US3055104A - Method of preparing steel blanks for drawing - Google Patents

Description

Sept. 25, 1962 G. A. LYON 3,055,104

METHOD OF PREPARING STEEL BLANKS FOR DRAWING Filed NOV. 7, 1955 2 Sheets-Sheet 1 Ell E I2 T George A/berz Lyozb b E7 444 4 4... 713W, *w 111 75 G. A. LYON Sept. 25, 1962 METHOD OF PREPARING STEEL BLANKS FOR DRAWING 2 Sheets-Sheet 2 Filed Nov. 7, 1955 v )NVENTOR. Geozye A/berz Lyol? 3,055,104 METHOD OF PREPARING STEEL BLANKS FOR DRAWING George Albert Lyon, Detroit, Mich., assignor to Lyon Incorporated, Detroit, Mich., a corporation of Dela ware Filed Nov. 7, 1955, Ser. No. 545,204 4 Claims. (Cl. 29-552.3)

The present invention relates to an improved method of preparing steel blanks especially suitable for drawing, such as for drawing into shell form, and is especially suitable for preparing such blanks for the manufacture of large size shells such as may be used as ordnance shells in bombs and the like, drawn steel tanks, etc.

Mass production of large size steel shells presents the serious problem of procurement of an adequate supply of steel blanks for the purpose. Where the blanks require large mases of material as, for example, in trimmed sizes of thirty or more inches in diameter and up to 1% in thickness, obtaining of such blanks from rolled steel plate or strip requires a very large investment in rolling mill equipment of a specialized character. Should such special rolling mill equipment break down or be destroyed during a period of hostilities, thus cutting oif the supply of plate or strip for the drawing blanks, production of drawn shells would also be halted.

Another disadvantage of using rolled blanks is that there is a high percentage of waste, running as high as 40% scrap. This results from the necessity of cutting the blanks round from square plate. Often imperfections are rolled into the plate and have a detrimental effeet in the drawn article. In addition, considerable work must be put on the blanks in order to crop them clean before drawing, not to mention the cost of cutting the blanks from the strip or plate. Moreover, if it is necessary to ship square blanks from the mill to the pressing plant, shipment of a large amount of scrap may be involved. If square blanks are first forged into round blanks by working the square perimeter into a round perimeter a time consuming and expensive step in preparation of the blanks is involved.

A further disadvantage of using rolled strip or plate for this purpose resides in that at least certain grades of steel that may be desirable for drawing show disadvanageous graining in the direction of rolling so that there may be a tendency to draw irregularly unless substantial heat treatment and grain refinement are resorted to before subjecting the blanks to cupping and drawing. In experiments with blanks derived from rolled plate, cracking at the radius of the cups has been found although careful heating of the blanks was resorted to.

According to the present invention, round blanks for drawing steel shells are prepared directly from sections of steel ingot, without rolling, but in a manner to prepare the blanks for immediate cupping and drawing.

An important object of the present invention is to provide a new and improved method of preparing steel blanks for drawing of shells, according to which the blanks are derived directly from steel ingots at low cost, with a minimum of waste or scrap, and with a grain structure that is especially suitable for uniform results in cupping and drawing.

Another object of the invention is to provide an improved method of preparing round blanks for drawing steel articles such'as shells, wherein the blanks are derived directly from pieces of steel ingot but free from surface impurities or imperfections or scale that might interfere with proper drawing of the articles.

A further object of the invention is to provide improved round steel blanks of improved structure for drawing of articles such as shells.

' aired States Patent G ar C Other objects, features and advantages of the present invention will be readily apparent from the following detailed description of a preferred embodiment thereof taken in conjunction with the accompanying drawings n which:

FIGURE 1 is a fragmental more or less schematic view of a steel ingot from which sections are to be derived for producing flattened round blanks for drawing into articles such as of shell form;

FIGURE 2 is a fragmentary, more or less schematic vertical diametrical sectional view through flattening die means for pressing the ingot pieces into flattened round blanks;

FIGURE 3 is a top plan view of the lowermost of the die members and an ingot piece thereon taken substantially in the plane of line III-III of FIGURE 2;

FIGURE 4 is a diametrical sectional view similar to FIGURE 2 but showing the die members and the ingot piece in an intermediate blank pressing position;

FIGURE 5 is a view similar to FIGURE 4 but showing the die members and the blank in a further stage in the pressing of the ingot piece into a blank;

FIGURE 6 is a diametrical sectional view through a round blank after pressing of the ingot into flattened blank form has been completed;

FIGURE 7 is a diametrical vertical sectional view through a cup that has been prepared from a pressed blank as shown in FIGURE 6;

FIGURE 8 is a one-hundred magnification photomicrograph of a steel ingot piece before pressing; and

FIGURE 9 is a one-hundred magnification photornicrograph of the same ingot after pressing into a flattened blank ready for cupping and drawing.

In practicing the method of the present invention, standard steel ingots such as an ingot 10 shown in FIGURE 1 may be used. Such an ingot is of substantial length and diameter and is generally tapered. It may be circular in periphery or fluted. The virgin cast steel ingot 10 may comprise any suitable heat treating steel that lends itself to hot or cold work, as the case may be, and is adaptable for the heat treatment that will meet the specification requirements in the finished article. In composition the steel may range from SAE 1010 to 1050, for example.

As the first step in the present method, the ingot 10 is divided into a plurality of sections or pieces 11 of equal mass calculated to afford a flattened round disk blank of predetermined thickness and diameter. This means, of course, that as the ingot 10 is divided the length of the pieces 11 must be increased gradually from the larger diameter end of the ingot to the smaller diameter end to compensate for the diminishing diameter as the taper of the ingot progresses. For example a comparison may be made between the upper end piece or section 11 and the section or piece below the horizontal line L at the opposite smaller diameter end of the ingot in FIGURE 1.

Separation of each piece or section 11 of the ingot may be effected by sawing or by means of a suitable cutting tool in a lathe type of machine to provide a severance gap 12 of as economically narrow width as practicable, running all the way through the ingot, or to a narrow neck 13. Where separation to a narrow neck between the several sections of the ingot is resorted to, the entire ingot may be thus subdivided and then the several sections separated by fracturing the necks 13 between the sections of the ingot, as by driving a wedge or other suitable tool between adjacent sections.

Since it is highly important that a blank to be drawn into shell form he as free as possible of surface imperfections or impurities such as pits, blow holes, cracks, wrinkles, slag particles, scale, or the like, it is highly desirable to clean up the surfaces of the ingot sections 11- and remove the usual very rough and dirty original ingot surface indicated at 14. By preference this is accomplished contemporaneously with forming the severance slots or gaps 12. That is, where the ingot 10 is turned incident to forming the transverse severance slots 12, the outer circular peripheral surface may be turned down to provide a smooth clean surface or skin 15 on the piece or section 11. The original extremities of the ingot are, of course, also turned down or trimmed off or scalped so that the entire piece or section 11 including its circular periphery and its end faces are clean and free from scale or other impurities, pits, cracks, blow holes, and the like. Such severance and cleaning of the ingot pieces may be done at room temperature.

In order to effect a smooth transition from the outer circular periphery of the ingot piece 11 t the end faces thereof, the juncture corners are preferably chamfered orrounded or radiused as indicated at 17.

If the surface-clean ingot pieces 11 are to be stored for any length of time they should immediately after the separating and scalping thereof be coated with a material to prevent oxidation and corrosion.

Where the ingot pieces 11 are to be immediately pressed, following surface cleaning and separation, they are heated to a good plasticizing temperature such as from 2000 F. to 2300 F. in a non-oxidizing gas atmosphere by induction heating, or in a reducing furnace, or in a salt bath, or in some other suitable manner whereby freedom of oxidation or corrosion can be assured during the heating. Of course, where the ingot piece is heated in a fused salt bath the salt coating thereon when it is removed from the bath provides a superficial protective layer thereon against oxidation. The salt also provides a lubricant during subsequent pressing.

The heated ingot piece 11 is then placed between upper and lower pressing die members 18 and 19 respectively which provide pressing surface areas of a diameter at least equal to the diameter of the ultimate flattened disk blank to be provided. To assist in centering and for maintaining uniform radial distribution of the material of the ingot piece as it is being flattened between the die members, the pressure surface of at least one of the members is preferably shaped slightly concave. As shown, the lower pressing die member 19 is provided with a slightly concave pressing surface 20.

Where the composition of the steel in the ingot piece 11 will permit, continuous pressure may be exerted between the pressing members 18 and 19 against the opposite ends of the ingot piece 11 to gradually compress and flatten the ingot piece as depicted in FIGURES 2 through with a steady compression force until without interruption the ingot piece has been compressed and radially and axially displaced into a substantially circular, pancake-like flattened disk 21 (FIG. 6).

It will be observed that as the ingot piece 11 is progressively reduced in length by the compression force toward the flattened condition, the unconfined circular longitudinal periphery bulges uniformly radially to a progressively diminishing radius as the diameter of the blank increases responsive to the compression exerted on the piece by the die members 18 and 19.

It will thus be clear that the provision of the radius corners 17 facilitates uniform transition from the more or less straight longitudinal wall or surface form to the laterally bulged form. Furthermore, as the disk gradually spreads out and becomes thinner under compression, the radius corners 17 become part of the end faces of the blank as do the progressively adjacent portions of the longitudinal wall to the point wherein, as shown in dash outline in FIGURE 5, the ultimate flattening of the blank is accomplished and but a narrow portion of the longitudinally median annular area of the original longitudinal surface of the ingot piece 11 provides a short radius rounded annular periphery or edge 22. A great advantage in having the longitudinal periphery of the ingot piece 11 thoroughly clean and free from scale or pits will now also be apparent, since any scale or pitting would, if present, he worked into the faces of the flattened disk blank.

Of course, where the steel composition precludes a onepass compression thereof to the pancake or flattened disk form, a multistage pressing of the ingot piece may be resorted to wherein after pressing the piece part Way, it is again heated as for example to dual annealing heat and then subjectedto further progressive pressing until the flattened disk blank form 21 is attained.

Preferably, the flattening of the disk blank is performed close enough to a trimming and cupping die assembly to enable trimming and cupping while the blank is still hot from the pancaking or flattening operation. If this is accomplished then protection of the disk blank 21 against scaling or corrosion need not be done. For example, where the temperature of the ingot piece on introduction into the flattening press is between 2000 and 2300 F. the temperature will still be at least close to 2000" F. unless the press members 18 and 19 are unusually cold to start. In any event after a plurality of the ingot pieces have been smashed to flattened form, the press members will have become heated enough to avoid lowering the temperature of the flattened disk blank unduly.

In the trimming and cupping die, the uniformly rounded edge 22 is trimmed and the blank 21 cupped as shown in FIGURES 6 and 7. It will be observed that the slight thickening toward the center of the blank produced by the concave pressing die surface 20 is of advantage in producing a substantially uniform wall cup and in easing the marginal portions of the blank into the cylindrical shape of the cup Wall as the blank is drawn through the cupping die. In view of the residual heat as the blank comes from the pressing die, an adequate trimming and drawing temperature of 1300 F. to 1400 F. will persist in the blank for trimming and cupping where the disk blank 21 is moved with reasonable promptness from the flattening dies to the trimming and cupping die assembly.

Of course, where conditions are such that the disk blank 21 cannot be immediately subjected to the cupping operation, the disk may be surface treated against corrosion and stored, or it may be placed in a fused hot salt bath of the proper temperature and held there until used or at least so heated just before it is placed in the cupping die press.

After the steel blank has been cupped, it may, if still hot enough be immediately passed through one or more elongation draws, and then dual annealed and subjected to further cold drawing and working. Where the cup is too cool or it is not convenient to elongate immediately after cupping, the cup is preferably dual annealed before cold drawing the same into the elongated shell form.

By preparing the disk blanks 21 according to the present invention, that is by flattening the same by compression from heated virgin cast ingot pieces that have been surface cleaned as described, great uniformity in grain structure in the disk blanks has been attained and flaw free outer surface. The improved grain structure can be readily ascertained from the exemplary before and after photomicrographs in FIGURES 8 and 9, respectively. In FIGURE 8 is shown the grain structure of an ingot of SAE 1050 steel at diameters magnification. FIGURE 9 shows the grain structure of the same ingot piece after it had been compression flattened according to the present invention. It will be seen that from a fairly open, coarse grain size of from 1 to 3 it has been transformed to a compact, refined 7 to 8 grain size, from ingot to compressed, flattened disk blank. In addition, the grain is uniformly distributed radially throughout the disk. This is emphasized by the fact that although the perimeter of the ingot piece is not at all confined during the flattening thereof, almost perfectly circular perimeter is developed in the flattened disk.

Since the work piece 11 starts out free from internal or superficial tensions such as develop where rolling or hammering or forging occurs before pressing, there is freedom in the piece to respond efficiently to the heavy axial compression loads which act internally of the piece not only to close and weld any porosity but also to flow uniformly from the center of the mass radially. Besides having a uniform dense fine grain structure throughout the disk, comparable to the best heat treated structure, it is free from tension stresses, which is evident from the circularity of periphery finally attained as a result of the steady compression to which the ingot piece is subjected.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

I claim as my invention:

1. A method of forming open-ended substantially cylindrical casings, comprising cutting a slot substantially into a generally cylindrical steel ingot, said ingot being formed of a carbon steel containing 0.08 to 0.56% carbon, 0.30 to 1.65% manganese, a maximum of 0.04% phosphorus and a maximum of 0.05% sulfur, grinding the circumference of the ingot to remove surface scale and the like therefrom, charnfering the ingot along the slot to provide radius corners outwardly thereof, separating the ingot into a plurality of slugs, heating the slug to substantially its forging temperature, locating the slug on one of its chamfered ends between a pair of parallel plate members and substantially centrally thereof With its peripheral side surfaces unrestrained by said members, directing the plate members continuously toward one another in a straight line path and compressing the slug therebetween While maintaining the peripheral side surfaces unrestrained to permit said surfaces to bulge and the chamfered ends to move radially outwardly during compression of the slug into an essentially pancake configuration having rounded peripheral side surfaces and a uniform dense fine grain structure throughout the pancake configuration, removing the rounded peripheral side surfaces from the blank thus formed, and locating the trimmed blank in a die and forming said blank into an open-ended substantially cylindrical casing having walls of essentially uniform thickness throughout.

2. A method as defined in claim 1, wherein the forging temperature comprises a good plasticizing temperature of about 2000 F. to 2300 F.

3. The method of claim 1, wherein the plate members are directed not only continuously toward one another in compressing the slug therebetween but such plate members are directed with steady uninterrupted compression force until the slug has been completely compressed into the essentially pancake configuration.

4. The method of claim 1, wherein the blank is trimmed and formed into a cylindrical casing While still hot from the compression from slug to pancake configuration, comprising a temperature of about 1300 F. to 1400 F.

References Cited in the file of this patent UNITED STATES PATENTS 353,931 Fitzgerald Dec. 7, 1886 965,039 Slick July 19, 1910 993,117 Slick May 23, 1911 1,242,127 Bell Oct. 9, 1917 1,396,281 Pague Nov. 8, 1921 1,486,365 Cummings Mar. 11, 1924 1,632,533 Brauchler June 14, 1927 1,999,205 Parish Apr. 30, 1935 2,057,669 Brauchler Oct. 20, 1936 2,112,653 MacLennan Mar. 29, 1938 2,360,354 Lyon Oct. 17, 1944 2,624,820 Payette Jan. 6, 1953 2,703,922 Brauchler et a1. Mar. 15, 1955 2,747,267 Schaming May 29, 1956 FOREIGN PATENTS 431,899 Great Britain July 17, 1935 OTHER REFERENCES Metals Handbook 1948 Edition, published American Society of Metals, pp. 341, 342, 399-406, 637-641.

Making, Shaping and Treating of Steel, 5th Edition, published by United States Steel, 1940, pp. 794-805 and 824-854.

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