JPH02148703A - Electromagnetic steel plate having insulating film - Google Patents

Abstract

PURPOSE:To reduce defective products by a method wherein an insulating film containing organic resin is formed on the surface of a steel plate on which protrusions or protruding stripes are formed so as not to form enclosed regions on the surface. CONSTITUTION:Protruding stripes are formed on an electromagnetic steel plate 2 and an insulating film containing organic resin and having an approximately uniform thickness is formed on the plate 2. Water soluble type or emulsion type acrylic resin, polyvinyl acetate resin, polyurethane resin, phenolic resin, epoxy resin and their mixtures can be exemplified as the organic resin contained in the insulating film. It is recommended to form protruding stripes so as to maintain gaps sufficient for degassing. If such electromagnetic steel plates are laminated, gas discharge paths can be stably and securely maintained between the respective contact surfaces of the steel plates. Therefore, even if gas is produced from the resin component in the film at the time of a high temperature treatment such as welding and dis-casting, the gas can be discharged quickly, so that defective products can be reduced significantly.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an electrical steel sheet formed with an insulating film containing an organic resin, and more specifically, the present invention relates to an electrical steel sheet formed with an insulating film containing an organic resin. This relates to an electromagnetic steel sheet with a unique surface shape that allows it to be easily dissipated from the gaps between NwI sheets.

[Conventional technology] Insulating coatings for electrical steel sheets include inorganic coatings whose main constituents are chromic acid, phosphoric acid, silicic acid, etc., and organic/inorganic mixed coatings in which organic resin components are blended with inorganic components as a base. Two types of films can be mentioned. Among these, organic/inorganic mixed films have superior punching properties compared to inorganic films, so they are widely applied to core materials for motors and transformers that employ a continuous punching process.

However, when steel sheets with this organic/inorganic mixed film are exposed to high-temperature conditions such as welding or aluminum die-casting in the post-punching process, the organic resin components contained in the film are exposed to heat. There is a problem in that gas is generated as a result of decomposition, and this gas gets caught up in, for example, weld beads and causes blowholes.

Various methods have been proposed in the past as means to deal with this problem. For example, as a method to relatively reliably dissipate the gas generated when laminating and welding insulating coated steel plates, continuous protrusions 1a are formed on the insulating coat 1 as shown in Fig. 2, and the laminated coated steel plates are A method is currently being put into practical use to ensure a gap between the two, which serves as a gas release path. Methods for forming such protrusions or protrusions on the coating include a method using a grooved coating roll, a method of adding coarse particles to the treatment solution and performing coating/baking, and a method using a roll with a large surface roughness. A method of forming protrusions on the uncured film during baking by applying pressure to the surface has been specifically considered.

By using an insulating film-coated steel plate with ridges or protrusions formed in this way, the gas generated during welding can easily dissipate from around the welding area, making it possible to perform welding work efficiently and without welding defects. Although it is possible to obtain weld metal, the problem is that the ridges are formed on the relatively soft coating itself, and the coating is easily damaged when processing the MSj plate, and the coating is easily damaged by the time of welding. There was a drawback that the protrusions etc. were crushed and the formation of the intended gas release path was insufficient. For example, when processing electromagnetic steel sheets into core materials,
First, a wide coil is subjected to slitting, but during slitting, the surface of the coating is strongly rubbed by the tension bat, and the protruding portion of the coating on the surface of the steel plate may be scraped off. As a result, when the steel plates are stacked together, the steel plates come into close contact with each other in missing parts such as protrusions, making it impossible to secure an appropriate gap necessary for gas release.

In addition, it is not always easy to stably form protrusions on the film using a coating roll or the like in actual operation.
This method not only tends to cause formation defects, but also has the disadvantage that special equipment is required to form protrusions on the film.

[Problems to be Solved by the Invention] The present invention has been made in view of these circumstances, and has a surface shape that can quickly and reliably dissipate the gas generated from the film during welding, etc. The purpose of this invention is to provide an electrical steel sheet having an insulating film at a relatively low cost.

[Means for Solving the Problems] The electrical steel sheet of the present invention that achieves the above object has an insulating coating containing an organic resin on the surface of the steel sheet on which protrusions or ridges are formed so as not to form a sealing flat portion on the surface. The gist of this is that it is formed by the following.

[Function] The electromagnetic steel sheet according to the present invention has protrusions or ridges formed not only on the coating, but on the surface of the steel plate that is the base layer of the coating, and the coating is formed on the surface of the steel plate, which is the base layer of the coating. The surface is coated with a substantially uniform thickness.

In the present invention, the shape of the protrusions or protrusions to be formed on the steel plate is not limited, but they must be formed to a height of at least 2 μm from the viewpoint of ensuring sufficient gaps for gas release. is desirable. However, if the height of the protrusion or protrusion is too large, the space factor will decrease, so it is desirable that the height be 8 μm or less, more preferably 5 μm or less. The protrusions may be formed intermittently at a constant pitch, but the protrusions may also be formed long in a certain direction and formed as continuous or intermittent protrusions. The essential requirement is that it does not form a closed planar area surrounded by protrusions or ridges, and as long as this is adhered to, an arabesque pattern, a polka dot pattern, a cross pattern, etc. can be freely adopted. Although the distance between the protrusions is not particularly limited, it is recommended that the protrusions be formed at a pitch of about 1+nm, and the direction in which the protrusions are formed is not particularly limited.

As a method for forming the above-mentioned protrusions or protrusions on the surface of a steel plate, for example, cold rolling or temper rolling is performed using a work roll with grooves formed on the surface, and the groove shape on the roll surface is transferred to the steel plate. A method of forming protrusions or protrusions on the surface can be mentioned.

The most suitable method for forming grooves on the surface of a work roll is to use a high-density energy beam such as a laser beam, in which the rotating roll is irradiated with a laser beam and the metal on the irradiated part is melted. Grooves can be formed by doing this. At this time, the depth of the grooves formed on the roll is determined by considering the transfer rate determined according to the rolling conditions.
The design may be such that protrusions or ridges of a required height (preferably 2 to 8 μm) are formed on the surface of the steel plate.

The electric inm board according to the present invention is a steel plate on which protrusions or protrusions are formed as described above, and is coated with an insulating film containing an organic resin. Examples include, but are not limited to, emulsion type acrylic resins, vinyl acetate resins, polyurethane resins, phenolic resins, epoxy resins, and mixtures thereof. The insulation film is made of chromic acid, phosphoric acid,
It can be obtained by adding 5 to 50% of the above organic resin to an inorganic liquid containing silicic acid or a salt thereof as a main constituent, coating it with a roll coater or the like, and baking it at 150 to 400°C. The amount of the insulating film after baking is preferably 0.5 g/m2 or more for the purpose of blocking air, but a sufficient blocking effect can be obtained even with 0.1 g/m' or more.

If the coating amount exceeds 5 g/...2, the adhesion of the coating will deteriorate.

[Example] An electromagnetic steel sheet (plate @ 0.5 mm ,
Longitudinal continuous protrusions (3 μm in depth and 15 μm in width) were formed on the surface of the sample (Si: 0.2%). Next, an insulating film is applied to the surface of this steel plate using a roll coater,
I did the baking. The film coating solution used was a mixture of lithium silicate (molar ratio SiO2/Li20=4.5) and water-soluble acrylic resin at a solid content ratio of 7:3. Baking was carried out at 250° C. for 60 seconds, and the amount of film deposited after baking was adjusted to 1.2 g/+2.

The above-mentioned insulating film-formed steel plate was punched into a transformer core, and after lamination, TIG welding was performed. The results are shown in Table 1.

Roll without groove processing (No. 80 grinding finish,
A steel plate that was treated in the same manner as above using a steel sheet (Ra=0.3) was used as a comparison material.

Table * Judgment of bead finish condition O...No pinholes △...Slight pinholes x...Large pinholes (welding conditions) Welding method: Argon TIG welding electrode material: Tungsten electrode for TrG welding diameter
: 2.4 Arc gap: 1mm Gas flow rate: 15 u/win Welding position Two downward torch angles: As a result of vertical welding tests, the electromagnetic steel sheet of the present invention was able to weld at a higher welding speed than the comparative material. It was found that good beads could be obtained. In addition, the protrusions formed on the surface were not damaged at all during slitting or the like.

[Effects of the Invention] The present invention is configured as described above, and the electromagnetic steel sheets of the present invention can stably and reliably secure a communication path for gas release between contact surfaces in a laminated state. Therefore, even if gas is generated from the resin components in the coating during processes that are exposed to high temperatures, such as welding or die casting, this gas can be quickly dissipated, making it possible to significantly reduce the occurrence of defective products in these processes. . Moreover, productivity can be further improved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the cross-sectional shape of an electromagnetic steel sheet according to the present invention, and FIG. 2 is an explanatory diagram showing the cross-sectional shape of a conventional electromagnetic steel sheet in which a protrusion is formed on the coating itself. 1... Insulating film 2... Steel plate

Claims (1)

[Claims] 1. An electrical steel sheet comprising: a steel sheet having protrusions or protrusions formed thereon so as not to form a sealing flat portion; and an insulating film containing an organic resin formed on the surface of the steel sheet.