JPH0195807A - Rolling roll - Google Patents

Abstract

PURPOSE:To improve uniformity and minuteness of coating in rolling rolls by flame spraying aggregated powder granulated with a WC series material and a self-fluxing alloy on the surface of a base metal. CONSTITUTION:The powder of WC series material and a self-fluxing alloy are granulated integrally by the ordinary spray granulating method to form the aggregation powder, and this powder is flame sprayed on the rolling roll 1 to form the flame sprayed coating layer. As the results of this spray method the required conditions as the rolling roll, i.e. the wear resistance, seizure resistance and thermal shock resistance are satisfied when loading conditions are considerably high.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a rolling roll having excellent thermal shock resistance, abrasion resistance, and seizure resistance. The present invention relates to a rolling roll having a thermally sprayed coating layer formed by thermally spraying an aggregate powder obtained by granulating a material and a self-fluxing alloy.

[Conventional technology]

In recent years, demands for improving quality, improving production efficiency, and reducing manufacturing costs have become increasingly strict in the field of rolling, such as hot rolling and cold rolling of steel materials, especially steel strips. Significant progress has been made in the advancement of high pressure and other control technologies.

Under these circumstances, the load on rolling rolls (work rolls, backup rolls, intermediate rolls) has become more severe than ever before, and there is a strong need for rolls that can withstand this load.

Taking hot rolling rolls as an example, adamite cast steel with a C content of 1.4 to 1.8 wt% has traditionally been used as the roll material in the front stand of a finishing tandem rolling mill with severe rolling conditions. However, due to high loads and high speeds, the problems of rough skin (seizing) and wear of the rolls have become more serious, and as a solution to this problem, high chromium cast iron containing 12 to 2 Qwt% of Cr has been used.

However, even with high chromium cast iron rolls, the wear resistance and seizure resistance are still not fully satisfactory under rolling conditions such as high loads, and improvements in roll manufacturing technology, hydraulic rolling, roll cooling, etc. Efforts have been made to reduce the load on the rolls by improving technology, but this has resulted in deterioration of the steel sheet profile and the occurrence of surface flaws in the copper strip, and shortening the rolling cycle (early roll replacement) has resulted in reduced production efficiency. This is causing a decline in the roll layer and deterioration of the roll layer unit.

To solve these problems, many methods have recently been proposed for thermally spraying wear-resistant materials onto the roll surface.

For example, JP-A No. 60-87910! 4 (hereinafter referred to as 1st
This is called the conventional example. ) and JP-A-58-110187 (hereinafter referred to as the second conventional example) disclose a method of coating the roll surface with a highly wear-resistant material such as ceramics; Publication No. 217670 (hereinafter referred to as
This is called the third conventional example.

) discloses a method of thermal spraying a WC-based material.

[Problems to be Solved by the Invention] However, the methods of spray coating the roll surface of the ceramic material in the first conventional example and the second conventional example described above have low adhesion to the roll base material, and the ceramic material itself ,
Due to its poor thermal shock resistance, in areas where the thermal cycle of heating and cooling is repeated, such as in hot rolling rolls, and where the rolling conditions are very severe, the ceramic layer may peel off, causing transfer problems to the product. . In order to prevent peeling, the method is disclosed in Japanese Patent Application Laid-Open No. 58-56901 (hereinafter referred to as the fourth conventional example).

) discloses a method for reducing fluctuations in thermal stress, but this method involves heating the roll itself to a temperature close to that of the rolled material.
This equipment is essential for keeping warm. For hot rolling of strip materials such as wire rods and round bars, this method requires relatively small capital investment and is highly practical, but it is difficult to use rolls with a width of 2000 m, such as in hot steel strip rolling. This is extremely impractical because the equipment is complicated and the sheet width changes constantly, and the thermal crown of the roll itself also changes, making it impossible to obtain a stable steel profile.

In addition, the third conventional example described above is a self-fluxing alloy of WC-based material and nickel-chromium base (35WC-11Cr-46Nf).
) has been disclosed, but a roll with a thermal spray coating made of the same components formed on the surface of the base material was manufactured and experiments were conducted to confirm the wear resistance and seizure resistance. However, as shown in FIGS. 4 and 5, good results were not obtained compared to adamite or high chromium cast iron (16% Cr cast iron), and problems still remain.

That is, in Fig. 4, 5S41 is used as the material to be rolled (counterpart material), the temperature is 800°C, the roll dimensions are 120φ x 80L, and the peripheral speed of the roll is 11 m/m.
In, when the sliding time was 40 m1n, a large seizure occurred with Adamite at a load of 1000 kg and a coefficient of friction of 0.18, and no experiments were conducted with higher loads. Also, load 20
00 kg, friction coefficients of 0.22 and 0.20, small seizures occurred and no experiments with higher loads were performed.

That is, the seizure property of the roll having the thermally sprayed coating layer according to the third conventional example is not particularly superior to that of the high chromium cast iron roll.

In addition, in FIG. 5, the rolled material 3341, temperature soo
″c, roll dimensions 120φX80L, roll circumferential speed 11
m/min, passing length 1000m, load 1000k
The results of measuring the amount of wear μm when g was found to be that although the amount of wear was slightly less for those with a thermally sprayed coating layer than for high chromium cast iron, it could not be said to be particularly excellent.

The inventors of the present invention have conducted extensive research in order to solve the above-mentioned problems with conventional rolling rolls, and have come to the following knowledge.

In other words, conventional WC-based materials and self-fusing alloys (Self-
Fluxing-Alloy, hereinafter simply referred to as SFA.

), it was found that a WC material was granulated or sintered to a particle size of several tens of micrometers1, and a coating was formed by simply mixing this with SFA of several tens of micrometers and spraying it. Therefore, the coating after thermal spraying lacked uniformity and density.

In order to solve these problems, it is possible to reduce the particle size of the powder, but if the particle size is made smaller, coating defects due to powder scattering and a decrease in manufacturing yield will occur when spraying onto the roll. The particle size of the thermal spray powder is several tens of microns.
There is no choice but to make it more than m.

The present invention was made to solve these conventional problems, and improves the uniformity and density of the coating sprayed onto the surface of the base material, and improves thermal shock resistance, abrasion resistance, and resistance to thermal shock. The object of the present invention is to provide a rolling roll with excellent seizure properties.

[Means for solving problems]

Therefore, the rolling roll of the present invention has WC on the surface of the base material.
A thermally sprayed coating layer is formed by thermally spraying an aggregate powder obtained by granulating a base material and a self-fusing alloy.

[Effect]

Both the WC-based material and the self-fusing alloy are granulated to form an aggregate powder, and the aggregate powder is thermally sprayed onto the surface of the base material of the roll to form a coating. Therefore, the thermal spray coating layer becomes uniform and dense, and the thermal shock resistance, abrasion resistance, and seizure resistance of the rolling roll are improved.

〔Example〕

An aggregate powder of several tens of micrometers was prepared by integrally granulating powders of WC-based materials and SFA with particle diameters of several micrometers using a boat fishing spray granulation method. A thermal spray coating layer was applied to the body (L) by a powder spraying method. After the thermal spraying, a grinding finish was performed so that the thermal spraying thickness was 0.2 mm.

Here, 5FA (self-fusing alloy) is a nickel-based, nickel-chromium-based, or cobalt-based superalloy with boron and silicon added, and has excellent wear resistance, erosion resistance, corrosion resistance, high temperature oxidation resistance, etc. It has excellent properties.

In addition, as mentioned above, we made a prototype powder by individually sintering the aggregate powder of several 10//m, which was made by integrally granulating the WC-based material and the SFA powder, and similarly, we made a powder by individually sintering this powder. A thermal spray coating layer was applied to the test roll using the powder spraying method.
After the thermal spraying, a grinding finish was performed so that the thermal spraying thickness was uniform to 0.2 fl.

Figure 1 shows an experimental device for examining surface properties under various loads at room temperature to 1000°C. In the figure, 1 is a test roll, 2 is a fixed roll, 3 is a rolled material, is driven by a motor 5 via a reducer 4, and a hydraulic cylinder 6 applies a load under the test load set by a load cell 7, 7°, and the material 3 to be rolled is rolled in the direction perpendicular to the plane of the paper, and by energizing. It is designed to be able to heat up to 1000°C. Note that 8 in the figure indicates a torque meter.

Further, in the state shown in FIG. 2, cooling water is jetted from a cooling nozzle 10 by a pump 9 to the exit side of the test roll 1 that comes into contact with the rolled material 3.

In the experiment, as shown in Table 1, an adamite roll was used as the base material of the test roll, and a 5,541 m strip (0° 2 mm thickness x 40 mm), which was the material to be rolled 3, was Width x
L length) was rolled. The rolls were driven by only the test roll I at a circumferential speed of 1 m/min, and a load equivalent to the rolling load was applied using a hydraulic cylinder 6 and a load cell 7.7' to 1000 kg, 2000 kg, 3000 kg, and 400 kg.
Cooling water was injected onto the test roll 1 at a rate of 3.51/min.

Table 1 Under these conditions, the operation was stopped when seizure resistance (rough skin) and thermal shock resistance (peeling) occurred during the 40-minute operation time. Note that this judgment was based on the rapid fluctuation of the torque meter 8. In addition, the roll diameter at room temperature was measured before and after the experiment, and the wear resistance was evaluated based on the difference. Table 2 shows experimental results at two temperatures: 500°C and 1000°C.

As is clear from Table 2, in conventional thermal spraying of mixed powder,
If the weight exceeds 3000 kg, the seizure resistance and thermal shock resistance will deteriorate.
However, in thermal spraying of the integrally granulated powder and sintered integrally granulated powder of the present invention, even under a load condition of 4000 kg, the required conditions for a rolling roll (wear resistance,
It can be seen that the properties (seizure resistance and thermal shock resistance) can be fully satisfied.

When the granulated aggregate powder is sintered, the binder of each individual powder vaporizes or thermally decomposes, leaving pores. However, since it is sintered, it is compressed and the pores disappear, resulting in a stronger and denser aggregate powder. can be formed. □ As mentioned above, by thermally spraying integrally granulated powder or sintered integrally granulated powder onto the roll surface and using it for hot rolling rolls, it is expected that seizure resistance, thermal shock resistance, and wear resistance will be significantly improved. It is possible.

Next, a thermal spray layer was formed using an integrally granulated powder of 60 W C-3G o-37S FA by a powder spraying method, and a rolling roll with a surface hardness of Hv840 and a thermal spray thickness of 0.2 fi was coated with 80 W C-4Co- Regarding an example in which a powder spray layer of 16S F A sintered integrally granulated powder is applied to a work roll of a hot Kundem finishing rolling mill with a 0.2 fin rolling roll, 16% without a conventional spray coating layer is applied.
A comparison will be made with Cr cast iron (Hv580).

All work roll dimensions are 700 Illφ×2032
The 1m1 initial roll curve was a sine curve of +2.5/100 dragons, and was incorporated into the upper and lower rolls of W2 stand among the 7 finishing stands, and rolling of approximately 1200 tons was performed. The results are shown in FIG. 3 and Table 3.

As shown in Figure 3 (al), with conventional 16% chromium cast iron, meteor-like roughness occurs on the roll surface, and 20 to 30 mm wide roughness (seizing) occurs on the edge of the passed rolled material.
occurred around the circumference.

On the other hand, as shown in FIG. 3('b), no seizure occurred on the roll surface in the present invention.

Further, as shown in Table 3, it can be seen that the present invention is superior to the conventional example in terms of wear resistance and roll roughness.

Table 3 Although this example describes a hot rolling roll,
However, since it is a granulated aggregate powder or a sintered granulated aggregate powder, a dense sprayed layer is formed, so other rolling rolls (for example, cold rolling rolls) It goes without saying that it can also be used for other products (e.g., long steel rolls, etc.).

〔Effect of the invention〕

As explained above, according to the rolling roll of the present invention,
The sprayed coating layer is formed by thermally spraying aggregate powder made of granulated WC material and self-fluxing alloy onto the surface of the base material, so the thermal sprayed coating layer formed on the surface of the base material is uniform and dense. Therefore, the thermal shock resistance, abrasion resistance, and seizure resistance are significantly improved, and the number of rolling wheels can be greatly increased.

[Brief explanation of the drawing]

FIG. 1 is a front view of an experimental apparatus for examining the surface properties of rolling rolls, FIG. 2 is a side view showing the rolling state of rolling rolls, and FIG. The front view, FIG. 4, and FIG. 5 showing experimental results of characteristics are graphs showing experimental examples of seizing property and abrasion property of conventional rolling rolls, respectively. ■... Test roll, 2... Fixed roll, 3... Rolled material, 7.7"... Load cell, 8... Torque meter. Figure 1 #41'-ε

Claims (2)

[Claims] (1) A rolling roll in which a thermal spray coating layer is formed on the surface of a base material by thermal spraying an aggregate powder obtained by granulating a tungsten carbide-based material and a self-fluxing alloy. (2) The rolling coating according to claim 1, wherein the thermal spray coating layer is formed by granulating a tungsten carbide material and a self-fusing alloy and then thermal spraying a sintered aggregate powder. roll.