KR20120132872A - Strip cutting method in continuous casting of steel - Google Patents

Abstract

PURPOSE: A slab cutting method in continuous casting of steel is provided to cut slab without a collision between saw blades by freely controlling the pressing end points of the saw blades. CONSTITUTION: A slab cutting method in continuous casting of steel bites and cuts slab(31) by pressing a pair of V-block type cutting saw blades perpendicularly to the axis of the slab. The pair of cutting saw blades are arranged to be misaligned with each other in a slab drawing direction and cuts the slab by pressing the slab over the middle of the slab thickness to provide shear and tension while preventing a collision in the middle of the slab thickness. The amount of misalignment between the saw blades is 1-5% of the slab thickness.

Description

Casting method for continuous casting of steel {STRIP CUTTING METHOD IN CONTINUOUS CASTING OF STEEL}

The present invention relates to a method for cutting a slab in continuous casting of steel.

When the steel piece is rolled into a predetermined hot rolled product, both cross sections deform into a unique shape in each pass, thereby inhibiting biting into subsequent passes. It also remains as a flaw in the product. The end is thus cut off in the proper pass. This is one cause of the rolling yield loss.

It is a long time for those skilled in the art to solve the above problem by forming an end portion into a shell shape when cutting a continuous cast slab into a steel slab, but a method that can be made at low cost is still not found.

In the past, the cutting method was a gas stage, but since cutting by a hydraulic shear is advantageous for the problem, the former is often used in large blooms and slabs of the cross section and the latter in small billets.

There are two problems with cutting. One is the yield loss of the rolling, and the other is the high speed of continuous casting, and the core is cut immediately after solidification or in the state of non-solidification, the risk of molten steel ejection at the melt, and the ejection at the shear (shear). The fragile portion is chopped, attached to the edge of the cast piece, and scratched, or interposed between the blades (blades) and becomes inoperable.

Patent Document 1 proposes a solution to both problems for billets. According to this, the cutting is performed in two stages, and at the first stage, the cut scheduled position of the cast piece is inclined to be sealed to seal the melt core, and at the second stage, the shear core is sheared at that position. By this method, in addition to improving casting efficiency by high-speed molten metal injection, hotter cast steel is supplied to a rolling furnace in the next step to save energy, improve bite-ability of rolling by end slope, and end cutting. It is disclosed that a reduction in amount is obtained.

In this method, the complexity and equipment cost of having to integrate a pressing device newly in a continuous casting machine are not implemented because of problems.

In patent document 2, the cutting method for the slab is proposed. According to this, a mating wedge-shaped saw tooth is press-fitted toward the center portion of the thickness of the cast steel, and the cut surface is inclined to segment the cast steel. The end shape is wedge-shaped (triangled column) when viewed from the side, and since the cutting burr is located at the center of the cross section, no flaw is generated by the burr. Although it is possible to inject molten metal, it has not been implemented for some reason.

Moreover, the opening angle of a wedge is an important factor in 4, 16-32 lines of patent document 2, The risk of a collision of a blade tip increases in 60 degrees or less, and in 60 degrees or more, between teeth is 10-20 of plate | board thickness. It is described that it is easily segmented by the separation force in the slab axial direction when the% is reached. It is very suitable if the method can be applied to continuous casting of billets.

In order to examine the possibility, the analysis by finite element method was conducted first. The V block serving as the cutting teeth was set to an open angle of 120 °, which is more advantageous for cutting, for the slab of the hollow angle cross section. The results are as follows: 1) No cutting occurs as described, even if both block ends are close to 10% or less of the slab thickness. 2) The widening of the cutting end (cutting burr) is unexpectedly large in hollow materials. Two things became clear. Since the widening is large enough that the jam during conveyance of the slab may interfere with the biting on the roll, a sure measure is indispensable.

Next, a simulation was performed with a plasticine model. The results were segmented just before both saw blades contacted, but there was no such case as 10% before segmentation as initiation. Plascin was originally elongated and was advantageous for cleavage but the disclosed effect was not obtained.

Subsequently, closer to each other, the indentation and cutting test of the V block having an opening angle of 90 ° was performed on the hot bars. The results were also more uncertain than plasticin by simple indentation alone. For example, even if the incidence rate is small, uncut generation is not allowed in operation. V block indentation alone is not practical. Some obvious measures are indispensable. However, in the experiment, it was found that the saw blades are slightly displaced back and forth, so that if the feed excess is excessively divided. A little more deviation and excess amount is better. It is believed that shear and tension act at the cutting end in this situation.

By the way, in the rolling process, a cutter of a biting cut method similar to the press-in of a wedge-shaped saw tooth is often used. If you look closely at the operation of the cutter, the cutting force is applied by pressing and pulling at the same time. It can be seen that there is a problem in the certainty of the cutting only by simple indentation.

Japanese Laid-Open Patent Publication No. H10-180428 Japanese Patent No. 1640730

The present invention has two objectives: 1) to facilitate injection of molten metal at high speed by continuous casting of steel billets in continuous casting of steel billets, and 2) to improve the rolling yield by forming a billet cross section into a wedge shape. In order to cut the continuous cast slab, two V blocks facing symmetrically with respect to the slab axis are used as cutting saw teeth, and a method of pressing and dividing the slab into the slab surface is adopted. At that time, 1) be sure to cut, 2) suppress excessive expansion of the cutting bur, and 3) the hydraulic shears currently used (usually attached to 4 to 8 continuous casting machines) due to equipment cost. It is a problem to be solved by three points that can be modified and implemented.

The first invention is a method of cutting a continuous cast slab for billet of steel, the method of cutting to bite-cut by vertically injecting the saw teeth on a pair of the V block to face each other with the cast between. WHEREIN: When the tooth blades of both cutting teeth are arrange | positioned mutually to the cast drawing direction, and when the both cutting teeth are press-fitted, it presses over an intermediate point, avoiding that the tooth teeth collide at the midpoint of a slab thickness. It is a method of cutting a continuous cast slab, characterized in that the shearing and tension at the end of the cutting by the action.

According to a second aspect of the invention, in the first aspect of the invention, the size of the deviation between the teeth is set to 1 to 5% of the thickness of the slab, and a means for setting and adjusting the end point of indentation of both cutting teeth is formed in the indentation mechanism. It is a method of cutting a continuous cast cast, characterized in that.

According to a third aspect of the invention, in the first invention or the second invention, a guard is formed in the indentation mechanism to restrain the widening of the cut portion accompanying the cutting.

According to a fourth aspect of the present invention, in one of the first to third inventions, one of the cutting teeth is used as a fixed tooth, and the other is a moving tooth.

In the above technique, when the tooth opening angle is relatively small, it is called wedge shape, and when it is large (for example, 90 °), it is called V block.

Although the casting efficiency can be improved by increasing the speed of continuous casting, in the present invention, when uncut solid slabs are cut, cutting is performed in one step of biting and cutting by press-fitting a V-block. Since it can be carried out simply by changing the structure of the blade of the existing hydraulic shearing machine, 1) the equipment and work are simple and stable, 2) there is no leakage of the molten core, and 3) the shape of the cut surface is smooth and tapered. . In addition to improving casting efficiency, the rolling yield is improved.

In biting cutting, the teeth are slightly different from each other in the traveling direction of the cast steel, and the heights are different. Has Therefore, the saw blade can be cut reliably without colliding with each other. Since the restraint guard is provided on the side for abnormal expansion of unsolidified slabs, the shape of the cutout is a simple bilateral inclination (a bow shape from the side), which does not cause any problems in subsequent work. Do not.

1 is a schematic side view of an example of a continuous casting machine embodying the present invention.
It is a figure which shows the structure of the cutting mold which is a principal part of the slab cutter which implements this invention.
3 is an explanatory view of a cutting method of the present invention.
4 is an explanatory diagram for adapting a hydraulic shear to the method of the present invention.
5 is a diagram illustrating an example in which the deformation behavior at the time of cutting is analyzed by the finite element method (FEM).

Hereinafter, the present invention will be described with reference to the drawings. 1 is a schematic side view of an example of a continuous casting machine embodying the present invention.

In FIG. 1, the molten steel Me supplied from the ladle 1 to the mold 3 through the tundish 2 is cooled in the mold 3 to form the slab 5 while forming a solidification cell. . The cast piece 5 is elongated while being drawn by the pinch roll 6 via the secondary cooling stand 4 at a higher speed than usual, for example, 1.5 times. The cutter 7 is passed through the cutter 7 in the state of leaving the molten core 8 inside the cast piece 5, and is cut by the cutter 7 to a predetermined length. The molten core 8 is sealed and the molten core encapsulated steel strip 9 is formed. Casting efficiency increases with speed.

The steel piece 9 is supplied by hot rolling of the next process directly or via a holding furnace (not shown). Solidification of a core part is complete | finished during conveyance to rolling, or hold | maintenance, and the fall and the cracking to the temperature suitable for rolling advance. Since the holding calorific value of the steel piece increases more than usual, the amount of heat of reheating, the amount of rolling power, and the like are reduced. In the middle of rough rolling, both ends of the material are cut and removed only because of inappropriate shape or surface properties. However, in the present invention, since the inappropriate part is short, the cutting length is shorter than in the prior art.

In Fig. 2, the cutting die 21 forming the main portion of the cutting machine 7 is formed on the base 22 and the base 22, and the V block 23 and the V block 23, which become cutting saw teeth, are formed. A widening suppression guard 24 fixed to the side and a stopper 25 for determining the indentation end point detachable on the guard 24. The mold 21 is arranged to be an up-down object and is installed to be press-fitted from the upper and lower surfaces of the cast steel. In the press-fitting, the stopper on the guard of one mold dies against the base surface of the other mold and becomes the press-fit end point.

3 shows a method of cutting a cast steel using the mold. In the pair of V blocks 32 and 32 'pressed into the upper and lower surfaces of the cast piece at right angles to the drawing direction with the cast pieces 31 interposed therebetween, the coagulation cell 33 is inclined and the melted core 34 is inclined. Is blocked.

Subsequently, the tip of the two V-blocks 32 and 32 'is close at the center of the slab, and the slab is about to be divided, but the cut end of the slab is surprisingly extensible and thus cannot be easily separated. When the tips of both blocks meet, they split, but the cogs are worn out. In the present invention, the two V blocks 32 and 33 'are provided a little outwardly in the cast piece drawing direction, and as a result, the side surfaces of the two teeth are contacted with each other beyond the intermediate point without colliding at the intermediate point of the cast steel thickness. Immediately before contact, the cast is divided. The form of deformation is pressing until the end, and the end + shear + tension. Therefore, it can be cut reliably.

The property of the cut surface is smoothed except for the end portion. The smoothness is not comparable with shearing (cracking occurs), and is equivalent to the rolled surface and is excellent. This shortens the end cutting length at the time of rolling.

The shift amount G of the tip may be several mm. Too much or too little creates a risk of collision or uncertainty of cutting. Excessively, the material of the gap blocks the progress of the cutting. It can be seen from the plasticine model that 5% or less of the slab size is preferred. The lower limit of the shift amount G is 1%.

The problem is that the cutting mold is returned when one tooth blade is in contact with the other side of the tooth blade so that the V block is not put into useless loads. The movement of the hydraulic cylinder is somewhat momentary and requires a firm stop mechanism. For this reason, the present invention employs reliable press-fit end point control means. Specifically, it is the stopper 25 of FIG. 2 mentioned above. The stopper 25 formed in the upper surface of one guard at the press end point collides with the upper surface of the other base 22, and stops subsequent press reduction. The thickness of the stopper 25 is adjusted to coincide with the end point and the collision time.

Fig. 4 shows the structure of a cutter for carrying out the cutting method of the present invention, and is a view seen from the direction of the cast axis. The structure is the same as a conventional hydraulic shear except a cutting mold. Therefore, the existing hydraulic shear can be partially retrofitted.

The bottom surface of the hydraulic cylinder 42 is fixed to the inner surface of the end portion of the edge 41 subjected to the press-in reaction force of the cutting mold, and one cutting mold 44 is formed in the cylinder head 43 to be a moving tooth. The other cutting mold 44 'is fixed to the other end in the range to become a fixed tooth, and both molds 44 and 44' face the cast piece 48 with the interposed portion therebetween. As the cylinder 42 expands, the V blocks 45 and 45 'are press-fitted into the cast steel, and one widening suppression guard 46 (or 46) is exceeded at the point where one tip contacts the other beyond the midpoint of the thickness of the cast steel. The thickness of the stopper 47 (or 47 ') is adjusted so that the stopper 47 (or 47' on ') collides with the surface of the other mold base 44' (or 44).

The above is an example of a means for setting and adjusting the press end point provided in the press fitting mechanism.

One problem with the biting cutting method is that in the case of unsolidified slabs (which are considered to be hollow materials in deformation), the cutting part widens at right angles to the indentation direction, and widens about 30% at the tip. . In the conventional shearing, there was no problem, but this size hinders subsequent conveyance and rolling biting. The above-mentioned widening restraint guards 46 and 46 'function, so that the widening stops within 10%. Examples of the widening restraint means include various structures (for example, attaching a guard to the edge 41).

The second problem is that 1) when the opening angle α of the tooth becomes excessive, the effective reduction area due to the indentation increases from the shear area (= slab cross-sectional area), 2) the friction between the tool and the material increases, and the like. This increases the cutting load than the shear. On the other hand, there are load reduction factors such as softening due to an increase in the average temperature of cast steels and reduction of effective cross-sectional area due to unsolidification due to high-speed molten metal injection. If the value of α is excessive, the reduction load increases. In undersized, like a knife, the behavior of the cutting changes in the same direction as the squeezing from indentation, resulting in a risk of leakage. At 90 °, the load is almost equal to the shear. Before and after the said angle is an appropriate value.

The cutting machine 7 of the present invention can be implemented simply by introducing an existing hydraulic shearing machine which is usually used. It is only necessary to change the shear blade portion to the pair of cutting molds described above. The renovation cost is very small compared with the preceding case (Patent Document 1). There is no crushing which is easy to occur in shear, so there is no trouble by crushed waste. The wear management of the tooth blade is also easy unlike shearing. Even if the shearing machine currently used is a structure having a diagonal direction of the cross section of the cast steel, it is easy to implement.

The present invention is not a problem at all even when high-speed molten metal injection is not performed. In that case, only an improvement of the rolling yield is obtained.

In the biting cutting method, both teeth are preferably driven but not necessarily. In the case of using or modifying an existing shearing machine, one side becomes a moving tooth and the other side becomes a fixed tooth. For this reason, both teeth do not face the path core of the cast steel, but are only shifted by the thickness of the cast steel in the moving direction of the teeth. Depending on the indentation, the cast may be slightly corrugated, but can be easily handled. The reason for the use of a tooth for one side of the invention is to use a conventional shearing machine.

( Example )

Example  One:

The deformation was analyzed by the finite element method. The steel grade was SS41, the slab cross-sectional shape was 100 mm square, the cutting temperature was constant at 1000 DEG C, and the deformation resistance was set to 80 MPa larger than usual for the estimation of the maximum load. The core 40mm diameter is made common, and the shape of the V-block cutting teeth is 150 mm wide, 50 mm high, and the open angle α is tan (α / 2) = 50/75.

As shown in FIG. 5, although the reduction ratio r is 0.5 and is unblocked (A of FIG. 5), the core part is completely blocked (0.7B) at 0.7. In the indentation of the tooth, the epidermal with the ductility of the tooth decays, and the flow such as the cutting of the core portion such as the splitting is not seen (E) (C).

The widening was 35% without restraint guard and 4% by guard.

The problem is that favorable results, such as the fact that the remaining dimensions are divided into 10-20% by the indentation, shown in Document 2, have not been obtained. It also resulted in that the teeth were not divided immediately before the meeting of the teeth.

The maximum load was 1.6 times that of the shear, but the prediction was reduced by modifying the block opening angle to the acute angle (eg 90 °).

Example  2:

The experiment of the plasticine model was carried out on a half scale of the above analysis. A pair of wooden wedge-shaped teeth was placed on the side of a 50 mm square test piece with a 20 mm diameter cavity, and cut by tightening with a vice. An internal pressure contact was confirmed at a reduction ratio of 0.6. Both saw blades were segmented so as to be bent at a point close to 1 to 2 mm. Pressing surface is very smooth, and only about 2mm width of end is jagged. The widening is about 30%. It was confirmed that this method is very good for the smoothness of the cross section. The same was true even when the opening angle α of the V block was 90 degrees. In the case of 60 °, the pressure welding of the center part was delayed slightly, and the pressure welding could be confirmed at the reduction ratio of about 70%.

The problem was that, as in Example 1, favorable results such as the remaining dimensions could be segmented at 10-20% were not obtained.

Example 3 :

Next, the steel bar of 20 mm angle was heated to about 1100 degreeC, and the indentation and cutting test of the V block of 90 degree of opening angle were done. The result is that unlike plasticine (which is malleable but small in ductility), the hot ductility of steel is large, and the cutting is uncertain only by indentation. Here, only the V-block press-fitting method is insufficient as a production facility, and another additional step is required.

It turned out that it can cut | disconnect when the tooth blade is a little bit back and forth and made into excess feed. Mistake and excess are good for a little. At the end of cutting, shear and tension act.

1: ladle 2: tundish
3: mold Me: molten steel
4: secondary cooling stand 5: cast steel
6: pinch roll 7: cutter
8: molten core 9: molten core
21: cutting mold 22: mold base
23: Vable 24: Widening Restraint Guard
25: stopper 31: cast
32, 32 ': V block 33: coagulation cell
34: melt core G: amount of displacement between teeth
41: rim 42: hydraulic cylinder
43: cylinder head 44, 44 ': mold base
45,45 ': V-block 46,46': Widening Restraint Guard
47, 47 ': stopper 48: cast

Claims (4)

A method of cutting a continuous cast slab for billet of steel, in which a pair of V-block cutting saw teeth which are opposed to each other with a cast slab are vertically press-fitted into the slab axis and cut to bite cutting. When the saw blades are arranged in a direction of casting of the cast pieces, and the cutting teeth are press-fitted, they are sheared at the end of cutting by press-fitting over the midpoint while avoiding the collision of the saw teeth at the midpoint of the thickness of the cast steel. A method of cutting a continuous cast slab, characterized in that the division by acting and tension. 2. The continuous device according to claim 1, wherein the amount of displacement between the two teeth is 1 to 5% of the thickness of the slab, and a means for setting and adjusting the end point of indentation of both cutting teeth is formed in the indentation mechanism. Cutting method of casting cast. The method for cutting a continuous cast slab according to claim 1 or 2, wherein a guard for restraining the widening of the cut portion according to the cut is formed in the indentation mechanism. 4. The method for cutting a continuous cast slab according to any one of claims 1 to 3, wherein one cutting tooth is a fixed tooth and the other is a moving tooth.

Images