JP7557782B2 - Piercing Method - Google Patents

Description

The present invention relates to a piercing method that uses a gas cutting tip, and in particular to a piercing method that can shorten the preheating time required for piercing.

Products are cut from steel plates using a gas cutting nozzle that has a cutting oxygen nozzle at its center and multiple preheat gas nozzles arranged around the cutting oxygen nozzle. In this case, it is common to form (pierce) a hole that penetrates the surface of the steel plate in the thickness direction at a preset position (piercing position), and then start cutting from the hole (hereinafter referred to as the "conventional method").

When piercing a steel plate, the cutting oxygen nozzle of the gas cutting nozzle is placed facing the piercing position set on the steel plate to be cut, and preheating is started by ejecting preheat gas from the preheat gas nozzle in this state to form a preheat flame. As the preheating time passes, the preheated area changes from red to yellow, and the area that has turned yellow melts. Then, after the preheated area has been sufficiently preheated, cutting oxygen is ejected, and the ejected cutting oxygen flow burns the base material at the piercing position, removing the combustion products and molten base material. This reaction grows to form a hole penetrating the steel plate in the thickness direction, and the piercing is completed (see, for example, Patent Document 1).

Patent No. 3751728

As mentioned above, when piercing a steel plate using a gas cutting nozzle, the cutting oxygen nozzle is placed facing a preset piercing position for preheating. As a result, the steel plate is preheated in a circular shape centered on the piercing position, and the piercing position is not heated by the preheating flame, so it remains in a low-temperature black spot state even though the surrounding area is preheated to a ring-shaped molten state.

As a result, it takes longer for the piercing position to heat up to a temperature where piercing can be performed. Even so, if the steel plate is about 12 mm thick, the preheating time is not significantly longer. However, when the thickness is about 20 mm or more, there is a problem in that the proportion of the time required for piercing to the total cutting time increases.

The object of the present invention is to provide a piercing method that can shorten the preheating time when piercing a steel plate.

A representative piercing method according to the present invention for solving the above problems is a method for piercing a steel plate using a gas cutting nozzle having multiple preheat gas nozzles arranged around a centrally located cutting oxygen nozzle, and is characterized in that the gas cutting nozzle is arranged at a piercing preheating position for piercing preheating, with the cutting oxygen nozzle separated from the piercing position previously set on the steel plate by a distance that approximately corresponds to the dimension from the cutting oxygen nozzle to the preheat gas nozzle, preheating the piercing position by ejecting preheat gas from the preheat gas nozzle of the gas cutting nozzle at the piercing preheating position, and after preheating the piercing position, moving the gas cutting nozzle from the piercing preheating position so that the cutting oxygen nozzle faces the piercing position, and then ejecting cutting oxygen from the cutting oxygen nozzle of the gas cutting nozzle to perform piercing.

In the piercing method according to the present invention, the cutting oxygen nozzle of the gas cutting nozzle (hereinafter simply referred to as the "nozzle") is not opposed to a piercing position preset on the steel plate, but is separated by a distance that approximately corresponds to the dimension from the cutting oxygen nozzle to the preheating gas nozzle. Therefore, one of the multiple preheating gas nozzles formed around the cutting oxygen nozzle faces or is very close to the piercing position, and the piercing position or a position very close to it can be preheated by the preheating flame.

This improves the preheating effect on the piercing position, thereby shortening the preheating time for piercing.

FIG. 1 is a diagram illustrating a typical configuration of a nozzle. FIG. 1 is a diagram illustrating a typical configuration of a nozzle. FIG. 13 is a diagram showing piercing positions when cutting a product from a steel plate. 1A to 1C are diagrams illustrating a procedure for performing piercing preheating. 1A to 1C are diagrams illustrating a procedure for performing piercing. FIG. 13 is a diagram illustrating the timing when piercing is performed.

The piercing method according to the present invention will be described below. In the piercing method according to the present invention, when piercing a steel plate using a nozzle, the piercing position is preheated in a concentrated manner by preheating the preheating gas nozzle facing or close to the piercing position that has been set in advance on the steel plate, without facing the cutting oxygen nozzle. After the piercing position has been sufficiently preheated, the nozzle is moved so that the cutting oxygen nozzle faces the piercing position, and cutting oxygen is sprayed from the cutting oxygen nozzle to pierce the preheated piercing position, thereby shortening the preheating time.

Before describing the piercing method, we will explain the piercing position P on the target steel plate A and the nozzles 5 and 6. Figure 3 is a diagram explaining the piercing position P. For example, the products B to be cut from the steel plate A are set in advance, and the positions of these products B relative to the steel plate A are set. The piercing position P and the lead-in cutting line C from the piercing position P to the product B are set in the scrap portion of the steel plate A on which the products B are placed. Then, after piercing the steel plate A at the piercing position P, it is possible to cut the product B in one stroke from the piercing position P via the lead-in line C.

Figures 1 and 2 are diagrams explaining the configuration of the nozzle. Figure 1 shows a nozzle 5 of a type that forms a preheat flame by burning a gas with a fast burning speed, such as acetylene gas. This nozzle 5 has a cutting oxygen nozzle 1 formed in the center for spraying cutting oxygen, and multiple preheat gas nozzles 2 are arranged on a circumference centered on the cutting oxygen nozzle 1. Each preheat gas nozzle 2 is formed as a circular hole.

Figure 2 shows a type of nozzle 6 that creates a preheat flame by burning a gas with a relatively slow burning speed, such as liquefied petroleum gas (LPG). This nozzle 6 has a cutting oxygen nozzle 1 at its center for spraying cutting oxygen, and multiple preheat gas nozzles 2 are arranged on a circumference centered on the cutting oxygen nozzle 1. Each of the preheat gas nozzles 2 is formed as a slit.

In addition, in Figures 1 and 2, the symbol 1a denotes a cutting oxygen passage that is continuous with the cutting oxygen nozzle 1 formed in the nozzle 5 and nozzle 6, respectively. Also, the symbol 2a denotes a preheat gas passage that is continuous with the preheat gas nozzle 2 formed in the nozzle 5 and nozzle 6, respectively.

The specifications of each of the nozzles 5 and 6, such as the diameter of the cutting oxygen nozzle 1 and the number of preheat gas nozzles 2, are set according to the thickness of the steel sheet A to be cut. Therefore, the circumferential diameter (PCD) of the circle on which the preheat gas nozzles 2 are arranged is also set according to the number of the preheat gas nozzles 2. Therefore, the dimension (PCD/2) from the cutting oxygen nozzle 1 to the preheat gas nozzle 2 is set according to the specifications of the nozzles 5 and 6.

The piercing method according to this embodiment will be described below with reference to Figures 4 to 6. Note that each figure describes the case where a nozzle 5 with a preheat gas ejection hole 2 consisting of a circular hole is used as shown in Figure 1, but the steps are the same even when a nozzle 6 with a preheat gas ejection hole 2 consisting of multiple slits is used.

First, when the surface of the steel sheet A is set to a reference height h0, the height of the nozzle 5 is adjusted so that the preheat gas is ejected from the preheat gas ejection hole 2 to form a preheat flame 3, and the height h1 is such that the hottest part comes into contact with the surface of the steel sheet A. In addition, the position of the cutting oxygen ejection hole 1 is set to the piercing preheat position Pp, which is separated by a distance that approximately corresponds to the dimension (PCD/2) from the piercing position P to the preheat gas ejection hole 2.

By setting the nozzle 5 to the piercing preheating position Pp as described above, one of the multiple preheat gas ejection holes 2 faces the piercing position P or a position very close to it, and preparation for the piercing operation is completed (t0). Note that in nozzles 6 in which the preheat gas ejection holes 2 are formed by slits, the spacing between adjacent slits is generally narrow, so it is possible to reliably position one of the slits (preheat gas ejection holes 2) facing the piercing position P.

After preparations for the piercing operation are complete, preheating gas is ejected from the preheating gas ejection hole 2 and ignited to form a preheating flame 3, which preheats the piercing position P. While maintaining this preheated state at the piercing preheating position Pp, when a preset time has elapsed, the nozzle 5 is moved so that the cutting oxygen ejection hole 1 faces the piercing position P from the piercing preheating position Pp.

When time t1 has elapsed since the formation of the preheating flame 3, the cutting oxygen stream 4 is ejected from the cutting oxygen nozzle 1 to perform piercing at the piercing position P, and at the same time the nozzle 5 is raised to a height h2. By raising the nozzle 5, it is possible to prevent the adhesion of combustion products and molten base material blown up from the piercing position P. Furthermore, by continuing to preheat the steel plate A with the preheating flame 3 and to eject the cutting oxygen, it is possible to form a hole 7 penetrating the steel plate A in the thickness direction with the cutting oxygen stream 4.

Then, after a predetermined time t2 has elapsed and a hole 7 penetrating the thickness direction of the steel plate A is formed or has been formed, the height of the nozzle 5 is lowered from h2 to the normal cutting height h1, and the cutting of the lead-in wire C begins.

In the above embodiment, the values of the preheating time t0-t1, the nozzle height h1, the nozzle rise height h2 during piercing, and the time t1-t2 required for the nozzle to rise and fall are not limited, and it is preferable to set them appropriately according to conditions such as the thickness of the steel sheet A and the surface condition.

In particular, when the nozzle is mounted on a numerically controlled cutting device, the PCD value of the preheat gas nozzle 2, the aforementioned preheat times t0-t1, t1-t2, nozzle heights h1, h2, and other numerical values are stored in the control device, making it possible to automatically perform the piercing operation on the steel plate A.

In addition, when automatically controlling and executing the program, in the program of the conventional method, as a pre-step of the series of operations described above, an additional operation is performed by moving the nozzle 5 or nozzle 6 so that the cutting oxygen nozzle 1 in the nozzle 5 or nozzle 6 faces the piercing preheating position Pp from the piercing position P, so that the program can be easily applied to the program of the conventional method and the same effect can be obtained.

In addition, by allowing the user to select whether to enable or disable the execution of the aforementioned additional operations using a hardware or software switch, it is possible to respond to conditions such as the thickness and surface condition of the steel sheet A.

The piercing method of the present invention can be used to pierce steel plates manually or automatically.

A Steel plate B Product C Lead-in cutting line P Piercing position Pp Piercing preheating position 1 Cutting oxygen jet hole 1a Cutting oxygen passage 2 Preheating gas jet hole 2a Preheating gas passage 3 Preheating flame 4 Cutting oxygen airflow 5, 6 Nozzle 7 Hole

Claims (2)

1. A method for piercing a steel plate with a gas cutting nozzle having a plurality of preheat gas jets arranged around a centrally located cutting oxygen jet, comprising:
a gas cutting nozzle is disposed at a piercing preheating position for performing piercing preheating such that a cutting oxygen nozzle is separated from a piercing position previously set on the steel plate by a distance substantially corresponding to a dimension from the cutting oxygen nozzle to a preheating gas nozzle;
preheating the piercing position by ejecting preheating gas from a preheating gas ejection hole of the gas cutting nozzle at the piercing preheating position;
After preheating the piercing position, the gas cutting nozzle is moved from the piercing preheating position so that the cutting oxygen nozzle faces the piercing position;
Thereafter, the piercing is performed by ejecting cutting oxygen from the cutting oxygen ejection holes of the gas cutting nozzle. The piercing method according to claim 1, characterized in that the gas cutting tip is raised as cutting oxygen is ejected from the cutting oxygen ejection hole of the gas cutting tip to perform piercing.

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