JPH0622739B2 - Wear plate member for slab support device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a slab support device in a top zone immediately below a mold of a continuous casting machine. More specifically, the present invention relates to a wear plate member having a two-layer structure that abuts a cast piece pulled out from a mold in such a cast piece supporting device.

(Prior Art) As a top zone slab support device in a continuous casting machine,
Cooling grids, cooling plates, walking beams, etc. are used.

Since these top zone cast piece supporting devices are used as a set with a mold, the life of the top zone immediately causes mold replacement. Recently, due to improvement of coating technology (multilayer plating, etc.) on the mold surface, the mold replacement cycle is determined by the life of the top zone cast piece supporting device.

In contact with the slab in this top zone slab support device,
Wear plates that determine the life of the top zone slab support device include small split type plates, lattice type plates, flat type plates, walking bar type, etc., but as these materials, conventionally, mild steel and cast iron ( JIS standard FCD material) has been used.

(Problems to be solved by the invention) However, since the wear plate of the top zone slab support device is frictionally contacted with the high temperature slab and is always externally cooled at the same time, the wear plate made of conventional mild steel or FCD material is used. The plate has a large amount of wear due to (1) sliding friction and corrosion, and has a short campaign life (online usage period).

(2) There are many heat cracks associated with the generation of thermal stress due to high temperature cast slabs and cooling water.

(3) Seizure trouble (deterioration of quality,
Breakout etc.) occurs.

Had problems such as. The wear plate was re-used with the surface removed after each campaign life (online use), but had to be scrapped after 3-4 campaigns (online use) due to the problems mentioned above.

Therefore, an object of the present invention is to solve the problems of the wear plate member of such a conventional top zone cast piece supporting device. In particular, a wear plate member is provided which improves wear resistance and lubricity and suppresses heat cracks to extend the campaign life of the member, and which can be repaired and reused any number of times even after the campaign life expires and which is inexpensive. The purpose is to

(Means for Solving Problems) Therefore, the present inventors conducted experiments to achieve these objects,
As a result of repeated research, high lubricity, wear resistance, and wear resistance suitable for wear plate surfaces used under severe conditions as described above.
We have developed a Ni-based alloy (high Ni-high Cr-high C steel) with a specified composition as a material with excellent heat crack resistance, and apply this alloy to the surface of the wear plate base material by welding overlay, spraying, etc. By coating the wear plate with a double structure consisting of steel base material and surface wear resistant material by coating with, it is possible not only to significantly extend the campaign life of the wear plate but also to repair and reuse it many times. I found it.

Therefore, the slab support device according to the present invention is a wear plate having a steel material as a base material, which is in contact with the slab in a slab support device that supports a slab drawn from a mold of a continuous casting machine immediately below the mold. In the material, Ni, Cr, and C are Ni: 55-75wt% and Cr: 25-35wt, respectively.
%, C: 0.5-1.0 wt%, and the balance is covered with a surface layer material of a Ni-based alloy consisting essentially of Fe.

(Operation) The surface material improves the wear rate of the wear plate of the top zone slab support device, and extends the campaign life of the top zone slab support device. Further, by forming the wear plate of the top zone slab support device in two layers, the generation of heat cracks is reduced, and the generated cracks are extremely fine, and the progress thereof can be stopped at the surface layer portion.

Furthermore, the wear-resistant material of the surface layer can be reused any number of times by repairing the weld overlay. That is, it can be reused by welding overlay even after being used for trimming after a plurality of campaign lives. Therefore, it is not necessary to dispose of the wear plate.

(Example) Next, an example of the present invention will be described with reference to the accompanying drawings.

FIG. 2 is a schematic vertical sectional view of a continuous casting machine in which the wear plate according to the present invention is used.

The molten steel 2 poured into the mold 1 is gradually cooled to form a solidified shell on the surface thereof, and is pulled downward while being supported as a cast piece 3 by a cast piece support device 4 and a plurality of rolls 5.

The slab support device 4 supports the slab 3 by the contact member 6 in the top zone immediately below the mold 1. FIG. 3 is a partial enlarged view of the contact member 6 as seen from the contact surface side with the cast piece 3. A large number of wear plates 7 that come into direct contact with the slab 3 are attached to the frame 8 by bolts or the like.
Fixed to. Further, the frame 8 is fixed to the fixing member 9. Although the drawing shows the case where a cooling grid is used as the slab support device 4, it goes without saying that the present invention can be applied to other support devices such as a cooling plate and a walking beam.

Wear plate 7 as shown in the cross section of FIG.
Has a two-layer structure composed of a base material 10 and a surface material 11.

The base material 10 is cast steel (JIS standard SC42 material) in this embodiment.
Consists of. However, mild steel, cast steel (JIS standard SC material, etc.), cast iron (JI
Any of steel materials such as S standard FCD material) may be used.

The surface layer material 11 in this example is Ni: 60 wt%, Cr: 30 wt%.
%, C: 0.8 wt% and the balance substantially consisting of Fe (hereinafter referred to as "high Ni-high Cr-high C steel") is formed by depositing on the surface of the base material 10 by arc welding. Was done.
However, the surface layer material 11 may be coated by another welding method, thermal spraying, clad steel forming, or the like. Also, the high Ni of the surface layer material 11
-High Cr-The composition of high C steel is Ni: 55-75wt%, Cr: 25-35wt%
%, C: 0.5 to 1.0 wt% can be selected.
The reason for limiting to this range will be described later in detail.

The thickness of the weld overlay of surface material 11 was 3 to 6 mm. The reason for this is as follows.

During welding, Ni and Cr in the surface layer material 11 diffuse into the base material 10. For this reason, of the surface layer material 11 with weld overlay, approximately 2 m
The lower layer 13 having a thickness of about m 3 has a composition different from the desired composition.

Therefore, the thickness of the top layer 12 having the desired composition (i.e.,
In order to secure an effective thickness of the surface layer material 11) of 1 mm or more, the thickness of the surface layer material 11 must be at least 3 mm. On the other hand, in order to save the expensive surface layer material 11, its thickness is preferably set to about 6 mm or less. In addition, the maximum thickness of the surface layer material 11
When the thickness is 6 mm or less, generation and progress of heat cracks can be suppressed.

Next, the reasons for limiting the components of the surface layer material 11 will be described. Here, the findings regarding the influence of each component element on the properties of steel will be summarized below.

Ni: Ni has the effect of increasing strength, hardness, corrosion resistance and heat resistance. Coexistence with Cr enhances oxidation resistance and high temperature strength.

Cr: Cr has a function of enhancing corrosion resistance, oxidation resistance, and thermal shock resistance. In particular, it has the effect of enhancing the oxidation resistance and high temperature strength in the coexistence with Ni, and also enhancing the wear resistance under high C. However, if added excessively, the castability and weldability deteriorate.

C: C has the effect of increasing strength. It combines with Cr to form a carbide, which improves wear resistance and also improves weldability and castability. However, if added excessively, the precipitation of carbides increases, the high temperature toughness, oxidation resistance, and weldability deteriorate, and the occurrence of heat cracks also increases. When the amount is small, the precipitation of carbides is small and the lubricity deteriorates.

With respect to each element having such properties, in order to determine the suitable composition range of the Ni-Cr-C steel used as the surface layer material 11, the wear rate, the seizure property (lubricity), and the heat crack of the steel of each composition are determined. Various experiments were conducted on the occurrence situation. In the following table, steel of each composition was actually welded on a wear plate, and the wear plate according to the present invention and a comparative example (Ni-Cr-C) were used.
2 shows the results of an online test of wear plates made of steel and Cr-C steel). For reference, cast iron (J
The test results of the conventional wear plate using IS standard FCD60 material) are also shown.

In the table, ◯ means good, Δ means about conventional product, and × means worse than conventional product. In addition, the wear rate is the amount of surface wear associated with a single molten steel charge in μ (micron)
Shown in units. The comparative product was difficult to re-repair as a result of warping and the like, whereas the product of the present invention showed excellent re-repairability.

Figure 4 gave favorable results in these experiments.
The composition range of Ni, Cr and the balance (C, Fe and impurities) is shown by diagonal lines (Ni: 55-75wt%, Cr: 25-35wt).
%). The circles in the figure indicate 60Ni-30Cr, which gave particularly favorable results.
Shows −0.8C steel. The range of C is 0.5-
1.0 wt% showed favorable results.

FIG. 5 is a block diagram showing a method of using the wear plate 7 according to the present invention.

As a result of being repeatedly charged during each online use period, the wear of the surface layer material 11 of the wear plate 7 progressed and reached the campaign life, and the surface layer material of each wear plate 7 was reached.
Align 11 with the position with the most wear and perform surface machining (machining).

In this way, surface material 11
Where Ni is worn out, high Ni-high Cr-high C according to the present invention is again obtained.
Weld up the steel and correct the surface. As a result, the wear plate 7 returns to the almost original state, and online use and surface removal can be further repeated.

By repeating the method described above, the wear plate according to the invention can be used semi-permanently and need not be scrapped.

(Effect of the invention) As shown in the above table, in the wear plate according to the present invention, the wear amount per heat is about 0.7μ, and therefore, continuous online use of 900 to 1000 charges is possible. It is (900-1000 heat / campaign). On the other hand, the conventional product shows wear of about 2.3 μ / heat, and the campaign life reaches only 200 to 300 heat / campaign.

Further, the Shore hardness of the contact surface of the product of the present invention shows a substantially constant value regardless of the number of heats, whereas the Shore hardness of the conventional product is 200
The hardness is significantly lower than the specified hardness before it is heated. It is considered that this decrease is due to the hardness obtained in the material structure process changing in hardness due to heat during use.

As described above, according to the present invention, the online use period of the continuous casting machine can be extended to 3 to 4 times that of the conventional one. This means that not only the number of maintenance and replacement of the slab support device 4 is reduced, but also the number of maintenance and replacement of the mold 1 installed as a set with the slab support device 4 is reduced. The economic effect of extending the online stable operation period of such a continuous casting machine is extremely large.

Further, according to the present invention, the wear plate 7 includes the base material 10 and the surface material.
Since it has a two-layer structure consisting of 11, the occurrence of heat cracks is extremely small, and even if it occurs, the crack width is very narrow.

This is the above campaign life (online usage period)
Has also contributed to the increase of.

Furthermore, according to the present invention, the surface layer material 11 can be repaired and reused any number of times by weld overlay, etc., and the wear plate can be substantially eliminated. In the past, after 3 to 4 campaigns (online use), wear plates had to be discarded, and the economic effect of resource saving was great.

Further, according to the present invention, the amount of wear can be reduced and the alignment between the mold and the top zone can be maintained in a normal state for a long time, so that the quality of the cast piece can be improved. In addition, since the amount of maintenance is reduced, there are related effects such as reduced handling work and the need for fewer spare machines.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of the wear plate according to the present invention near the contact surface; FIG. 2 is a schematic vertical cross-sectional view of a continuous casting machine in which the wear plate of the present invention is used; FIG. 5 is a partially enlarged view of the contact member of the slab supporting device included in the continuous casting machine of FIG. 2 as viewed from the contact surface side; FIG. 4 is a graph showing the composition range of the steel according to the present invention; FIG. 4 is a block diagram showing a method of using the wear plate according to the present invention. 1: Mold, 3: Cast piece 4: Cast piece support device, 5: Roll 7: Wear plate, 8: Frame 10: Base material, 11: Surface material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-9146 (JP, A) JP-A-58-67804 (JP, A) JP-A-55-9109 (JP, A) JP-B-45- 2822 (JP, B1)

Claims (3)

[Claims] 1. A wear plate member comprising a steel material as a base material, which abuts against a cast piece in a cast piece supporting device for supporting a cast piece drawn out from a mold of a continuous casting machine, Ni, Cr, C: Ni: 55-75wt%, Cr: 25-35wt
%, C: 0.5-1.0 wt%, the balance of the slab is covered with a surface layer material of Ni-based alloy with the balance substantially Fe. . 2. A surface layer material of a Ni-based alloy is coated on a base material with a thickness of 3 to 5 mm.
A wear plate member of the slab support device according to the item. 3. The surface material of the Ni-based alloy is characterized in that the base material is coated by welding overlay, thermal spraying or cladding.
The wear plate member of the slab support device according to claim 1.