DE2045302A1 - Method and device for Her put sheet metal blanks from hot strip - Google Patents

Description

Dipl.-Ing. H. Sauerland ■ Dr.-Ing. R. King Patent Attorneys · 4qao Düsseldorf · Cecilienallee 76 -Telephone 43 273a

Our file: 26 152 12 ₀ September 1970

NIPPON STEEL CORPORATION, No. 6-3, 2-chome, Ote-machi, Chiyoda-ku, Tokyo, Japan

"Method and device for the production of sheet metal blanks from hot strip"

The invention relates to a method and an apparatus for the production of heavy plate blanks, in particular, from hot strip.

Numerous attempts and suggestions have been made for method of making proportionate thick heavy-plate blanks from that to be cut to size Hot-rolled strip has been made in order to obtain heavy-plate blanks that are comparable to conventionally rolled heavy plates ~ are. However, the previous attempts and suggestions have not led to success., The reason for the previous Failure lies in the fact that when heavy plate is cut from hot strip, severe warping occurs because that Cutting as in the case of flame cutting with feed large amounts of heat takes place, so that the use of such Heavy plate is limited and this is not the case in all cases can be used in which conventionally rolled heavy plates are used.

But there is no question from an economic point of view the production of heavy plate from hot strip is much more advantageous than conventional sheet metal rolling. For this Great efforts have been made in the past.

has been adopted to a method of making heavy plate blanks from hot strip, without having yet succeeded in solving the pending problems «

The object on which the invention is based is now to provide a method and a device for its implementation to create, with which heavy plate blanks can be made from warning tape, the conventional ones Heavy plates are comparable or even surpass them and especially after machining, for example A flame cutting, of excellent shape and quality.

In the conventional processes for producing heavy plate from hot strip, skin pass stands with leveling machines or even individual leveling machines have already been used in order to produce warp-free heavy plates. However, since skin pass stands and / or straightening machines are used to bring the sheet metal into a flat or even shape as a whole, compressive or tensile stresses are retained locally after the heavy plate has been straightened, while stress compensation only results over the entire sheet metal. Accordingly, the balance of voltages inner ™ is lost in cutting and yields the following the known distortions ,, The reason for this is that the straightening has been realized only in a conventional manner, "deh _e directing takes place exclusively, flat to the sheet in a to bring or flat shape, but not to avoid warping.

Since it was usually assumed that a stronger straightening than necessary with regard to the straightness per se would also impair the mechanical properties of the sheet metal, straightening only takes place within relatively narrow limits.

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Based on extensive studies of the effects of cutting on heavy plate, it was found that cold straightening of hot strip with previously unusually high Directional forces, not: just significantly less distortion after cutting, than the conventional one Straightening with lower forces is the case, but also the risk of an impairment to be expected the mechanical properties does not exist.

The invention makes it possible to increase productivity when Production of large sheet metal blanks about twice as much as compared to conventional sheet metal production increase. In addition, there are better contours, more precise dimensions and cuts as well as fewer errors and Deflections, so that the sheet metal produced according to the invention is particularly suitable for motor vehicle bodies Shipbuilding and tank manufacture are suitable.

The invention came about only after removing the obstacles possible that is based on previous ideas or resulted in prejudices; it is based on the observation that a cold judging within certain, outside of conventional forfeiture limits, is suitable, Avoid warping when cutting. It is based the invention on the clarification of the underlying cold straightening Principles, the application of cold straightening to stretch the outer fibers of steel strip and the investigation their relationship to sheet thickness.

The solution to the above-mentioned problem consists essentially in the fact that the hot strip is cold-leveled in such a way that a maximum bending elongation E of the sheet surface of 0.60% to 5.096 results, and the strip is then cut to length _e

The device for performing the inventive method

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driving consists essentially of a decoiler, a cold straightening machine with a straightening force that is sufficient to reduce the residual stresses in the hot strip, as well as a cold straightening machine with lower straightening force to reduce the residual stresses in the outer fiber of the Tape and scissors.

The term hot strip in the context of the invention also includes surface-treated, for example dry or wet-scaled hot strip.

The invention is explained in more detail below on the basis of exemplary embodiments shown in the drawing. In the drawing show:

Fig. 1 is a schematic representation of a cross section through three straightening rolls,

Figo 2 shows the sector of a straightening roll,

3 shows a diagram to illustrate the method for measuring deflections on metal sheets,

4 is a diagram showing the relationship between sheet metal thickness and bending elongation,

FIG _o 5 is a diagram showing measured values of the deflection L in the longitudinal and the rolling direction of kaltgerichtetem in a conventional manner and sheet of sheet metal blanks made of hot-rolled strip to be cut by flame cutting,

6 to 11 diagrams with measured values of the deflection L of cold-straightened conventional sheet metal, cold-straightened hot strip according to the invention and its blanks after flame cutting,

Fig. 12 and 13 are diagrams to illustrate the relationship between the mechanical properties and the bending elongation of sheet metal,

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a diagram to illustrate the relationships between the deformation factor plotted on the ordinate, ie. the ratio to the elastic elongation, and that plotted on the abscissa Number of repeated bends,

15 is a diagram showing the change in the distribution of the residual stress caused by λ_ the cold straightening in various processes,

Fig. 15a shows the change in distribution in the case of exclusive cold straightening with a maximum bending elongation of 0.60 to 3.0%,

15b shows the changes in light cold straightening with a bending elongation of up to 2.0%,

15c shows the changes in cold straightening with a high leveling pressure and a maximum bending elongation of 0.6% to 3.0% with subsequent slight cold straightening with a bending elongation of up to 2.0% and

16 shows an apparatus for carrying out the method according to the invention.

First of all, the flexural strain is used in the context of the invention as a yardstick for the cold straightening of a hot strip, the elongation resulting from the permanent deformation under the following Assumption is calculated.

1. The central plane of the hot strip is called neutral Adopted fiber that is neither stretched nor compressed;

2ο the shape of the cold-straightened strip is as a result assumed by arcs.

According to FIG. 1, the hot strip 3 is between several upper Rolls 1 and lower rolls 2 bent and cold straightened «,

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The neutral fiber is marked with 4, the sheet thickness with T _9, the space between the roller surfaces with I and the roller pitch circle with P ,,

With the above assumption, the curvature AOB of the neutral fiber between the straightening rollers can be viewed as an arc of a circle The following relationship results according to FIG. 2, where R is the radius of curvature of the neutral fiber:

AD: DB = 1/4 P no - ^τ Ζ ^τ

JL / V / - ρ

••• so · ® ····

Hence the radius of curvature results in:

DO = r (i-cos Λ)
AD = R sin cC
and if dL is eliminated:

ρ - AD ² + DO ²

rs. -

ρ TiCi

οοοβοβββ

R can therefore be determined from equations (1) and (2) will"

On the other hand, the bending strain is given by: T

(3)

R 2R

From equation (3) above, can be substituted on the equation (2) for R as a function of the strip thickness T can be determined.

The following is an example of measuring a warpage of the sheet 7 with reference to FIG. 3 of the drawings described. If the band 7 is bent 7% in the direction of its rear side, as shown in solid lines, so is

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this warping is to be regarded as a positive warping (+), while bending towards the opposite side 7 ¹ 'is to be considered a negative warping (-).

As can be seen from Fig. 3, the sheet 7 is suspended from its central part 5 or ₀ is upright and a strand is tensioned in the rolling direction at points A to E, which are distributed over the width. The resulting largest distance between the tensioned strand and the sheet 7 represents the warping of the plate. L denotes the length of the plate in the rolling direction.

If sheet metal blanks are produced from sheet metal 7 by flame cutting, the warpage in these is in the measured in the manner shown in FIG. The width b is 150 mm, the length L 3 m and the warp or deflection a is specified in mm

The reason for specifying the width as 150 mm results from the fact that sheet metal blanks of this thickness are usually produced. In addition, the rejection of Sheet metal blanks of different thicknesses easily from the rejection of a sheet metal blank of the aforementioned Thickness can be determined. .

Under the above-mentioned conditions of the warpage measurement, the sheet metal blank, insofar as its warpage a is less is than 20 mm and the length is 3 m, can be regarded as normally rolled, i.e. not cut sheet, Thus, a warpage or deflection a of 20 mm with a sheet length of 3 m is a practical limit that "

In a test, hot strip with a thickness of 4.5 to 16 mm was unwound from a bundle, initially slightly smoothed and then cold-straightened according to the invention, as well as

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cut to length and finally stacked.

The operation is shown in FIG. Thereafter, the bundle of the rolling mill by means of a bundle conveyor 1 is a Coil crane 2 is supplied, which places the coils on a trolley 3, which brings them to a pay-off reel 4. During unwinding, the bundle is aligned and the tape is first of all over block shears 11 and trimming shears 2 fed to a straightening machine 5, in which the strip is straightened according to the method according to the invention the way happen that the band is initially bent repeatedly and given it a certain elongation and then the residual elongation is reduced with the usual increase in the distance between the rollers, but it is necessary Above all, to reduce the residual elongation in the outer fiber of the tape, which is why straightening halfway with high bending elongation the outer fiber and in the second half slightly only with a slight elongation of the outer fiber.

The advantage of the aforementioned method is that the number of bending rollers compared to conventional methods is about half less. ”In the present case, there are two straightening stands, one straightening stand 5 for a high bending elongation and a second straightening frame 6 for a low bending elongation for use. Between Straightening machines 5 and 6 are sheet metal shears so that only sheet metal blanks are fed to the roller straightening machine 6 will. The reason for this is that, in view of the roll straightening machine 5 giving the strip a strong Bending elongation is granted and the beginning of the strip is difficult to grasp, the caliber pressure for inserting the beginning of the strip into the roller straightener must be reduced and then a high bending elongation must be achieved; in the case of tape straightening can be carried out continuously, however, since only the beginning of the strip requires a change in the caliber pressure.

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changes and consequently a high throughput is possible. The beginning of the strip must go into the straightening machine 5 or «, in its gap to be pushed into; this is done with the help of of the decoiler 4. If the impact force is low, the tape often damaged by grinding marks, and the The start of the tape often comes from the nip.

If 5 blanks are fed to the roller straightener, the dimensional accuracy of the blank is lost and must the blanks then cut to size again Jj

which results in a noticeable decrease in performance.

The roller straightening machine 6, on the other hand, only works relatively low flexural elongation, so that the aforementioned difficulties do not occur here even when sheet metal blanks be judged. Rather, the cutting accuracy and dimensional accuracy are significantly improved.

After leaving the roll straightening machine 6, the Sheet metal blanks fed to a measuring device 8 and

Cold straightening in the two roller straightening machines 5, 6 takes place under the following conditions:

Intensive tests have shown that the warpage or curvature of a sheet metal blank is under 20 mm and there is no impairment of the mechanical Properties results when the bending elongation of the outer fiber is 0.60% to 3.0%. This follows from the diagram of FIG. 4, in which the relationship between Sheet thickness and elongation of the outer fiber is shown. In conventional processes, the bending elongation is · for heavy plate to 0.50%, while the flexural elongation according to the invention Is 0.60% to 3.0%.

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The deflection is in particular with a bending elongation of up to 0.60% of the sheet metal blank larger than 20 mm, while with a bending elongation of more than 3.0% difficulties arise on the roller straightener, result in particular at the inlet angle and also adversely affects the mechanical properties of the sheet metal will. The second light cold straightening takes place with a bending elongation that slowly decreases from less than 2.0%, preferably 0.6 to 0.4%, reduced to the elastic limit.

mk In particular, a hot strip quality SS 41 having a thickness of 6.0 mm in a conventional manner trained and directed sowie'anschließend mm cut to a length of the 3040th In FIG. 5, the curve of the deflections at points A to E (FIG. 3) of a cut sheet metal are shown in dashed lines, and the curve of the deflections of a sheet metal cut to size by means of flame cutting is shown with dashed lines. As the dashed curve shows, the deflection of the sheet after flame cutting varies by more than 100 mm between plus and minus. Such sheet metal blanks can therefore no longer be used universally.

The solid curve in FIG. 6 relates to the deflections or curvatures of a sheet metal blank from the same collar as the sheets in FIG. 5, but this sheet was subjected to a slight straightening with about 20% of the usual bending elongations. The dashed curve in FIG. 5 relates to a steel sheet of the same collar which has been straightened with a bending elongation of the outer fibers of £, _s1 = 0.54%, while the dashed curve relates to a cut of the aforementioned sheet. The individual values were measured along the cutting lines A to E (FIG. 4). The above-mentioned deflection of the outer fiber Eg ^ is less than the bending elongation according to the invention of L = 0.60%, so that the deflections are more than 20 mm.

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gene and these sheets are outside the invention.

The dashed curve of Figure 7 · refers to the bending of a sheet from the absolute in connection with FIG. 5 mentioned collar, which has, however, learned "during straightening a bending strain ■ £ .g ₂ = 0.88% and cut with Deflections of less than 20 mm resulted, that is to say that the heating tape was given a flexural elongation according to the invention during straightening.

In the diagram of FIG. 8, deflections are plotted, A

which resulted from a bending elongation of ^ g = 1.07%. It turns out that the deflections of the blanks after cutting were even less than when trying to Fig. 7.

The dashed curve in the diagram in FIG. 9 relates to a three meter long and 1.25 mm thick sheet metal blank of a steel strip (X-46) with a thickness of 12.7 m, which has a bending elongation E ™ = 0.54% was judged. The dashed curve shows the deflections after the flame cutting of the straightened strip section. Due to the bending elongation £ ™, which is less than 0.6%, the deflections of the blank exceed 30 mm and show that the bending elongation of this test was insufficient ₀

10 shows the deflections when straightening the band mentioned in connection with FIG. 9 with a bending elongation of E _x ? ⁼ 0.62%, ie in the order of magnitude of the lower limit value for the bending elongation according to the invention, with the dashed curve showing that the deflections after cutting are around 20 mm,

The diagram in FIG. 11 shows the deflections,

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as they were found when straightening the tape with a bending elongation of £, _χ , = 0.77%. It can be seen that the deflections after the flame cutting were in each case less than 20 mm.

The mechanical properties of the aforementioned sheets are evident from the charts of FIGS. 12 and 13. Here, FIG. 12 shows the influence of different expansions of the bending in connection with Figures 5 _e mentioned to 8 sheets on the yield strength, elongation and tensile strength. The individual diagrams show that, with the exception of the unchanged or slightly reduced yield strength after straightening, the values obtained after straightening are better than those of the original sheets. The solid curves L relate to the mechanical properties in the rolling direction, while the dashed curves C relate to the mechanical properties transverse to the rolling direction or across the width. In a similar way, FIG. 13 shows an improvement in the mechanical properties of the metal sheets in the experiments relating to FIGS. 9 to 11.

In the case of cutting between the two straightening machines, the sheet metal cross-section and the warps are from the Cutting corrected again by subsequent cold straightening.

The shape of a large sheet is difficult to determine, but in the case of cutting during the Straightening by a subsequent light cold straightening to remove residual stresses resulting from hot rolling corrected in the outer fiber.

Cold straightening takes place in two stages, one with a strong deflection and one with a slight deflection work is done »The first, i.e. strong straightening, takes place in such a way that at the beginning there is an intensive bending with

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a bending elongation of 0.6 to 3.0% and a gradient that is greater than that which, according to curve A in FIG steel in question. The final or second straightening takes place with only low bending elongation and a gradient that is lower than that between a bending elongation of the outer fiber of 0.6% to 3.0% and the elastic yield point of the steel in question according to curve C in Fig. 14a results. The diagrams in FIG. 5 show the importance of the straightening according to the invention in two stages, ie with a strong cold straightening and a slight cold straightening as well as a strong reduction in the directivity at the beginning of the straightening and a weak reduction in the directivity in the end phase . With regard to strong and easy judging, judging is divided into three types.

The three straightening phases are shown schematically in FIG. 14a. Curve A relates to normal straightening with a standard gradient, curve C to the straightening according to the invention and the curve B to straightening, in which the strong cold straightening takes place with a gradient, _ which is lower than the standard gradient and the easy ™ Cold straightening with a gradient that is greater than the standard gradient,

The curves in diagrams 14b, 14c and 14a show the distribution the residual stress in hot-rolled sheets that have been cold-straightened according to the three types of processes mentioned above.

The three curves clearly show that the conventional According to curve A in FIG. 14a, the average residual stress is relatively large in comparison with the Residual stresses of the other two straightening methods according to curves B and G in FIG. 14a and that the residual stress is the

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The outer fiber of the steel sheet is not significantly reduced.

When straightening according to curve B in FIG. 14a, the reduction in the residual stress is worst, in particular In this case, the residual stress in the outer fiber has only been reduced to a very small extent.

While in the inventive straightening according to curve C in 14a shows the average residual stress and the residual stress are lowest both in the outer fiber and in the area of the neutral fiber.

Referring to Fig. 15, it can be seen that the combination of strong straightening and easy straightening in view of an effective cold straightening with regard to the distribution of the residual stresses is necessary. As Fig. 15a shows, in the above-mentioned cold straightening alone only reduces the residual stresses in the area of the neutral fiber, while the residual stresses in the outer fiber remain unchanged. On the other hand, according to FIG Cold straightening only reduces the residual stresses in the outer fiber.

Through the combination according to the invention of an initially strong cold straightening with a subsequent light cold straightening this results in an optimal distribution and effective reduction of the residual stresses according to FIG. 15c "

In addition, the stress compensation in the sheet metal is achieved by subsequent processing, for example flame cutting not disturbed, so that hot-rolled sheets with technological properties can be obtained by the process according to the invention result in terms of the absolute deflections of the sheet metal blanks and the mechanical properties without further ado a comparison with conventional coarse sheet

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to withstand.

With regard to the initial gradual decrease in deflection during strong cold straightening and the subsequent gradual decrease in deflection during light cold straightening within the scope of the values according to the invention, the intermediate gradual decrease in deflection between strong cold straightening and light cold straightening is not essential, _o

From the foregoing it follows that even then none Impairment of mechanical properties results when the severe cold straightening from the standpoint of conventional Judging procedure is not permitted.

The invention makes it possible to produce sheet metal blanks from hot strip, which are comparable in terms of their properties to the usual heavy plates, but are far more economical can be produced.

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Claims (1)

NIPPON STEEL CORPORATION, No. 6-3, 2-chome, Ote-machi, Chiyoda-ku, Tokyo, Japan Claims; Γ 1 J process for the production of steel sheet blanks Hot strip, characterized in that the hot strip undergoes strong cold straightening with a bending elongation from 0.60 to 3.0% in the outer fiber. 2. The method according to claim 1, characterized in that the tape after the strong cold straightening is subjected to further straightening to remove the residual stresses in the outer fiber. 3. The method according to claim 2, characterized in that the strong cold straightening with faster The bending elongation is reduced by 0.6% to 3.0%. 4. The method according to claim 2 or 3, characterized in that the light cold straightening takes place with a gradual reduction of the bending elongation up to the elastic yield point » 5. The method according to one or more of claims 1 to 4, characterized in that the band between the strong straightening and the easy straightening is cut. 6. The method according to one or more of claims 1 to 5, characterized in that the bending strain at least at the beginning of the strong cold straightening in the outer fiber is rapidly reduced from 0.60 to 3.0% with a gradient that is greater than that of the bending 109824/1019 expansion of the outer fiber from 0.60 to 3.0% with the elastic Yield strength of the steel in question connecting gradient (A) and at least in the end phase of the light Straighten the bending strain in the outer fiber with a gradient which is smaller than the gradient (A). Method according to one or more of claims 1 to 6, characterized in that the tape is first cold-straightened to prove the residual stresses in the area ä of the neutral fiber and then again cold-straightened to remove the residual stresses of the outer fiber. 8. Device for performing the method according to the claims 1 to 7, marked by a decoiler (4), a straightening machine (5) with greater deflection ^ a straightening machine (6) with slight deflection and a pair of scissors (7) 9. Apparatus according to claim 8, characterized in that that the scissors (7) is arranged between the cold straightening machines (5, 6). ~ 1 10. Apparatus according to claim 8 or 9, characterized by flying scissors (7). 109824/1019 Blank page