JP2005105362A - Process roll of excellent toughness - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process roll having a WC-based cermet spray deposit film which is dense, has high hardness and is excellent in toughness on a surface layer. <P>SOLUTION: In the process roll, a WC-based cermet spray deposit film of the porosity of ≤ 0.5% is deposited by thermal spraying WC-based cermet thermal spraying powder containing Ni powder. The quantitative value of oxygen in the spray deposit film is set to be ≤ 2.0 mass %. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a process roll formed by spraying a WC-based cermet sprayed powder containing Ni powder on a surface layer to form a WC-based cermet sprayed coating having a porosity of 0.5% or less. Such a process roll is suitable, for example, for use in cold rolling equipment for metal strips.

  Conventionally, chromium-plated rolls have been used as process rolls for cold rolling equipment, particularly those that require wear resistance. Recently, WC-based cermet sprayed rolls have been used instead of chromium-plated rolls. It is getting to be. This thermal spray roll is excellent in wear resistance.

  Here, the “process roll” means a roll excluding the rolling work roll (work roll) among the rolls through which the metal plate to be treated comes into contact. Specifically, the guide roll, the bridle roll, the tension meter Examples thereof include a roll, a deflector roll, a looper roll, and a masher support roll.

  As a roll having a WC-based cermet sprayed coating, for example, in Patent Document 1, oxygen-hydrogen gas is used as a heat source, and the supply pressure to the spraying gun is increased, thereby reducing the porosity of the sprayed coating to 1.8% or less. A roll for rolling process in which the coating surface roughness Rmax is 3.0 μm or less by mirror-polishing the surface of the sprayed coating with a small porosity has been described. It is shown that surface flaws such as scratches are not generated, that oils and fats, metal-based and non-metallic dust hardly adhere to the surface, and that the above performances can be maintained for a long time.

  However, when the present inventors investigated in detail about the roll having the above-mentioned thermal spray coating on the surface layer, the thermal spray coating was indeed dense and high in hardness, but only a slight biting of iron powder or the like occurred during use. In some cases, cracks occurred in the sprayed coating, resulting in troubles resulting in peeling of the sprayed coating. The cause of this is that due to subtle changes in the thermal spraying application conditions, metals such as Ni that are binders in the thermal spray coating are oxidized and sufficient toughness cannot be obtained, and Ni oxide falls off from the thermal spray coating. There exists a problem that it becomes easy to peel a film | membrane and, as a result, the period which can use a roll becomes short. In addition, the roll described in Patent Document 1 employs a method of increasing the fuel gas supply pressure as a specific means for reducing the porosity of the sprayed coating to 1.8% or less. In addition, the specifications of the thermal spraying apparatus must be changed, such as adding a device for pressurizing the fuel gas.

  By the way, the present inventor also performs the impregnation treatment of the intermediate sprayed coating with a sealing agent as a method of forming the sprayed coating having high peel resistance, and further plastically deforms the binder of the intermediate sprayed coating to seal the opening portion. A processing method was proposed in Patent Document 2.

However, although the process roll manufactured by the method described in Patent Document 2 also has a dense and high-hardness sprayed coating, it is patented that a metal such as Ni as a binder in the sprayed coating is oxidized. As in Reference 1, no consideration was given. For this reason, there is still a problem that the period in which the roll can be used may be shortened. In particular, as process rolls are applied to places where durability is required more than before, the occurrence of troubles due to insufficient toughness of the thermal spray coating tends to become more prominent. In addition, in Patent Document 2, it is necessary to perform an impregnation treatment and a sealing treatment in forming a thermal spray coating, and it is necessary to perform an additional special process in addition to the normal thermal spraying process. There was also the problem of getting worse.
JP-A 64-87006 JP2003-113462

  As described above, in addition to being dense and having high hardness, the process roll is formed with a thermal spray coating having excellent toughness on the surface layer so that the roll can be used stably over a long period of time. is necessary.

  The object of the present invention is to provide a surface layer of a WC-based cermet sprayed coating that has excellent toughness in addition to being dense and high hardness by optimizing the quantitative value of oxygen in the sprayed coating. It is to provide a process role possessed by.

  The inventor pays attention to the quantitative value of oxygen in the formed WC-based cermet sprayed coating, and by adjusting this to a predetermined range from the relationship with the action of Ni that functions as a binder, it is dense and has high hardness. In addition, the inventors have found that a WC-based cermet sprayed coating having excellent toughness can be formed and a highly durable process roll can be obtained, and the present invention has been conceived.

  That is, the present invention is a process roll formed by spraying a WC-based cermet sprayed powder containing Ni powder to form a WC-based cermet sprayed coating having a porosity of 0.5% or less on the surface layer, It is a process roll excellent in toughness characterized by having a quantitative value of oxygen of 2.0% by mass or less.

  According to the present invention, it has become possible to provide a highly durable process roll having a WC-based cermet sprayed coating on the surface layer that has excellent toughness in addition to being dense and high in hardness. In addition, since the roll can be used stably for a long period of time, the frequency of replacing the roll can be reduced, the roll cost associated with the replacement can be reduced, and the metal band required for the replacement can be cooled. Since the operation stoppage time of the rolling equipment can be reduced, the operation operating rate of the cold rolling equipment for the metal strip can be improved, and the manufacturing cost can be reduced together with the reduction of the roll cost.

The present invention is described in further detail below.
This invention is a process roll formed by spraying a WC cermet sprayed powder containing Ni powder to form a WC cermet sprayed coating having a porosity of 0.5% or less on the surface layer.

The WC-based cermet thermal spraying powder containing Ni powder may be a WC-based cermet thermal spraying powder containing Ni powder as a binder, is not particularly limited, for example, 70WC-19Cr ₃ C ₂ -11Ni and 73WC-20Cr ₃ C and the like are preferably used ₂ -7Ni.

  The reason why the porosity of the thermal spray coating is limited to 0.5% or less is that when the porosity exceeds 0.5%, the toughness tends to decrease and the wear resistance of the process roll tends to decrease. It is easy to define the porosity by the area ratio when the part with the sprayed coating is polished flat and micrographed, but the specific gravity of the part excluding the pores is measured by cutting out the specimen and measuring the weight and volume. There is a way to figure out the difference.

  In the present invention, it is necessary that the quantitative value of oxygen in the sprayed coating is 2.0% by mass or less.

  The inventor conducted an intensive study on the improvement of the durability of the process roll. While maintaining the high hardness of the sprayed coating by containing ceramics such as WC, the toughness was increased by the metal such as Ni in the sprayed coating functioning as a binder. In order to improve the toughness by Ni in the thermal spray coating, it is found that it is effective to improve, and it is necessary to suppress the oxidation of Ni, which is included in the thermal spray coating from another angle. What is necessary is to increase the ratio of the quantitative value of Ni to the quantitative value of the Ni powder used for the thermal spraying, and from another angle, if the quantitative value of oxygen in the sprayed coating is limited to 2.0 mass% or less The present invention has been found and the present invention has been completed.

  This is the reason why the quantitative value of oxygen in the thermal spray coating is regulated to 2.0% by mass or less. This is because the quantitative value of oxygen is 2.0% by mass or less, and there is no abnormal oxidation of Ni during thermal spraying. As a result, it appears as a condition for obtaining a thermal spray coating excellent in toughness.

  In connection with the oxygen contained in the thermal spray coating or the following, the quantitative value of Ni and the quantitative value of the Ni powder used for thermal spraying are both analyzed by electron probe microanalysis (EPMA). It went by.

Figure 1 is a WC-based cermet thermal spray powder, particle size using a 70WC-19Cr ₃ C ₂ -11Ni of 20～53Myuemu as spraying equipment, spraying equipment for HVOF (High Velocity Oxygen Fuel) (Praxair / Tafa's trade Name: JP5000), and spraying by changing the ratio of fuel (kerosene) and oxygen (F / O ratio), the quantitative value of oxygen in the sprayed coating is different in the range of 0-6.0 mass% The thermal sprayed roll was prepared, and the hardness and toughness of the thermal sprayed coating (the number of rolls in the roll rolling test described later) were plotted against the quantitative value of oxygen in the thermal sprayed coating. In addition, all of the produced thermal spray rolls have a porosity of 0.5% or less of the thermal spray coating, and this is related to the fall of Ni due to oxidation in the process of thermal spray roll creation, but is included in the thermal spray coating. As for the ratio of the quantitative value of Ni to the quantitative value of the Ni powder used for the thermal spraying, a percentage was added to the upper position of each plot.

The hardness was measured with a Vickers hardness meter.
As for toughness, the roll roll test was conducted at three levels of rotation speed: 50rpm, surface pressure: 196MPa, 392MPa and 784MPa with the propelling roll 1 and test roll 2 as shown in Fig. 2, and the thermal spray roll When using as a test roll, the number of revolutions until the thermal spray coating peeled was evaluated. The propulsion roll 1 has dimensions: φ160 × 80 ^L , material: S45C and hardness: Shore hardness HS75 to 78, and the test roll 2 has dimensions: φ160 × 100 ^L , and is 100 μm on the iron core. A thermal spray coating is formed.

From FIG. 1, when the quantitative value of oxygen in the sprayed coating is 2.0 mass% or less, the number of rollings is 1 × 10 ⁷ when tested at any surface pressure while maintaining a hardness of 1100 HV or higher. It can be seen that the toughness is excellent and the toughness is excellent.

  FIG. 3 shows that a plurality of different spray rolls were prepared so that the ratio of the quantitative value of Ni in the thermal spray coating to the quantitative value of the Ni powder used for the thermal spraying was changed in the range of 64 to 99%. It is a plot of the hardness and toughness of the sprayed coating. In addition, all of the produced sprayed rolls have a porosity of 0.5% or less of the sprayed coating, and the quantitative value of oxygen in the sprayed coating is indicated by a numerical value indicating mass% at the upper position of each plot. did.

From FIG. 3, the quantitative value of oxygen in the thermal spray coating is 2.0% or less, and the ratio of the quantitative value of Ni in the thermal spray coating to the quantitative value of the Ni powder used for the thermal spraying is 80% or more, preferably 90%. In this case, while maintaining a hardness of 1100 HV or higher, the number of rolling is 1 × 10 ⁷ times or more, preferably 1 × 10 ⁸ times or more at any surface pressure, and excellent toughness Understand.

  From the above, the process roll of the present invention maintains the hardness of 1100 HV or more by setting the porosity of the sprayed coating to 0.5% or less and the quantitative value of oxygen in the sprayed coating to 2.0 mass% or less. A WC cermet sprayed coating with excellent toughness can be formed on the surface.

  As a means for setting the porosity of the thermal spray coating to 0.5% or less, it is preferable to form the thermal spray coating using JP5000 of HVOF, and the quantitative value of oxygen in the thermal spray coating is 2.0 mass% or less. It is preferable to use a method for changing the ratio of fuel (kerosene) to oxygen (F / O ratio) as means for achieving this.

Figure 4 is a WC-based cermet thermal spray powder, particle size using a 70WC-19Cr ₃ C ₂ -11Ni of 20～53Myuemu as spraying equipment, spraying equipment for HVOF (High Velocity Oxygen Fuel) (Praxair / Tafa's trade No .: JP5000), and plotting the quantitative value of oxygen in the sprayed coating when spraying by changing the ratio of fuel (kerosene) and oxygen (F / O ratio).

  FIG. 4 shows that when the F / O ratio is 0.7 to 0.82, the quantitative value of oxygen in the sprayed coating can be stably reduced to 2.0 mass% or less. If it exceeds 1.0, it is not preferable for another reason of incomplete combustion.

The above description is merely an example of an embodiment of the present invention, and various modifications can be made in the present invention.
For example, WC based cermets, such as those described above 70WC-19Cr ₃ C ₂ -11Ni and 73WC-20Cr ₃ C ₂ -7Ni, if short ones WC system may be of any material, size also Even if it is outside the range of 20 to 53 μm, it may be anything as long as it provides a dense and high hardness thermal spray coating in the range required by those skilled in the art. Further, the thermal spraying apparatus is not limited to the HVOF type as described above, and may be of any kind as long as the quantitative value of oxygen in the thermal spray coating can be reduced to 2.0% by mass or less.

  Next, the present invention will be specifically described with reference to examples. In addition, this invention is not limited to this Example.

As WC cermet thermal spray powder, particle size using a 70WC-19Cr ₃ C ₂ -11Ni of 20～53Myuemu, as spraying equipment, HVOF spraying device (High Velocity Oxygen Fuel) (Praxair / Tafa Inc., trade name: JP5000) Was used to prepare a roll having a WC cermet sprayed coating according to the present invention, and this roll was applied to a CGL skin pass mill exit deflector roll. CGL is a continuous hot dip galvanizing facility. At this time, the porosity of the thermal spray coating was 0.3%, and the quantitative value of oxygen in the thermal spray coating was 1.2% by mass. The ratio of the quantitative value of Ni in the thermal spray coating to the quantitative value of the Ni powder used for the thermal spraying was 92%.

  For comparison, regarding the three defective deflector rolls, in which the sprayed coatings were all separated early within 6 months and were suddenly replaced, the porosity of the sprayed coating, the quantitative value of oxygen in the sprayed coating, and the spraying The ratio of the quantitative value of Ni in the coating to the quantitative value of the Ni powder used for the thermal spraying was also measured. The first deflector roll has a thermal spray coating porosity of 0.2%, a quantitative value of oxygen in the thermal spray coating of 2.5% by mass, and a quantitative value of Ni in the thermal spray coating of the Ni powder used for the thermal spraying. The ratio to the quantitative value is 75%, and the second deflector roll has a porosity of 0.3% of the sprayed coating, the quantitative value of oxygen in the sprayed coating is 3.5% by mass, and the determination of Ni in the sprayed coating. The ratio of the value to the quantitative value of the Ni powder used for spraying is 62%, and the third deflector roll has a porosity of 0.4% of the sprayed coating, and the quantitative value of oxygen in the sprayed coating is 5.8. The ratio of the quantitative value of Ni in the thermal spray coating to the quantitative value of the Ni powder used for the thermal spraying was 56%.

  The deflector roll of the present invention could be continuously used without problems for 20 months or more.

  According to the present invention, by optimizing the quantitative value of oxygen in the sprayed coating, in addition to being dense and high hardness, a process roll having a WC-based cermet sprayed coating having excellent toughness on the surface layer It becomes possible to provide.

The hardness and toughness of the thermal spray coating are plotted against the quantitative value of oxygen in the thermal spray coating. It is a figure for demonstrating the roll rolling test for evaluating toughness. The hardness and toughness of the thermal spray coating are plotted against the ratio of the quantitative value of Ni in the thermal spray coating to the quantitative value of the Ni powder used for the thermal spraying. This is a plot of the quantitative value of oxygen in the thermal spray coating when spraying by changing the ratio of fuel (kerosene) and oxygen (F / O ratio).

Explanation of symbols

1 Propulsion roll 2 Test roll

Claims (1)

A process roll formed by spraying a WC-based cermet sprayed powder containing Ni powder to form a WC-based cermet sprayed coating with a porosity of 0.5% or less on the surface layer,
A process roll excellent in toughness, characterized in that the quantitative value of oxygen in the sprayed coating is 2.0% by mass or less.

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