DE2742151C2 - Process for the continuous production of steel strip by hot rolling - Google Patents

Description

at a remarkably low speed

be held while the front end is out of the

55 finishing mill comes out and reaches the winding machine, so that it is almost impossible to produce a

The invention relates to a method for the continuous irregularity of the heating process in the longitudinal direction

the manufacture of steel strip by hot rolling, avoiding hot strip processing,

according to the preamble of claim 1.Fourth, the front end and the final

One method of the kind indicated is to be cut off from the end of the warm ribbon as it is

JA-OS Sho 51-1 12 459 known. tongue-like or fishtail-like shape

Continuous hot rolling is one of the following, which lowers the production yield

Reasons necessary or appropriate: will.

For the production of a warm roll of tape from a JA-OS Sho 51-1 12 459 mentioned at the beginning

Steel slab is the steel slab on surface 65 was in order to carry out the hot rolling continuously

flaws investigated, and the surface flaws are proposed to be able to roll the steel mate-

removed by hot flaming and the like. To connect to these rials successively. After every

Way surface-conditioned steel slab is used in the end region of a process to be rolled

previous steel material with the. front End portion of a subsequent steel material to be rolled overlaps, and rolling is carried out on the overlapped areas to connect the preceding and succeeding steel materials, and thus bonded materials are fed to the finish hot rolling step to make the hot rolling continuous perform. In this method, however, it is necessary that both sides of the overlapped areas are temporarily welded that the thickness of the scale on both, internally opposite surfaces of the overlapped areas is kept to be 40 µm or less that the length in the rolling direction of the overlapped areas at least half the width of the steel material to be rolled and that the overlapped parts with a percentage decrease of 30% or higher can be rolled in the entry stage of the finish rolling stage.

Thus, that method has the above JA publication the disadvantages that a welding device to carry out the temporary welding of both Sides of the overlapped parts, while the material is running, is required that the production yield is low because the materials over a length of at least half the width of the material must be overlapped, and that a large-capacity rolling mill is required because a decrease in at least 30% on the overlapped parts when initially rolling the subsequent material in the finishing mill takes place.

In DE-OS 16 02 016 it is proposed that the rest of the end parts of two to be connected To weld sections of wires or rods. However, this is a complicated system for Formation of a loop provided. The information provided in this publication, not explained in detail, In any case, types of connection are such that they can only be carried out when the sections are at rest.

In DE-GM 17 30 132 can only be quasi-continuous be worked, and it must be provided complicated devices to the necessary To compensate for the temporarily idle quantities of material in the overall process.

Technica, No. 21, 1961, p. 1385, is a Process specified in which the rolling tongues must be cut off. Then the ends Butt-welded by an additional device (Argonarc process). Such an additional facility requires a considerable amount of effort, and in addition either must be welded Belts stand still, or the welding system has to be carried with considerable additional effort.

From Rügen, Handbuch der Schweißtechnik, Heidelberg 1974, p. 351, it is known for soft soldering - for better connection of solder and metallic material - to use so-called flux.

The object of the invention is to make the temporary welding of the overlapped parts unnecessary make and also with thicker scale the two areas also with a lower percentage To be able to connect decreases in the input stage of the finishing stage.

According to the invention, this object is achieved by the further development according to the characterizing part of claim 1 solved.

According to the invention is therefore in a method in which a heated to its rolling temperature Steel slab a pre-hot rolling process, possibly an intermediate hot rolling process and a final hot rolling process to obtain a warm band, a leading end portion of a through the tub rolling process and, if necessary, the steel strip rolled by the intermediate hot rolling process with a the final end region of a preceding steel strip that has been rolled in the same way or overlapped during the finish hot rolling step, with between the overlapped parts of the two An oxide scale flux is inserted into warm bands, which is opposite to that on the other Surfaces of the overlapped parts present oxide scale reacts by the heat of the overlapped parts and forms a substance having a low melting point and a high fluidity, and at least one metallic one nail-like component driven into the overlapped parts to temporarily fix the overlapped parts, and the overlapped parts are joined by rolling reduction, pressure, and the finish hot rolling process subjected to continuously obtain a hot strip steel.

The solution according to the invention is particularly important the following advantages:

The features of the invention make it possible that the connected parts are not detrimental to the Rolling conditions are, and joining can within a very short period of time, and the bond strength can at least be the rolling under tension withstand in the finishing stage.

By inserting the specified oxide scale fluxes, the pressure connection can through Contact connection of the opposite surfaces of the base metals of the overlapped parts of the warm bands can be achieved. Thus, the oxide scale present on the surface of the steel strip can die Do not prevent the bonding of the base metals under pressure. The oxide scale must be used in the invention not by a mechanical grinding process such as brushing or by a gas grinding process, such as hot flaming can be removed using oxygen gas. The scale flux reacts with the oxide scale at the temperature of the steel strips to be joined and forms a substance of low melting point with high fluidity, which is squeezed out. Consequently the oxide scale becomes substantially together with the pinched low melting point substance removed from the tape surfaces of the overlapped end portions, so that a satisfactory connection of the opposite metal surfaces can be achieved.

Due to the temporary fixing by means of the metallic nail-like ".n Eduteils the connection is ensured and a Sliding of the opposing surfaces in the overlapped parts prior to completion of the connection dung avoided. Furthermore, an increase in the width and a warping of the overlapped parts during the Avoid rolling.

For the continuous production of the hot strip through the preheating stage, if necessary the intermediate stage and the finish hot rolling step. knew the steel slabs one after the other before Pre-hot rolling are connected, or the steel strips are after the pre-rolling between the The roughing stage and the finishing stage are connected or, in some cases, between the intermediate stage and the finishing stage or the roughing stage.

However, if the steel slabs were to be joined before the preheating step, the roughing step would have to be performed and the finishing rolling stage are connected; however, such a connection is across the entire roll stands difficult to achieve by the existing rolling techniques, and if the steel slabs are a relatively have a large thickness, the connected (lapped) part takes a considerable amount after the finishing rolling step Length in the finished warm band that has to be cut off, creating considerable Reduction of the production yield results.

On the other hand, if the steel strips are joined after the roughing step as mentioned above, the disadvantages of the slab joining can be eliminated. Therefore, in the present invention, it is particularly preferable to join the steel strips after the roughing step.

The temperature of the steel strips at the time of their connection by pressure is advantageously not less than 1000 ⁰ C, and if the steel strip is supplied to the finishing hot rolling train normally at a temperature between about 1000 and 1050 ⁰ C, a favorable pressure connection temperature can be maintained without any special Concerns if rolling is done under normal hot rolling conditions.

The scale melting agents are preferably applied in powder form.

To ^r application of the scale melting agent on the surfaces of each to be connected hot steel strips it, in the case of the oxides or complex oxides may be directly applied, for example in the form of B2Oi example, boron oxides or Borkomplexoxide, or they may be in the form of boric acid (HiBOj) are applied, which is dehydrated directly to the boron oxide, since the warm band is not below 1000 ^C C at high temperatures, so that the same result as with dcT application of boron oxide (B: Oj) can be achieved. According to the invention, the oxides or complex oxides therefore contain substances which decompose at a temperature not below 1000 ° C. to produce an oxide.

The nail-like component is preferably made of carbon steel or low-alloy steel. It will driven through the overlapped parts. This can be done in a simple manner within a very short period of time, while the steel belts are running. As a means for driving in the nail-like component due to the overlapping parts, this can be done by one or more known types of nail blow guns Explosion type, high pressure gas or compressed air type.

The nail-like component must have a higher strength than that which is to be driven through the overlapped parts at the high temperature is required when, however, the strength of the nail-like Component is excessively high, this will cause the surface of the roll during the subsequent rolling process damaged, and thus an excessively high strength of the nail-like member should be avoided will. The nail-like components should preferably be chosen so that their strength is reduced when they absorb heat from the steel strip, and practically equal to the strength of the steel strip during of the subsequent rolling process.

The number of nail-like components to be driven in per unit area of the overlapped areas should be limited to the minimum necessary to maintain the rolling stability of the overlapped areas. An excessive number of nail-like members driven through the overlapped areas reduces the strength of the overlapped areas, which often leads to their breakage during the subsequent rolling process.

The invention is explained below on the basis of preferred embodiments with reference to the drawings ίο explained in more detail. It shows

1 shows an example of the device used to carry out the method according to the invention,

F i g. 2 the overlapped parts of the temporarily through the nail-like components fixed steel strips and

Fig. 3 (a), (b) and (c) each ways of driving the nail-shaped components into the overlapped parts.

In Fig. 1, 1 represents the last roll stand of a hot roughing line. A hot strip 2, which was produced by rolling a steel slab in the hot roughing line, comes from the last roll stand I of this rolling line and moves on the rollers of the Preferential roller table in the direction of arrow (a) with alignment on the first roll stand 9 of a finishing hot rolling train. The delay roller table arranged between the last roll stand 1 and the first roll stand 9 consists of a fixed delay table: i0 with rollers 12, a tiltable delay table 10 'with rollers 12' and a fixed delay table 10 "with rollers 12". The tiltable delay table i0 'is designed so that it moves from its horizontal position to its tilted position when the piston rod 13 of the hydraulic system 11 attached to the front ii end goes up.

In Fig. 1 the preceding hot-rolled hot strip 3 is shown in such a way that it already leads into the n ~ - »; ~ .. _rn , -miwilvcfraRp * -» inori »ici uunhpi ςρϊη nh- ¹ * ->» '6 ""'"'" ^M '" ^J "σ -" -

closing end part is overlapped with the front end part of the following warm band 2. the rear edge of the preceding warm strip 3 is determined by an infrared measuring device 4, which is about is attached to the rear end of the deceleration roller table. while the warm band 3 on the rollers 12 "of the delay table 10" is running and the display signal becomes a spray device 5 forwarded, which the oxide scale flux stored and sprayed, and it is above the on rolls 12 "of running warm tape 3 and in front

so placed the infrared measuring device 4 with respect to the advancing direction of the warm strip, whereby the Spray device is actuated during a certain constant period of time and the scale melting agent is sprayed on the upper surface of the final end portion of the warm ribbon 3. The infrared measuring device 4 sends the display signal to the tiltable hydraulic system 11 after perceiving the rear edge of the warm belt 3 and actuates the lifting rod 13 of the system and also sends the Display signal to the device for controlling the rotation of the rollers 12, 12 'of the delay table 10, 10 'to increase the rotation of the rollers and thus the running speed of the warm belt 2 raise. Before the rear edge of the warm belt 3 is perceived, the rotation of the rollers 12, 12 'and 12 "of the delay table 10, 10' and 10" so regulated that the preceding warm band 3 and the following warm band 2 with a constant

Distance between them run at the same speed.

When the hydraulic lift rod 13 moves up, the deceleration table 10 'extends a horizontal position to its tilted position as shown, and on the other hand begins when the The running speed of the warm belt 2 increases over that of the warm belt 3, the front one End part f ^ s warm band 2 over the final End part of the previous warm band 3 to overlap.

At a front position in the direction of the forward movement of the warm bands is another X-ray measuring device 6 arranged above the warm belt 3. When the leading edge of the warm Band 2 is detected by the X-ray measuring device 6 while it is running and the final End portion of the warm belt 3 overlaps, the lifting rod 13 of the hydraulic system 11 is caused to Restoration of the delayed sound SO 'to κ goes down from its original horizontal state, and at the same time turns the rotation control device of the rollers 12, 12 'of the deceleration table 10, 10' operated to increase the running speed of the to synchronize warm belt 3 with that of the warm belt 2. This way the overlap becomes of the end parts of the two warm bands.

The overlapped parts run on the rollers 12 "of the delay table 10" and are in the first Roll stand 9 of the finishing hot rolling mill introduced, where the overlapped parts due to the rolling reduction get connected. During the rolling reduction or decrease, oxide scale is deposited on the opposite ones Surfaces of the overlapped parts squeezed out as it was already in the liquid substance has been converted from a low melting point by reaction with the oxide scale flux. so that the base metal of the opposing surfaces is thereby practically exposed and a Metal-to-metal bond is obtained. The connection can by a pressing device such as a rotary press (not shown) before the overlapped Parts enter the first roll stand 9 are carried out.

The hot strips connected in this way are continuously finish-rolled in the finishing hot-rolling train.

During the joining of the overlapped parts by rolling or pressing, it occasionally happens that the overlapped parts differ from each other, increase in width or deform. Therefore, it is desirable that the overlapped parts are set temporarily as described below and then rolled or pressed to join them together.

A hammer device 7 is in front of the X-ray measuring device 6 arranged in the direction of the forward movement of the warm belt and above the warm belt, and an X-ray measuring device 8 is arranged in front of the hammer device 7. The X-ray measuring device 8 determines the leading edge of the warm strip 2 running in the overlapped parts, and that The perception signal actuates the hammer device 7 in order to move the metallic nail-like components 14 into the «5 to drive overlapped parts of both warm belts, causing the overlapped parts to intermittently are then fixed, the temporarily fixed overlapped parts in the first roll stand 9 of the Introduced finishing hot rolling mill, where the overlapped parts are joined by rolling reduction, and then the warm ribbons thus bonded are continuously subjected to finish rolling through the first and second Subsequent roll stands subjected to the finishing hot rolling mill.

The hammering of the nail-like components 14 in the overlapped parts can be done in such a way that they the warm bands 2 and 3, as shown in Fig.2, pierce straight through or in such a way that they the pierce warm straps 2 and 3, with both ends protruding from the two surfaces or the overlapped parts as shown in Figure 3 (a) to (c), partially penetrate across.

In the above embodiment, the preceding and succeeding warm ribbons are between the last stand of the preheating mill and the first stand of the finishing hot mill connected to continuously generate the warm band. However, without the scope of the invention to leave the last roll stand 1 of the pre-hot rolling train through the first roll stand of the finishing hot rolling train can be replaced, and the first roll stand 9 of the finishing hot rolling mill can be replaced by the second roll stand the finishing hot rolling mill will be replaced in order to keep the hot strips between these rolling stands during of the finish rolling process.

Furthermore, joining the preceding and succeeding warm straps may in certain cases take place after an intermediate rolling stage following the preheating stage.

Thus, the preceding and succeeding hot strips passed through the intermediate rolling step have passed, between the finish hot rolling step or during the continuous finish hot rolling process tied together.

The present invention is explained in more detail by means of the following examples.

A low carbon steel slab 250 mm thick and 10 mm long is obtained of a warm steel strip continuously hot-rolled.

The above low carbon steel slabs were subjected to the equalization annealing 1200 ° C, through the preheating mill 1 reduced or rolled in order to obtain warm steel strips of 30 mm thickness, and these warm strips are connected successively one by one and continuously among those in the The following table specified conditions hot-rolled.

No. 1 and No. 2 in the table are comparative examples in which no oxide scale melting agent is used and the overlapped parts were temporarily fixed by the nail-shaped members. In No. 3 to 12, which represent examples according to the invention, the joining of the warm straps took place before the Finished hot rolling. This was done in Nos. 13 and 14, which also represent examples according to the invention Joining the hot strips during finish hot rolling.

As can be seen clearly from the table, although the temporary fixation by the nail-shaped components alone is the subsequent continuous one Hot rolling is made possible, a relatively large number of nail-shaped components necessary to produce a to bring about sufficient bond strength of the overlapped parts, which satisfactorily

withstands subsequent finishing hot rolls. The number of nail-shaped ones driven into the overlapped parts Components should be suitable. If the number is too small, the nail-shaped components are replaced by the Tensile broken during the finishing rolling step, so that the desired effects of the temporary setting

10

cannot be achieved. On the other hand, if the number is too large i. <= T, the overlapped parts break in which the nail-shaped components are driven in during the finish rolling process due to too many Penetrations through the nail-shaped components.

No. steel material

broad

mm

Oxide scale flux)

lot

g / rrr

Over- number contraption away temperature lapping collected to the press took where the length bener link extent link nail- he follows more shaped Components

Low carbon steel slab

the same
the same
the same
the same
the same

7 the same.

8 the same.

9 the same.

10 the same.

11 the same.

12 the same.

13 the same.

14 the same

1200

1200 1200 1200 1200 1200 1200 1200 1200 1200 1200 1200 1200 1200

No. No. No. No. No. No. No. No. No. No. No. No. No.

30 30 30 100 100 200 200 200 200 200 200 100 100

200 200 300 200 100 300 100 100 100

10

20 4

4 4

4 4 4 4 4 4

40

1050

F ₁ ***) 30th 1045 R. P. 40 1050 R. P. 40 1060 F, 30th 1060 R. P. 20th 1040 R. P. 20th 1050 R. P. 20th 1050 R. P. 20th 1065 R. P. 20th 1055 R. P. 20th 1050 R. P. 20th 1050 R.P. 40 1010 R. P. 40 1010

Footnotes:
·) Composition of the oxide scale flux:

No. 1: B ₂ O ₃ (50%) - Na ₂ B ₄ O ₇ (50%)

No. 2: B ₂ O ₃ (45.6%) - SiO ₂ (17.5%) - Na ₂ O (25.0 ^s ») - Al ₂ O ₃ (4.5%) - CaO (5, 0%) - MgO (2.4%) No. 3: P ₂ O ₅ (60.9%) - B ₂ O ₃ (5.3%) - K ₂ O (16.0%) - Na ₂ O (9.8 %) - LiO (4.3%) - Al ₂ O ₃ (3.2%) No. 4: NaCl No. 5: NaNO ₃ No. 6: Na ₂ SO ₄ ♦ *) RP = rotary press ***) Fi = first roll stand the finishing hot rolling mill

According to the invention, wherein the oxide scale flux is on the opposing surfaces of the overlapping parts is applied, a firm bond is created by pressure between the exposed or bare metals of the opposite surfaces brought about and thus a continuous and stable hot rolling process even under the strict conditions in the reached the subsequent finish hot rolling stage. Furthermore, so it is. when the overlapped parts temporarily through the nail-shaped components are set, the deviation of the opposing surfaces is possible of the overlapped parts and to avoid the increase in width and deformation of the overlapped parts, so that

55 an accurate and firm connection can be obtained. It is also possible to change the length of the overlapped Parts to decrease. Thus, a good production yield can be made possible.

For this purpose 2 sheets of drawings

Claims (8)

1 2 heated in a reheating furnace, then the preliminary patent claims: rolling process, in some cases the intermediate rolling process, finishing rolling, cooling on a run-out roller 1. Process for the continuous production of gang, subjected and is on a winding machine Strip steel by hot rolling, wound up in front of the 5. If the rolling process takes place intermittently or during the finish hot rolling one front slab by slab, the front end of the is made End area of a steel strip over the rear end area that comes to the last roll stand of the finishing train a steel belt is overlapped and the warm belt is usually in a running die overlapped parts then held by rolling speed of 480 to 540 m / min, from where be connected, characterized by 10 from it runs on the run-out roller table If the front net that between the overlapped areas of the end of the warm strip on the outfeed roller table with At least one of the two warm bands runs at a higher speed, it jumps powerfully. Group of oxides, complex oxides, sulfates, When the front end of the warm tape on the Nitrates, carbonates and / or phosphates of Li, Na, winding machine is wound up, the run is Mg, Ca, Ba, B, AL Si, Pb, P and / or iron 15 speed of the hot strip up to that through the is inserted and the overlapped parts by a speed determined in the rolling process or by the overlapped parts are driven in by a specific hot strip production line Component can be set temporarily. th speed increased 2. The method according to claim 1, characterized in this way it is in the case of an intermittent draws that the steel strip an intermediate rolling 20 rolling process, in which the rolling slab for Process K <= ch the slab subjected to preheating is carried out, if necessary, the running speed will. of the warm ribbon, while the leading end of the 3. The method according to claim 1 or 2, thereby warm tape comes out and the winding machine characterized in that the oxides and complexes achieved, maintain, and the productivity of the Oxides have a substance that is low in the 25 steel strip hot rolling mill because an idling temperature of the steel strip to which it is applied operating time between completion of the rolling process are decomposed to form an oxide of a preceding slab and the beginning of the 4. The method according to any one of claims 1 to 3, the rolling process consists of a subsequent slab,
characterized in that the oxide scale also reduces the temperature of the warm flux on the steel strip at a temperature of the strip considerably before the front end of the door is not applied below 1000 ° C. warm ribbon reaches the winding machine as the 5. The method according to any one of claims 1 to 4, running speed of the hot strip at a rate characterized in that the nail-like component is kept at a remarkably low speed higher than the strength of the while it comes out of the finishing train and overlapped parts of the hot strip reaches the winding machine at the time, as mentioned above,
point of overlap. However, it is when rolling a warm strip 6. The method according to any one of claims 1 to 5, required that the temperature of the hot strip characterized in that the nail-like component of the outlet side of the finishing train within a is made of a metal that has a final strength specific zone to a required quality equal to that of the overlapped portions of the warm ribbons 40 of the warm ribbon, and to this if it needs to be warm by the heat of the temperature, both the steel slab tape being affected. me taken out of a Brarnmenheizofen 7. The method according to any one of claims 1 to 6, will be held higher so that the above characterized in that the decrease in temperature is compensated for. This is warm strips for their connection by the 45 the reason why the heating system in the hot rolling pre-finishing hot rolling stand or by a separate gear of the belt not to be set lower reducing device takes place. can. 8. The method according to any one of claims 1 to 7, Thirdly, it is necessary that the warm band of characterized in that the reduction of its front end to the final end one warm ribbons to connect them takes place when 50 is subjected to uniform heating to the the warm ribbons settle at a quality temperature, but must as above above 1000 "C. mentioned, the running speed of the warm belt