US2369805A - Wire drawing process and apparatus - Google Patents

Description

' Feb. zo, 1945.

W. O. SCHULTZ WIRE DRAWING PROCESS AND APPARATUS Filed Feb. 10, 1943 y I5 Sheets-Sheet 1 Byfwz We m ATTORNEYS Feb. 20,v 1945. w. o. SCHUL-rz WIRE DRAWING PROCESS AND APiARATUS Filed Feb. V1o, 194s s sheets-sheet 2 R i i i .i i

3 Sheets-Sheet 5 INVENTOR.

hg N @fm o@ M M .UWM WB Feb. 20, 1945. wl o, sc||u| 'rz WIRE DRAWING PROCESS AND APPARATUS Filed Feb. 10. 1943 vmami mi. zo, i945 UNITED STATES PATENT orifice WIRE DRAWING PROCESS AND APPARATUS William' 0. Schultz, Scarsdale, N. Y., asslgnor to Crucible Steel Company of America, New York, `N. Y., a corporation o! New Jersey 4 Application February 10, 1943Serlal No. 475,366

' l (ci. 205-16) l2 Clalms.

The invention relates to the art of wire drawing, and especially to the reduction'by drawing e .of hot rolled alloy steels which are so hardened by thermal treatment or mechanical working as to make them diilicult or impractical to draw by usual methods. The principles of the invention are also applicable to the reduction of such alloy steel bars to rod form by drawing operations instead of by hot rolling as heretofore, and wire or rod of special shapes other than circular may be produced. A

In reducing hot rolled steel rod down to drawn wire, the conventional practice has long been to cold-draw the rod and resulting wire in successive drafts to the gauge desired. An objection to this is that following only-relatively small re duction by each drawing step, the wiremust be subjected to a heat treatment in the nature of referred to, as to which the drawing operations have been difficult and impractical.

In a general way the invention aims to provide conditions of operation under which diiilcult-todraw alloy steel wire may be successfully drawn in actual practice in such a way as to largely eliminate the objections attendant upon the customary cold drawing practices of the prior art, en-

. abling the diiIlcult-to-draw alloy steels to be satisfactorily and reliably drawn into wire or rod hardening aigZrieve the strains sufficiently for the ensuing r wing step to be satisfactorily performed within the temperature range above mentioned. The sub-critical strain relieving treatment above referred to will be sufficient even in respect to the most diillcult-to-draw alloy steels such as tungsten or molybdenum high speed steels, martensitic stainless steels, bearing steels, or high carbon, high chromium die steels, and austenitic stainless steels such as 18-8 or 25-20, and likewise as to strain relieving heat treatment if required after the final drawing step, unless a grain structure is desired which requires final heat treatment at a higher temperature.y A. similar sub-critical strain relieving treatment will be used preliminary to the first drawing step, unless the stock has been previously subjected to a strain relieving or annealing heattreatment.

A number of important practical requirements are satisfied by drawing alloy steels of the above type within the temperature range above speci.- fied, after the preliminary strain relieving treatment. Within this range the metal is hot enough and which lower temperatures from thestand-f point of reduction obtainable in actual' practice and from the standpoint of avoidingy excessive form, at a cost many times less than heretofore,

and resulting inthe elimination of extra steps and the reduction of excessive strains in the metal such as have been attendant upon the cold drawing operations customarily used for steel wire.

I have discovered that the satisfactory drawing of elongated alloy steel stock of the above char- 'acter to secure the objectives of the'invention may be achieved by subjecting the stock between successive drawing steps, to a sub-critical strain relieving treatment, following which the stock is cooled or quenched to a temperature ranging strains in the metal, afford no advantages as com'- pared to cold drawing. As compared yto substantially higher drawing temperatures, ,the range above referred .to avoids the danger of vundue loss of diameter enabling the wire to be pulled through at higher speed and with greater reduction.

A drawing temperature within the range above Vspecified also enables effective lubrication to be securedv by a simple and inexpensive lubricant such as a graphitic lubricant consisting for example of by weight of graphite and 40% of finely divided clay as a binder. Such a lubricant may be applied by spraying an aqueous suspension thereof on the wire after the stock has been of thestock more than 20 or 30 degrees in passing.

to the drawing die, but at temperatures materially tubular retort of Fig. 3, and

2 l escasos higherthan the range above specified this type of lubrication becomes impractical, and the matter or providing proper lubrication becomes much more expensive and diilicult at higher temperatures.

For successful operation it is important that the temperature to which the stock is heated, both during heat treatment and for the drawing operation, be exceedingly constant as to all portions of the stock passing through, and it is important that accurate and quickly responsive regulation and control of the temperature conditions be provided. For these reasons I prefer to carry out the steps above referred to in successive heating apparatus having certain features of construction as hereinafter described in greater detail, the strain-relieving treatment being carried out preferably in a bath of molten lead or other suitablecomposition and the stock then passing to a second bath of molten babbitt or the like having a melting point of about 400 F. and acting as a quenching bath to quickly cool the metal fed to it at the hotter temperature of from 9501300 F. down to a temperature of between 500-700 F. at which latter temperature 25 the quenching bath is constantly maintained. The metal being drawn'is thus kept under nondecarburizing and non-oxidizing conditions while passing to the die, which together with the moderate temperatures required, avoids scaling and 30 pitting.

As examples of alloysteels dimcult to cold draw, but which may be easily drawn in accordance with the present invention, the following The invention is thus applicable in general to the hot drawing of alloy steels which are hardenable either thermally or by working, and which it has been difficult and impractical to reduce by the conventional cold drawing practice. 55

In the drawingsv Figs, la and 1b and lc show in side elevation an assemblage of apparatus for drawing iron or steel rod and wire in accordance with the invention, Fig. lb being an extension of la at X-X, and Fig. 1c an extension of Fig. 1b at YY,

Fig. 2 is a vertical section taken through a molten metal bath apparatus appropriate to be used in carrying out the heatingl treating and drawing operations of Figs. 1b and 1c.

Fig. 3 is a section on line 3-3 of Fig. 2 looking, in the direction of the arrows.

Fig. 4 is an enlarged detail section through the Fig. 5 is a similar section taken at right angles ltofthe section of Fig. 4.

"7. Fig. 6 is an enlarged side view partly in sec- '.tion of the drawing die and pulling mechanism.

Fig. 7 is a plan view of the drawing die and Fig, 8 is a section on line 3 3 of Fig. 6 look ing in the direction of the arrows.

Referring to the drawings, the rod or wire t to be drawn, is mounted in the form of a coil on reel 2 on an unwinding drum 3 which is freely rotatable on a spindle 4. The rod l is fed from the reel through a guide stand 5 consisting of an eyelet mounted on a support as shown. From the guide stand 5, the rod passes into the tubular retort or pipe-like container 3, which is filled with molten lead as indicated at l, Fig. 2, this container being provided with upwardly extending goosenecked ends at the entrance and amt, as indicated at 3 and 9, to prevent the lead from flowing out, the lead rising to about the level ld in the goosenecked portions as shown.

`The lead bath retort 8 is housed in a tubular furnace 122 consisting of a metal base 23a, Fig.

3, built up of angle members as shown, supporting a hearth or licor 24 and lateral walls 2d, 25 of refractory brick, the walls being surmounted by a semi-circular metal shell 2l lined with refractory brick 28. The retort 6 is supported at spaced intervals upon transversely extending bars welded thereto, which in turn extend into the side walls 25, 26. Also the upper portion of the retort 6 is slotted at intervals for reception of rounded bars 3| for submerging the rod or wire l beneath the level of the lead bath in its passing therethrough.

Extending longitudinally of the furnace and resting on the hearth 24 is a fuel pipe or gas header 32 provided with uniformly spaced upstanding nipples, such as 33a, provided with burner tips, as at 34, these burners being disposed beneath the retort 6 as shown.

For supplying the fuel mixture to the header or manifold 32, an injector valve 33 extends through the hearth and opens into the manifold. The injector valve 33 is fed from a source (not shown) over a. supply line 34a, in which is interposed a motorized valve 35 operated by a thermostatically controlled motor 36 for automatically regulating the burners in accordance with the temperature desired for the bath. This automatic regulation is effected by meansV including a thermo-couple pyrometer 31 mounted in a protective tube 33 extending through the roof of the furnace and welded onto the retort 5to pro vide an opening thereinto for exposing the thermo-couple pyrometer to the temperature of the lead bath. From the pyrometer 31, appropriate electrical connections 33a extend to a potentiometric indicating recorder 33, from whence in turn other appropriate electrical connections 40 extend to the motor 36 controlling the valve 35, in a well-known manner, for operating the valve in accordance with the temperature at which the lead bath is to be regulated.

For the purpose of accurately controlling the temperature of the rod or wire I, it is important that the thermo-responsive element 31 project in through the upper wall of the retort 3 into contact with the molten lead which is immediately in contact with the wire l, and it is important that the wire be held spaced from the upper wall of the retort, otherwise the temperature of different portions of the wire will not be uniform and the thermo element 3l will not respond accurately to temperature conditions in different parts of the wire.

The furnace 22 performs the subcritical strain-relieving step previously described, and the wire or rod thus heated to a temperature of 950-1300 F. then passes to a heating apparatus 4I (Fig. 1c) which may be understood as exactly similar to the apparatus 22 previously v described in connection with Figs. 2l to 5, except in heating apparatus 4|, and while the wire is passing from thence to the drawing die. As

`shown in Fig. lc, the lubricant may be applied to the wire in a lubricating chamber 42 having apertured guides 43 for the wire or rod, and as the latter passes throughvchamber 42 it receives a coating of the lubricant which is sprayed thereon as at 44, by nozzles 45 to which an aqueous mix of the lubricant is supplied under pressure by pipe lines 4B leading from a pump 41 connected to a reservoir 48 containing a supply of the lubricant. The lubricating chamber 42 may be shaped as shown so that excess lubricant will drain back to reservoir 48 through a return pipe 49. As previously stated the lubricant preferably consists .of a mixture of 60% graphite with 40% comminuted clay as a binder in aqueous suspension.

The stock need not be materiallyl cooled by spraying of the lubricant thereon as above described, and sufcient space is left between the chamber 42 and the drawing die hereinafter described, to afford time for the lubricant to dry on the surface of the stock before reaching the die.

The rod or wire then passes to the drawing die 54 'which is shown as mounted in a die-box 55 illled lwith Babbitt metal 56 which is maintained in molten condltionby means of a burner 51 fed from the injector valve 52 by means of a fuel feed pipe 58, a suitable control valve 59 being provided to regulatethe heat and thus keep the die 54 at substantially the same temperature as the rod or wire passing through it. This matter of heating the die to substantially the same temperatureas the wire passing through it, is irnportant to the success of the drawing operation. The die-box is shown as mounted in a holding frame 60, in'which it is clamped by a suitable screw 6 I As shown in Figs. 1c and 6. the wind-up drum 63 is provided with a series of hooks 64 which are axially slidable with respect to the'drum for the purpose lof receiving the overow of the wire being reeled up on the drum. Fastened to one end of a chain 65 having its opposite end secured to the drum, is a clamp E6 which grips the wire being fed through the die.

It should be understood that successive drawing operations, each involving a reduction of 2535% as above described, may be performed until the stock has been reduced lto the desired. diameter or other dimensions, the strainrelieving and quenching operations being carried out as above described preliminary to each successive drawing step. The process thus lends itself to the production of wire in successive and continuous drawing steps. Referenceris here made vtn my earlier copending application Serial No. v 457,154 filed Sept. 3, 1942, and also to my earlier 75 rst bath, thereby to produce a temperature beapplication Serial ber 21, 1941.

While the invention has been disclosed ascarried out by apparatus of the above described specinc construction, it should be understood that many changes may be made therein without departing from the invention in its broader aspects, within the scope of the appended claims.

4 I claim:

1. The method of treating elongated alloy steel stock of the diillcult-to-draw types which are hardenable thermally, or by mechanical working, which includes progressively passing the same through a bath heated to atemperature near the critical, thereafter progressively quenching said stock by passing same through a bath of lower temperature to reduce the temperature of the stock to -a value between about 50df700 F., and

' drawing said stock through a die substantially at said last mentioned temperature.

2. The method of treating elongated alloy steel stock of the dimcult-to-draw types which are hardenable thermally, or by mechanical working, which includes progressively subjecting the same to a strain relieving heat treatment, thereafter quenching said stock by passing same y through a, liquid heated to a temperature between about W-700 F., and thereafter progressivelydrawing said stock through a die while ,said stock is substantially at the temperature of said liquid.

3. The method of treating elongatedalloy steel stock of the dilcult-to-draw types which are hardenable thermally, or by mechanical Working, which includes passing the same through a bath prior to the application of lubricant thereto, regulating the temperature of said bath to maintain same between about 500700 F., applying lubricant to such stock after passing through said bath, and drawing the lubricated stock through 9, die at substantially the temperature of said bath.

4. The method of treating elongated alloy steel stock of the difiicult-to-draw types which are hardenable thermally, or by mechanical working, which includes subjecting the same to a strain-relieving heat treatment, thereafter passing said stock progressively through a fluid medium which is heated to a temperature ben tween about 500-700 F. to cool said stock subthrough a die while said stock is substantially atthe temperature of said fluid medium.

6. Apparatus of the class described for producing drawn elongated wire and like purposes, said apparatus including means for maintaining a liquid treating bath at a temperature near the critical point of said stock, a drawing die, means interposed between said rst mentioned bath and said die for maintaining a second uid medium at a temperature substantially lower than the Number 419,822. illed NovemVV tween about 500-'100 s'. in the stock passing through said second mentioned fluid medium. and means for drawing the stock successively through said bath, iluid medium, and said die.

7. Apparatus of the class described, for producing drawn elongated wire and like purposes, said apparatus including means for maintaining a liquid treating bath at a temperature near the critical point of said stock, a drawing die, means interposed between said first mentioned bath and said die for maintaining a second treating bath at a temperature substantially. lower than the first, to producefa temperature between about 500-'700 F. in the stock leaving said second mentioned bath, and means for drawing the stock successively through said baths and said die, means being interposed between said second mentioned bath and said die for applying lubricant to the stock before it passes fto thedie.

8. Apparatus of the class described for producing drawn elongated wire and like purposes,

.said apparatus including a chamber having means associated therewith for heatingthe stock to a temperature near its critical point, a drawing die, means interposed between said chamber and said die for quenching the stock to a temperature between about 50G-'700 F. and mechanism for drawing the stock successively through said chamber, said quenching means and said die.

9. The method of treating elongated alloy steel stock of the difficult-to-draw types.` which are hardenable thermally or by mechanical working, which includes progressively subjecting the stock to a heat treatment near the critical point of said stock, thereafter suddenly cooling the stock from a temperature near the critical to a temperature several hundred degrees F. lower but above about 500 F., said heat treating and cooling operations the stock to a heat treatment near the critical point ot said stock, thereafter suddenly cooling the stock from a temperature near the critical to a temperature several hundred degrees F. lower but above about 500 F., said heat treating and cooling operations being conducted without intervening drawing operations. and then progressively drawing the cooled stock through a die while said stock is still at a temperature above about 500 F., the aforesaid method ineluding the step of applying lubricant to said stock between the above mentioned heat treating and drawing operations.

11. Apparatus of the class described for producing drawn elongatedwire and like purposes, said apparatus including a chamber having means associated therewith for heating the stock toa temperature near its critical point, a drawing die, means interposed between said chamber and said die for suddenly cooling the stock from a temperature near the critical to a temperature several hundred degrees F. lower but above about 500 F. and mechanism for drawing the stock f successively through said chamber, said cooling being conducted without intervening drawing operations, and theny progressively drawing the cooled stock through a die while said stock is still at a temperature above about 500 F.

10. The method o1' treatingv elongated alloy steel stock of the dimcult-to-draw types, which are hardenable thermally or by mechanical working, which includes progressively subjecting means and said die, said apparatus being con structed and arranged to maintain said stock at a" temperature above about 500 F. when passing to said die.

12. Apparatus of the class described for producing drawn elongated wire and like purposes, said apparatus including a chamber having means associated therewith for heating the stock to a temperature near itscritical point, a drawing die, means interposed between said chamber and said die for suddenly cooling the stock from a temperature near the critical to a temperature several hundred degrees F. lower but above about 500 F., and mechanism for drawing the stock successively through said chamber, said cooling means and said die, said apparatus being constructed and arranged to maintain said stock at a temperature above about 500 F. when passing to said die and said apparatus including means interposed between said chamber and said die for applying lubricant to said stock.

WILLIAM O. SCHULTZ.

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