JPS60221152A - Continuous casting method of hollow billet and dummy bar for continuous casting machine - Google Patents

Abstract

PURPOSE:To produce a hollow billet having good dimensional accuracy without trouble during casting by providing a cooling water spray nozzle to the bottom end of a water-cooled core and cooling directly the inside circumferential surface of the hollow billet by the cooling water from said nozzle. CONSTITUTION:The body of the water-cooled core 3 is made into the double- pipe construction consisting of a central flow passage 3a on a cooling water introducing side communicating with said body at the bottom end thereof and an outside annular flow passage 3b. A spray pipe 9 is penetrated in the passage 3a and the nozzle 9a is provided to the projecting top end thereof. The water is injected from said nozzle 9a to the hollow inside circumferential surface of the billet to cool directly said surface with the water and to form a secure solidified shell. A passage for releasing the cooling water is provided to a dummy bar 10 for drawing the billet. More specifically the passage is made into such construction in which plural pieces of detaining pieces 11 such as bolts are attached to the top end of the bar 10 and that a through-hole 12 for accepting the bottom end of the core 3 and the extension thereof in the axial direction are communicated with a water drain port 13 provided to the side part.

Description

Detailed Description of the Invention Technical Field The present invention relates to a method for continuous casting of hollow slabs and a dummy bar for a continuous casting machine. This paper proposes a method for directly water-cooling the hollow inner surface of a slab during continuous casting using a mold with a casting space, and a new dummy bar head structure used to eliminate the inconveniences that occur at that time.

Conventional technology and its problems The conventional technology for continuous casting of hollow slabs using a core uses a mold with an annular cylindrical casting space formed by a combination of a water-cooled outer mold and a water-cooled core. The inner and outer screens are cooled simultaneously to produce a hollow cylindrical slab, which is then pulled downward using a dummy bar while promoting the sequential growth of the cylindrical shell to produce a hollow slab as a seamless pipe material. This is a method of manufacturing.

In such prior art, the outer circumferential surface of the hot slab extracted from the mold can be supported and straightened using an hourglass roll or the like, but the hollow inner surface cannot be guided and has been neglected. In particular, the inner solidified shell that is cooled and formed facing the core often does not have enough strength to withstand the static pressure from the unsolidified molten steel in the center, and this is the cause of bulging. It became. In addition, bulging causes deviations in inner diameter dimensions, uneven wall thickness, and in extreme cases, breakouts.

OBJECTIVES AND SUMMARY OF THE INVENTION The objects of the present invention are, firstly, to overcome the drawbacks of the prior art that the hollow inner circumferential surface of the hollow slab is insufficiently supported and straightened and cooled, and secondly, to provide forcible water cooling of the inner surface of the hollow slab. The goal is to overcome the inconveniences that come with being busy. To deal with the former, we proposed a method of direct water cooling by spraying water onto the hollow inner peripheral surface of the slab, and to deal with the latter, we proposed a dummy bar head structure in which a drainage channel was formed at the center of the dummy bar's axis. By making proposals, we will solve each of the above technical issues.

Structure of the Invention The present invention involves injecting molten steel into a mold having an annular cylindrical space formed by a combination of a water-cooled outer mold and a water-cooled core, and cooling both the inner and outer circumferential surfaces of the outer mold and the core. A method of continuously casting hollow slabs by simultaneously generating and growing solidified shells and gradually pulling the resulting hollow cylindrical shell-shaped pieces downward, and in particular spraying cooling water onto the lower end of the water-cooled core. A nozzle is installed, and through this nozzle, cooling water is injected onto the hollow inner peripheral surface of the drawn slab for direct water cooling, which quickly generates a thickened and strong inner solidified shell that can overcome the static pressure of molten steel, resulting in a stable and sound product. It is distinctive in that it is a hollow slab.

FIG. 1 is a diagram of the mold part of a continuous hollow slab casting machine,
The illustrated reference numeral 1 is a steel mold, and 2 is a steel backup frame, both of which constitute a cylindrical outer mold.Although not shown, the mold 1 is water-cooled. Reference numeral 8 denotes a water-cooled core installed at the center of the mold 1. The annular cylindrical space formed between the core 8 and the mold 1 is a casting space 4, and a predetermined metal is placed in this space 4. Molten metal, or molten steel, is injected and cylindrical slabs are directly cast.

In addition, 4 in the figure is a cooling water branch pipe, 5 is a cooling water introduction pipe,
6 is a drain pipe, 7 is a fitting, 8 is a seal ring, and the core 8 is connected to the lower end of the branch pipe 4 by a flange. That is, the core is supported at a fixed position in the mold by the inlet pipe 5, drain pipe 6, and branch pipe 4 fixed to the mold wall via the fixture 7, and therefore moves together with the mold oscillation. do.

Figure 2 shows the details of the core 8, the main body is 0.9~1.6
9o/m (D draft angle [Dt-Db/Db, Hx10
0], with a double pipe structure that communicates at the lower end,
A spray water supply pipe 9 penetrates into the central flow passage Ba on one cooling water introduction side of the pipe. Cooling of the main body is effected by cooling water that is introduced from the inlet pipe 5 through the branch pipe center flow path 4a, passes through the outer annular flow path 8b at the lower end communication part, and flows to the drain pipe 6 via the branch pipe outer passage 4b. be done.

The tip of a spray water supply pipe 9 projects from the lower end of the core 8, and is configured to be able to spray water, and in some cases, a water spray nozzle 9a is attached to this protrusion.
Water can be sprayed onto the hollow inner surface of the slab that descends while being guided by the outer peripheral surface of the core. Therefore, as soon as the slab to be drawn leaves the mold, that is, the core wall, the nozzle 9
When it is directly cooled by the spray water from a and forms a strong solidified shell, it becomes K.

At the start of casting, the slab is pulled out by a dummy bar 10 that also serves to support the injected molten steel. The head of this dummy bar 10 has a locking piece 1, preferably a bolt, on the upper end surface.
Attach multiple pieces of 1. Further, in the case of the present invention, a nozzle 1O may protrude from the lower end of the core 8, and a through hole 12 forming a drainage channel is provided along the axial center for receiving the lower end of the core.

The extension of this through hole 12 leads to a plurality of water drain ports 18 opened at the side of the dummy par 10, and is not necessary for releasing cooling water and steam used for cooling the hollow inner surface of the slab. It is a passageway. Without this passage, there would be no place for the discharged cooling water to escape, leading to various problems.

According to the experiments conducted by the present inventors, the cross-sectional dimensions of the slab and the outer diameter of 286
0 dragonφ, inner diameter: 120mφ (core extraction device, 8%/1
) When a hollow slab was continuously cast, the formation of a strong inner solidified shell was observed, and as a result, there was no deviation of the inner dimension, shape, or breakout that was observed in the past, and good casting was achieved. .

DETAILED DESCRIPTION OF THE INVENTION As described in detail, according to the present invention, there are no troubles during casting and it is possible to manufacture hollow slabs with good dimensional accuracy.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway front view of a continuous hollow slab casting machine, and Fig. 2 (al is a sectional view showing details of the branch pipe and core; , d-d' are shown as fbl I (cl + (al), Figure 8 is a diagram of the dummy par (at is a plan view, (b)
is a partially cutaway front view. 8... Core 4... Casting space 5... Inlet pipe -6... Discharge pipe 8... Seal ring 9... Spray supply pipe 9a.
... Nozzle 10 ... Dummy par 11 ... Locking piece
12...Through hole 18...Water drain port.

Claims (1)

[Scope of Claims] L Molten steel injected into a mold having an annular cylindrical space formed by a combination of a water-cooled outer joint and a water-cooled core is cooled by the respective cooling effects of the outer mold and the core. A method of continuously casting hollow slabs by generating and growing solidified shells from both the inner and outer periphery surfaces and gradually pulling the resulting hollow cylindrical shell-shaped slabs downward, the cooling provided at the lower end of the water-cooled core A method for continuous casting of hollow slabs, characterized by spraying cooling water from a water spray nozzle to directly cool the inner peripheral surface of the drawn hollow slabs with water. λ A dummy par used for drawing out hollow slabs when continuously casting hollow slabs using a mold that has a combination of a water-cooled outer diameter and a water-cooled core, and has a through hole that receives the lower end of the core that can spray water onto the upper end, and A dummy par for a continuous hollow cast slab casting machine having a head structure in which a one-piece locking piece is provided and an extension of the through hole extending in the axial direction is communicated with a drain port provided on the side.