JPS6021330A - Production of nondirectionally oriented silicon steel sheet having good surface characteristic - Google Patents

Abstract

PURPOSE:To obtain a nondirectionally oriented silicon sheet having a good surface characteristic in the stage of producing the steel sheet from a slab for a nondirectionally oriented silicon steel sheet having a specific compsn. by specifying the rolling end temp. and rolling reduction in the final pass in hot finish rolling and succeeding coiling temp. CONSTITUTION:A slab for a nondirectionally oriented silicon steel contg., by wt%, 0.02% C, 1.5-4.0% Si and <=1.0% Al is heated to about 1,000-1,200 deg.C and is then hot rolled and coiled. The coil is annealed and is subjected further to cold rolling and final finish annealing to produce a nondirectionally oriented silicon steel sheet. The steel sheet is subjected to hot finish rolling under the conditions of 800-700 deg.C rolling end temp. and >=15% draft in the final pass and at the same time the coiling temp. is regulated to >=500 deg.C. The steel sheet which obviates generation of ridging in the product is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a method for producing a non-oriented silicon steel sheet with good surface properties, and particularly to advantageously prevents the occurrence of zinc, which has been a concern in the past, in this type of sheet. It is something.

As is well known, non-oriented silicon steel sheets are mainly used in laminated form as the iron core of stationary equipment such as transformers and ballasts, or rotating equipment such as motors and generators. There are many. Therefore, in order to improve electromagnetic properties, which require not only excellent electromagnetic properties but also good surface properties that have a large effect on the space factor and interlayer resistance, we have recently reduced the carbon level as much as possible at the molten steel stage. Further improvements were achieved by reducing or omitting the decarburization step during annealing, but the following problems with surface quality still remained.

In other words, in silicon steel containing 1.5% by weight or more of Sl (hereinafter simply expressed as %), wrinkle-like surface defects called ridging are likely to occur in products after cold rolling. This not only spoils the appearance, but also reduces the space factor and interlayer resistance when laminated, so motors and transformers incorporating such zinc-generating steel plates are not recommended. This resulted in deterioration of its characteristics.

The occurrence of ridging has not yet been clearly clarified, but it is thought to be roughly as follows.

In other words, if the columnar crystals in the slab remain as elongated grains even after hot rolling, and some of them remain unrecrystallized even after annealing after hot rolling, the deformation flB will be different from other recrystallized parts during cold rolling. As a result, the surface becomes wrinkled.

Conventional measures to prevent ridging include: (11) reducing the columnar crystallinity of the slab by utilizing low-temperature casting and electromagnetic stirring (2) by utilizing the γ→α transformation and rolling reduction at the slab stage; (8) A rolling process has been proposed in which strain energy is introduced in the rough hot rolling process to achieve fine crystallization of columnar crystals.

However, all of the above methods still have the following problems.

(Although low-temperature casting (No. 11) can be expected to have some effect, it is difficult to ensure steady operation, and it is electromagnetic.

The method using stirring requires investment in equipment, which increases the equipment cost.

Utilization of γ→α transformation in (2) is not possible in the current extremely low coal region containing 1.5% or more of Sl.
Further, the method of rolling down the slab at the slab stage requires investment in equipment, and according to experiments conducted by the inventors, no effect was observed.

The strain energy introduced in the hot rough rolling stage (8) was released by the finish rolling due to the high temperature and was not accumulated.

The present invention advantageously solves the above-mentioned problems, and even in continuously cast slabs with a high columnar crystal content, the rolling end temperature and reduction amount in the finish rolling stage of hot rolling, as well as the subsequent By controlling the winding temperature in the winding process, it is possible to completely recrystallize elongated grains that are difficult to recrystallize in the subsequent annealing process of the hot-rolled sheet, and thus to eliminate product paste zinc. Based on new knowledge.

That is, in this invention, C: 0.1% or less, Sl: 1
．． 5 to 4.0% and Ae: 1.0% or less, a non-oriented silicon steel slab containing 1.0% or less is hot-rolled into a hot-rolled plate, and then wound into a -tan coil. In a method for producing a non-oriented silicon steel sheet, which consists of a series of steps of annealing, then cold rolling, and final finish annealing, hot finish rolling is performed, rolling end temperature = 800 to 700 ° C., final bath reduction rate: 15%. Under the above conditions, 500
A means for solving the above problem is to wind the film at a temperature range of 0.degree. C. or lower.

The present invention will be specifically explained below based on the experimental results that led to its origin.

First, the reason why the basic components of the silicon steel in this invention are limited to the above range will be described.

If C exceeds 0.02%, the decarburization process during final annealing will not only increase the load and reduce efficiency, but also cause deterioration of electromagnetic properties due to the oxide film formed during the decarburization process. It was limited to 0.2% or less.

Si increases the electrical resistance of the material and effectively contributes to reducing eddy current loss, but if the content is less than 1.5%, the effect is poor, while if the content exceeds 4.0%, it is difficult to cold process. The S1 content was limited to a range of 1.5% to 4.0% since the properties of the resin deteriorated.

AI is an element useful for developing a predetermined texture, but if the content exceeds 1.0%, it becomes brittle like 81, deteriorates cold workability, and also increases cost. Therefore, the Ae content was limited to 1% or less.

Now, the slab adjusted to the above component composition range has 1000
After heating at ~1200°C, hot rough rolling and finish rolling are performed to obtain the desired hot-rolled plate thickness. Furthermore, by controlling the subsequent winding temperature, strain energy is effectively stored in the material, which effectively acts as a driving force for recrystallization in the subsequent annealing step, thus achieving a ridging-free surface texture. It was discovered that a good product could be obtained, and this invention was completed. .

In FIG. 1, C: 0.005%, Si: 2. flO
% and AJ: A continuous cast slab containing 0.805% was hot-rolled after heating by changing the finish rolling end temperature and the final pass reduction rate in U, and then coiled at 450 °C and then rolled in a conventional manner. The results of investigating the surface properties of non-oriented silicon steel sheets obtained by annealing, cold rolling, and final annealing according to the above are summarized in terms of the relationship between hot finish rolling end temperature, J, and final pass reduction ratio. . The surface quality was evaluated as follows: (): No unevenness, peak height 0 to 7 μm
) 0: Small unevenness (crest height 8-l5tt7rl) Δ: Medium unevenness (crest height 16-25 μm) X: Large unevenness (crest height 26 μm or more) This b ((j+, ○ is a passed product.

11) As is clear from Figure 1, the temperature at the end of finish rolling! 1
(When the temperature exceeds 800"C, the occurrence of zinc is significant.
Further, even if the temperature is 800° C. or less, the rolling reduction in the final pass is less than 15%, the ridging is still not canceled. On the other hand, the finishing rolling temperature is 800"
(: If the final pass reduction rate is 15% or more,
There are almost no surface irregularities.

Next, Fig. 2 shows a continuously cast slab made of the same material as in Fig. 1, after heating, the final pass reduction rate of hot finish rolling was kept constant at 20%, and the finish rolling end temperature and coiling temperature were varied variously. The results of an investigation on the surface properties of the non-oriented silicon steel sheet produced in this manner are shown in terms of the relationship between finish rolling end temperature and coiling temperature.

As is clear from Fig. 2, the finishing rolling temperature is 80°C.
If the temperature exceeds 0°C, ridging will occur significantly, but even if the temperature is below 800°C, if the winding temperature exceeds 500°C, a recovery phenomenon will occur due to recuperation, and the strain energy accumulated in the plate will be transferred to the piece. The surface quality was poor because of the number of particles.

In all of the experiments that yielded the results shown in FIGS. 1 and 2, when the final rolling temperature was lower than 700° C., the sheet shape deteriorated.

For the above reasons, in this invention, the finishing temperature of hot finish rolling is 800 to 700°C, and the final pass reduction rate is 15%.
As mentioned above, the winding 1 temperature was limited to a range of 500°C or less.

Examples of the present invention will be described below.

(?: 0.005%, Si: 2.80%, A/
: 0.805%, Mn: O, 1.7%, P:
A molten ladle containing 0.015% and S: 0.001%, with the remainder being essentially iron, was made into a slab by continuous casting, and then slab-processed under various conditions shown in Structure 1. Convex, hot rough rolling, finish rolling, winding, and hot rolled plate annealing were performed in sequence, followed by cold rolling at a reduction rate of 76%, and final finish annealing over 1 m1 in a temperature range of 850 to (150 ° C.). A non-oriented silicon 3 < steel plate was manufactured by using t + i. Same as shown.

As is clear from the results shown in Table 1, it is clear from the comparative examples (slab seats 1 to B ), while ridging occurred in the products, Slab/164, 5 obtained according to the present invention did not have ridging and had a beautiful surface texture.

As described above, according to the present invention, it is possible to effectively prevent the generation of zinc, which was a concern in the past in non-oriented silicon steel sheets containing 1.5% or more of Sl, and to produce a product with a beautiful surface without unevenness. can be obtained.

[Brief explanation of drawings]

Figure 1 shows the effects of hot finish rolling end temperature and final pass rolling reduction on the occurrence of ridging, and Figure 2 shows the effects of hot finish rolling end temperature and coiling temperature on the occurrence of ridging. It is a diagram showing the influence. Figure 1 1 艷端ノ? X compression base c%) Fig. 2 Yoko Sarasumi five cliffs (τ) O unevenness QLC le I! lp: θ~ It's a cram school fun 0 uneven small immortal θ~! Hano Δ unevenness medium c mountain, 1!1 zel θ~? Zo2 x unevenness 'LC small 21ytHJJ (Oobaji #n

Claims (1)

[Claims] A slab for non-oriented silicon steel having a composition containing L C: 0.02% by weight or less, Si: 1.5 to 4.0% by weight or less, and Ag: 1.0% by weight or less. In producing a non-oriented silicon steel sheet, hot rolling is performed to produce a hot rolled sheet, which is then wound into a -tan coil and annealed, followed by cold rolling and final finish annealing. Finish rolling, rolling end temperature = 800 to 700°C, ii↓
Final pass rolling reduction: Performed under conditions of 15% or more, then 50%
A method for producing a non-oriented silicon steel sheet with good surface properties, characterized by winding at a temperature range of 0° C. or lower.