JPH083128B2 - Continuous decarbonitizing annealing equipment for grain-oriented electrical steel - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous decarburizing and nitriding equipment for grain oriented electrical steel sheets, and more particularly to a continuous decarburizing and anneal equipment for reducing the amount of atmosphere used so that a uniform oxide film and nitriding are performed on the steel sheet.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are obtained by secondary recrystallization by finish annealing to develop crystal grains having a (110) plane in the rolling surface and a Goss orientation with a [001] axis in the rolling direction. In order to sufficiently develop the secondary recrystallization, it is necessary to allow the presence of fine inhibitors such as AlN, MnS, and MnSe that suppress the growth of primary crystal grains up to the secondary recrystallization temperature range of finish annealing.

For this reason, electromagnetic steel slabs are heated to a high temperature of 1300 ° C. or higher to form an inhibitor-forming component such as A.
There is a method for producing a grain-oriented electrical steel sheet by completely dissolving 1, 1, Mn, S, Se, N, etc., and performing annealing for finely precipitating an inhibitor on a hot-rolled sheet or an intermediate sheet before final cold rolling. (For example, JP-A-56-84420). This manufacturing method is useful. However, since the slab heating temperature is high, molten slag is generated, which hinders the operation of the heating furnace and causes cracks in the edges of the steel sheet and deterioration of the surface quality. There is also a problem that the amount of heat energy used increases.
For this reason, there is a method of producing a grain-oriented electrical steel sheet by lowering the slab heating temperature, not sufficiently dissolving the inhibitor-forming components in the slab heating stage, and forming the inhibitor by the subsequent nitriding treatment (see, for example, Japanese Patent Laid-Open Publication No. Sho. 62-40315
Gazette, Japanese Patent Application No. 1-21963).

In the production of grain-oriented electrical steel sheet, for example, after cold rolling to a predetermined sheet thickness, decarburization annealing is performed. In the decarburization annealing, carbon in the steel sheet is removed and an oxide layer is formed on the steel sheet surface. This oxide layer and the annealing separator applied to the steel sheet react with each other in the finish annealing process to form a glass film, but the oxide layer greatly influences the quality of the film, so that it is important to form it uniformly.

By the way, in order to manufacture grain-oriented electrical steel sheets by low-temperature slab heating, it is considered that forming an inhibitor in the decarburization annealing process is advantageous in terms of productivity and process. As a conventional decarburization annealing furnace for grain-oriented electrical steel sheets, for example, in Japanese Utility Model Publication No. 54-160514, a nozzle for blowing an atmospheric gas onto the surface of the grain-oriented electrical steel sheet is provided in the decarburizing zone, and the atmospheric gas is blown onto the steel sheet. It has been disclosed to accelerate the decarburization reaction. This has a certain effect,
When sprayed with a nozzle, the oxide layer formed in the width direction or the length direction of the steel sheet is not necessarily uniform.

Further, Japanese Patent Laid-Open No. 61-48529 discloses a furnace in which a partition wall is provided between a heating zone and a decarburizing zone of a decarburizing annealing furnace, which heats in a neutral gas atmosphere and decarburizes in a wet atmosphere. It is disclosed. This is done by heating in a neutral atmosphere different from the decarburizing atmosphere and then decarburizing, preventing the decrease of S in the steel in the neutral gas atmosphere and improving the magnetic properties. Is played.

[0007]

Since the conventional decarburization annealing furnaces for grain oriented electrical steel sheets are mainly aimed at removing carbon, it is difficult to perform nitriding to form an inhibitor, and decarburization is difficult to perform. There is a problem that a large amount of atmosphere is required and the running cost becomes high.

According to the present invention, in decarbonitriding and annealing of a grain-oriented electrical steel sheet, not only the amount of atmosphere used is reduced but carbon is removed, but also an oxide layer can be uniformly formed over the entire width and the entire length of the steel sheet. The object is to provide a decarbonitriding annealing equipment capable of stably performing the above and obtaining a base material for forming an excellent glass film.

[0009]

The gist of the present invention is to decarburize a grain-oriented electrical steel sheet provided with a heating zone which exerts a decarburizing action on a steel sheet in a humid atmosphere and a soaking zone, a reduction zone, a cooling zone and a nitriding zone. In the nitriding annealing furnace, the atmosphere outlet provided in the front part of the heating zone and the circulation supply port provided in the rear part of the soaking zone are connected by providing an atmosphere circulation path, and the atmosphere inlet is provided in at least one of the reduction zone and the cooling zone. An outlet is provided to connect the outlet to the atmosphere circulation passage through an atmosphere circulation passage, and a purification device for purifying the circulating gas to the atmosphere circulation passage after the connection point and a control device for the atmosphere supply amount are provided to take out the atmosphere. Continuous decarburization of grain-oriented electrical steel sheets, characterized in that a control device for controlling the flow rate is provided in the atmosphere circulation passage and the atmosphere flow passage, and further, a device for heating the supply atmosphere is provided in front of the circulation supply port. For nitriding annealing equipment .

Next, the present invention will be described in detail with reference to the drawings based on one embodiment. In the drawings, 1 is a decarburization annealing furnace, in which a cold-rolled grain-oriented electrical steel sheet is decarburized prior to finish annealing. Reference numeral 2 denotes a heating zone provided in the decarburization annealing furnace 1, 3 denotes a soaking zone, and these zones 2 and 3 have a humid atmosphere such as H ₂ and N for removing carbon in the steel sheet and forming an oxide layer on the steel sheet surface. ₂ , H ₂ O. Reference numeral 4 denotes a zone for reducing the oxidation layer formed on the surface of the steel sheet in the reduction zone to stabilize the nitridation that forms an inhibitor, and the reduction zone 4 is supplied with a reducing gas such as H ₂ .

Numeral 5 is a primary cooling zone in which the temperature is suitable for nitriding, and the steel sheet is cooled with, for example, H ₂ and N ₂ . Reference numeral 6 is a nitriding zone, which is a zone for nitriding with a nitriding gas such as NH ₃ to form an inhibitor on the grain-oriented electrical steel sheet S, and 7 is a secondary cooling zone. Reference numeral 8 denotes an atmosphere partition, which is provided between the soaking zone 3 and the reduction zone 4, between the primary cooling zone 5 and the nitriding zone 6, and between the nitriding zone 6 and the secondary cooling zone 7 in this embodiment. It prevents the mixture of atmosphere.

By the way, in the heating zone 2 and the soaking zone 3, the grain-oriented electrical steel sheet S has a carbon moist atmosphere such as H ₂ , N ₂ , H.
It is removed by the reaction with ₂ O, and an oxide layer is formed on the steel plate surface. At this time, in order to reduce the consumption of the atmosphere and remove the carbon as well as form the oxide layer evenly, in the present invention, an atmosphere circulating device is provided between the heating zone 2 and the soaking zone 3 as described below. At least one of the reduction zone 4 and the cooling zones 5 and 6 is connected to the atmosphere circulation device, and the atmosphere is circulated from the rear of the soaking zone 3 to the front of the heating zone 2.

An outlet 9 for extracting atmospheric gas is provided in the front part of the heating zone 2, and a supply port 10 for circulating and introducing the atmospheric gas is provided in the rear part of the soaking zone 3 and these are connected by an atmosphere circulation path 11. ing. Reference numeral 12 is a gas refining device provided in the atmosphere circulation path 11, which is C generated by reacting with carbon in the steel sheet.
O, CO ₂ or H ₂ decarbonization reaction product gases and suspended dust O, etc. were removed purification, also those to be reproduced as a wet gas having the adjusted decarburized act separately H ₂ O ratio was added to H _2, N ₂ Thus, for example, an adsorption type refiner, a filtration type refiner or the like is adopted.

Reference numeral 13 is an extraction flow rate control device for controlling the atmosphere extraction flow rate, and 14 is a supply flow rate control device provided on the output side of the gas purification device 12. In this embodiment, 15 is an atmosphere outlet provided in the reduction zone 4, and an atmosphere flow passage 16 is provided in the outlet 15 and is connected to the atmosphere circulation passage 11 via this. The atmosphere gas taken out from the reduction zone 4 is also purified at the connection point before the installation position of the gas purification device 12. Reference numeral 17 denotes a flow control device for taking out from the reduction zone 4 provided in the atmosphere flow passage 16.

These take-out flow rate control devices 13 and 17 control the amount of atmospheric gas taken out from the furnace and the supply flow rate control device 14.
To prevent the furnace pressure from fluctuating, and the circulating atmosphere gas supplied to the furnace flows in a turbulent state from the soaking zone 3 to the heating zone 2 side and the grain-oriented electrical steel sheet S and unevenness. However, the decarburization reaction and the oxide layer formation reaction uniformly occur in contact with these zones 3 and 2 over the entire width. 18-1 and 18-2 detect the gas pressure inside the furnace with a furnace pressure gauge, and the signals are input to the take-out flow rate control device 13 and the take-out flow rate control device 17, respectively, and the take-out flow rate control makes the furnace pressure higher than that outside the furnace. Can be prevented from entering. Reference numeral 19 is an apparatus for heating a circulating atmosphere gas provided as necessary, which heats the gas circulated and supplied into the furnace. Reference numeral 20 is a device for supplying supplemental atmospheric gas to the soaking zone 3, and when the amount of circulating atmospheric gas decreases for some reason and becomes insufficient, atmospheric gas such as H ₂ and N
Supply ₂ .

Next, the operation will be described. Decarburization annealing furnace 1
The grain-oriented electrical steel sheet S is passed through and heated in a heating zone 2 and a soaking zone 3 to a decarburization annealing temperature, for example, 750 to 850 ° C., and moistened H ₂ and / or N ₂ gas is supplied to remove carbon. However, an oxide layer is formed on the surface of the steel sheet. Subsequently, the oxide layer of the steel sheet undergoes a reducing action, and is nitrided in the nitriding zone 6 to form an inhibitor. During this decarburization annealing, the atmosphere partition 8 is closed and the desired atmosphere is maintained in the zone.

By the way, the atmospheric gas is taken out to the atmosphere circulation path 11 from the outlet 9 provided in the front part of the heating zone 2. Since the gas taken out is after the decarburization reaction, H ₂ , N
_In addition to ₂ , CO, CO ₂ and H ₂ O generated by decarburization are excessively mixed and cannot be further subjected to decarburization annealing as they are. In addition, the gas taken out from the reduction zone 4 such as H ₂ ,
Since N ₂ may be mixed with impurities such as suspended dust, the circulating gas taken out by the gas purifier 12 removes the decarburization reaction products such as CO and CO ₂ and impurities, and H ₂ The circulating gas purified by removing excess O is supplied into the furnace from the rear of the soaking zone 3.

The gas circulated and supplied from the rear part of the soaking zone 3 to the front part of the heating zone 2 whose temperature in the furnace is lower than that of the soaking zone 3 is taken out, so that the atmosphere from the soaking zone 3 to the heating zone 2 is changed. The gas flow becomes turbulent and contacts the steel plate evenly in the plate width direction, forming a uniform oxide layer. Also, carbon removal can be done without problems. If the oxide layer is uniform, the subsequent nitriding reaction will occur evenly and stably on the steel sheet. In this embodiment, the atmospheric gas is taken out from the reduction zone and fed to the atmosphere circulation path, but it can be similarly applied and the operation effect can be obtained even if it is taken out from the cooling zone and put in the circulation path.

[0019]

According to the present invention, during decarbonitriding and annealing of grain-oriented electrical steel sheets, the amount of atmospheric gas used can be reduced, and a uniform oxide layer is formed on the steel sheet to stabilize nitriding and further finish. An excellent glass film is obtained by the reaction with the annealing separator during annealing.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of continuous decarburizing annealing equipment for grain-oriented electrical steel sheets according to an embodiment of the present invention.

[Explanation of symbols]

 1 Decarburization Annealing Furnace 2 Heating Zone 3 Soaking Zone 4 Reduction Zone 5 Primary Cooling Zone 6 Nitriding Zone 7 Secondary Cooling Zone 8 Atmosphere Partition 9 Outlet 10 Supply Port 11 Atmosphere Circulation Path 12 Gas Purification Device 13 Extraction Flow Control Device 14 Supply Flow control device 15 Atmosphere outlet 16 Atmosphere flow passage 17 Extraction flow control device 18-1, 18-2 Furnace pressure gauge 19 Gas heating device 20 Atmosphere gas replenishment supply device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Morifumi Yonemaru 1-1 Tobahata-cho, Tobata-ku, Kitakyushu City, Fukuoka Prefecture Shin Nippon Steel Co., Ltd. Yawata Works (72) Inventor Taiko Kondo, Tobata-ku, Kitakyushu, Kitakyushu, Fukuoka Prefecture No. 1 No. 1 within the Yawata Works, Nippon Steel Co., Ltd. (72) Inventor Katsuhiro Fujita No. 1 Tobahata-cho, Tobata-ku, Kitakyushu City, Fukuoka Prefecture No. 1 within the Yawata Works (72) Inventor Nomura Naruhiko 1-1-1 Edamitsu, Hachiman-Higashi-ku, Kitakyushu, Fukuoka Prefecture, Nippon Steel Co., Ltd. (72) Inventor, Yuko Tanaka No. 1 Tobita-cho, Tobata-ku, Kitakyushu, Fukuoka Shin-Nippon Steel Hachiman Co., Ltd. Inside the steelworks

Claims (2)

[Claims] 1. A decarbonitriding of a grain-oriented electrical steel sheet comprising a heating zone, a soaking zone, a reduction zone, a cooling zone, and a nitriding zone, which exert a decarburizing action on a steel sheet in a humid atmosphere, and an atmosphere partition is provided between the zones. In the annealing furnace, the atmosphere outlet provided in the front part of the heating zone and the circulation supply port provided in the rear part of the soaking zone are connected by providing an atmosphere circulation path, and the atmosphere outlet is provided in at least one of the reduction zone and the cooling zone. The atmosphere outlet is connected to the atmosphere circulation passage through an atmosphere flow passage, and a purification device for purifying the circulating gas in the atmosphere circulation passage after the connection point and a control device for the atmosphere supply amount are provided to remove the atmosphere. Continuous decarbonitriding and annealing equipment for grain-oriented electrical steel sheets, characterized in that a control device for controlling the flow rate is provided in the atmosphere circulation path and the atmosphere flow path. 2. Decarbonitriding of a grain-oriented electrical steel sheet having a heating zone, a soaking zone, a reduction zone, a cooling zone, and a nitriding zone, which exert a decarburizing action on the steel sheet in a humid atmosphere, and an atmosphere partition is provided between the zones. In the annealing furnace, the atmosphere outlet provided in the front part of the heating zone and the circulation supply port provided in the rear part of the soaking zone are connected by providing an atmosphere circulation path, and the atmosphere outlet is provided in at least one of the reduction zone and the cooling zone. Is provided, the outlet is connected to the atmosphere circulation path via an atmosphere passage, and a refining device for refining the circulating gas to the atmosphere circulation path after the connection point, a controller for controlling the atmosphere supply amount, and heating the supply atmosphere A continuous decarbonitriding / annealing equipment for grain-oriented electrical steel sheets, characterized in that a control device for controlling the flow rate for extracting the atmosphere is provided in the atmosphere circulation path and the atmosphere flow path.