JPH02192878A - Cutting method for steel ingot - Google Patents

Abstract

PURPOSE:To reduce cutting loss of a cast billet and to improve its cutting efficiency by injecting high pressure preheating oxygen and high pressure fuel gas, and low pressure preheating oxygen and intermediate pressure fuel gas for a period of time from the start of notching to the start of cutting and for a period of time from the start of cutting to the completion of cutting, respectively. CONSTITUTION:The preheating oxygen, fuel gas and cutting oxygen are used at the same time to cut the steel ingot. For a period of time from the start of notching to the completion of cutting, the high pressure cutting oxygen is then injected through piping 8. In addition, for a period of time from the start of notching to the start of cutting, the high pressure preheating oxygen and the high pressure fuel gas are injected through piping 10 and piping 12, respectively. For a period of time from the start of cutting to the completion of cutting, the low pressure preheating oxygen and the intermediate pressure fuel gas are injected through piping 14 and piping 16, respectively. By this method, upper droop of a steel ingot cut part are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for cutting slabs with the aim of reducing cutting loss of slabs and improving cutting efficiency.

[Prior Art] Generally, slabs continuously pulled out from a mold are guided to a slab cutting device, and the slab is clamped by a clamp of this slab cutting device, and the moving speed of the slab is controlled. The slab is cut by a cutting tip that moves in the width direction of the slab, which is installed on a cart that moves synchronously with the slab. FIG. 5 is a longitudinal sectional view of a cutting nozzle used for cutting slabs. 1 is a cutting oxygen hole, 2 is an inner heating oxygen hole, 3 is a fuel gas hole, and 4 is an external preheating oxygen hole. The fuel gas in the fuel gas hole 3 mixes with oxygen in the externally preheated oxygen hole 4 and internally preheated oxygen inside or outside the cutting nozzle, and is injected into a preheated flame. On the other hand, the high pressure of the cutting oxygen hole 1 (10 kg
/cni) of oxygen is injected into the slab heated to the ignition temperature by a preheating flame, melts the slab, and uses its mechanical energy to blow away and cut the molten metal. FIG. 7 is a piping system diagram for supplying oxygen and fuel gas to the cutting nozzle. The pressure of the cutting oxygen is regulated by the pressure Ill valve 9, and the cutting oxygen is supplied to the cutting nozzle lower through the piping 8. Pressure regulating valve 11 for internal and external preheating oxygen
The pressure is regulated at , and the gas is supplied to the cutting nozzle 7 through the pipe 10 . The pressure of the fuel gas (coke gas, etc.) is regulated by a pressure regulating valve 13, and the fuel gas is supplied to the lower cutting flame through a pipe 12. Figure 6 is an ON-OFF diagram of oxygen and fuel gas during slab cutting, from the start of cutting into the slab to the completion of cutting, cutting oxygen is 10 kg/c+++ (high pressure), preheating oxygen and fuel gas are 2,0 kg/cn (high pressure). In this way, the slab is cut at a constant pressure from the start of cutting to the completion of cutting, with the supply pressures of cutting oxygen, preheated oxygen, and fuel gas during cutting of the slab.

[Problems to be Solved by the Invention] Conventionally, the supply pressure of preheated oxygen and fuel gas when cutting slabs is set to a pressure that allows cutting into the slab, and cutting and cutting are carried out. There were problems in that the area became wider, upward wobbling occurred, and there was a lot of cutting loss. Additionally, because the cutting oxygen was not sufficiently sealed by the preheated flame, the momentum of the cutting oxygen was attenuated, and it was necessary to reduce the cutting speed to achieve proper cutting.

[Means for Solving the Problems] The present invention aims to solve the above-mentioned problems, and includes a method for cutting slabs that uses cutting oxygen, preheated oxygen, and fuel gas in combination. High-pressure cutting oxygen is injected until the cut is completed, high-pressure preheated oxygen and high-pressure fuel gas are injected between the start of the cut and the cut is completed, and low-pressure preheated oxygen and medium pressure are injected from the start of the cut until the cut is completed. This is a method for cutting slabs, characterized by cutting by injecting fuel gas.

[Operation] High-pressure cutting oxygen is injected from the start of cutting to the completion of cutting, and the supply pressure of preheating oxygen and fuel gas is maintained at high pressure (2.0 kg/- or more) from the start of cutting into the slab to the completion of cutting.
From the start of cutting to the completion of cutting, the preheating oxygen supply pressure is low pressure (less than 1.0 kg/cn1), and the fuel gas supply pressure is medium pressure (1.0 to less than 2.0 kg/eta).
By doing so, the upper part of the slab is not overheated when cutting the slab, so that the top sag is eliminated. Further, the sealing function of the preheated gas flame does not deteriorate, and the momentum of cutting oxygen can be prevented from attenuating, so that the cutting width can be narrowed. Moreover, the cutting speed can be made faster than before, and the cutting efficiency can be improved.

[Examples] Examples of the present invention will be described below. The second (21 is a piping system diagram for oxygen and fuel gas for carrying out the method of the present invention. 8 is a cutting oxygen supply piping provided with a pressure regulating valve 9 and a solenoid valve 18, and 10 is a pressure regulating for high pressure. A pipe for supplying high-pressure preheated oxygen is provided with a valve 11 and a solenoid valve 19. A pipe 14 is a pipe for supplying low-pressure preheated oxygen and is provided with a low-pressure pressure regulating valve 15 and a solenoid valve 20.12 is a high-pressure pressure regulating pipe. valve 13
and a high-pressure fuel gas supply pipe provided with a solenoid valve 21,
16 is a pipe for supplying medium pressure fuel gas provided with a low pressure pressure regulating valve 17 and a solenoid valve 22.

Using the above piping equipment, the slab is cut as follows. First, the pressure regulating valve 9 of the cutting oxygen pipe 8 is
Connect the pressure regulating valve 11 of the high pressure preheating oxygen pipe 10 to cnl 2.
, Okg/C: IA, the pressure regulating valve 15 of the low pressure preheating oxygen pipe 14 to 0.1 kg/a11, the high pressure fuel gas pipe 1
The pressure regulating valve 13 of No. 2 is set to 2.0 kg/cnt, and the pressure regulating valve 17 of the intermediate pressure fuel gas pipe 16 is set to 1.0 kg/cntl. When cutting, the solenoid valve 18 of the cutting oxygen pipe 8,
The solenoid valve 19 of the high-pressure preheated oxygen pipe 10 and the solenoid valve 21 of the high-pressure fuel gas pipe 12 are opened, and 10 kg/d of oxygen is cut at 2.0 kg/cffl along the route shown by the thick line in FIG.
of preheated oxygen and 2.0 kg/- of fuel gas are supplied to the cutting fire lower. When disconnecting, the solenoid valve 18 of the disconnected oxygen pipe 8
, the solenoid valve 20 of the low-pressure preheated oxygen pipe 14 and the solenoid valve 22 of the medium-pressure fuel gas pipe 16 are opened, and 10 kg/- of oxygen is cut at a rate of 0.1 kg/cnt along the route shown by the thick line in FIG.
of preheated oxygen and 1. okg/cat of fuel gas is supplied to the cutting fire lower. Piping switching at the start of cutting, the start of cutting, and the completion of cutting is performed by automatically opening and closing each electromagnetic valve. FIG. 1 is an ON-OFF diagram of oxygen and fuel gas in the method of the present invention, showing how the operating pressure is changed from the start of cutting into the slab to the completion of cutting.

When a slab with a thickness of 220 am is cut using the method of the present invention, the cutting width is as shown in Fig. 4.
What used to be 2 dragons now has 7 dragons, and the width of the underside has changed from the previous 5 dragons to 41. This results in an unfinished yield of 0.
Improve by 1%. Furthermore, when cutting a slab with a slab temperature of 800°C, the cutting speed of the slab was 350+u/- in the conventional method, but it was increased to 430 am/m, improving cutting efficiency by about 20%.

[Effects of the invention] Since the present invention performs cutting by setting the working pressure of preheated oxygen and fuel gas to be high at the time of cutting and low at the time of cutting, there is no upper sag at the cut part of the slab, and the cutting width is narrower than that of the conventional method. Become. Therefore, the cutting loss of the slab is reduced and the cutting efficiency is improved.

[Brief explanation of the drawing]

0N-OFF diagram, Fig. 2 is a piping system diagram for oxygen and fuel gas to implement the method of the present invention, Fig. 3 is a piping system diagram showing the piping used during cutting, and Fig. 4 is a piping system diagram showing the piping used during cutting. A sectional view showing the cutting part, FIG. 5 is a partial longitudinal sectional view of a cutting nozzle used for cutting slabs, and FIG. 6 is an ON-OFF diagram of oxygen and fuel gas during conventional slab cutting. FIG. 7 is a conventional oxygen and fuel gas piping system diagram. 1...Cut oxygen hole, 2...Inner thermal oxygen hole, 3...
Fuel gas hole, 4...External preheating oxygen hole, 5...Mixing chamber, 6
... Skirt, 8 ... Cut oxygen pipe, 9 ... Cut oxygen pressure regulating valve, 10 ... High pressure preheated oxygen pipe, 11 ...
Preheating oxygen high pressure pressure regulation valve, 12... High pressure fuel gas piping, 13... Fuel gas high pressure pressure regulation valve, 14... Low pressure preheating oxygen piping, 15... Preheating oxygen low pressure pressure regulation valve, 1
6... Medium pressure fuel gas piping, 17... Fuel gas medium pressure pressure regulating valve, 18, 19. 20, 21. ．． 22... Solenoid valve.

Claims (1)

[Claims] In a slab cutting method that uses preheated oxygen in combination with fuel gas and cutting oxygen, high pressure cutting oxygen is injected from the start of the cut to the end of the cut, and high pressure preheated oxygen is injected from the start of the cut to the end of the cut. A method for cutting slabs characterized by injecting high-pressure fuel gas and injecting low-pressure preheated oxygen and medium-pressure fuel gas from the start of cutting to the completion of cutting.