JPS5851777B2 - Renzokuteki Kinzokuchi Yuzo Igata - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for regenerating a cylindrical copper mold for continuous metal casting.

Tubular molds for continuous casting are currently made from extruded tubing and typically range from 2x2" to 6x6" and sometimes about 254x304. It has a mold cavity with a cross-sectional area of up to 10 x 12''.

In order to provide such extruded tubing with the necessary bends, especially as curved molds, accuracy is reduced when the tube is subjected to bending operations.

For example, the mold tolerance is 0.63511!7+1(0,
025''), the mold's external curved surface satisfies this tolerance, but the internal curved surface does not necessarily satisfy this tolerance by inspecting the longitudinal contour of the mold using a contour template. Then you'll understand.

Additionally, some degree of helix, or twist, results from extrusion or drawing.

Known cylindrical molds do not have a precise mold taper that changes the longitudinal cross-section of the mold so that the mold remains in contact with the billet as the molten metal solidifies and is drawn as a billet.

During continuous casting, the inner surface of the cylindrical mold is damaged by molten metal and solidified metal, and the mold is irregularly deformed due to thermal stress, pulling force, and the like.

If the formation of flaws or deformation progresses to such an extent that the shape and inner surface condition of the mold become abnormal, the mold cannot be used for continuous casting.

Used molds are not currently available for reuse, and used molds have no other use than as scrap.

Split molds, in which mold segments are mechanically assembled, have a higher degree of freedom in designing the mold taper, curved shape, etc. than cylindrical molds made of extruded steel. The lifespan of molds is short.

Furthermore, if the segments are cast or forged segments, the mold walls will be considerably thicker and require machining of the mold walls to form cooling passages and cavities therein.

Therefore, segmented molds with mechanically assembled cast or forged segments require large amounts of expensive copper and increase the cost of machining cavities and cooling passages.

After being used for continuous casting, the very expensive molds are simply scrapped.

An object of the present invention is to provide a method for regenerating a cylindrical copper mold used for continuous casting.

Although the recycled cylindrical copper mold is an integral part, it has a highly precise mold cavity and does not warp or twist.

Therefore, the cylindrical molds regenerated according to the present invention have substantially higher productivity and provide higher quality castings than conventional cylindrical molds.

The method for regenerating a continuous casting mold according to the present invention involves converting a used continuous casting mold made of a copper sleeve whose shape and inner surface condition have been abnormalized into a core mold having the same outer surface shape as the mold hollow part of a new continuous casting mold. placing an explosive directly on the outer surface of the used mold, or placing an explosive at a distance from the outer surface, and submerging the core mold and the used mold fitted therein in a liquid; detonating the explosive;
The method is characterized in that the used mold is inwardly compressed by shock waves until it comes into close contact with the core mold to correct and normalize its shape and inner surface condition, and then the core mold is pulled out from the corrected mold.

In the method of the present invention, a used mold (hereinafter referred to as sleeve) is used for a core mold or core whose exterior is machined to have the same finished surface and the same mold hollow part as the new mold.
is loosely fitted onto the core mold, and the lid plate and bottom plate are fitted over the top and bottom of the core mold/sleeve assembly, respectively, to form an explosive cladding assembly with the explosive deposited around the sleeve. The sheathing assembly is completely immersed in the liquid.

The explosive is then detonated from one end of the assembly to the other, causing the detonation wave front to travel uniformly in one direction.

The sleeve is then pulled out of the core mold, which after the explosion becomes a regenerated mold.

If any external machining of the remanufactured mold is required to make it compatible with the continuous casting equipment in which it will be used, this is done.

The accompanying drawings illustrate, in a partially cut away perspective view, a typical core and sleeve assembly and an explosive sheath attached to the assembly.

The core mold is preferably made of metal and its outer surface shape is machined to close tolerances and has the same finish as that desired for the inner surface of the new mold.

If the core mold 1 has sufficient durability to withstand the forces applied during sleeve regeneration without deformation and to allow the core mold 1 to be used repeatedly, the material of the core mold 1 There is no limit to this.

A synthetic resin may have sufficient strength and durability as the core mold 1 in some cases.

The sleeve 2 is loosely fitted over the core mold 1.

This sleeve 2 is a used mold that requires regeneration in order to restore the original shape of the mold cavity.

A lid plate 3 and a bottom plate 4 are fixed to the top and bottom of the core/sleeve assembly, respectively.

If liquid in which the assembly is submerged is present in the gap between core mold 1 and sleeve 2, the liquid will interfere with the molding process.

Therefore, the liquid is expelled from this gap and the gap is sealed against the liquid using the gasket 5.

When the liquid is discharged from the gap through the discharge port 6 penetrating the lid flat plate 3, air is interposed between the sleeve 2 and the core mold 1, and air bubbles no longer interfere with the molding process.

The explosive 7 attached around the sleeve 2 is
It is installed so that the front of the explosion wave advances in the longitudinal direction from one end to the other.

The explosive charge 7 may be in the form of a plate, strip, rod or string, and the amount of explosive charge 7 may be distributed around the circumference of the sleeve 2 so as to distribute the force applied to the sleeve 2 in the desired manner over its circumference. It may also be distributed non-uniformly.

Furthermore, when remanufacturing a sleeve 2 having a square cross section, it is generally necessary to apply greater molding pressure to the edges than to the flat or curved portions between the edges.

The applied molding pressure is not only controlled by varying the type, distribution, and amount of explosives installed;
It is also controlled by placing all or part of the explosive charge 7 at a distance from the sleeve 2.

When the explosive 7 is placed at a distance from the sleeve 2 in this way, the shock waves reaching the sleeve 2 are relaxed, and the molding pressure is reduced.

It should be noted that a rubber plate (not shown) or a belt of appropriate thickness (not shown) may be placed between the explosive 7 and the sleeve 2, or it may be placed around the sleeve 2 to keep the explosive at the required separation distance. By using a supporting frame or cage, the explosive charge 7 can be placed at a distance from the sleeve.

The amount of explosive used and the manner of attachment are related to the properties of the copper making up the sleeve and the shape of the sleeve.

Also, the pressure for molding the sleeve (used mold) is slightly higher than about 10 times the yield stress of copper required for molding a new mold.

The yield stress of copper is approximately 6.33ky/m4 for fully annealed copper.
(ranging from 9,000 Ib/1n2 to about 28.10 9/mvt (40,000 Ib/1n2) for hardened steel.

The molding pressure also depends on the desired degree of work hardening of the copper during the molding process.

When the explosive is not placed at a distance from the outer surface of the sleeve, the hardness of the sleeve before molding is Brinell 45 (500 kg load) and Brinell 75 (500 kg load) on the inner surface of the mold in contact with the core.
It is not difficult to harden to Brinell 10100 (500 kg load) 9 or higher on the outer surface of the mold.

The inner surface of the mold can be prehardened if it is desired to provide a higher hardness to the inner surface of the mold.

The type, quantity, and degree of spacing of the explosives are determined using known methods such that the forming pressure exerted on the sleeve by submerging the explosive cladding assembly in the liquid and detonating the explosives is the required value on the outer surface of the sleeve. Can be changed according to explosives usage techniques.

Explosives, such as P, which have a relatively high detonation velocity,
An explosive containing ETN (pentaerythritol tetranitrate) is used.

The magnitude of the shock wave is such that the sleeve is inwardly compressed until it comes into close contact with the core mold, and the inner surface of the sleeve that is in close contact with the core mold flows plastically.

In continuous casting, when the slab is pulled out of the mold, the solidified shell scratches the inner surface of the mold, and many scratches are observed on the inner surface of the sleeve before regeneration.

When the life of the mold expires, the inner surface of the sleeve becomes abnormal due to the countless deep scratches found on the inner surface of the sleeve.

Such an abnormal inner surface state of the sleeve cannot be corrected or normalized even if the sleeve is subjected to low-speed plastic working such as rolling or extrusion.

Therefore, in the past, used molds were discarded.

However, according to the present invention, the inner surface of the sleeve is corrected and normalized, and a recycled mold that is no different from a new mold is manufactured.

Presumably, the groove is crimped or flattened due to the instantaneous plastic flow of the copper toward the inside of the groove of the scratch.

The speed of shock wave transmission must be significantly greater than the speed of sound transmission through the liquid in which the assembly is submerged.

The sound wave transmission speed in water is 1500771/sec.
It is.

Preference is given to using string explosives and plate or band explosives (sold by DuPont under the trademarks Primacord and "Pig Sheet", respectively) which produce shock waves with a velocity of 6000 m/Sec.

The explosive is detonated from one end of the assembly to the other so that the detonation progresses in one direction.

The explosion is carried out in a liquid to produce sufficient use of the explosion energy and eliminate noise problems.

Furthermore, by carrying out the explosion in a pit located on the floor or below the ground, the explosive force is not easily transmitted to the outside, and the explosion also eliminates the need to constantly replace the container by applying a blow to the container. .

Any liquid that can transmit the necessary regenerative force to the sleeve.
The explosion may be carried out in any liquid.

In order to properly distribute the explosive force over the explosive cladding assembly, the assembly must be coated with a sufficient depth of liquid.

Of course, water is the most convenient liquid because it is cheap and the loss of water is not significant.

Covering the assembly with approximately 2 feet or more of water is generally necessary to effectively utilize the energy of the explosion.

After the explosion, the assembly is removed from the water and the core mold 1 is pulled out of the sleeve, which has become a regenerated mold, resulting in a regenerated sleeve having a hollow section whose shape is completely complementary to the shape of the mold core 1. A mold is obtained.

To suit continuous casting equipment that plans to use recycled molds,
The desired external machining is then performed on the recycled mold.

According to the present invention, the wall thickness is 9.52 mm (3/8
A used mold that is approximately 50.8 mm (2") or less from front to back is regenerated.

In most cases, the length of the mold is less than 915 moe (3 feet).

The invention is further illustrated by the following examples.

Example 1 (Remanufacturing of straight billet molds) (a) A rectangular sleeve of hardened steel 813 mm (32") long was cut into 133 x 133 mm (5,25 x 5.25
Loosely fit the sleeve into a square core mold of the same length as the sleeve, then attach flat plates to both ends of the sleeve, and exhaust the inside of the sleeve and the flat plates at both ends.

Next, at the edge of the sleeve, the distance between the explosive and the sleeve is 3.1
Four rubber plates are attached as supports to each edge of the sleeve so that they are spaced apart by 7 mm (0,125"), and on the flat surface of the sleeve, there is a distance of 7.938 mm (0.125") between the explosive and the sleeve.
Four striations were attached as supports to each flat surface of the sleeve, spaced apart by 0.3125").

followed by 0, each with a length of 813 bites (32”).
, 127,! ? /CIrL (60gr/foot) PET N-Explosive-11 Brimacord (DuPont Trademark)
The I+-2 strips were placed at a distance from each flat portion on the outer surface of the sleeve via a support.

Also, the cross section is between 28.57 x 820 (1,125 x 32”)
), and the weight per cross-sectional area is 31.1 g/'mm (
2fl/1n2) of PETN explosive-11 Detasheet (trademark of DuPont) 1 was placed via a support at a distance from each edge of the outer surface of the sleeve.

The total amount of explosives is 371. ! 9 (5730 grains).

The sleeve was submerged in a pit filled with water so that the sides of the sleeve with the explosives were covered with 2 feet of water, and the explosives were detonated from one end of the sleeve.

Next, the sleeve is removed from the hole, the end plate is removed,
Then, the core mold was pulled out from the sleeve.

It was found that the inner surface of the sleeve had a completely core-shaped shape and finished surface, and that the inner surface of the sleeve was corrected and normalized.

Example 2 (Reproduction of curved billet mold) In order to reproduce a sleeve with a length of 813 mm by repeating the process of Example 1, the cross section was 102102 x 152, i//
x 6// ) and a total amount of 371 g of explosive, the sleeve was regenerated.

Prior to this application, numerous continuous casting machines were in operation on a worldwide scale for the production of billets and small blooms, and in every continuous casting machine the cylindrical mold was replaced after 120 to 150 castings. and the worn-out used molds are discarded.

Accordingly, the method of the present invention for making exhausted used molds reusable represents a significant advance in the field of continuous billet and bloom casting.

In addition, the remanufactured molds have improved quality compared to conventional molds and therefore have the advantage of reducing breakouts.

[Brief explanation of the drawing]

The accompanying drawing is a partially cut away perspective view illustrating a typical core and sleeve assembly and the explosive coating applied to the assembly. 1... Core type, 2... Sleeve, 3...
...Lid plate, 4...Bottom plate, 5...
・Gasket, 6...Discharge port, 7...
explosive.

Claims (1)

[Claims] 1. A used continuous casting mold made of a copper sleeve whose shape and internal state have been abnormalized is inserted into a core mold having the same outer surface shape as the mold hollow part of a new continuous casting mold, and then directly inserted into the outer surface of the used mold. Attach an explosive or place an explosive at a distance from the outer surface, submerge the core mold and the used mold fitted therein in a liquid, detonate the explosive, and remove the spent mold from the core mold. A method for regenerating a continuous casting mold, which comprises compressing the core inwardly by shock waves until it comes into close contact with the core to correct and normalize its shape and inner surface condition, and then pulling out the core from the corrected mold.