JPS61159247A - Quick cooling roll for producing high-silicon thin steel strip - Google Patents

Abstract

PURPOSE:To prevent the seizure of the surface of quick cooling rolls for producing a high-silicon thin steel strip by coating the surface of said rolls with the 1st layer consisting of Ni plating and the 2nd layer consisting of a thermally sprayed layer of a metallic carbide or metallic nitride and having a prescribed thickness. CONSTITUTION:A high-temp. molten steel of about >=1,500 deg.C tapped from a melting furnace 2 is poured from a tundish 4 into the gap of the quick cooling rolls 6 and a thin steel strip 12 produced in such a manner is coiled in the stage of producing the 2-7% Si-Fe thin steel strip. The 1st layer consisting of the Ni plating and the 2nd layer formed by spraying thermally either of the metallic carbide or metallic nitride to 10-200mum thickness are preliminarily coated on the surface of the rolls 6. The seizure of the high-temp. molten steel to the surface of the quick cooling rolls is thus prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a quench roll for producing high-silicon thin steel strip, and in particular to a quench roll that can prevent roll seizure during production. Widely used as rolls for manufacturing steel strips.

[Conventional technology]

High-silicon steel strips with a main composition of 2 to 7% 5i-Fe have excellent low core loss characteristics, and demand is expected to increase rapidly in the future along with amorphous alloy thin steel strips as wound core materials.

However, there are several problems in producing 2 to 7% 5i-Fe high silicon thin steel strip, one of which is roll seizure.

The manufacturing process of the high-silicon thin steel strip will be explained with reference to FIG. The high temperature molten steel tapped from the melting furnace 2 is passed through the tundish nozzle 4.
It is then injected into the gap between a set of rolls 6 for manufacturing thin steel strips. The roll 6 for manufacturing thin steel strip has a sleeve-type water-cooled structure, and the lower part and side surfaces are protected by a guide frame 10 having an external spray nozzle 8. The thin steel strip 12 produced by the rolls 6 passes through a first pinch roll 14, a deflection roll 16, and a second pinch roll 18, and is then wound onto a take-up roll 20.

In the production of high-silicon thin steel strips, molten steel at a high temperature of 1,500°C or higher is injected into the gap between the two rolls 6 as described above, so seizure occurs in the rolls 6, causing splashes and steel ingots on the surface of the rolls 6. It often happens that the product is completely unmanufacturable due to the adhesion of the product.

Conventionally, there have been no sufficient measures to prevent seizure of rolls used for molten steel that reaches approximately 1,500°C.
The target temperature is approximately 1,500°C.
Cannot be used at high temperatures.

[Problem that the invention seeks to solve]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art described above and to provide a quench roll for producing a high-silicon thin steel strip that does not cause roll seizure.

[Means and operations for solving the problems] The gist of the present invention is as follows.

That is, in a quench roll for manufacturing a high-silicon thin steel strip, in which a molten metal whose main composition is 2 to 7% SiF6 is flowed from a nozzle onto the roll surface and directly quenched and solidified to continuously produce a thin steel strip, the roll has a first layer consisting of Ni plating on its surface, a metal carbide with a thickness of 10 to 200 μm,
The present invention is a quenching roll for producing a high-silicon thin steel strip, characterized in that it has a coating layer consisting of a second layer consisting of a thermally sprayed layer having one composition selected from metal nitrides.

The present inventors have conducted a number of studies regarding roll seizure during the manufacturing process of high-silicon thin steel strip. JIS for its good thermal conductivity and high strength as a roll material for manufacturing high-silicon thin steel strips.
Iron or copper rolls such as 845C and SKD are used. When high-temperature molten steel is injected into the gap between a pair of rolls, the roll surfaces are exposed to high temperatures of 1500°C or higher. On the other hand, the molten steel that has been heat removed on the roll surface solidifies and is rolled under high pressure by the rolls, and a portion of the steel may be welded to the roll surface. According to this study, it was found that this welding greatly depends on the surface material of the roll and the affinity for the molten steel.

Also, the surface pressure during rolling under high temperature with rolls is 10 to 30 kg.
□There is a risk that the roll will reach □ and the roll will undergo indentation deformation, and this indentation deformation will be the main cause of roll seizure. Figure 2 shows the relationship between the surface temperature and hardness of rolls made of 8450 and 5KD-6.As the temperature increases, the hardness decreases.In particular, when the molten steel temperature is 1540℃, the average surface temperature of the roll is approximately The temperature is about 600°C, but if the temperature exceeds 600°C, there is a noticeable tendency for hardness to decrease. Therefore, in order to prevent roll deformation due to indentation, the hardness of the roll base material is insufficient, and it is necessary to increase the surface hardness by other methods.

In other words, in order to prevent splash and adhesion of steel ingots on the roll surface and prevent seizure, it is necessary to increase the high temperature hardness of the roll surface and reduce its affinity with molten steel.
In addition, from the viewpoint of the function of direct rolling, it was found that the rolls are required to have excellent thermal conductivity in order to quickly solidify the rolled steel and to eliminate various problems caused by high temperatures.

Based on the above findings, the present invention provides the roll base material with a coating layer that has high high temperature strength, low affinity with molten steel, excellent thermal conductivity, has excellent adhesion to the roll base material, and is resistant to thermal shock. He caused it to form.

The present invention consists of a first layer of Ni plating and a second layer of thermal spraying, and the purpose of the first layer is to improve the adhesion of the second layer. Second
The layer is made of metal carbide such as CrC1WC9ZrC or BN.
The second layer has a composition selected from metal nitrides such as nitrides, etc., and the thickness of the second layer is in the range of 10 to 200 μm, and is thermally sprayed by a conventional method.

The reason for limiting the thickness of the sprayed layer is that if it is less than 10 μm, the hardness
The thickness is limited to a range of 10 to 200 μm because it does not have sufficient durability and is likely to peel off, and if it exceeds 200 μm, heat conduction will be significantly reduced, heat removal to the roll will be reduced, and there is a risk that the molten steel will not solidify.

That is, in the present invention, the molten metal contains 2 to 7% Si-1;'e
Since the Si value is higher than before, the wettability of the surface of the quenching roll is important, and especially the oxide film layer has a Si value on the surface.
, which may cause burn-in, so it is not suitable. In addition, rapid solidification requires high thermal conductivity, as well as adhesion between the coating layer and the base material and thermal shock resistance. In the present invention, the former characteristic is determined by the material of the second coating layer and the total thickness of the coating layer, and the latter characteristic is determined by the N of the first layer, taking into account the difference in thermal expansion.
i-metsuki and 1st. This is what is intended to be achieved with the adhesion of the second layer. Therefore, the most important points of the present invention are the type and thickness of the first plating layer, which also limits the thickness of the second coating layer. Particularly in the rapid solidification of molten metal, the latent heat of the molten metal becomes a problem, and as the heat size increases, the latent heat also increases.

According to the present invention, even in contact with molten metal as described above, it can sufficiently withstand thermal shock and melting damage, and can prevent peeling of the coating due to thermal expansion, wrapping of the thin steel strip during manufacture, breakout, etc. This enabled smooth operation without any malfunctions.

〔Example〕

A base material roll as shown in Table 1 was used to form the coating layer of the present invention shown in Table 1, and a high silicon thin steel strip was manufactured using this roll. Sample material 1'I&11 of the present invention example. 2
produced 10 kg of thin steel strip with a width of 50 mm and a thickness of 100 μm from 1540° C. molten steel, but no seizure occurred and the shape was good. Sample materials 3 and 4 of the present invention were manufactured from 1530° C. molten steel into 15 kg of thin steel strips with a width of 45 mm and a thickness of 110 μm, but no burning occurred and the shapes were good. Sample material No. 1 of the present invention example Table 111kL5-8 is made from 1550℃ molten steel with a width of 50cnL
, 15 kg of thin steel strips with a thickness of 150 μm were produced, and none of them suffered from seizure and had good shapes. Sample teeth 9 to 10 of the present invention were manufactured from molten steel at 1540° C. by producing 10 kg of thin steel strips with a width of 40 gK and a thickness of 150/jm, but no seizure occurred and the shapes were good.

In contrast, sample tooth 11.1 of a comparative example without a coating layer
No. 2 had such severe seizure that it was impossible to manufacture a thin steel strip, and the root mean square roughness Hrms of the roll surface was 10 μm or more.

The relationship between the surface temperature and hardness of the rolls of the examples shown in Table 1 was investigated, and the results are shown in FIG. 2 described above. The first Ni plating layer of the test material tooth 1, the thermal sprayed layer of the second layer WC, the first layer N1 plating of the test material NCL3, the second thermal spray layer of CrC, and the first layer of the test material tooth 10. The relationship between the surface temperature and Hv hardness of the quench roll of the present invention, which has a composite coating layer in which the first layer is Ni-plated and the second layer is a BN-based thermal sprayed layer, is also shown in Figure 2. Compared to the surface of the roll base material of 545C and 8KI)6, the high-temperature hardness is high, and the difference is particularly noticeable at temperatures above 600°C.

〔Effect of the invention〕

The present invention is a quenching roll for producing a high-silicon thin steel strip, in which a molten metal whose main composition is 2 to 7% 5i-Fe flows out from a nozzle onto the roll surface, and is directly quenched and solidified to continuously produce a thin steel strip. , the first layer is plated with Ni to a thickness of approximately 50 μm, and a second layer consisting of a thermally sprayed layer having a thickness of 10 to 200 μm and having one composition selected from metal carbides and metal nitrides is formed on the first layer.
By coating the layer, the following effects could be achieved.

(a) The coating layer of the present invention, which is composed of the first layer and the second layer, has good adhesion to the roll and has strong thermal shock resistance against high-temperature molten metal, so the coating layer does not peel off. Does not cause burn-in.

(b) The coating layer according to the present invention has the effect of increasing the high-temperature hardness of the roll surface and decreasing the affinity with the molten metal.

(c) The coating layer according to the present invention has excellent thermal conductivity and rapidly solidifies the molten metal.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing a method for directly producing a high-silicon thin steel strip from molten steel, and FIG. 2 is a diagram showing the relationship between roll surface temperature and hardness. 6...Quick cooling roll for manufacturing thin steel strip 12...High silicon thin steel strip Agent Patent attorney Takeo Nakaji Figure 2 o 200 400 600
800 roll surface (burned (0C) February 4, 1986)

Claims (1)

[Claims] (1) In a quenching roll for producing a high-silicon thin steel strip, in which a molten metal whose main composition is 2 to 7% Si-Fe flows out from a nozzle onto the roll surface and is directly quenched and solidified to continuously produce a thin steel strip, The roll has a coating layer on its surface comprising a first layer made of Ni plating and a second layer made of a thermally sprayed layer of one composition selected from metal carbide and metal nitride with a thickness of 10 to 200 μm. A quenching roll for producing high-silicon thin steel strip, characterized in that it has: