JPH03230847A - Method for repairing roll in twin roll type continuous casting machine - Google Patents

Abstract

PURPOSE:To repair a roll without taking off the roll by executing Ni build-up welding to broken part of Ni plating layer at the most outer layer on the stainless steel roll while holding Cu diffusion welding part at the specific temp. CONSTITUTION:The diffusion welding of Cu layer 3 is executed on surface of the stainless steel-made roll base body 2. Ni layer 4 is plated as the most outer layer on the Cu layer to form the roll 1. Padding repair is executed to the broken part 6 in the Ni layer 4 on this roll 1 with Ni welding while holding the temp. of diffusion welding part 5 at <=250 deg.C. By this method, the roll can be repaired without developing crack on the roll.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a roll repair method for a twin-roll continuous casting machine.

[Conventional technology]

In a twin-roll continuous casting machine, as shown in the plan view in Fig. 3, a pair of rolls R1 and R2 are used, and the axes a1, (1) and a2 are aligned parallel to each other with a distance d corresponding to the thickness of the slab. A pair of side weirs Sl and S2 are pressed against both end surfaces e1 and e2 of these rolls R1 and R2 to form a bottomless mold. The hatched area in the figure is the sump inside the mold. Rolls R1 and R2 are
A Cu layer is diffusion welded to the surface of the stainless steel roll base, and a Ni layer is further plated on the Cu layer as the outermost layer that comes into direct contact with the molten metal. The Cu layer is a layer on the outer peripheral surface of the roll to increase thermal conductivity and ensure the necessary heat removal from the molten metal, and the Ni layer is a layer on the outer peripheral surface of the roll that is made of Cu.
This layer adjusts the thermal conductivity of the roll to ensure proper solidification, and also ensures wear resistance between the roll end face and the side weir. The side weirs S1 and S2 are heated before the start of casting to prevent solidification and adhesion of molten metal.
Also, during casting, it is vibrated in a direction perpendicular to the roll axis (al, a2).

[Problem to be solved by the invention]

Therefore, a minute gap is created between the side weir and the end face of the roll due to thermal deformation and vibration (backlash), and the molten metal in the pool M (Fig. 3) is inserted into this minute gap. Cast burr B is formed.

If this cast burr formation is significant, during casting, the part of the corner from the outer peripheral surface of the roll to the end face of the roll may be affected by the burr.
Peeling of the plating layer occurs, and the sealing of the mold sump M becomes incomplete, causing molten metal leakage.

In actual operation, it is required to repair any damage to the Ni plating layer that occurs without removing the roll. -Such repairs for boat fishing are carried out by overlaying the damaged part of the N1 layer with Ni welding. Therefore, it is necessary to repair the roll by fully considering the influence of welding heat and reliably preventing the occurrence of cracks around the damaged part of the roll.

The present invention aims to provide a roll repair method for a twin-roll continuous casting machine that can be performed without removing the rolls while reliably preventing roll cracking by performing Ni welding under appropriate conditions. purpose.

(3) [Means for Solving the Problems] According to the present invention, the above object is achieved by diffusion welding a Cu layer on the surface of a stainless steel roll base and further plating an N1 layer as an outermost layer on the Cu layer. A roll repair method for a twin-roll continuous casting machine, characterized in that the damaged part of the N1 layer of the rolled roll is repaired by Ni welding, which is performed while maintaining the temperature of the diffusion welded part at 250 ° C. or less. achieved.

As a result of analyzing the welding thermal stress generated in the roll repaired area and its surroundings through various numerical calculations, the inventor found that the joint strength of the diffusion weld that joins the stainless steel roll base and the Cu layer is 15 kg/cut. It has been found that if N1 welding is performed under the above conditions, there is no risk of cracking of the roll and a good repair can be performed. As shown in FIG. 1, the bond strength decreases as the temperature of the diffusion weld increases. As is clear from the figure, the temperature of the diffusion welded part was set to 25
If Ni welding is performed while maintaining the temperature at 0° C. or lower, the joint strength can be maintained at 15 kg/cff1 or higher.

(4) The present invention will be explained in more detail with reference to Examples below.

〔Example〕

The rolls of a twin-roll continuous caster were repaired in accordance with the present invention.

FIG. 2 is a partially cross-sectional perspective view showing the vicinity of a part of the corner from the outer peripheral surface to the end surface of the roll to be repaired. The roll 1 has a Cu layer 3 (thickness 9++nn) on the surface of a roll base 2 made of JIS standard SUS 304 stainless steel.
) is diffusion welded and further N is applied as the outermost layer on this CU layer 3.
The i-layer 4 (thickness 1) is plated. 5 in the figure is a diffusion bonding portion.

During casting, damage occurred at position 6 in which the N1 layer was peeled off due to cast burrs.

This damaged part 6 was repaired by Ni welding under the following conditions.

Ni welding conditions Welding method: TIG welding (5) Welding rod: JIS T-4-Ni (wire diameter 1.6mm) Current: 170A Shielding gas:・Helium (flow rate: 15 liters/min) Welding speed: 1.25 mm/sec or more Bead length:
Width: number ffll11~30mmL x 5fl] I[lW
Below/times Temperature before welding: 50°C or below Due to the Ni welding described above, the temperature of the diffusion welded part during Ni welding is maintained at 250°C or below, there is no cracking of the roll, and the N1 layer damaged part 6 is I was able to make some repairs.

In this example, under the above welding conditions, the diffusion welded area was
Although Ni weld build-up was performed while maintaining the temperature at 0° C. or lower, Ni welding conditions other than those described above that can maintain the diffusion welded portion at 250° C. or lower may be used.

〔Effect of the invention〕

As explained above, according to the present invention, the rolls of a twin roll continuous casting machine can be repaired without removing the rolls (6) and without causing cracks in the rolls.

[Brief explanation of drawings]

Fig. 1 is a graph showing the change in bonding strength of the diffusion welded part that joins the stainless steel roll base and the Cu layer with respect to temperature. Fig. 2 is a graph showing the twin-roll continuous casting method using the roll repair method of the present invention. FIG. 3 is a perspective view partially showing the structure of the rolls of the machine, partially shown in cross section in the roll axis direction, and FIG. 3 is a plan view partially showing a mold composed of a pair of rolls and a side weir. . 1: Roll, 2: Stainless steel roll base, 3: Cu layer, 4: Ni layer, 5: Diffusion welding layer, 6: Roll damaged part,
al, a2: roll axis, d: roll interval, el, e2:
Roll end face, M: sump, R1, R2: roll, SL, S2: side weir. (7) 0ε 0 OtsuL (2 mountains 1.L115n) Summer vote doφsae 3rd time 332-

Claims (1)

[Claims] 1. A Cu layer was diffusion welded to the surface of a stainless steel roll base, and a Ni layer was plated as the outermost layer on the Cu layer. The damaged part of the Ni layer was heated to 250°C at the temperature of the diffusion welded part. A roll repair method for a twin-roll continuous casting machine, characterized in that overlay repair is performed by Ni welding while maintaining the following.