JPS60108165A - Method for gas cutting of steel material - Google Patents

Abstract

PURPOSE:To remove the slag sticking to nozzles during cutting and to improve the life of the nozzles by moving two cutting torches in the direction where the torches approach to each other and replacing the preheating flame to be blown together with the gaseous oxygen of the rear nozzle facing one torch which is retreated just prior to completion of cutting with an inert gas. CONSTITUTION:Ejection of gaseous oxygen is continued with a rear side nozzle 52 facing a torch 22 to be retreated during the course of cutting in one way as the final stage of cutting and an inert gas is ejected in place of a preheating flame. The nozzle 52 on the retreat side during the process for cutting in one way is thus less covered with the slag formed by blowing from the nozzle 51 on the other side and the clogging of the hole for ejecting the preheating flame is prevented. The oxidation combustion force of the gaseous oxygen from the nozzle 52 is weakened by the ejection of the inert gas and the rear surface of a steel material 1 is prevented from flawing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas cutting method for removing slag generated during gas cutting of steel materials at the same time as cutting.

When the steel material (1) shown in Fig. 1 is cut with a cutting torch (2) facing the upper surface side, a part of the molten metal generated by the cutting is formed into a cutting groove ( 4)
It is generated by moving from the surface to the back side and adhering to the immediate vicinity of both sides of the cutting groove (4) as shown by reference numeral (3).

Particularly in the case of slabs, such cutting slags have a large effect, such as causing product rolling flaws and roll flaws in subsequent rolling, and their removal is essential.

Now, as a method for removing slag during such cutting, it is reasonable to process the slag in the same way as the cutting progresses (hereinafter referred to as simultaneous processing), which is also advantageous in terms of work efficiency. be able to. Regarding this simultaneous processing method, conventionally! 14i proposals have been made, and currently there are a variety of
There are several known methods, one of which is a method using gas spraying (hereinafter referred to as "method"). In principle, as shown in Figure 2, during cutting, a nozzle (5) is placed on the back side of the steel material, and while moving as the cutting progresses, the nozzle (5) generated by cutting (3) is removed as the cutting progresses. Oxygen gas is sprayed from the rear (hereinafter simply referred to as "back") to oxidize the slag, increase its fluidity, and blow it away.
If a preheating flame type nozzle is used as the ill nozzle, and the back surface of the steel material is tended to be scarfed along with the slag, stable slag removal is possible, and it is the most effective simultaneous treatment method. It can be said to be Ishikawa's work.

However, this method has the following problems. That is, when cutting slabs, particularly continuously cast slabs, two cutting torches are used simultaneously in consideration of the cutting rate. Tsumashi, 2 pieces 1 as shown in Figure 3
The set of cutting torches (2/) (2,2) are simultaneously moved from both end positions (g) and (g) of the planned cutting line of the slab in the direction toward each other to perform cutting, but at this time, there is no interference between the two torches. In order to avoid this, one of the cutting torches (22) stops advancing and cutting at a position just before the interference, immediately moves backwards and retreats, and the other torch (2/) is used until the cutting is complete. A method (hereinafter referred to as the bidirectional cutting method) is adopted in which the process is advanced until the end (this process is called one-way cutting superanalysis). In such bidirectional cutting, both torches (2/X2-
], the back side nozzle /l/ (5/X5) is applied to each of the holes to create a gas blowing area. In other words, in the case of the gas blowing process that involves cutting in both directions, the slag that accompanies both cuts is removed from the steel material by the force of the gas from behind. After it was removed, the removed slag was scattered along the back side of the steel material towards the nozzle at 11111 exactly opposite, and some of it was there (what?). t'i. This tendency of cutting or cutting is caused by the one-way cutting 11R, which causes one of the torches (22) of iJ to regress before the completion of cutting. In the process its degenerating torch (
22) When the jetting of oxygen gas and preheating flame from the back side nozzles (5, 2), which move together with the nozzles (5, 2), is stopped, this phenomenon is particularly noticeable in the nozzles (5). Such slags are repeated at the cutting angle, resulting in
In particular, the preheating flame ejection holes of the nozzle, which are formed from a large number of small holes (1"4), eventually lead to clogging, but this clogging actually occurs in a very short period of time. Therefore, lnJ j!, fj.

The present invention aims to provide a gas cutting method that prevents as much as possible the clogging of the back side nozzle due to slag or shaving, and enables long-term use of the nozzle. The difference is most noticeable when the gas blowing from the backward nozzle (5, 2) is stopped during the final unidirectional cutting process mentioned above. Needless to say, this is because no gas is ejected to prevent the slag that has been blown off by the other nozzle from adhering, but in this process, the gas is blown from the nozzle (5, 2) in question. If this is done, the back side of the steel material will be scarfed unnecessarily, resulting in easy scratches.

The inventors of the present invention conducted a fire test to find an effective measure to prevent slag of the back side nozzle on the side that will regress in the future. It was discovered that switching the preheating flame to an inert gas is an effective measure as the above measure A.

That is, first of all, the present invention is compatible with two torches that are retracted as shown in FIG. Back 11' old lυ1 nozzle (5,2
), the gist of the cutting method is that the oxygen gas is continuously ejected and an inert gas is emitted instead of the preheating flame.

According to this method, inert gas is ejected in place of the preloaded flame, and during the cutting process in one direction, the nozzle on the retreating side (5/) blows out the nozzle on the other side (5/), causing slag fogging. can be effectively reduced, and clogging of the preheating flame outlet can be effectively prevented.

Moreover, the oxidative combustion power of the oxygen gas from the nozzle is weakened by the jetting of the inert gas, and the ηiM
This prevents the occurrence of scratches on the back surface of the film. .

Note that this inert gas blowout occurs at the one-way cutting point 4″J1
It is also effective in the sense of removing the slag caused by the slag in the previous stage.

In the present invention, in place of the preheating flame, [the pressure of the inert gas to be emitted is not particularly limited, but for practical purposes, it is desirable that this pressure be 1 kg/c7n or more.

FIG. 4 illustrates the relationship between the inert gas pressure and the nozzle life (the number of times that can be slaged) (according to the examples described later) for the backside nozzle that blows inert gas according to the present invention. As is clear from the figure, the nozzle/L/life is particularly effectively extended when the inert gas pressure is 1 kg/cm or more, and even at a pressure of 1% h without switching to inert gas. (Preheating flame gas pressure '''' kg/ca
) can ensure a lifespan approximately twice as long as that of Incidentally 1
kVca or more means about 5% compared to the normal preheating flame gas pressure.
It is more than twice the size.

The backside nozzle used in the method of the present invention includes a nozzle hole (7) for spouting oxygen gas, as shown in FIG. 5(a).
is a circular 9), 1! Basically, any type of nozzle may be used, such as a nozzle (6), a slit nozzle (8) with a nozzle hole (7) shaped like a slit as shown in FIG. However, as shown in Figure 5 (a) and (b), it must be of the preheating flame combination type, which has a preheating flame outlet (9) consisting of many small holes around the nozzle hole (7). No.

Regarding the arrangement of the nozzles on the back side, when a round nozzle is used, as shown in the schematic plan view of Fig. 6 (a) (the figure shows unidirectional cutting as an example), it is necessary to place the nozzles on the left and right sides of the cutting groove (4). It is advantageous in terms of the slag removal effect to blow gas from a slightly diagonal rearward position in the direction of cutting progress with a nozzle of 1" (5) (5) for each slag generated in the process. Advantage When using the nozzle (8), the width of the gas spray is wide!
It is not necessary to adopt the above-mentioned method, and it is sufficiently effective to use one cutting IIY (4) (7 for the 1110 generated slag) as shown in the same figure (b). be. The use of the latter slit nozzle is immediately recommended in terms of the stable slag removal effect.

Note that the nozzle on the back side is blown at a corner (upward angle) and the position (goods) of the gas blowing angle is about 10 to 25 degrees; ) is the cutting destination h'u f convex A + 11 r - Junshi helicopter n ~ 1 et t1 π1
It is appropriate to write 1 in J-+.

The backside nozzle may be moved by being directly connected to each cutting torch C2/)C2C)K.

In addition, in the method of the present invention described above, the back side nozzle 1 corresponding to the cutting torch on the side that is retracted first in bidirectional cutting is applied to the %J image, but the cutting operation is also performed on the other back side nozzle. If you blow inert gas from the preheating flame nozzle when returning to the original position after finishing, the slag that adhered during cutting will be effectively removed and the nozzle life will be extended. As is clear from the above explanation, the main cause of nozzle clogging is slag, especially during the unidirectional cutting process at the final stage of cutting. It can be said that the influence of In other words, as shown in Fig. 7, when the cutting torch (2) starts making a cut, when the torch (2J) is advanced from the end face (1a) of the steel material, the slag generated by the cutting is not in the direction directly below, but in the backward direction indicated by the arrow (1). This causes the so-called slag to flow to the side, and the back side nozzle (5) located at the rear of the torch is just covered with the slag. This cannot be prevented by blowing gas.

The present invention also provides a countermeasure against nozzle clogging that takes into account not only the final stage of cutting but also slag at the beginning of cutting. That is, in addition to the operations based on the method of the present invention described above, the method includes setting the cutting speed at the start of cutting to 40% or less of a predetermined standard speed, and then
When the cut has been made more than Njη, the cutting speed is gradually increased to the standard speed, and the point at which cutting is performed at this standard speed is defined as '1°' and the 'D' mark.

In the above invention, the setting range of the cutting speed at the start of cutting is set to 20% or less of the standard speed for the following reason. In other words, the standard speed for gas cutting of steel materials is, of course, determined by conditions such as the thickness of the steel plate to be cut, the temperature, and the gas pressure of the cutting torch. By setting the cutting speed to 20% or less of the standard speed, slag reversal at the start of cutting can be avoided, and the flow of cutting slag can be corrected in a substantially downward direction.

Also, this cut 11? It is necessary to start returning the starting speed to the standard speed at a point at least 10 feet deep from the end face (la) of the steel material. If the cutting speed starts to increase before the depth of cut reaches 10M, the cutting tip line (4a) will take on a so-called drag line shape, so the cutting speed will have to be increased before the cutting has completely reached the back side of the steel material. In such cases, rolling back is unavoidable. If the cutting speed is gradually increased after waiting for a depth of cut of at least 10M, the occurrence of slag can be substantially prevented. However, if the notch on the end face of the steel material has a bulging shape,
It is necessary to ignore the depth of cut of the bulging part.

That is, if the cutting speed is controlled according to the present invention at the start of cutting, the occurrence of slag slag can be virtually eliminated, and the resulting slag slag can be prevented.

Next, an uninvented example will be described.

270.7 # IJ Kyo The back side nozzle (5/
) (5, 2) and the cutting torch (
2) In the positional relationship with the 9grill material (1) (only one side is shown), the same slag treatment was applied by blowing gas.

The standard speed for cutting was 800''/min, and the oxygen gas sprayed from the back side nozzle was 997% pure, with a pressure of 1.ohH, and a preload of flame gas pressure of 02kVC7.

During this cutting, the cutting speed at the start of cutting was set at 50''/m1n.
(167% of the standard speed 300 N5rn'xn), then after cutting 15N, set it to the standard speed 80
An operation was performed to raise the speed up to 0''/min.

In the same process, when one of the torches is retracted in the final stage of cutting, the back nozzle of the torch is
There are two methods: switching the preheating flame to an inert gas (gas pressure = 3) based on the invention (A), or extinguishing the preheating flame at the time of regression without doing this (G). Yes. In either method, oxygen gas was continuously ejected from the nozzle even during regression.

Such bidirectional cutting with simultaneous processing is repeated, and each time the amount of scarf on the back side of the steel material (rl
] x depth) was investigated.

The results are shown in Figure 9.

In order to completely remove the cutting slag, it is necessary to scarf the back side of the steel A' and A to some extent along with the slag. CG that looks like it was raised
When cutting a slab, approximately 257 millimeters is required, and if the cut is lower than this, there will be concerns about slag residue. In this example, the scarf amount (target) on the back side of the steel material was set at 50 m from the beginning of collapse, and the life of the Nosurire was determined as the time when the actual scarf amount (standard) became less than 257 after repeated cutting.

As a result, as is clear from the figure, in (A) in which inert gas switching was performed according to the present invention, the life of the back side nozzle was approximately 2.5 times longer than in @, which also did not have switching.

Incidentally, even when the inert gas switching method according to the present invention is applied, clogging will eventually occur. This is because a small amount of spherical Fe, which cannot be pushed back, is included, and as the cutting operation is repeated, this gradually clogs the preheating flame outlet.

As described in detail above, the cutting method of the present invention can dramatically extend the life of the backside nozzle that performs gas blowing in bidirectional cutting that involves simultaneous treatment of slag by gas blowing, Moreover, there is no need to worry about the disadvantages such as the occurrence of scratches on the back surface of the 1'11111 cut, and therefore, the lack of invention greatly contributes to making the cutting work easier and reducing the number of cuts.

[Brief explanation of the drawing]

Figure 1 shows the cutting slag (・J'
nl:j A front view showing the situation, Fig. 2 is a schematic diagram of an example of gas blowing without showing the method, Fig. 3 is a diagram explaining gas blowing in bidirectional cutting (= J method, Fig. 4 is a diagram illustrating the non-inventive method) Figure 5 illustrates the relationship between the inert gas pressure and the life of the nozzle in the inert gas blowing treatment of the back side nonure, and shows two specific examples of the back side nozzle used in the method of the present invention. stomach)
is a large nozzle, and (b) is a slit nozzle. 6th
The figure shows two specific examples of the gas spraying method; (a) shows the use of a large nozzle, and (b) shows the use of a slit nozzle. Fig. 7 is an explanatory diagram showing the slag condition of the back side nozzle at the start of cutting, Fig. 8 is an explanatory diagram showing how to arrange the back side nozzle (111) used for the experiment shown in Fig. 9, which will be described later. The figure is an experimental result showing the effect of extending the life of the nozzle by inert gas blowing treatment of the back side nonurere. In the figure, 1: steel material, 2: cutting torch,
3: Cutting groove, 4: Cutting groove, 5: Back side groove, 6:
Large nozzle hole, 7: Nozzle hole for oxygen gas injection, 8: Surin I nozzle, 9: Preheating flame injection hole Applicant: Sumitomo Metal Industries, Ltd. Beast No. 7 Figure No. 81;

Claims (3)

[Claims] (1) Cutting is performed by simultaneously moving a set of two cutting torches toward each other along the planned cutting line of the steel material,
At this time, in gas cutting of steel materials, the cutting slag generated on the back side of the steel material is removed by spraying oxygen gas with a preheating flame from the rear in the cutting direction by the back side nozzle that moves to follow each step. , When stopping or retracting one of the torches before the two torches interfere at the stage just before cutting is completed, the backside nozzle corresponding to that torch continues to eject oxygen gas and uses a non-heating flame instead of a preheating flame. A method for gas cutting steel materials, which is characterized by the ability to emit active gas. (2) Cutting is performed by simultaneously moving a set of two cutting torches toward each other along the planned cutting line of the steel material;
At this time, the cutting slag generated on the back side of the steel material is removed by spraying oxygen gas with a preheating flame from the rear in the direction of cutting progress by the back side nozzle that moves to follow each 1.
In 4-phase gas cutting, the cutting speed at the start of cutting is set to 20% or less of the predetermined standard speed, and then 1011
When the cut is more than g1, the speed is gradually increased to the standard speed, and the cutting is then performed at this standard speed.Also, just before the cutting is completed, one of the torches is stopped and retracted before the two torches interfere. A gas cutting method for steel material, characterized in that the back nozzle corresponding to the torch continues to eject oxygen gas and ejects inert gas instead of the preheating flame. (3) The pressure of the inert gas that is ejected in place of the preheating flame from the back side nozzle corresponding to the torch that is stopped and retracted immediately before the completion of cutting is 1 or more. A method for gas cutting steel materials as described in item 1) or item (2).