JP4754279B2 - Gas cutting method for rolled steel - Google Patents

Description

  The present invention relates to a gas cutting method for a rolled steel material, which performs a slit cutting of a rolled steel material such as a shape steel.

  Conventionally, a rolled steel material such as an H-shaped steel is sometimes cut into a longitudinal direction and used as CT steel. Conventionally, cutting of such rolled steel material has been performed by gas cutting, and as gas cutting, flame cutting using LPG or the like as fuel is usually performed.

  On the other hand, in the strip cutting of rolled steel material, since the rolled steel material has a residual stress, there is a problem that a lateral curve (camber) is generated in the strip cut after the strip cutting.

  That is, in recent years, in the manufacturing process of rolled steel sheets, accelerated cooling rolling is widely performed to obtain high strength and high toughness steel sheets by strongly water-cooling the control-rolled steel sheets. In such accelerated cooling, slight unevenness in the surface properties of the steel sheet, such as the water density of the cooling water, the surface temperature of the steel sheet, and the scale thickness, causes a large temperature unevenness in the steel sheet. When such temperature unevenness occurs, residual stress is generated during the production of the steel sheet, and camber is generated after the cutting.

  Further, a slight difference in temperature history at each position in the sheet width direction in each process such as heating, rolling, water cooling, correction, and air cooling also causes variations in the yield stress of the steel sheet. As a result, the residual stress generated with heat input at the time of fusing becomes asymmetric at both ends of the strip, and camber is generated.

  The cambers accompanying such residual stresses are particularly prominent in the shape steel having an irregular cross section, and it is desired to suppress the camber as much as possible when slicing rolled steel such as H-section steel. Therefore, attempts have been made to suppress the camber by preheating the steel material or controlling the flow rate of the combustion gas.

Here, the following patent documents 1 and 2 are presented as what the applicant grasps as the prior art regarding the gas cutting method.
Japanese Patent No. 3563660 JP 2003-251463 A

  However, if only normal gas cutting is performed, the camber as described above is generated, and much time and cost are required for correction. Further, in the cutting by LPG, since the calories of LPG are high, it is difficult to delicately control the flow rate, and it is very difficult to prevent the camber by controlling the amount of heat input. Moreover, although cutting | disconnection using the oxyhydrogen gas with a low calorie is also examined, since the oxyhydrogen gas itself is an explosive gas, it is unpreferable in terms of safety. In addition, the control of the heat input requires a work such as pre-measurement of residual stress, which is very troublesome.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a gas cutting method for a rolled steel material that safely cuts while suppressing deformation of the rolled steel material such as a shape steel.

In order to achieve the above object, the method for gas cutting of rolled steel according to the present invention is characterized in that a cutting heating flame in which combustion gas is burned is ejected from a cutting crater, and the rolled steel material to be cut is cut in the longitudinal direction by the cutting heating flame. It is a gas cutting method of rolled steel that melts into
When cutting while post-heating the vicinity of the cut location after cutting by the heating flame for cutting,
The combustion gas for the heating flame for cutting is a mixed gas in which a hydrocarbon gas is mixed with an oxyhydrogen gas so that the concentration of the oxyhydrogen gas is less than the lower explosion limit,
The post-heating combustion gas is a mixed gas in which hydrocarbon gas is mixed with oxyhydrogen gas so that the concentration of oxyhydrogen gas is less than the lower explosion limit,
Without quenching the cut part near by not provided with a cooling mechanism of the cutting portion near, LPG only the combustion gas for cutting heat flame as the fuel, compared with the case of no post-heating, the rolled steel after cutting The gist is that the camber is suppressed.

Gas cutting method of rolling steel of the present invention, the combustion gases, since the main component have less calories oxyhydrogen gas compared to LPG, the combustion gas flow rate control without a cooling mechanism of the cutting portion near Therefore, it becomes relatively easy to prevent the camber by controlling the amount of heat input. Therefore, it is possible to significantly reduce the time and cost required to correct the camber and correct it. In addition, the combustion gas is mixed with hydrocarbon gas so that the concentration of oxyhydrogen gas is less than the lower limit of explosion with respect to oxyhydrogen gas. In addition to the increase in performance, it is not necessary to prepare explosion-proof equipment, and equipment costs can be greatly reduced.

Further , when cutting the vicinity of the cut portion after the cutting with the heating flame for cutting, the combustion gas for the heating flame for cutting is less than the lower explosion limit with respect to the oxyhydrogen gas. A mixed gas in which hydrocarbon gas is mixed so as to have a concentration, and the above-mentioned combustion gas for post-heating is a mixed gas in which hydrocarbon gas is mixed with oxyhydrogen gas so that the concentration of oxyhydrogen gas is lower than the lower explosion limit. By doing so, it is possible to significantly reduce the camber without providing a cooling mechanism in the vicinity of the cut portion . The reason for this is not clear, but can be considered as follows. That is, the cutting point reaches a high temperature above the melting point, and the temperature in the vicinity also rises to near the melting point, but when cooled rapidly from that state, camber may occur due to residual stress due to rapid cooling. Although the camber remains, by cutting the vicinity of the cutting point while post-heating, the cutting point that has reached a locally high temperature and the cooling rate in the vicinity of the cutting point are slowed down, the residual stress and crystal distortion caused by rapid cooling It is considered that the camber is suppressed by relaxing. Further, when the residual stress was in the steel before the cutting is released in the cutting process is a cause of camber occurs, for advancing the cutting while reheating the rear of the cut part, divided by the disconnect The camber due to the residual stress is reduced. In this way, since the camber is suppressed by cutting while post-heating, operations such as conventional control of heat input and pre-measurement of residual stress are not required, and the camber is suppressed by an extremely simple operation. It can be done.

  In the present invention, in the case of cutting while preheating the vicinity of the planned cutting location before cutting with the heating flame for cutting, in order to advance the cutting while preheating the front of the cutting location, it was in the steel before cutting. Since the residual stress is released in the cutting process, the camber due to the residual stress when divided by cutting is relaxed. In this way, since the camber is suppressed by cutting while preheating, the conventional operations such as control of heat input and prior measurement of residual stress are not required, and the camber is suppressed by an extremely simple operation. It can be done.

  In the present invention, when the rolled steel material is a shaped steel, the shaped steel having an irregular cross section has a large unevenness in residual stress due to uneven cooling during rolling, and a large camber tends to occur. Thus, the effect of relaxing the camber is remarkable and effective.

  In the present invention, when the shape steel is an H-shaped steel and the web portion of the H-shaped steel is cut by the heating flame for cutting, in the H-shaped steel, the residual stress caused by uneven cooling during rolling, etc. Therefore, the present invention has a remarkable and effective effect of mitigating the camber.

In the present invention, when the post-heating and preheating are performed on both sides of the steel material surface around the cutting line, camber due to residual stress can be effectively suppressed.

  Next, the best mode for carrying out the present invention will be described in detail.

  FIG. 1 is a block diagram showing an apparatus used for a gas cutting method for a rolled steel sheet according to the present invention.

  This apparatus includes a combustion gas generator 20 that generates combustion gas, and a fusing device 21 that performs fusing of the thick rolled steel material 5 to be cut by the combustion gas.

  The combustion gas generator 20 includes an oxyhydrogen gas generator 1 and a cylinder 2 filled with a hydrocarbon gas such as LPG, and the oxyhydrogen gas (oxygen gas) generated by the oxyhydrogen gas generator 1 is obtained. And a hydrogen gas (in this example, the ratio is 1: 2) and a hydrocarbon gas.

  The oxyhydrogen gas generator 1 includes an electrolysis cell 7 for generating gas by electrolysis of water, and a gas and water in a mixed state of hydrogen and oxygen electrolyzed in the electrolysis cell 7 connected to the electrolysis cell 7. It comprises an electrolytic tank 6 for storage.

  The electrolytic cell 7 electrolyzes internal water or water or water vapor supplied from other sources by applying a direct current to both electrodes, and generates oxyhydrogen gas, which is a mixed gas of oxygen and hydrogen, in the electrolytic tank 6. Let The electrolytic tank 6 and the electrolytic cell 7 are connected by a circulation path, and water in the electrolytic tank 6 is supplied to the electrolytic cell 7 through the circulation path and circulated. A water supply path 23 supplies water into the electrolytic tank 6.

  The oxyhydrogen gas generator 1 is introduced with a hydrocarbon gas such as LPG taken out from the cylinder 2, and the oxyhydrogen gas and hydrocarbon gas generated in the oxyhydrogen gas generator 1 are mixed. The hydrocarbon gas in the cylinder 2 is introduced into the oxyhydrogen gas generator 1 by the flow rate regulator 8 and mixed with the oxyhydrogen gas at a predetermined mixing ratio to produce combustion gas. A predetermined flow rate of the combustion gas obtained by mixing in the oxyhydrogen gas generator 1 is taken out by the flow controller 9 and supplied to the cutting crater 3 and the heating crater 4.

  The mixing ratio of the oxyhydrogen gas and the hydrocarbon gas is such that the oxyhydrogen gas is mixed with the oxyhydrogen gas so that the concentration of the oxyhydrogen gas is less than the lower explosion limit. The mixing ratio is appropriately set according to the type of hydrocarbon gas. Specifically, in the case of propane gas, 21% by volume or more of hydrocarbon gas is mixed with oxyhydrogen gas, and propylene gas is mixed. 26% or more by volume, 32% by volume or more by city gas, 33.5% by volume or more by methane gas, 24.2% by volume or more by butane gas, 58% by volume or more by ethylene gas, respectively. Mix to make combustion gas. Note that the values given here are theoretical values, and the actual values are slightly lower than these, and are intended to include the limit values.

  Here, the hydrocarbon gas is not limited to those described above, and various hydrocarbon gases such as ethane gas and natural gas can be used.

  The fusing device 21 includes a cutting burner 17 having a cutting crater 3 for fusing the thick rolled steel material 5 and a heating burner 18 having two heating craters 4 for heating the vicinity of the cut portion of the thick rolled steel material 5. And is configured. The cutting burner 17 and the heating burner 18 are connected to flow rate regulators 24 and 25, respectively, so that the combustion gas can be supplied at a flow rate suitable for fusing and heating.

  FIG. 2 is a diagram showing an H-section steel 10 that is an example of a thick rolled steel material 5 such as a section steel that is a member to be cut. The H-section steel 10 is a steel bar having an H-shaped cross section by connecting two flanges 12 to a central web 11. And in this invention, the heating flame for cutting which burned the said combustion gas is ejected from the cutting crater 3, and the plate-rolled steel material 5 which is a cutting object is blown out to a longitudinal direction by the said heating flame for cutting, and is cut. In the case of the H-shaped steel 10, the center portion of the web 11 is melted in the longitudinal direction.

  In the present invention, after cutting with the cutting heating flame, the vicinity of the cutting portion is cut while being post-heated, or before cutting with the cutting heating flame, the portion near the planned cutting portion is cut with preheating. Is done.

  FIG. 3 illustrates a state of post-heating and preheating when the H-section steel 10 is cut as the thick rolled steel material 5.

  FIG. 3 (A) shows a state in which the vicinity of the cutting portion is cut while being post-heated by the gas cutting device after cutting by the heating flame for cutting.

  The figure shows a state in which the center of the web 11 of the H-section steel 10 is melted in the longitudinal direction. In the figure, a cutting point 13 is a point where a flame is injected by the cutting crater 3, and two post-heating points 14 are shown. Is a location where flames from the two heating craters 4 are injected. The cutting crater 3 is disposed in front of the cutting direction C, and two heating craters 4 are disposed behind the cutting crater 3 by a predetermined distance L1. The two heating craters 4 are respectively arranged on both sides of the fusing line 16 blown by the cutting crater 3 and are arranged at positions that maintain an equal distance M1 from the center of the web 11 (that is, the center of the fusing line 16).

  Therefore, the cutting crater 3 and the two heating craters 4 are arranged so as to exhibit an isosceles triangle with the cutting crater 3 being the foremost position in the cutting direction C. Here, the distance L1 between the cutting crater 3 and the heating crater 4 and the distance M1 between the heating crater 4 and the center line can be appropriately set according to the dimensional standard of the H-section steel to be cut and the cutting conditions.

  Then, the cutting crater 3 and the two heating craters 4 are moved in the cutting direction C while maintaining the above-described positional relationship, so that the cutting portion 13 is blown by the cutting crater 3 and the fusing line 16 after cutting is cut. Can be post-heated on both sides.

  FIG. 3 (B) shows a state in which the gas cutting device cuts the vicinity of the planned cutting portion while preheating before cutting with the heating flame for cutting.

  The figure shows a state in which the center of the web 11 of the H-section steel 10 is melted in the longitudinal direction. In the figure, a cutting point 13 is a point where a flame from the cutting crater 3 is injected, and two preheating points 15 are shown. Is a location where flames from the two heating craters 4 are injected. The cutting crater 3 is arranged behind the cutting direction, and two heating craters 4 are arranged ahead of the cutting crater 3 by a predetermined distance L2. The two heating craters 4 are respectively arranged on both sides of a planned fusing line (the central line of the web 11) that is melted by the cutting crater 3, and are kept at an equal distance M2 from the center of the web 11 (that is, the center of the fusing planned line). Is arranged.

  Therefore, the cutting crater 3 and the two heating craters 4 are arranged to form an isosceles triangle with the cutting crater 3 as the last position in the cutting direction C. Here, the distance L2 between the cutting crater 3 and the heating crater 4 and the distance M2 between the heating crater 4 and the center line can be appropriately set according to the dimensional standard of the H-section steel to be cut and the cutting conditions.

  Then, the cutting crater 3 and the two heating craters 4 are moved in the cutting direction C while maintaining the above-described positional relationship, so that preliminary heating of both sides of the planned fusing line before cutting and the cutting crater 3 are performed. The cutting location 13 can be melted and cut.

  FIG. 3 (C) shows a state in which the vicinity of the cutting scheduled portion is preheated before cutting by the cutting heating flame and the vicinity of the cutting portion is cut while post-heating after the cutting by the cutting heating flame. Is. In this case, in the cutting device, cutting is performed by a gas cutting device including two heating burners 18 having two heating craters 4.

  The figure shows a state in which the center of the web 11 of the H-section steel 10 is melted in the longitudinal direction. In the figure, a cutting point 13 is a point where a flame from the cutting crater 3 is injected, and two preheating points 15 are shown. Is a location where the flames by the two preheating heating craters 4 are injected. Moreover, the two post-heating places 14 are places where the flame by the two heating craters 4 for post-heating is injected.

  Two heating craters 4 for preheating are arranged in front of the cutting crater 3 by a predetermined distance L2, and two heating craters 4 for post heating are arranged behind the cutting crater 3 by a predetermined distance L1. The heating crater 4 for preheating and the heating crater 4 for post-heating are respectively arranged on both sides of a fusing schedule line (center line of the web 11, fusing line 16) to be melted by the cutting crater 3, and the like from the center of the web 11. It arrange | positions in the position which maintains the distance M1, M2.

  Accordingly, the cutting crater 3 and the two preheating heating craters 4 are arranged to form an isosceles triangle having the cutting crater 3 as a vertex, and the cutting crater 3 and the two heating craters 4 for post-heating are also cut. They are arranged to present an isosceles triangle with the crater 3 as a vertex. Here, the distances L1, L2, M1, and M2 can be set as appropriate depending on the dimensional standards and cutting conditions of the H-section steel to be cut.

  Then, the cutting crater 3, the two preheating heating craters 4 and the two post heating heating craters 4 are moved toward the cutting direction C while maintaining the above-described positional relationship, thereby cutting before cutting. Preheating of both sides of the planned line, fusing of the cut portion 13 by the cutting crater 3, and post-heating of both sides of the fusing line 16 after cutting can be performed.

  Next, examples will be described.

  As shown in FIG. 4, about the predetermined | prescribed H-section steel, the center of the web 11 was blown out to the longitudinal direction on the following conditions, and the maximum distortion, the camber rate, and the distortion direction were measured. As shown in FIG. 4 (A), the maximum strain is the distance that the flange 12 is displaced the maximum from the line connecting both ends of the flange 12 of the curved cut steel. The camber rate was calculated from the maximum strain / the length of the H-section steel. Further, as shown in FIG. 4B, the strain direction was set as A when the web 11 side of the cut steel swells, and conversely as B when the flange 12 side swells.

(1) First, LPG was used as the combustion gas, and it was cut without preheating and afterheating. The cutting target was an H-shaped steel having a web of 12 t × 700 mm, a flange of 23 t × 300 mm, and a total length of 13000 mm. The combustion gas was used at a flow rate of 5 liters / minute, and the cutting speed was 390 mm / minute.

At this time, the maximum strain was 115 mm, the camber rate was 0.88%, and the strain direction was A. The results are shown in Table 1 below.

(2) Next, a mixed gas of oxyhydrogen gas + 22% LPG was used as the combustion gas, and cutting was performed without preheating and afterheating. The object to be cut was an H-shaped steel having a web of 15 t × 700 mm, a flange of 25 t × 300 mm, and a total length of 13000 mm, the combustion gas was used at a flow rate of 8 liters / min, and the cutting speed was 250 mm / min.

At this time, the maximum strain was 90 mm, the camber rate was 0.69%, and the strain direction was A. The results are shown in Table 2 below. As can be seen from these results, the maximum strain and the camber rate were both smaller when oxyhydrogen gas + 22% LPG was cut as a combustion gas than when LPG was cut as a combustion gas.

(3) Next, a mixed gas of oxyhydrogen gas + 22% LPG was used as the combustion gas, and the mixture was cut by post-heating. The object to be cut was an H-section steel having a web of 10 t × 500 mm, a flange of 16 t × 200 mm, and a total length of 12,500 mm. The combustion gas was used at a flow rate of 8 liters / minute, and the cutting speed was 350 mm / minute.

  Further, post-heating was performed using a mixed gas of oxyhydrogen gas + 22% LPG as a post-heating combustion gas at a flow rate of 10 liters / minute per two heating craters 4. The arrangement of the cutting crater 3 and the heating crater 4 at this time is as shown in FIG. 3A, the distance L1 between the cutting crater 3 and the heating crater 4 is 100 mm, and the distance M1 between the heating crater 4 and the center line is It was 10 mm.

The maximum strain at this time was 0 mm, and the camber rate was 0%. The results are shown in Table 3 below. As can be seen from this result, the camber was greatly suppressed when the post-heating was performed with oxyhydrogen gas + 22% LPG as the combustion gas, rather than when LPG was used as the combustion gas or when it was cut without heating. .

(4) Next, a mixed gas of oxyhydrogen gas + 22% LPG was used as the combustion gas, and preheating was performed for cutting. The object to be cut was an H-shaped steel having a web of 10 t × 500 mm, a flange of 16 t × 200 mm, and a total length of 13500 mm. The combustion gas was used at a flow rate of 8 liters / minute, and the cutting speed was 350 mm / minute.

  Further, post-heating was performed using a mixed gas of oxyhydrogen gas + 22% LPG as a post-heating combustion gas at a flow rate of 10 liters / minute per two heating craters 4. The arrangement of the cutting crater 3 and the heating crater 4 at this time is as shown in FIG. 3A, the distance L2 between the cutting crater 3 and the heating crater 4 is 100 mm, and the distance M2 between the heating crater 4 and the center line is It was 10 mm.

The maximum strain at this time was 16 mm, and the camber rate was 0.13%. The results are shown in Table 4 below. As can be seen from this result, the camber was greatly suppressed when the preheating was performed with the oxyhydrogen gas + 22% LPG as the combustion gas when the LPG was used as the combustion gas or when the cutting was performed without heating. .

  As described above, since the combustion gas is mainly composed of oxyhydrogen gas having a lower calorie than LPG, it is relatively easy to prevent camber by controlling the amount of heat input by controlling the flow rate. Therefore, it is possible to significantly reduce the time and cost required to correct the camber and correct it. In addition, the combustion gas is mixed with hydrocarbon gas so that the concentration of oxyhydrogen gas is less than the lower limit of explosion with respect to oxyhydrogen gas. In addition to the increase in performance, it is not necessary to prepare explosion-proof equipment, and equipment costs can be greatly reduced.

  In addition, since the vicinity of the cut portion is cut while being post-heated after the cutting by the cutting heating flame, the camber can be greatly reduced. The reason for this is not clear, but can be considered as follows. That is, the cutting point reaches a high temperature above the melting point, and the temperature in the vicinity also rises to near the melting point, but when cooled rapidly from that state, camber may occur due to residual stress due to rapid cooling. Although the camber remains, by cutting the vicinity of the cutting point while post-heating, the cutting point that has reached a locally high temperature and the cooling rate in the vicinity of the cutting point are slowed down, the residual stress and crystal distortion caused by rapid cooling It is considered that the camber is suppressed by relaxing. In addition, since the cutting is advanced while post-heating the cutting part, the residual stress that was in the steel material before cutting is released in the cutting process, so that the camber due to the residual stress when divided by cutting is relaxed . In this way, since the camber is suppressed by cutting while post-heating, operations such as conventional control of heat input and pre-measurement of residual stress are not required, and the camber is suppressed by an extremely simple operation. It can be done.

  In addition, in the case of cutting while preheating the vicinity of the planned cutting site before cutting with the above-mentioned heating flame for cutting, in order to proceed with cutting while preheating the front of the cutting site, the residual stress that was in the steel before cutting Is released in the cutting process, the camber due to the residual stress when divided by cutting is relieved. In this way, since the camber is suppressed by cutting while preheating, the conventional operations such as control of heat input and prior measurement of residual stress are not required, and the camber is suppressed by an extremely simple operation. It can be done.

  Further, when the rolled steel material is a section steel, the shape steel having an irregular cross section has a large residual stress unevenness due to uneven cooling during rolling and tends to generate a large camber. The effect of alleviating is remarkable and effective.

  Further, when the shape steel is an H-shaped steel and the web portion of the H-shaped steel is cut by the cutting heating flame, the H-shaped steel has uneven residual stress caused by uneven cooling during rolling. Since a large and large camber tends to be generated, the effect of mitigating the camber according to the present invention is remarkable and effective.

  In addition, in order to obtain the effect of significantly reducing the camber by cutting the vicinity of the cutting portion after the cutting with the heating flame for cutting, the combustion gas as the heat source is oxyhydrogen gas and hydrocarbon gas. The gas mixture is not limited to the above gas mixture, but can be applied to so-called separation-type hydrogen cutting that supplies oxygen gas and hydrogen gas separately, and can be used for gas cutting using various gas cutting combustion gases such as LPG. Can also be applied.

  Moreover, although the example which cuts H-section steel as a shape steel of cutting object was shown in the description mentioned above, it is not limited to this as cutting object, This invention is I-shaped steel, groove-shaped steel. It can be applied to the cutting of various shape steels, such as T-shaped steel, equilateral angle steel, unequal angle iron, and unequal uneven thickness steel. Moreover, as a cutting object of this invention, if it is not only a deformed shape steel but a rolled steel plate of a thick plate, it can be applied also to the cutting of a flat steel plate.

It is a block diagram which shows the apparatus used for the gas cutting method of the rolled steel material of this invention. It is a perspective view which shows an example of the rolled steel material of cutting object. It is a figure explaining the gas cutting method of the rolled steel materials of this invention. It is a figure explaining the definition of maximum distortion and a distortion direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Oxyhydrogen gas generator 2 Cylinder 3 Cutting crater 4 Heating crater 5 Thick rolled steel material 6 Electrolytic tank 7 Electrolytic cell 8, 9 Flow path regulator 10 H-section steel 11 Web 12 Flange 13 Cutting part 14 Post-heating part 15 Preheating Location 16 Fusing line 17 Cutting burner 18 Heating burner 20 Combustion gas generator 21 Fusing device 23 Water supply path 24, 25 Flow controller

Claims (3)

A gas cutting method for a rolled steel material in which a heating flame for cutting in which combustion gas is combusted is ejected from a cutting crater, and the rolled steel material to be cut by the cutting heating flame is melted in the longitudinal direction,
When cutting while post-heating the vicinity of the cut location after cutting by the heating flame for cutting,
The combustion gas for the heating flame for cutting is a mixed gas in which a hydrocarbon gas is mixed with an oxyhydrogen gas so that the concentration of the oxyhydrogen gas is less than the lower explosion limit,
The post-heating combustion gas is a mixed gas in which hydrocarbon gas is mixed with oxyhydrogen gas so that the concentration of oxyhydrogen gas is less than the lower explosion limit,
Without quenching the cut part near by not provided with a cooling mechanism of the cutting portion near, LPG only the combustion gas for cutting heat flame as the fuel, compared with the case of no post-heating, the rolled steel after cutting A gas cutting method for a rolled steel material, characterized in that the camber is suppressed.   The method for gas cutting of a rolled steel material according to claim 1, wherein the cutting is performed while preheating the vicinity of the planned cutting site before cutting with the heating flame for cutting.   The method for gas cutting of a rolled steel material according to claim 2, wherein the post-heating and the preheating are performed on both sides centering on a cutting line on the surface of the steel material.

Images