JPS6086211A - Continuous annealing process for non-directional electromagnetic steel plate - Google Patents

Abstract

PURPOSE:To prevent generation of a surfacial scar completely on cold-rolled steel by specifying the dew point and temperature of an atmospheric gas in a furnace and at the same time, specifying a tension of steel plate passing through the furnace when it is finally annealed in a vertical-type continuous annealing furnace. CONSTITUTION:After hot-rolling a slab for non-directional electromagnetic steel plate, the hot-rolled slab is cold-rolled into steel plate finally through one-or two- cold roll process in addition to an intermediate annealing process carried out in between. Then when final annealing process is applied, a vertical-type continuous annealing furnace is used as an annealing furnace and it is arranged so that the dew point dp and temperature T of an atmospheric gas in the furnace may meet the formula dp( deg.C)<=5.74X10<4>.1/T61 and T(K)>=973 and the tension of steel of steel plate when running through the furnace be equivalent to less than 1.2kg/mm.<2>. Thus it is possible to prevent generation of a surfacial scar on a finished product such as pickup and improve its quality.

Description

[Detailed description of the invention] This invention includes a non-oriented electrical steel sheet (including a copper strip).

Regarding the continuous annealing method (the same applies hereinafter), this is an advantageous annealing method that does not cause surface defects such as pick-up even when a vertical continuous annealing furnace is used as the annealing furnace and is operated at high efficiency. We propose that J:5.

Now, non-oriented electrical steel sheets are produced by cold-rolling a hot-rolled sheet once or twice with an intermediate annealing to achieve the final thickness, and then final annealing. By causing growth, certain electromagnetic properties are imparted.

By the way, final annealing of such electrical steel sheets has conventionally been generally performed in a horizontal continuous annealing furnace.

In this horizontal series U1; the contact pressure between the strip and the hearth roll is small due to its structure, so even if the operation is carried out in an atmosphere where 5102, Ae20s, etc. are generated, the product surface will not deteriorate. Almost never occurred. However, in the case of horizontal furnaces, the operational efficiency is controlled by the furnace manager, so in order to achieve high efficiency, a long furnace is required, which requires the occupation of a vast area, and is disadvantageous because it leads to a rise in construction costs. was there.

In this regard, vertical continuous annealing furnaces that process general cold-rolled steel sheets and plastic plates, which have recently become popular under names such as CAL,
Since it is a loop-type pass line, the effective pass line is long, and therefore, it can be operated at higher efficiency compared to the case of processing electrical steel sheets (even in the case of processing in a conventional horizontal continuous annealing furnace. However, since the contact pressure between the hearth roll and the IJ tube in the furnace is large, this vertical continuous annealing furnace is more likely to produce pick-up scratches than a horizontal furnace. In vertical continuous annealing furnaces, which are used for multiple purposes mainly for making plastic plates, from the viewpoint of operating costs and operability, there remains a problem in that H2 in the furnace is likely to occur. Atmosphere is usually 7%
However, when an electromagnetic steel sheet containing Sl or Sl or Ae is processed in a vertical continuous annealing furnace in such an atmosphere, 5iO8, A+!
Oxides such as '208 adhered to the hearth rolls in the furnace, and as mentioned above, the contact pressure between the rolls and the strip was high, so these oxides were easily transferred to the steel plate, resulting in uneven defects called pickups. It is.

Therefore, the inventors have attempted to prevent the occurrence of such surface defects.
After extensive research, we found that the occurrence of pick-up has a strong correlation with the atmospheric gas temperature and dew point in the annealing furnace, as well as the tension in the furnace during the threading of the steel plate, and that pick-up can be prevented by appropriately controlling these factors. They discovered that it is possible to completely prevent the occurrence of this phenomenon, and have completed this invention.

・In other words, this invention involves a series of steps in which a slab for a non-oriented electrical steel sheet is hot-rolled, then cold-rolled once or twice with intermediate annealing to achieve the final thickness, and then final annealed. In a method for producing a non-oriented electrical steel sheet, which consists of a process, a vertical continuous annealing furnace is used as an annealing furnace when final annealing is performed on a cold-rolled steel sheet, and the dew point (dp) and temperature of the atmospheric gas in the furnace are (T) is the following formula (11, (2), d
p ('C)≦5.74xlO'・1/T -61・・
・(1) T (K)≧978 ... (2) is satisfied, and the tension when passing through the furnace is 1.2 kVm
This is a continuous annealing method for a non-oriented electrical steel sheet, characterized in that annealing is performed under conditions such that the temperature is less than m2.

This invention will be specifically explained below based on the experimental results that led to this invention.

FIG. 1 summarizes the results of an investigation into the effects of the temperature and dew point of the furnace atmosphere gas on the occurrence of pickup in the final annealing of non-oriented electrical steel sheets using a vertical continuous annealing furnace.

The experiment was conducted as follows. Table 1 Below: Several types of steel slabs with the composition shown in Table 1 (wt%) are 2.137y177
1, and then cold rolled once to a plate thickness of 0.
A cold-rolled sheet of 49-Q and 51 mm was prepared.

Then, these cold-rolled sheets were heated to a furnace temperature of 700 to 800°C.
Further, continuous annealing was performed under various conditions in which the dew point of the atmospheric gas was varied from θ to −10° C., and the surface properties of the steel sheets on the exit side of the annealing furnace were observed. The soaking time in the above continuous annealing was 1 minute in each case, and the tension during passing through the furnace was 0.95 to 1.05 k$.

From the results shown in FIG. 1, it can be seen that the occurrence of the pickup can be prevented by controlling the atmospheric gas dew point according to the atmospheric temperature in the furnace. Therefore, when we looked for a relationship between the two that can completely prevent the occurrence of pickup, we derived the following equation.

dp (℃)≦5,74x l Q'・1/T-61・
... (1) Here, dp ('C): Dew point of the surrounding gas inside the furnace T (K): Temperature of the atmospheric gas inside the furnace Even if the condition of the above formula (1) is satisfied If the furnace atmosphere gas temperature T is less than 978K, recrystallization and grain growth in the final annealing will be insufficient, so T
was limited to the range of the following formula (2) % formula % (2).

Next, FIG. 2 shows the results of an investigation into the effect of tension on the surface properties of the steel sheet when the steel sheet is passed through the furnace. The experiment was conducted on a cold-rolled steel plate (thickness 0.50 mm) whose composition satisfies the composition range of Clothing 1 above, with a soaking zone furnace temperature, atmospheric gas dew point, and soaking time of 800°C, respectively.
Annealing was carried out at a constant temperature of -8° C. and 1 min, and only the tension in the furnace was changed as needed, and an evaluation was made based on the tonnage processed until pickup occurred.

As is clear from the figure, the tension when passing through the furnace is t
, 2okV2 or less, no pick-up occurred even when processing 200 tons or more, whereas when the furnace tension exceeded 1.20kVrnrn2, the amount that could be processed decreased rapidly, and in the case of 1.25ki2. Pick-up occurred even after processing only about 50m tons.

Therefore, in this invention, the tension during passing the cold rolled steel sheet through the furnace is limited to a range of 1.20 kg/mm2 or less.

Examples of the present invention will be described below.

Example lc: o, oos%, Si: 0.64%, Mn
: 0.29%, P: 0.028%, S: 0.
005% and Al? : A slab having a component composition of 0.261% was hot rolled to a thickness of 2.8 mm, and then cold rolled to a cold rolled plate of 0.50 mm. The obtained cold-rolled sheet was then heated to a furnace temperature of -810°C and an atmospheric gas dew point of 10°C.
℃, soaking time = 1nlins and furnace lining 1.1
Final annealing was performed successively under conditions of 5 fit-z.

In such continuous annealing treatment, no pickup was observed in the annealed plate even when the throughput exceeded 250 tons.

Example 2 C: 0. (105%, Si: 1.05%, Mn:
0.31%, P: 0.018%, S: 0.00
5% and Ali! : A slab having a component composition of 0.282% was hot-rolled to a thickness of 2.0 mm, and then cold-rolled into a cold-rolled sheet of o, 5 o@m. Then, the obtained cold-rolled sheet was heated to a furnace temperature of 820'C1 and an atmospheric gas dew point of 12°C.
, soaking time: 1 min and furnace tension 1.00”
Final annealing was performed continuously under the conditions of 9/, rn2.

In such continuous annealing treatment, no pickup was observed in the annealed plate even when the throughput exceeded 200 tons.

As described above, according to the present invention, even if the final annealing of a non-oriented electrical steel sheet is performed with high efficiency using a vertical continuous annealing furnace, surface defects such as pick-ups occur. can be completely prevented, thus improving product quality.”
useful for.

[Brief explanation of drawings]

Figure 1 shows the influence of the temperature and dew point of the atmosphere gas in the furnace in a vertical continuous annealing furnace on the occurrence of pick-up, and Figure 2 shows the effects of tension during continuous annealing and passing the steel plate through the furnace. It is a graph showing the relationship with the amount of processing until pickup occurs. Patent Applicant Kawasaki Steel Co., Ltd. Figure 1

Claims (1)

[Claims] 1. A slab for non-oriented electrical steel sheet is hot rolled, and then 1.
In the manufacturing method of non-oriented electrical steel sheet, which consists of a series of steps of cold rolling twice or intermediate annealing and two times of dulling to achieve the final thickness, and then final annealing, the cold rolled steel sheet is subjected to final annealing. In performing this, a vertical continuous annealing furnace is used as the annealing furnace, and the dew point (dp) of the atmospheric gas in the furnace and the diopter (T) are expressed by the following equations (1), (2), do(' C)≦
5.74XIQ'・'/T-61...(1)T(K)
≧978 Continuous annealing of non-oriented electrical steel sheets satisfying (2) and annealing under conditions such that the tension during passing through the furnace is 1,2 vertical-2 or less.*e Processing method.