WO2012113184A1 - Non-oriented electric steel produced by thin slab continuously casting and rolling and producing method thereof - Google Patents

Abstract

A non-oriented electric steel comprises, in weight percentage, C≤0．008%，Si：0.15～2.2%，A1≤0.008%, Mn0.15～1.5%, P0.004～0.15%, S≤0.008%,［O］≤ 40 PPm, N≤0.005%, Ti≤0.008%, balance Fe and unavoidable impurities. A method for producing the non-oriented electrical steel is also provided, which comprises the following steps: smelting in converter and treating in vacuum, continuously casting into plate blank with thickness of 50-90mm, soaking in a tunnel furnace, continuously rolling with seven-roller mill, coiling, pickling, cold rolling, re-crystallization annealing and standby.

Description

 Non-oriented electrical steel produced by thin slab continuous casting and rolling and method thereof Technical field

The invention relates to non-oriented electrical steel and a production method thereof, and particularly relates to a cold-rolled non-oriented electrical steel with stable castability and excellent magnetic properties and a production method by thin slab continuous casting and rolling.

Background technique

Thin slab continuous casting and rolling production of non-oriented electrical steel has the characteristics of large energy saving, improved yield, shortened process flow, etc., greatly reducing production costs; thin slab continuous casting and rolling production of non-oriented electrical steel can achieve low temperature heating, high temperature end Rolling and high-temperature coiling, with the conditions of preparing magnetic non-oriented electrical steel; thin slab continuous casting and rolling soaking process can ensure uniform temperature during slab and rolling process, and obtain good shape-oriented non-oriented electrical steel. Compared with the conventional long process, the production of non-oriented electrical steel by thin slab continuous casting and rolling has obvious advantages.

However, the thin slab continuous casting and rolling slab has a narrow section and a high drawing speed, and there are inherent defects in the control of casting property and surface quality, especially for the non-oriented electrical steel with poor fluidity and thin product, which greatly limits the cold. Rolled non-oriented electrical steel sheets are stably produced in batches. Manufacturers of thin slab continuous casting and rolling at home and abroad generally reduce the Al ₂ O ₃ content in molten steel by calcium treatment (feeding silicon calcium wire or adding calcium alloy), improve its casting performance and achieve stable production. The implementation of the calcium treatment process increases the difficulty of production organization and greatly increases the cost. The calcium content in the molten steel needs to be strictly controlled to obtain calcium aluminate having a lower melting point, and the high-melting calcium aluminate is obtained by insufficient or excessive calcium treatment during the casting process. Block the nozzle and even stop pouring.

In addition, compared with the conventional process, the non-oriented electrical steel produced by thin slab continuous casting and rolling has different thermal history. In the high-temperature rolling process and the cooling process, the second phase such as AlN and MnS is easy to be finely dispersed, and the magnetic properties of the finished product are poor. Unstable. In the conventional long-flow process, the addition of Sn/Sb alloy elements can improve the texture of the finished board, and produce high-magnetic non-oriented electrical steel with less influence on iron loss, but greatly increase the cost of the alloy, and hot-rolled acid Difficult to wash. Hot-rolled sheet pre-annealing (normalization) can also obtain high-magnetic low-iron loss non-oriented electrical steel, but need to add regular equipment, greatly increasing the production cycle and cost. These measures are not suitable for the thin slab continuous casting and rolling process, and can not reflect the low cost advantages of the thin slab continuous casting and rolling process.

technical problem

The object of the present invention is to solve the problem that the current non-oriented electrical steel continuous casting process in the non-oriented electrical steel continuous casting process using the thin slab continuous casting and rolling is easy to block the nozzle and even the pouring, the magnetic property is poor and unstable, and the nozzle is provided during the continuous casting process. Cold-rolled non-oriented electrical steel and its method which are not easy to block, have high magnetic induction, low iron loss, stable magnetic properties, simple process, thin slab continuous casting and rolling production.

Technical solution

Technical measures to achieve the above objectives:

Non-oriented electrical steel produced by thin slab continuous casting and rolling, its chemical composition and weight percentage are: C: ≤ 0.008%, Si: 0.15 ~ 2.2%, Al: ≤ 0.008%, Mn: 0.15 to 1.5%, P: 0.004 to 0.15%, S: ≤0.008%, [O] ≤ 40 ppm, N: ≤0.005%, Ti: ≤0.008%, and the rest are Fe and unavoidable impurities.

It is characterized in that Al ≤ 0.005%.

A method for producing non-oriented electrical steel produced by thin slab continuous casting and rolling, the steps of which:

1) Performing converter smelting and vacuum treatment;

2) continuous casting into a slab of 50-90 mm thick, the casting speed is controlled at 3 to 5 m / min;

3) soaking in the tunnel furnace, the soaking temperature is controlled at 1000 ~ 1200 ° C;

4) Carrying out seven rolling mills for continuous rolling, controlling the final rolling temperature at 800-900 ° C;

5) winding, the coiling temperature is controlled to 650 ~ 800 ° C;

6) performing pickling;

7) performing cold rolling and controlling the total reduction ratio to be 50-85%;

8) performing recrystallization annealing, and the return temperature is controlled at 750 to 1000 ° C;

9) Standby.

It is characterized in that a conventional decarburization treatment is carried out when C>0.003%.

The design principle of the present invention is as follows:

The invention adopts ultra-low aluminum (Al≤0.008%) design on the composition, reasonably matches the content of Si and Mn of the main alloying elements, and minimizes the content of impurity elements S, N, O and Ti; the process does not need calcium treatment, Produce high-magnetic low-iron loss cold-rolled non-oriented electrical steel sheets.

The composition is based on the following design:

C: C ≤ 0.008%, the lower the C, the better, when C> 0.008%, it is necessary to prolong the decarburization time and affect the continuous annealing efficiency.

Si: 0.15% ≤ Si ≤ 2.2%, Si is the main element for increasing the resistivity, and is the most important alloying element for reducing iron loss. Si element is also significantly reduced in the γ phase region element, and more than 2.2% Si is not in the rolling process. After undergoing a phase change or only a partial phase change, the columnar crystals in the slab are difficult to refine, and the finished product has corrugated defects.

Al: Al ≤ 0.008%, and the lower the aluminum content, the better. The non-aluminum steel can avoid the formation of Al2O3, which leads to the interruption of the nozzle plugging and pouring, and achieves stable mass production. In addition, in the aluminum-free non-oriented electrical steel, the residual traces of Al and N are in a solid solution state, and it is difficult to form a fine AlN second phase, which can improve the hot-rolled microstructure and texture, promote the growth of the finished grain, and improve the magnetic properties of the iron. damage.

Mn: Mn is an alloy element that significantly enlarges the γ phase region and has little effect on magnetism. The proper content of Mn can play a role in sulfur fixation and improve hot rolling ductility. When the content exceeds 1.5%, the rolling load is increased to affect the shape of the plate.

P: P: 0.004 to 0.15%, Adding an appropriate amount of P can replace part of Si to reduce iron loss. Adding an appropriate amount of P in low-silicon non-oriented electrical steel can also improve the sheeting performance of the finished product, but when it is higher than 0.15%, the brittleness of the steel strip during cold rolling and annealing increases.

O: [O] ≤ 40ppm, [O] The lower the better, the higher than 40ppm is easy to form a large amount of oxide inclusions, the slab is easy to generate bubbles, affecting the surface quality and magnetic properties of the finished product.

S ≤ 0.008%, N ≤ 0.005%, and the lower the content of the S and N impurity elements, the better.

The invention adopts the process characteristics of producing non-oriented electrical steel by thin slab continuous casting and rolling:

1) The soaking temperature of the tunnel furnace is 1000-1200 ° C, lower than 1000 ° C, the hot rolling process temperature is low, recrystallization is insufficient, and corrugated defects are prone to occur. Above 1200 ° C, the precipitated MnS second phase is re-dissolved, and finely dispersed during the subsequent rolling process, hindering grain growth and increasing iron loss.

2) High-temperature finish rolling and high-temperature coiling, improve hot-rolled structure, improve magnetic properties, final rolling temperature of 800-900 ° C, coiling temperature of 650-800 ° C, but not too high, so as not to cause pickling difficulties.

3) Recrystallization annealing, annealing temperature 750 ~ 1000 ° C, temperature below 750 ° C, recrystallization is insufficient, high iron loss. Above 1000 ° C, the magnetic induction is low.

Beneficial effect

The alloy of the invention has reasonable design, no need of calcium treatment, low aluminum content, simple production process and low cost, and the water nozzle is not easy to block during the continuous casting process, and can effectively solve the shortcomings of poor casting cast of continuous thin slab continuous casting and rolling, and prepare high magnetic The low-iron loss cold-rolled non-oriented electrical steel fully reflects the advantages of cost and magnetic properties of non-oriented electrical steel for thin slab continuous casting and rolling, and greatly improves the market competitiveness of the product.

Embodiments of the invention

The following is a detailed description in tabular form:

Non-oriented electrical steel produced by thin slab continuous casting and rolling, the following examples have chemical compositions and weight percentages: C: ≤ 0.008%, Si: 0.15 - 2.2%, Al: ≤0.008%, Mn: 0.15 to 1.5%, P: 0.004 to 0.15%, S: ≤0.008%, [O] ≤40 ppm, N: ≤0.005%, Ti: ≤0.008% value; process and process parameters take the following steps and ranges:

A method for producing non-oriented electrical steel produced by thin slab continuous casting and rolling, the steps of which:

1) Performing converter smelting and vacuum treatment;

2) continuous casting into a slab of 50-90 mm thick, the casting speed is controlled at 3 to 5 m / min;

3) soaking in the tunnel furnace, the soaking temperature is controlled at 1000 ~ 1200 ° C;

4) Carrying out seven rolling mills for continuous rolling, controlling the final rolling temperature at 800-900 ° C;

5) winding, the coiling temperature is controlled to 650 ~ 800 ° C;

6) performing pickling;

7) performing cold rolling and controlling the total reduction ratio to be 50-85%;

8) performing recrystallization annealing, and the return temperature is controlled at 750 to 1000 ° C;

9) Standby.

When C > 0.003%, a conventional decarburization treatment was carried out.

Table 1 is a table of chemical composition values of the examples and comparative examples of the present invention; Table 2 is a process parameter of the examples and comparative examples of the present invention; Table 3 is a statistical table of experimental performance results of the examples and comparative examples of the present invention. Among them, Examples 1-10 and Comparative Examples 1-4 were carried out by a thin slab continuous casting and rolling process, and Comparative Examples 5-8 were carried out by a conventional long process.

Table 1:

Table 2:

table 3:

Industrial applicability

It can be seen from Table 3 that compared with the comparative example, the present invention has lower control of the aluminum content, and not only the production cost is lowered, but also the magnetic induction intensity B _{5000 is} 0.025T to 0.038T higher than that under the condition of producing silicon content. The core loss P _{1.5/50 is} 0.4 to _1.3 w/kg lower and has good casting stability.

Claims (4)

 1. Non-oriented electrical steel produced by thin slab continuous casting and rolling, its chemical composition and weight percentage are: C: ≤ 0.008%, Si: 0.15 ~ 2.2%, Al: ≤0.008%, Mn: 0.15 to 1.5%, P: 0.004 to 0.15%, S: ≤0.008%, [O] ≤40 ppm, N: ≤0.005%, Ti: ≤0.008%, and the rest are Fe and unavoidable impurities.

2. A non-oriented electrical steel produced by thin slab continuous casting and rolling according to claim 1, wherein Al ≤ 0.005%.

3. A method of producing non-oriented electrical steel produced by thin slab continuous casting and rolling according to claim 1, the steps of:

1) Performing converter smelting and vacuum treatment;

2) continuous casting into a slab of 50-90 mm thick, the casting speed is controlled at 3 to 5 m / min;

3) soaking in the tunnel furnace, the soaking temperature is controlled at 1000 ~ 1200 ° C;

4) Carrying out seven rolling mills for continuous rolling, controlling the final rolling temperature at 800-900 ° C;

5) winding, the coiling temperature is controlled to 650 ~ 800 ° C;

6) performing pickling;

7) performing cold rolling and controlling the total reduction ratio to be 50-85%;

8) performing recrystallization annealing, and the return temperature is controlled at 750 to 1000 ° C;

9) Standby.

A method of producing non-oriented electrical steel produced by thin slab continuous casting and rolling according to claim 3, wherein a conventional decarburization treatment is carried out when C > 0.003%.