JP2003064460A - Member for hot dip metal plating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a member for a hot dip metal plating apparatus, which is provided with a composite thermal spray coating excellent in toughness, hot dip metal resistance and wear resistance. SOLUTION: The surface of a base material is coated with a carbide based composite coating film having a composition containing 8 to 25 wt.% Co and/or Cr, and the balance mainly carbide of at least one metal selected from W, Ti, Nb and Mo, and in which the total C content as the total of C composing the carbide and free C is 0.94 to 1.15 by weight ratio to the stoichiometric composition with each element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a member for a hot-dip galvanizing apparatus, and more particularly to a roll shank (equipment in a hot-dip galvanized steel sheet production line or a heat treatment equipment such as an alloying furnace in a hot-dip galvanizing line). Shaft),
This is a proposal for a member obtained by coating the surface of a portion such as a sleeve that supports this with a rotational load with a film having excellent toughness, molten metal resistance, and durability.

[0002]

2. Description of the Related Art Rolls for plating equipment such as sink rolls, support rolls, stabilizer rolls (above, members in the bath) or touch rolls (on the bath, between alloying furnaces), especially roll shanks, that is, roll shafts and , Sleeves, bearing metals, etc. have sliding rolling surfaces and are used under severe conditions.

As described above, the mechanical load (rolling load) of the roll shaft is usually larger than that of the roll barrel. Therefore, in order to protect the roll shaft portion, conventionally, when the substrate material is a stainless steel member, a protective coating layer such as a Co—W—Cr alloy welding layer or a carbide cermet is formed on the surface thereof. However, the fact is that the body and shaft of the roll have not yet reached a balanced service life.

For example, as a technique for forming a protective coating layer on the surface of a roll body, there is one disclosed in Japanese Patent Publication No. 58-37386. In this technique, a roll cermet film containing WC, CrC, or TiC on the surface of one or more of WC, CrC, and TiC, and the balance consisting of a hot-corrosion-resistant metal or an oxide thereof is used for 0.1 to 2.4 m.
It is formed to a thickness of m. Also, Japanese Patent No. 1771
No. 297 has a porosity of 1.8% and a thickness of 0.040-0.
Rolls with a 10 mm WC-Co spray coating have been proposed.

Further, Japanese Patent No. 2955625 proposes an example in which a carbide is coated and then an oxide ceramic containing SiO ₂ or the like is coated thereon. The film thickness in this example is 0.08 to 0.10 mm for the lower layer and 0.25 for the upper layer.
.About.0.30 mm is said to be suitable.

These known protective coating layers have been developed for the purpose of protecting the roll by suppressing the reaction between the surface of the roll body made of steel and the bath components, that is, the formation and growth of a so-called alloyed layer. It is a thing. Of these, WC-12
The method of coating the Co carbide cermet has been quite successful in the past, but still insufficient. The reason is that, when looking at the entire roll, only the life of the roll body is extended, the useful life of the roll shaft portion does not correspond to this, and the life of the entire roll is not extended.

In addition, in order to extend the life of the roll shaft,
Conventionally, a method of forming a composite coating of a two-layer structure of a self-fluxing alloy and a carbide cermet on its shaft has also been proposed (Japanese Patent No. 2949443). However, this composite coating was not sufficient to support the life of the roll body. This is because the adhesion between the lower layer self-fluxing alloy film and the upper layer WC cermet film was not sufficient.

As described above, although the conventional protective film formed on the surface of the body or shaft of the roll has certainly achieved some results, it is still in view of improving the durability of the roll as a whole. It left a challenge to overcome. In many cases, the durability of the roll body (working part) is improved, but the service life of the roll shaft does not follow the life of the roll body, so the life of the roll as a whole is improved. Because it did not lead to.

[0009]

As described above, in the prior art, since the mechanical load of the roll shaft is larger than that of the roll body in which only the steel sheet is guided and run, the durability of the roll body is not guaranteed. Even if the durability is improved, there is a problem that the durability of the roll shaft portion is not correspondingly improved.

Therefore, an object of the present invention is to propose a member for a molten metal plating apparatus, especially a roll shaft member, which is excellent in toughness, durability against molten metal and durability (wear resistance).

[0011]

As a result of intensive studies to realize the above-mentioned object, the inventors have found that, among the equipment in the plating bath, the roll shaft portion used especially under relatively high load conditions, When a carbide-based composite coating with an adjusted total C content is formed on the rolling and sliding surface of a member such as a sleeve, the toughness of the coating does not deteriorate even if this coating is relatively thick. I found out that. That is, the present invention was developed on the basis of such new knowledge, and 8 to 25 Co and / or Cr was added to the surface of the base material.
wt% and the balance mainly consists of at least one kind of carbide selected from W, Ti, Nb and Mo, and the total amount of C, which is the sum of C and free C constituting the carbide, is 0.94 by weight to stoichiometric composition
A member for a molten metal plating apparatus, characterized by being coated with a carbide-based composite film of 1.15.

In the present invention, the total amount of C and free C constituting the carbide is more preferably more than 1.0 by weight ratio with respect to the chemical equivalent composition of each element with respect to the total C amount.
It is desirable to set it to 1.10. Further, the above-mentioned carbide-based composite film further contains at least one boride selected from W, Ti, Nb and Mo, and the above-mentioned carbide-based composite film has a thickness of 500 μm to 500 μm. It has a thickness of 2000 μm and contains free C in an amount of at least 0.5%, preferably 0.8 to 1.6% of the total amount of C, and the above-mentioned carbide-based composite coating has a roll shaft portion with respect to It is a preferred embodiment to form a coating by applying a thermal spraying method using a plasma flame and a gas combustion flame.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION When manufacturing a plated steel sheet with a hot-dip galvanizing apparatus, a hot-dip galvanizing bath is one of the main facilities that influence the quality. In the plating bath, various in-bath devices are usually immersed and arranged. The core of these is various rolls called sink rolls and support rolls that are in direct contact with the strip material and control the transport. Various characteristics are required for these rolls. For example, the aging accuracy is small over time, the busbar straightness is excellent, the surface of the molten metal bath is in direct contact with the molten metal so that it is not easily wetted by the plating bath and is non-reactive. Fe-Al-Zn intermetallic compound is hard to stick to the roll surface and it is hard to grow, and the surface shape accuracy can be maintained for a long time,
Particularly, the roll shaft portion and the bearing portion thereof are excellent in resistance to abrasion and abrasion with respect to the hard intermetallic compound particles present in the molten metal plating bath.

Particularly, in the hot-dip galvanizing bath, the strip material,
For example, the roll surface (body) that controls the guide running of steel plates is
It is desirable that the reactivity with the molten metal be essentially low. Therefore, the surface of the roll body has been coated with a Co-based self-fluxing alloy or a WC cermet thermal spray coating. In particular, the latter has shown remarkable results in recent years and has contributed to extending the life of the roll body. However, members having rolling sliding surfaces, such as roll shafts and shaft sleeves, which are under more severe conditions than the roll body, are often neglected, and some improvements have been made. Co at best
It was only enough to cover a -Cr-W alloy or the like. But,
These coating materials have a fatal problem that they have a short durability life. The present invention was developed to meet exactly these problems.

Now, in the conventional WC-Co cermet coated on the surface of the roll body, when observing paying attention to the compounding amount of C, it is not the stoichiometric composition and the equivalent, but rather C.
It is usually used as a state of insufficient quantity. The reason for this is that by making the amount of C insufficient, only a double carbide such as W ₃ Co ₃ C is efficiently produced. Therefore, in the carbide thus obtained, free C is not contained, and at the same time, so-called free metallic Co is also reduced to such an extent that it can hardly be identified by the X-ray diffraction method. Therefore, such a coating is a WC-Co pseudo binary system, but can be said to be substantially a WC-double carbide binary system. That is, the conventional WC-Co-based cermet thermal spray coating contains a large amount of double carbide that becomes a brittle layer in a substantially metallic Co-free state, and in this sense,
It can be said that the film exhibits excellent molten metal resistance.

On the contrary, since this sprayed coating contains almost no metallic phase (Co), its toughness is extremely low,
In particular, it has been pointed out that in the case where the thickness exceeds about 300 μm, the film often self-exfoliates due to the action of internal residual stress. Therefore, it can be said that the thermal spray coating according to the conventional component composition is suitable for coating the roll body. Because the roll body is not so demanding for wear resistance,
This is because the film thickness of about 100 μm is sufficient, and the self-peeling at the time of thick film as described above does not have to be a problem. However, when the surface of a member such as a roll shaft is coated with a large thickness, the above coating is not sufficient.

Therefore, in the present invention, by controlling the amount of the metal component that plays a role as the binder phase of the carbide cermet material and the total C amount that mainly controls the formation behavior of the double carbide, the thick film carbide cermet is controlled. Even if it is a coating, we have developed a composite coating of carbide-based cermet that does not deteriorate the toughness of the coating and is also excellent in molten metal resistance and wear resistance.

Tests were carried out in order to find out the preferable component composition of the carbide-based cermet composite coating according to the present invention. The contents will be described below. Therefore, the inventors first investigated the characteristics of the metal layer, which is a component that contributes to the interparticle bonding of the cermet. In this test, the chemical composition of the coating material, the susceptibility of the formed coating to crack initiation during thermal spray deposition,
The sliding wear characteristics with a silicon nitride ceramics material in a molten metal bath immersion environment were investigated. As the cermet constituent components of the tested materials, W and T having excellent non-reactivity with Zn-Al molten alloy which is a hot dip galvanizing bath component.
One kind or two or more kinds were selected from the group of each carbide of i, Nb and Mo and each boride of W, Ti, Nb and Mo. In addition, Co or Cr was used as the metal component which becomes the binder phase.

Table 1 shows the change in the total C and Co contents and the diameter 2 for the carbide-Co composite material system such as WC.
It shows the relationship with the crack initiation susceptibility for each thickness of the coating film coated on the outer circumference of a steel pipe having a thickness of 00 mm and a thickness of 10 mm. Here, the crack susceptibility test is performed according to JIS Z 2
Based on the 343 penetrant flaw detection test method and the classification of penetrant flaw indication patterns, it was performed by examining the number of indication patterns exposed on the film surface and having a length of more than 3 mm. With respect to the coated area, those in which no pattern was observed were judged as acceptable, and those in which the pattern was observed were judged as not.

[0020]

[Table 1]

The composition ratio of the metal binder phase of the cermet spray coating of carbide or boride which has been put to practical use in the hot metal plating bath is 12% or less in the case of Co, for example. This is because the molten metal resistance and abrasion resistance of the coating are prioritized, and in this sense, the toughness of the coating is sacrificed. In this respect, in the present invention, C
8 to 25 wt% of O and / or Cr, preferably 1
2 to 25 wt%, more preferably 15 to 25 wt%. As described above, by containing a larger amount of a metal component such as Co, the toughness of the coating is first prevented from being lowered, and the toughness and the self-peeling do not occur even if the coating is thick. That is, according to the knowledge of the inventors, if the metal component is less than 8 wt%, the toughness deteriorates. However, if the amount of this metal component is 25 wt% or more, the wear resistance deteriorates, so the above range is set.

As described above, and as can be seen from the results shown in Comparative Examples 10 to 13, the amount of carbon constituting the carbide is generally set to be smaller than the chemical equivalent to the carbide forming metal. This is to prevent the formation of free metal and free C by positively forming double carbides as described above.

As can be seen from the test results shown in Table 1, if the content of metallic Co as the metallic binder phase is increased and the total amount of C is increased to an amount that exceeds the chemical equivalent, the film thickness is increased. However, it was found that the susceptibility to crack initiation can be reduced with this.

From the above test results, the total C amount, which is the sum of C and free C forming carbides, may be contained at a lower limit of 0.94 by weight ratio to the chemical equivalent of each element. I found it necessary. On the other hand, the upper limit is 1.
It is 15. The reason for this is that if the total amount of C is 1.15 or more, the amount of free carbon may increase. The reason is that when the amount of free carbon increases (> 1.15), the film strength (wear resistance) is reduced.
Preferably, the weight ratio is more than 1.0 to 1.05.

As can be seen from the above-mentioned test results, the present invention provides a composite film having a large film thickness while satisfying the crack initiation susceptibility, at least as long as the wear resistance is not a problem, that is, only by controlling the total C content. Can be obtained.

Next, a test was conducted to examine the influence of the film thickness on the durability (wear resistance) of the WC cermet film in the plating bath environment. In this test, the support sleeve shaft sleeve used in the plating bath was used as a test member, and Zn
A dynamic test of rotating and sliding in a 0.15% Al bath. The test piece used is a 13Cr-based steel base material having a diameter of 80 mm, a thickness of 10 mm, and a length of 100 mm. The coating layer is WC
Only the thickness of the cermet layer is 150, 300, 600, 1
It was changed to 200 and 2000 μm, and the other levels were set to the same level. The mating bearing material was a silicon nitride material. Table 2 shows this result.

[0027]

[Table 2]

As a result of the above test, the smaller the thickness of the WC cermet film, the thinner the WC cermet film and the shorter the service life due to the exposure of the substrate due to the thickness reduction due to wear. That is, in the thickness up to 300 μm, the service life did not exceed 5 days in any of the test examples, and the performance recognized as superior to the conventional alloy coating material was not obtained. On the other hand, when the film thickness exceeds 600 μm, there is a clear difference in durability depending on the film thickness. And, depending on the film composition, there were cases where it exceeded 20 days. The durability of these WC cermet coatings is basically dominated by the thinning due to mechanical wear, not as a result of the reaction with the plating bath components, and therefore it is sufficient to increase the thickness. It turned out that it can be put to practical use.

As described above, the present invention improves the toughness and molten metal resistance by adjusting the total amount of C and the amounts of the metal components (Co, Cr) as the binder phase. By increasing the thickness of the coating on the premise (increasing the amounts of metal Co and metal Cr), the wear resistance can also be improved.

[0030]

【Example】Example 1 In this example, the axial roll of the support roll for the galvanizing bath is
An example of using it as a protective film for a probe is shown. Three prepared
The dimensions of the substrate are 90 mm in diameter and 160 mm in total length.
It Roughening treatment of coated surface as pretreatment prior to coating with coating layer
It made sense. Roughening is a white alumina artificial grinding material W
A # 60 is used, the driving air pressure is 0.2 to 0.3 MPa,
The blast distance was 200 to 250 mm. At this time
The surface roughness of the substrate was an arithmetic average roughness of 2 μmRa.

Using a plasma spraying device, WC-17%
The Co composition powder material was coated to a thickness of 900 to 1000 μm. Then, the coating surface was roughly ground using an artificial diamond and stone. The arithmetic average roughness of the coating layer surface after the grinding treatment is Ra.
≦ 1.5 μm. The sleeve thus produced was mounted on a support roll for hot dip galvanizing bath, dipped in a galvanizing steel sheet producing bath, and used. As a result, the service life shown in Table 3 was obtained, and an effect was observed in extending the continuous service time of the roll body.

[0032]

[Table 3]

[0033]Example 2 A support roll sleeve base was used in the same plating bath as in Example 1.
The coating of the present invention applied to the material as a protective coating was applied. Quasi
The dimensions of the provided substrate are 90 mm in diameter and 160 mm in face length.
is there. Same as Example 1 as pretreatment prior to coating
The coated surface was roughened. High-speed gas flame spraying equipment
WC-10% WB-18% Co composition powder material
The coating was coated to a thickness of 1000 to 1100 μm. afterwards,
The surface of the film was roughly ground using an artificial diamond and stone. Grinding process
Arithmetic mean roughness of the coating layer surface after processing is Ra ≦ 1.0 μm
Met. The sleeve manufactured in this way is
Mounted on a support roll for plating bath, made of galvanized steel plate
It was immersed in a bath for making and used. As a result, as shown in Table 4.
Long service life and extended continuous operation time of the roll body
The effect was recognized.

[0034]

[Table 4]

[0035]

As described above, according to the present invention, equipment such as rolls in a plating bath of a hot-dip galvanized steel sheet production line, particularly W, Ti, Nb, and By forming a composite material consisting of a carbide of Mo, or a carbide thereof and a boride of W, Ti, Nb, Mo, and Co and / or Cr by a thermal spraying method or the like, formation of double carbide that becomes an embrittlement layer is minimized. In addition to controlling the total amount of C, a sound coating layer having an appropriate hardness and rolling and sliding wear resistance in a molten metal plating bath and having a relatively large thickness is formed on the roll shaft portion, in particular. Since it can be formed on the rolling sliding surface, the durability of the entire roll can be significantly improved.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshihisa Sawasaki             142, Fujito, Fujito-cho, Kurashiki-shi, Okayama (72) Inventor Masanobu Fujisawa             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor ▲ Mawata Naganori             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Yuzo Nakashibu             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Tatsuya Fukushima             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Ryuo Keizo             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Masayuki Hatakeyama             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. F-term (reference) 4K027 AA15 AB42 AD15 AD17                 4K031 AA02 AB08 AB09 CB44 CB45                       DA01 DA04

Claims (4)

[Claims] 1. Co and / or Cr on the surface of a substrate
Of 8 to 25 wt%, the balance mainly consisting of at least one kind of carbide selected from W, Ti, Nb and Mo, and the total amount of C which is the sum of C and free C constituting the carbide is A member for a molten metal plating apparatus, characterized by being coated with a carbide-based composite coating having a weight ratio of 0.94 to 1.15 with respect to a stoichiometric composition with an element. 2. The carbide-based composite coating further comprises:
The member for a molten metal plating apparatus according to claim 1, which contains at least one boride selected from W, Ti, Nb, and Mo. 3. The carbide-based composite coating has a thickness of from 500 μm.
2. It has a thickness of 2000 μm.
Alternatively, the member for a molten metal plating apparatus according to item 2. 4. The carbide-based composite coating is formed by applying a thermal spraying method using a plasma flame or a gas combustion flame to a roll shaft portion, according to any one of claims 1 to 3. A member for a molten metal plating apparatus as described above.