GB1576145A - Process for manufacture of thin steel strips for production of cans - Google Patents

Description

(54) PROCESS FOR MANUFACTURE OF THIN STEEL STRIPS FOR PRODUCTION OF CANS (71) I, KOZO YOSHIZAKI, a citizen of Japan of 4-37-8, Nogata, Nakanoku, Tokyo, Japan, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a process for the preparation of thin steel strips for the production of cans.

The invention relates, more particularly to a process for the preparation of improved thin steel strips for production of cans, such strips having good shape characteristics and levelness. By the term "good shape characteristics" it is meant that the steel strip is largely free of local shape defects such as full center and edge wave, and by the term "good in levelness" is meant that the steel strip is free of gutter (which is warp in the lateral direction of the strip) or curl (which is warp in the longitudinal direction of the strip).

In the field of manufacture of metal vessels, at the present there is generally used a method in which multicolor printing is directly conducted on the steel strips.

However, if the steel strip is of poor shape characteristics, smears in the printing appear and the commercial value of the resulting metal vessels is drastically lowered. Moreover, in the actual production of can, if steel strips are inferior in shape characteristics or levelness, the continuous feeding of blanks becomes difficult or impossible at the step of making the can bodies, and other troubles are caused, resulting in a reduction of productivity. This is a serious demerit in the art of manufacture of cans where mass production is a first and indispensible requirement.

For the foregoing reasons, the standards of shape characteristics required of steel strips for use in manufacturing cans are very severe, and it is desired that in any strip the deviations of the height of edge wave or full center or the thickness be substantially zero. When steel strips for the production of cans meeting such severe shape standards are manufactured in large quantities at profitable running costs according to conventional processes, the lowest thickness attainable is about 0.16 mm. When thinner steel strips are manufactured according to conventional processes, satisfactory shape characteristics cannot be attained and yields are drastically lowered, so that the cost of production is raised. Because of these difficulties, the lower limit of the strip thickness is about 0.16 mm.

The usual means for improving the shape characteristics of steel strips are levellers such as roller levellers and tension levellers. However, for steel strips of small thickness, e.g. below 0.16 mm, a high rolling reduction ratio of 20 to 70 /O is employed and this, with a high strip hardness such as corresponds to a tensile strength of about 50 to about 100 Kg/mm2, means that with the conventional levellers, no substantial levelling effect can be obtained because the minimum work roll diameter customarily adopted is about 20 mm.

We previously proposed in the specifications of U.S. Patents No. 3,812,697 and No. 3,812,701 apparatus for correcting shape defects of steel strips by bending at a very small curvature radius. According to the former Specification, shape defects are corrected by supporting a steel strip while it is bent in the stretched state by a fluid pressure produced as a film uniformly jetted along the widthwise direction of the steel strip. In the latter Specification, shape defects are corrected by bending a steel strip by contacting it with a roll having a very small diameter, which is supported by such a fluid film. However, if such apparatus alone is employed, it is impossible to correct warps, namely to improve the levelness.

We have also proposed in U.S. Specification No. 3834202 an apparatus in which, according to the principle of the above-mentioned latter specification, a small-diameter roll is used and the levelness is improved, but it has been found that the small-diameter roll is not suitable for high-speed continuous operation because it is rapidly worn away.

As far as we know, in conventional apparatus and methods for correcting shape defects and improving the levelness of steel strips, because of galling occurring on a bearing supporting a tool, it is very difficult to obtain under high speed conditions an elongation necessary for correction. Accordingly, in order to attain the intended correcting effect, it is necessary to maintain the steel strip feed rate at a relatively low level of 200 to 300 ni/min, and the known apparatus and methods are apparently unsuitable for conducting the correcting operation subsequently to the cold-rolling step from which steel strips are discharged at such high speeds as 500 to 3000 m/min.

According to the present invention there is provided a process for the preparation of thin steel strip for the manufacture of cans including the steps of: (1) forcibly bending around a stationary curved surface of a tool, a steel strip prepared by cold rolling, with a uniformly distributed film of a fluid being provided at the curved surface of the tool and the steel strip being bent under such conditions that the ratio of the bend radius (r1, mm) to the strip thickness (t, mm) is within the range of 10 to 50, thereby to correct shape defects of the steel strip; (2) then subjecting the steel strip to at least one bending operation at which it experiences a bending radius (r2) which is 1 to 2 times as large as the bending radius (r,), thereby to correct gutter on the steel strip; and (3) then subjecting the steel strip to at least one bending operation at which it experiences a bending radius (r3) which is 2 to 6 times as large as the bending radius (r,), thereby to correct curl on the steel strip, the bending direction in each bending operation being opposite to that in the preceding operation.

Preferably, in the first said bending step, the following requirements are satisfied: T 0.02 > 4.351 - H] > 0.002 (1) 2r,Ayb E and T < bytb (2) wherein p is a coefficient in the range of from 0.2 to 1.0, T stands for the tension (Kg) applied to the steel strip, ay stands for the tensile strength (Kg/mm2) of the steel strip, E is the longitudinal elasticity modulus (kg/mm2) of the steel strip, r, and t are as defined above, and b is the width (mm) of the steel strip.

We have now found that correction of shape defects in steel strips prepared by cold rolling is not only determined by the ratio of the bend radius of a correcting tool to the thickness of a strip to be processed but also significantly influenced by the state of contact between the tool surface and the steel strip at the step of bending the steel strip and the tension applied to the strip, and that when the steel strip is bent on a stationary curved surface of the tool with a fluid film present on the curved surface and preferably, the tension applied to the steel strip is adjusted within a certain range determined depending on the thickness, width, tensile strength and longitudinal elasticity modulus (Young's modulus) of the steel strip and the bending radius of the correcting tool, shape defects of the steel strip can be effectively corrected while feeding and travelling the steel strip at a high speed. It is also found that when the operation of bending a steel strip is conducted in a plurality of stages and the ratio of the bending radius of the steel strip to the thickness of the steel strip in the first stage and the ratios of the bending radius in the first stage to the bending radii in the second and third stages are selected within specific ranges, both correction of shape defects and levelling of the steel strip can be simultaneously accomplished.

With the invention, therefore, the steel strip, of a thickness preferably of 0.08 to 0.18 mm can be prepared at high productivity and still be satisfactory as to shape characteristics.

In order that the invention may be more clearly understood, the following description is given, merely by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a side view showing diagrammatically one method of the present invention.

Fig. 2 is a sectional side view showing a correcting tool used in the embodiment illustrated in Fig. 1.

Fig. 3 is a side view showing diagrammatically another method of the present invention in which cold rolling and correction are performed in one subsequent process.

Referring now to Fig. I illustrating one embodiment of the process of the present invention, a steel strip 1 is fed from a coil of a rewinding reel 2, and after it has passed through a driven inlet bridle 3, it is bent in succession by a shape defect-correcting tool 4 and warp-correcting tools 5 and 6 so that bending directions are alternately reversed. Then, the steel strip I passes through a driven outlet bridle 7 and is wound on a coil by a winding reel 8. The shape defect correcting tool 4 is for correcting shape defects such as edge wave and full center, and the warp-correcting tool 5 is disposed mainly for correcting gutter and the warp-correcting-tool 6 is disposed mainly for correcting curl.

In this embodiment, the steel strip I is bent two times by the shape defectcorrecting tool 4 and subsequently, one bending is given to the steel strip 1 by each of the warp-correcting tools 5 and 6. Since the bending directions are alternately reversed in these bending operations, excellent shape characteristics and levelness can be attained. A certain tension is given to the steel strip 1 by the driven inlet bridle 3 and the driven outlet bridle 7.

In the present invention, any of steel strips prepared through one cold rolling step or a plurality of cold rolling steps can optionally be used as the steel strip to be subjected to the correcting treatment. However, for the purpose of preparing thin steel sheets for use in manufacture of cans, it is preferred to use cold-rolled steel strips having a thickness of 0.18 to 0.08 mm, especially 0.16 to 0.11 mm, and a tensile strength of 50 to 100 Kg/mm2, especially 56 to 90 Kg/mm2. These cold-rolled steel sheets, in general, have conspicuous shape defects such as full center and edge wave and conspicuous levelness defects such as gutter and curl, but when they are subjected to the correcting treatment according to the present invention, these defects can be substantially corrected. Cold-rolled steel sheets may be subjected to the correcting treatment of the present invention after they have been wound on reels, but in the present invention, as described in detail hereinafter, cold-rolled steel sheets can be subjected directly to the correcting treatment without winding on reels.

In the present invention, in order to correct shape defects effectively while forwarding a steel strip at a high speed, it is important to bend the steel strip which is supported on a stationary curved surface of a tool via a film of a fluid uniformly distributed on the curved surface of the tool. In the case where the steel strip is bent by forcibly contacting the steel strip with the curved surface of a rotating tool as disclosed in the specification of U.S. Patent No. 3,812,701 or 3,824,205, satisfactory correction of shape defects can be attained if the steel strip feed rate is lower than 600 m/min, but if the steel strip feed rate is as high as intended in the present invention, for example, 600 m/min or higher, correction of shape defects becomes difficult because of swinging or buckling of the roll or the like. In the present invention, the stationary curved surface of a tool is used and the steel strip is forcibly bent on the curved surface of the tool through a film of a fluid uniformly supplied on the tool surface, whereby correction of shape defects can be accomplished at a very high speed.

The principle of forcible bending of a steel strip on a stationary curved tool surface through a fluid film and the structure of a tool to be used for this forcible bending have already been known from the specification of U.S. Patent No.

3,812,697.

Fig. 2 is an enlarged sectional view showing the shape defect-correcting tool 4 to be used in the process shown in Fig. 1. This tool 4 has a top end portion 13 including a curved face extending in the widthwise direction of the steel strip 1 and in the central part of the top end portion 13, a number of dents spaced at small intervals in the widthwise direction of the strip are formed and also fine holes 11 connected to these dents 12 are formed. A compressed fluid such as compressed water or rolling coolant emulsion (not shown) is jetted outwardly from the dents 12 through the fine holes 11 to form a fluid film intervening between the steel strip 1 and the stationary curved surface 13 of the tool. The steel strip I is stretched by two pairs of bridles 3 and 3 and bridles 7 and 7, and it is forcibly bent in the state floating on the curved tool surface 13 through the fluid film.

In the present invention, in order to prevent occurrence of shape defects effectively, it is important to adjust the ratio of the bending radius (rl, mm) of the steel strip to the thickness (t, mm) of the steel strip, namely the ratio of r,/t, to 10 to 50, and especially good results are obtained when this ratio is in the range of from 25 to 40. When this ratio (r,/t) is larger than the above range, it is difficult to correct shape defects of a steel strip to such an extent that the steel strip can be effectively used for manufacture of cans. Further, when this ratio (r,/t) is smaller than the above range, the surface of the steel strip is readily roughened or scratches are readily formed on the strip surface, and good results can not be obtained.

The bending radius (r,) of the steel strip is determined by the shape and dimensions of the top curved face 13 of the tool 4 shown in Fig. 2, and in general, it is not improper to regard the bend radius of the curved surface 13 of the tool 4 as the bending radius (rl) of the steel strip.

In the present invention, it is preferred that at the above-mentioned bending step, the tension (T, Kg) imposed on the steel strip be determined depending on the tensile strength, longitudinal elasticity modulus, width and thickness of the steel strip and the bending radius (rl) of the steel strip so that the requirements represented by the above empirical formulae (I) and (2). More specifically, when the value ED represented by the following formula: T Ep=4.35[ p ] (3) 2r,Ayb E is smaller than 0.002, even if the foregoing indispensable conditions are satisfied, it is difficult to correct shape defects so that the height of full center or edge wave is reduced substantially to zero. When the ED value is larger than 0.02, the characteristics, namely mechanical properties, of the steel strip are severely altered and the steel strip becomes unsuitable for manufacture of cans.

In the present invention, it is especially preferred that the tension (T) be determined so that the Ep value is in the range of from 0.01 to 0.003.

There is an optimum value also for the pressure of the fluid fed between the stationary curved surface 13 of the tool and the steel strip I, and in general, it is preferred that the fluid be fed under a pressure (Po, Kg/mm2 gauge) satisfying the requirement represented by the following empirical formula: T Po= X xa (4) r1.b wherein rl stands for the bending radius (mm) of the tool, b designates the width (mm) of the steel strip, T indicates the tension (Kg) imposed on the steel strip, and a is a value in the range of from 0.5 to 2.0, especially from 1.0 to 1.8.

When the pressure of the fluid is lower than the pressure defined by the empirical formula (4), scratches are readily formed on the steel strip during the bending operation and it is difficult to correct shape defects, especially at a high speed. If the fluid pressure exceeds the pressure defined by the empirical formula (4), variations are readily caused between the pressure on each of the dents 12 of the tool 4 and the pressure on each part intervening between two vents 12, whereby longitudinal wrinkles are readily formed on the steel strip.

Incidentally, the reason why the coefficient a in the above empirical formula (4) is a value varying in a cetain range is that an optimum fluid pressure varies to some extent depending on the area of the stationary curved surface of the tool on which the steel strip is wrapped (namely the wrap angle).

In order to attain the foregoing objects of the present invention, it is preferred that the wrap angle (0) of the steel strip on the stationary curved surface of the tool be adjusted to 10 to 600, and especially good results are obtained when this angle (0) is adjusted 20 to 350. and especially good results are obtained when When this wrap angle (0) is relatively large, it is preferred to adopt a relatively large value as the coefficient (a) in the empirical formula (4), and on the other hand, when the wrap angle (0) is relatively small, it is preferred to adopt a relatively small value as the coefficient (a).

In the shape defect-correcting process of the present invention, it is preferred to use a pair of correcting tools 4 of which the bending directions are reversed to each other as shown in Fig. 1. Of course, in the present invention, shape defects can be corrected by using one correcting tool.

In accordance with the present invention, the steel strip coming from the above-mentioned shape defect-correcting step is subjected to at least one bending operation at a bending radius (r2) I to 2 times as large as the above-mentioned bending radius (r1), thereby to correct gutter on the steel strip, and the steel strip having gutter thus corrected is then subjected to at least one bending operation at a bending radius (r3) 2 to 6 times as large as the above-mentioned bending radius (r,), thereby to correct curl on the steel strip.

Tools to be used for correcting these levelness defects may be substantially the same as the above-mentioned tool used for correction of shape defects, except that the bending radius is changed as mentioned above. Further, at these levelness defect-correcting steps, the steel strip is forcibly bent through a fluid film as at the shape defect-correcting step.

At the gutter- or curl-correcting step, if the bend radius (r2) or (r3) is larger or smaller beyond or below the above range, it is difficult to remove these warps completely.

According to the above-illustrated process of the present invention, shape defects and levelness defects of steel strips can be largely corrected while feeding them at such high speeds as 500 to 3000 m/min, and thin steel sheets for manufacture of cans can be produced at high manufacturing rates in high yields.

Moreover, the apparatus for use in conducting the correcting treatment according to the present invention has a simple structure and its equipment cost is low, and further, when this apparatus is combined with cold strip mills, thin steel sheets for manufacture of cans can be produced at very low running costs.

Excellent effects attained by the present invention will now be described by reference to the following Examples that by no means limit the scope of the present invention.

According to the above-illustrated process of the present invention, shape defects and levelness defects of steel strips can be largely corrected while feeding them at such high speeds as 500 to 3000 m/min, and thin steel sheets for manufacture of cans can be produced at high manufacturing rates in high yields.

Moreover, the apparatus for use in conducting the correcting treatment according to the present invention has a simple structure and its equipment cost is low, and further, when this apparatus is combined with cold strip mills, thin steel sheets for manufacture of cans can be produced at very low running costs.

Excellent effects attained by the present invention will now be described by reference to the following Examples that by no means limit the scope of the present invention.

Example 1 A hot-rolled steel strip having a thickness of 2.0 mm was cold-rolled to a thickness of 0.20 mm by 5-stand tandem cold strip mills, and the cold-rolled steel strip was degreased by electrolytic cleaning and was subjected 'to intermediate annealing. Then, the strip was once passed through 2-stand cold strip mills to coldroll the strip so that its thickness was reduced to 0.14 mm. The thus rolled steel strip was characterized by a tensile strength of 60 Kg/mm2, a longitudinal elasticity modulus of 21000 Kg/mm2 and a width of 900 mm (this steel strip is designated as "strip A"). The average height of full center in this rolled strip was 3.2 mm and its shape characteristics were inferior. Further, warps were large in this strip.

Therefore, it was not suitable as a steel sheet for manufacture of cans.

In the above 2-stand mills, the rolling reduction ratio by one passage was lowered, and the steel strip was passed through this mill two times so that the thickness was finally reduced to 0.14 mm. The resulting rolled steel strip was characterized by a tensile strength of 62 Kg/mm2, a longitudinal elasticity modulus of 21000 Kg/mm2 and a width of 900 mm (this steel strip is designated as "strip B").

The average height of full center in this strip was 2.2 mm and the shape characteristics were relatively improved, but the strip was still unsuitable as a steel sheet for manufacture of cans.

The steel strip A was fed at a rate of 1000 m/min to the correcting apparatus shown in Fig. 1 under the conditions indicated below.

Shape defect-correcting tool 4: r,=4 mm, 01=25 Gutter-correcting tool 5: r2=4 mm, 02=20 Curl-correcting tool 6: r3=12.0 mm, 03=150 Tension on steel strip: T/b=l.9 Kgimm Fluid fed to tools 4, 5 and 6: 10% aqueous emulsion of rolling coolant Fluid pressure: Po=90 Kg/mm2 By this correcting treatment, the quantity of either the full center or the warp in the resulting steel sheet was reduced substantially to zero. Thus, it was confirmed that a steel strip that cannot be used as a steel sheet for manufacture of cans according to the conventional process can be corrected according to the present invention so that it can be effectively used for manufacture of cans, and that yields of steel strips can be remarkably enhanced using the present invention.

Example 2 Correction of steel strips was carried out under the same conditions as described in Example 1 except that the kind of the steel strip 1 and the bending radius (r,) of the tool 4 were changed as indicated in Table 1. Obtained results are shown in Table 1.

TABLE I Steel Strip Shape after Tensile Bending Radius/ Correcting Run Thickness Strength Bending Radius Strip Thickness (full center No. (mm) (Kg/mm2) (mm) of Tool 4 Ratio height, mm) 0.14 60 4 28.6 0 2 0.13 75 4 30.8 0 3 0.12 66 4 33.3 0 4 0.14 60 6.5 46.4 0.5 5 0.12 66 8 66.7 3.0 Example 3 Correction of steel strips was carried out under the same conditions as described in Example 1 except that the kind of the steel strip and the tension (T) imposed on the steel strip were changed as indicated in Table 2. Obtained results are shown in Table 2.

TABLE 2 Steel Strip Bending Shape after Tensile Radius Strip Correcting Run Thickness Strength (mm) of Width Tension (height of full No. (mm) (Kg/mm2) Tool 4 (mm) (Kg) E center, mm) 1 0.10 90 4 250 300 0.0000 3.0 2 0.10 90 4 250 610 0.0005 0.5 3 0.10 90 4 250 675 0.002 0.0 4 0.10 90 4 250 788 0.005 0.0 5 0.10 90 10 250 1150 0.000 3.0 Example 4 Correction of steel strips was carried out under the same conditions as described in Example 1 except that the pressure of the fluid fed to the tool 4 was changed as shown in Table 3. Obtained results are shown in Table 3.

TABLE 3 Steel Strip Bending Surface Tensile Radius Strip Fluid Condition Run Thickness Strength (mm) of Width Tension Pressure of Treated No. (mm) (Kg/mm2) Tool 4 (mm) (kg) (Kg/cm2) Strip 0.1 90 4 250 788 30 large scratches 2 0.1 90 4 250 788 45 good 3 0.1 90 4 250 788 80 good 4 0.1 90 4 250 788 100 good 5 0.1 90 4 250 788 158 good Example 5 Correction of steel strips was carried out under the same conditions as described in Example 1 except that the ratio of the bend radius of the tool 5 to the bend radius of the tool 4 was changed as indicated in Table 4. Obtained results are shown in Table 4.

TABLE 4 Steel Strip Bending Bending Bending Tensile Radius Radius Radius Gutter Run Thickness Strength (r1, mm) of (r2, mm) of Ratio after No. (mm) (Kg/mm2) Tool 4 Tool 5 (r2/r,) Correction 1 0.10 75 4 4 1 not observed 2 0.12 66 5 5 I ditto 3 0.12 66 4 6 1.5 ditto 4 0.12 66 4 8 2.0 ditto 5 0.12 66 4 10 2.5 hardly corrected Example 6 Correction of steel strips was carried out under the same conditions as described in Example I except that the ratio of the bend radius of the tool 6 to the bend radius of the tool 4 was changed as indicated in Table 5. Obtained results are shown in Table 5.

TABLE 5 Steel Strip Bending Bending Bending Tensile Radius Radius Radius Run Thickness Strength (r1, mm) of (r3, mm) of Ratio After Correcting No. (mm) (Kg/mm2) Tool 4 Tool 6 (r,/r3) Gutter Curl I 0.12 66 4 6 1.5 not not completely observed corrected 2 0.12 66 4 8 2 not ditto observed 3 0.12 66 4 12 3 ditto ditto 4 0.12 66 4 24 6 ditto ditto 5 0.12 66 4 28 7 ditto hardly corrected Note: In each run, the bending radius of the tool 5 was adjusted to 4 mm.

From the experimental results shown in the foregoing Examples, it will readily be understood that when steel strips are treated so that the requirements of the present invention are satisfied, shape defects and levelness defects can be eliminated completely and thin steel sheets free of surface roughness and scratches can be obtained at high manufacturing speeds.

When shape defect-correcting and warp-correcting tools are disposed on the outlet side of a cold rolling mill and the rolling and correcting are carried out subsequently in one process as in an embodiment illustrated in Fig. 3, the above correcting effects can be attained with more economical advantages. Referring to Fig. 3, a steel strip 14 rolled by a work roll 15 is bent two times by a shape defectcorrecting tool 16 and is then bent one time, respectively, by a warp-correcting tool 17 mainly for correcting gutter and a warp-correcting tool 18 mainly for correcting curl, so that the bending directions are reversed alternately. Then, the steel strip is passed through an outlet bridle 19 and wound on a coil by a winding reel 20.

The foregoing illustration and drawing are given only for explaining the principle of the invention, and they are not given to limit the scope of the invention and various changes and modifications can be made within the scope defined by

Claims (8)

the claims. WHAT WE CLAIM IS:-

1. A process for the preparation of thin steel strip for the manufacture of cans including the steps of: (1) forcibly bending around a stationary curved surface of a tool, a steel strip prepared by cold rolling, with a uniformly distributed film of a fluid being provided at the curved surface of the tool and steel strip being bent under such conditions that the ratio of the bend radius (r1, mm) to the strip thickness (t, mm) is within the range of 10 to 50, thereby to correct shape defects of the steel strip; (2) then subjecting the steel strip to at least one bending operation at which it experiences a bending radius (r2) which is 1 to 2 times as large as the bending radius (r,), thereby to correct gutter on the steel strip; and (3) then subjecting the steel strip to at least one bending operation at which it experiences a bending radius (r3) which is 2 to 6 times as large as the bending radius (r,), thereby to correct curl on the steel strip, the bending direction in each bending operation being opposite to that in the preceding operation.

2. A process according to claim I wherein, in the first said bending step, the following requirements are satisfied: T 0.02 > =4.35[ -H]'0.002 2r,Ayb E and T < Xytb wherein p is a coefficient in the range of from 0.2 to 1.0, T stands for the tension (Kg) applied to the steel strip, Ny stands for the tensile strength (Kg/mm2) of the steel strip, E is the longitudinal elasticity modulus (Kg/mm2) of the steel strip, r, and t are as defined above, and b is the width (mm) of the steel strip.

3. A process according to claim 1 or 2, wherein the steel strip has a thickness of 0.18 to 0.08 mm and a tensile strength of 50 to 100 Kg/mm2.

4. A process according to claim 1, 2 or 3, wherein the cold-rolled steel strip is fed at a speed of 500 to 3000 m/min.

5. A process according to claim 1, 2, 3 or 4, wherein the fluid is applied between the curved face of the tool and the steel strip at a pressure (Po, Kg/mm2 gauge) satisfying the requirement represented by the following empirical formula: T Po xa r, b wherein r, stands for the bend radius (mm) of the tool, b designates the width (mm) of the steel strip, T indicates the tension (Kg) imposed on the steel strip, and a is a value in the range of from 0.5 to 2.0.

6. A process according to any preceding claim, wherein the bending steps (1), (2) and (3) are conducted on the cold-rolled steel strip directly in sequence without intermediate winding the cold-rolled steel.

7. Process for the preparation of thin steel strip substantially as hereinbefore described with reference to the accompanying drawings.

8. Thin steel strip formed by the process of any one of the preceding claims.