US2351710A - Cold-drawing pipes and tubes - Google Patents

Description

June 20, 1.944. E N, SANDERS COLD-DRAWING PIPE AND TUBE Filed March 5, 1941 ing adjacent to the inlet side of the die.

Patented June 20, 1944 COLD-DRAWING PIPES AND TUBES Elmer N. Sanders, Mount Lebanon, Pa., assigner to National Tube Company, a corporation of New Jersey Application March 5, 19'41, Serial No. 381,902

(Cl. 205--8l 2 Claims.

. to a water-bearing mixture of flour and tallow by dipping bundles of the tubing in tanks containing such compound. After this, the tubing was either placed ondrying racks for sufficient time for most of thewater to evaporate, or the moisture was driven therefrom by running the tubing through a continuous drying oven. As is readily apparent, the first-mentioned drying method was very slow and the second quite expensive. In addition, the water in the compound caused an oxide to form on the pipe, necessitating pickling, and frequently resulted in localized corrosion or etch-pitting which seriously affected the quality and appearance of the tubing and caused excessive rejections.

The present invention comprises a method of cold-drawing which is calculated to overcome the foregoing difficulties in present-day methods, which include slow and expensive lubricant drying periods, rusting or corrosion `causing extra pickling operations, and etch-pitting causing poor surface Aand many rejections.

According to the teachings of the present invention, the hot-rolled tubing is pickled (placed in an acid bath to remove the scale) and after passing through a neutralizing and washing bath is taken directly to the draw-bench. Here the pickled and washed tubing is drawn through a die and over an interiorly disposed mandrel to reduce the outer diameter and/or wall thickness. An oil base non-water-bearing lubricant is directed onto the exterior and-interior of the tub-I The oil base non-water-bearing lubricant gives the tubing a rust preventative coating which prevents rusting should there be any appreciable delay before the tubing can be annealed.

After the drawing operation, the tubing is conventionally annealed (low temperature heat treatment which removes drawing strains and hardness). This is preferably done in an inert or reducing atmosphere to prevent scaling, and accordingly no pickling is necessary in this method except the initial pickling prior -to the first drawing. Ordinarily the hot-rolled tube must be drawn several times to attain the desired diameter and wall thickness, and according to the present method the annealed tube can be immediately redrawn in theforegong manner and CII annealed in sequence without intermediate pickling or other treatment until the desired dimensions are obtained. By materially reducing the time cycle for one drawing until the next drawing, there is obtained a great saving in the cost of the finished tube.

Referring to the accompanying drawing, there is illustrated therein a preferred form of apparatus which may be employed for practicing the method described hereinbefore.

More specifically:

Figure l is a side elevation of a part of the apparatus of the present invention;

Figure 2 is an enlarged fragmentary elevation, mostly in section, and illustrating those elements of the apparatus which are disposed nteriorly of the tubular workpiece.

Referring more particularly to the drawing, the numeral I generally designates a drawbench of a type widely used in the cold-drawing of metallic pipes and tubes` and adjacent one end of which there is disposed the usual drawing die 2.

According to the teachings of the present invention there is provided adjacent the drawing die 2, and on the entry side thereof, a spray ring 3 which receives lubricant under pressure in a manner which will be more fully described hereinafter and ejects the same around the periphvery of the workpiece.

Disposed within the pipe or tube to be colddrawn, which is designated hereinafter at X, is a hollow mandrel bar 4 carrying on its forward end a mandrel 5 having an enlarged .cylindrical head l for disposal immediately opposite the working surfaces of the drawing die 2. As shown at 8 in Figure 2, the forward end of the enlarged cylindrical head l of the mandrel is relieved 'or beveled.

The extreme forward end of the hollow mandrel bar 4 and the extreme rearward end of the mandrel 5 are of substantially the same diameter and are center bored and screw threaded as shown at II to accommodate between them a threaded stud I2 whereby the mandrel is rigidly secured to the hollow mandrel bar, thus permitting easy replacement of the mandrel with its enlarged cylindrical head l when such is desired.

The rearward end of the hollow mandrel bar 4 carries an integral collar I4 which by means of nuts I6 and Il is secured to the forward endv the central bore 27 and extend forwardly and4 convergently with respect to the mandrel 5 for the purpose of supplying lubricant to the exterior of the latter.

Due to the foregoing construction and arr-angement, the hollow mandrel bar il may be quickly replaced when necessary without disturbing the piping connection afforded by the iitting 2| and flexible tube 23.

Referring more particularly to Figure l, beneath the draw-bench I and the drawing die 2 there is disposed a sump '3G for the reception of lubricant stripped from the tube by the drawing die 2 and the hollow mandrel bar l5.. This sump 3l) has disposed thereabove a pair of sloping trough plates 3| and 32 which extend in both directions along the draw bench i, as shown at 33 and 34 respectively, to provide receiving surfaces for the lubricant; thus the lubricant is collected from both the front and back of the drawing die 2. A pressure pump 35 is connected with the sump 30 by means of a suction line 3l and has connected therewith a piping system 38 which delivers lubricant to the flexible hose 23 referred to hereinbefore and also the spray ring 3 which is disposed around the aperture of the drawing die 2. Disposed inlthe piping system 33 is a pressure relief valve l which permits eX- cess lubricant to return to the sump 30, whereby there is maintained a uniform pressure in the lubricating system. Control valves are provided as indicated at 44 and 45, to permit the separate regulation of supply of lubricant to both the flexible hose 23 and the cylindrical ring 5.

The operation of drawing a tube is as follows:

The valves 44 and 45 are closed or throttled down to permit only a small flow' of lubricant. The hollow mandrel bar d is pushed back axially about two feet to clear the drawing die 21, and the end of the mandrel 5 is moved either vertically or horizontally away from the pass line and a tube is threaded over the Amandrel and mandrel bar until the pointed or reduced end reaches the mandrel. Enough lubricant is admitted to the mandrel to assure its having flooded the inside of the tube past the mandrel, which is always somewhat smaller than the inside of the undrawn tube. The'tube and mandrel are then pushed back into the pass line and moved axially until the point extends through the die. The valves 41% and 635 are then opened and lubricant floods both the outside and inside surfaces of the tube near the die and mandrel. A plyer 5u grips the pointed end of the tube extending through the die and the tube is drawn through the die and over the mandrel.

It will be noted that as the tube is drawn down tight on the mandrel 5, no excess lubricant will pass the mandrel or through the die, during the drawing operation. Just before the tube is completely drawn, the valves Ml and d5 are closed, thus stopping or reducing the flow of lubricant until the next tube is ready for its passage through the die.

While I have shown and described certain specic embodiments of my invention, I do not intend to be specically limited thereto, since many departures may be made from the embodiments disclosed herein without departing from the spirit of the invention or the scope of the appended lclaims.

I claim: l. The method of producing cold-drawn tubing, which comprises providing a hot-rolled pickled tube which has been subjected to a neutralizing washing operation, then immediately after the washing operation transferring the tube directly to a draw-bench and there passing it through a die and over a mandrel disposed interiorly of said die and tube, applying a liquid non-water-bearing lubricant simultaneously to both the interior and the exterior surfaces of said tube as it is being drawn through said die and prior to their passage therethrough.

2. The method of producing cold-dravm tubv ing, which comprises providing a hot-rolled pick- ELMER N. SANDERS.

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