing metal tubes, in particular copper alloy, characterized in that it consists in casting continuously or semi-continuously   io by gravity a tubular blank, and cold drawing the blank.   3. Installation for manufacturing metal tubes, characterized in that it comprises a) a tool for casting tubular blanks consisting of - a tank (12) for liquid metal, the bottom of which comprises an opening in which a mandrel is engaged (14) - of an ingot mold (13) surrounding at a distance the part of the mandrel leaving the reservoir (12), so that liquid metal leaving the reservoir solidifies in a transition zone (T) between the mandrel (14) and the ingot mold (13) - of an electromagnetic stirring ring (15) surrounding the ingot mold (13) approximately at the level of the transition zone (T) - of a cooling ring (16) surrounding the ingot mold ( 13) below the stirring ring (15), and - an extraction system (18) intended to draw the blanks from the casting tool b) a set of cold drawing and processing thermal consisting of - a shrinking machine, - a stretching bench (21 to 26), and - a madman annealing.