US2497164A - Manufacture of tin plate - Google Patents

Description

Feb. M9 39555@ N. c. GEORGE ETAL 2,497,164

MANUFACTURE OF' TIN PLATE Filed June 25, 1946 {Quiz/22H5: /Vao/V C 650,965 mf Patented Feb. 14, 195() UNITED STATES PATENT OFFICE MANUFACTURE OF TIN PLATE Nelson C. George, Crown Point, and Rolf Cj. Haab, A Y' Gary, Ind., assignors to Carnegie-Illinois Steel Corporation, a corporation of New Jersey Application June 25, 194B, Serial No. 679,305

2 Claims. (Cl. 148-12) This invention relates to the manufacture of tin plate, and more particularlyto the improvement of the drawing properties thereof.

In the shaping of cold-reduced tin plateto form various articles considerable difficulty is experienced in eliminatmg defectsf caused by unevendrawingfof Ithe-metal.` rIhis results -in a drawn `article of abnormal dimensions. That is, the .drawn article at pertainl points will be of proper dimensions oneven undersized, while at other ,.points, the dimensions will be so increased as to produce what are `knownas earsJ In the manufacture of bottle` caps, for example, extreme cases lof, uneven drawingnecessitate the use of a kshell with a serratededge to assure firm holding of the inside washer on curling; whereas `a smooth-edged shellis much more preferable, of course, to minimizetheexposure of the steel on the vcut edge and thereby reduce the possibilities of internal rusting. When the bottle caps are formed with serrated edges, the uneven drawing, or earing, manifests itself in uneven teeth or serrations, the same being readily perceived when two bottle caps are placed in opposition.

Numerous attempts have been made to denitely ascertain the cause of uneven drawing, or caring Ourinvestigations have shown that in order to eliminate or materially reduce tendencies toward uneven drawing, it isnecessary to maintain close gage tolerance, uniform hardness, and uniform grain structure from the edge o f the tin plate -to the centerthereof; ,and also that mechanically capped steelis forthese purposes to be preferred over rimmedvor killed grades.

Among other factors influencing the behavior of the tin plate during drawing is that of crystal anisotropy, and it involves numerous problems since present day microscopic study does not reflect preferred orientation in the shape of the grains composing the metal.

Our experiments regarding the question of crystal orientation involved investigation of the magnetic torque characteristics of the tin plate. A satisfactory method of investigating magnetic torque characteristics may be practiced by utilizing a simple apparatus comprising a rotatable magnetic eld in which a disk-shaped test-piece is suspended on a wire having predetermined mechanical torque characteristics. Rotating the magnetic field through 360 brings forth the tendency of the test disk to align itself with the field, and the amount of torque induced by the alignment can be measured in u nits of force by determining the degree of suspension-wire twist. The number of dynes per square centimeter divided by 1000 is a convenient variable for expressing the magnetic torque observed. Plotting this number against the angle of rotation of the test disk generates curves characteristic of anisotropy of the test specimens. The reversals Afromplotting the rotation of the magnetic field and the magnitudes Vof-the curve resulting versus the induced torsional force indicate the degreeiof .preferred orientation of the specimen. Since the rotation of the test-pieces causes a type of phenomena whichwmay be held las substanttially recurrent, the curves produced apparently correspond to Waves. c

-We have discovered thatsatisfactory tin plate is characterized by,I generating a magnetic ltorque cur-,ve of substantie.lly` sinusoidal shape whichgis: substantially freefrom harmonics; and that tin plate having. unevendrawing characteristicspis characterized by generatingv a-magnetic torque curve;A` of sinusoidal shape which includes4 har.- monics. When the magnetic torque curve isgfre from harmonics., `v`the tinkplate has random crystalline orientation; when harmonicsare presnii, the ti v,plate has preferred orientation which is undesirable for ourpurposes.K ,Accordingto thei..teacl'-i ingy ofl fthe present ingvention there is correlation between the magnetic torque test results andthe response tofabricating practice including thel .grade of steel, the-.steel making. practice,the hot-rolling methods, temper-rolling procedures, and influences in gage variation. None .ofthe aforementioned factors .is alone responsible'v for lthe peculiar behavior of sheets, but the present invention teaches that uneyen drawing and thevdefect known, as earing can be eliminated by aspecific combination of variables, as will appear more fully-,hereinafteri The invention, t, then, comprises the 1features hereinafter idescribed and as vparticularly pointed out inthe claims, `the following description and the annexed drawings setting forth in detail cer. tain illustrative embodiments of the invention, these being indicative of several of the number of ways in which the principles of the invention may be employed.

In said drawings:

Figure 1 is an elevation of two pairs of superposed bottle caps, the pair at the left, designated as A, representing articles which are pracv tically entirely free from the condition known asl earing; while in the right-hand pair of bottle caps, designated as B, caring is so marked as to render them unacceptable to the trade; and

Figure 2 is a chart illustrating the magnetic torque in dynes per CMZXlO-i; and from whic it will be noted that the curve A is substantially sinusoidal and substantially free fro harmonics, while the curve B includes har monies.

In accordance with the teachings of the pres ent invention there isl produced a low carbo (.12% maximum carbon) steel which is hot rolled into strip, coiled, pickled, cold-reduced annealed, temper-rolled, and tinned by a com 3 bination of steps which are individually old. The composition of the steel of the present invention is approximately within the following ranges:

and the remainder substantially iron.

A preferred embodiment comprises a steel the composition of which is approximately within the following ranges:

Percent Carbon 0.05 to 0.08 Manganese 0.30 to 0.45 Phosphorus 0.12 maximum Sulphur 0.035 maximum Silicon 0.010 maximum Copper 0.20 maximum The steel of the invention is teemed into 30 x 48" ingot molds, mechanically capped with the capping time not longer than 3 minutes, and 30 seconds being preferable. The steel so capped is hot-rolled in steps to strip of approximately 0.080 inch thickness and the strip rolling is finished at a minimum temperature of approximately 1580 F. The strip so produced is coiled at a minimum temperature of 1300 F., then continuously pickled in sulphuric acid, cold-reduced from substantially 0.080 inch to substantially 0.0110 inch, electrolytically cleaned, box annealed in a controlled atmosphere to deoxidize at between approximately 1200 F. and approximately 1280 F., the following atmosphere being preferable: approximately 4% CO2, approximately 9.5 CO, approximately 16 H2, approximately 1.2'CH4, approximately 71.2 N, dew point between approximately n40" and approximately +80 F. The annealed strip is temper-rolled approximately 4%, and electrolytically coated with approximately 0.5 lb. of tin per base box. If the foregoing minimum i'lnishing and coiling temperatures are not maintained, the random crystalline orientation, which is necessary for a nonearing tin plate, is lost. The magnetic torque curve furnishes a ready test for such orientation.

We have discovered that tin plate made in substantial accordance with the practice described immediately hereinbefore possesses properties expected of a high quality commercial tin plate, namely Rockwell 30 T. hardness of 54/60, grain size showing absolute values of 7 to 9 equiaxed grains, elongation of 15 to 25% in two inches, yield point of 38,000 to 42,000 pounds per, square inch, tensile strength of 43,000 to 49,000 pounds per square inch; and in addition is characterized by sinusoidal magnetic torque curve devoid of harmonics. This steel is further characterized by being practically entirely free from tendency toward uneven drawing, or earing.

While we have shown and described certain pecific embodiments of the present invention, t will be readily understood by those skilled in he art that we do not wish to be limited exact- 4 ly thereto, since various modifications may be made without departing from the scope of the invention as defined in the appended claims.

We claim:

1. In the manufacture of cold reduced steel strip for tin plating and subsequent deep drawing of symmetrical shapes, wherein capped steel of approximately the composition:

Percent Carbon 0.030 to 0.15 Manganese 0.60 maximum Phosphorus 0.150 maximum Sulphur 0.050 maximum Silicon 0.010 maximum Copper 0.30 maximum and the balance iron and incidental impurities, is hot rolled into strip, the hot rolled strip is coiled, pickled and cold reduced, and the cold reduced strip is annealed at approximately 1100 F. to 1300L1 F., a method of producing random crystalline orientation in the steel as measured by its magnetic torque characteristics which, when expressed in a sinusoidal curve, are practically entirely free of harmonics, and thereby of preventing caring when the steel is drawn, comprising finishing the hot rolling at a temperature above 1580 F. and performing the coiling at a temperature above 1300 F.

2. In the manufacture of cold reduced steel strip for tin plating and subsequent deep drawing of symmetrical shapes, wherein steel of approximately the composition:

Percent Carbon 0.030 to 0.15 Manganese 0.60 maximum Phosphorus 0.150 maximum Sulphur 0.050 maximum Silicon 0.010 maximum Copper 0.30 maximum and the balance iron and incidental impurities, is hot rolled into strip, the hot rolled strip is coiled, pickled and cold reduced, and the cold reduced strip is annealed at approximately 1100 F. to 1300" F., a method of producing random crystalline orientation in the steel as measured by its magnetic torque characteristics which, when expressed in a sinusoidal curve, are practically entirely free of harmonics, and thereby of preventing earing when the steel is drawn, comprising finishing the hot rolling at a temperature above 1580 F. and performing the coiling at a temperature above 1300o F.

NELSON C. GEORGE. ROLF C. HAAB.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,994,276 Graham et al. Mar. 12, 1935 2,264,266 Jacobs et al. Nov. 25, 1941 2,309,801 Veeder Feb. 2, 1943 2,377,922 Campbell et al. June 12, 1945 OTHER REFERENCES The Making, Shaping, and Treating of Steel, 5th ed., pp. 1277-1283, by Camp 8; Francis. Carnegie-Ill. Steel Corp., Pitts., Pa., 1940.

YCerticate of Correction Patent N o. 2,497,164 February 14, 1950 NELSON C. GEORGE ET AL.

It is hereby certified that error appears in the printed speccfttion of the above numbered patent requiring correction as follows:

Column 3, line 20, for and that the said Letters Patent should be read with this same rnay conform to th Slgned and sealed this 30th day of M 0.12 maximum THOMAS F. MURPHY,

Assistant 'ommz'ssz'oner of Patents.

Claims (1)

1. 2. IN THE MANUFACTURE OF COLD REDUCED STEEL STRIP FOR TIN PLATING AND SUBSEQUENT DEEP DRAWING OF SYMMETRICAL SHAPES, WHEREIN STEEL OF APPROXIMATELY THE COMPOSITION:

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