RU2529326C1 - Production method of cold-rolled semi-finished alloy electric steel - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: there performed are steel making, pouring, hot rolling, water cooling, strip rolling, etching, cold rolling and processing in a continuous multiple unit installation, steel containing the following components is molten, wt %: carbon 0.020-0.045, silicon 0.50-2.10, manganese 0.10-0.80, sulphur maximum 0.015, phosphorum maximum 0.015, chromium maximum 0.10, nickel maximum 0.15, copper maximum 0.15, aluminium 0.10-0.60, nitrogen 0.002-0.010, iron and unavoidable impurities making the rest; final deformation of a strip in a finishing mill group of a continuous wide-strip mill is carried out under the temperature of process workpiece input - maximum 1070°C, rolling end temperature is kept at the level of 780-880°C, accelerated cooling is performed at the rate of 20-45°C/s, reeling temperature is set at the level of 480-640°C, recrystallisation annealing of cold-rolled mill products in the continuous multiple unit installation is carried out with partial decarbonisation up to the carbon content of 0.012-0.030%, under the temperature of 780-820°C, afterwards tempering of steel is performed under the temperature of 450-600°C for 150-250 seconds. Metal killing with cobbing of 0.5-5% follows the thermal treatment of the cold-rolled mill products if necessary.

EFFECT: higher quality of rolled metal due to the achievement of stable mechanical properties with full compliance with requirements to magnetic properties.

2 cl, 3 tbl

Description

The invention relates to the field of metallurgy, specifically to the production technology of cold-rolled semi-finished alloyed electrical isotropic steel with improved mechanical and magnetic properties, intended for the manufacture of magnetic circuit parts, namely the stator and rotor of an electric motor, by the method of high-speed stamping, assembly and annealing of packages.

One of the defining qualities of semi-finished electrical steel is its ability to stamp into plates without failures at high speeds of stamps up to 300 or more beats per minute, while on the manufactured plates there should be no burr and other edge defects. Semi-finished electrical steel must meet a certain set of mechanical properties, for example, Baranovichi Machine Tool Plant (a company manufacturing compressors for refrigerators) using M450-50K steel in accordance with EN 10341, in order to ensure the steel's ability to stamp at high speeds without creating defects, makes the requirements indicated in table 1:

Table 1 steel grade Hardness HV, units, not less Strength σ _in , N / mm ² , not less than Elongation δ,% The ratio of yield strength to ultimate strength (recommended value) Specific magnetic losses at 1.5 T (50 Hz), W / kg, no more M450-50K 148 420 2032 0.80-0.86 4,5

A known method for the production of semi-finished electrical steel, including hot rolling of a steel slab, annealing a hot rolled strip, cold rolling and annealing a cold rolled strip, according to which the holding temperature during annealing of a hot rolled strip containing wt.%: 0.2-2.6 silicon; 0.01-0.5 aluminum; no more than 0.05 carbon; 0.1-1.5 manganese; 0.01-0.16 phosphorus; not more than 0.01 sulfur is established according to:

TV = 911 + K × (Si-Mn), ° C

where Tv is the holding temperature during annealing of the hot rolled strip, ° C;

911 - the temperature of the phase transformation of perlite to austenite in pure iron, ° C;

Si — silicon content in steel, wt.%;

Mn — manganese content in steel, wt.%;

K is an empirical coefficient that takes into account the effect of the content of silicon and manganese in steel on the temperature of the phase transformation of perlite to austenite, equal to (10-20) ° C /%,

holding at this temperature is carried out for 80-200 s, and annealing of cold-rolled steel strips is carried out at a temperature of 780-850 ° C with decarburization of the metal to a carbon content of ≤0.010%. If necessary, after decarburization annealing of the cold-rolled strip, training is performed with compression of 1.0-7.0% (RF Patent No. 2180925, IPC C21D 8/12, publ. March 27, 2002).

The disadvantage of this method is the decarburization of steel to a carbon content of ≤0.010%, which can lead to heterogeneity in the carbon content and structure of the finished metal, the electromagnetic properties of the steel deteriorate. Also, metal processing by a known method leads to an increase in the cost of production, since after hot rolling before etching, it is necessary to carry out processing in a separate unit (annealing of a hot-rolled strip in a continuous furnace).

The closest in technical essence is the method of producing cold rolled semi-finished electrical steel, including hot rolling of steel deoxidized slab, cold rolling and annealing of cold rolled strip, according to which annealing of cold rolled steel containing, wt.%: 0.01-1.6 silicon; 0.02-0.5 aluminum; not more than 0.07 carbon; 0.1-1.5 manganese; 0.01-0.20 phosphorus; not more than 0.025 sulfur is produced in a protective gas atmosphere for 5.5-11 minutes at a temperature in accordance with the ratio t = K1 + K2 × Si ± 20 ° C,

where t is the annealing temperature of steel, ° C;

K1, K2 - experimentally determined coefficients: K1 = 600 ° C; K2 = 100 ° C /%;

Si is the silicon content in steel, wt.%.

If necessary, after annealing of cold rolled steel, metal is trained with compression of 2-8% (RF Patent No. 2178006, IPC C21D 8/12, publ. 10.01.2002).

The disadvantage of this method is that the finished metal may have: internal structural stresses due to a single annealing after cold rolling, the heterogeneity of the ferrite grains. This does not provide mechanical properties at the finished product, which stably guaranteed a high speed of the dies without interruptions in supply, as well as the absence of burrs and other edge defects on the manufactured plates.

The technical result of the invention is to improve the quality of rolled products by obtaining stable mechanical properties that can guarantee a high speed of dies in the manufacture of blanks (stator and rotor plates), as well as the absence of edge and burr defects after stamping, while fully preserving the requirements for magnetic properties.

The technical result is achieved by the fact that in a method for the production of cold rolled semi-processed alloyed electrical steel, including steel smelting, casting, hot rolling, water cooling, strip winding, pickling, cold rolling and processing in a continuous combined unit, according to the invention, steel containing mas .%: 0.020-0.045 carbon, 0.5-2.10 silicon, 0.10-0.80 manganese, not more than 0.015 sulfur, not more than 0.15 phosphorus, not more than 0.10 chromium, not more than 0.15 nickel, not more than 0.15 copper, 0.10-0.60 aluminum, 0.002-0.010 nitrogen, ost iron and inevitable impurities, the final deformation of the strip in the finishing group of a continuous broadband mill is carried out at the temperature of the roll inlet - not more than 1070 ° C, the temperature of the end of rolling is maintained at 780-880 ° C, accelerated cooling with water is carried out at a speed of 20-45 ° C / s , the winding temperature is set to 480-640 ° C, the recrystallization annealing of cold-rolled steel in a continuous combined unit is carried out with partial decarburization, to a carbon content of 0.012-0.030% with a temperature of 780-820 ° C, after which vacation is carried out with t mperaturoy 450-600 ° C for 150-250 seconds. If necessary, after heat treatment of cold-rolled steel, training is carried out with a compression of 0.5-5%.

The invention consists in the following. The mechanical and magnetic properties of semi-processed alloyed electrical steel are affected by both the chemical composition of the steel and the modes of deformation-heat treatment at the hot rolling mill, the mode of recrystallization annealing, the possibility of decarburization and tempering of steel.

Carbon is one of the reinforcing elements that determines the final structure of steel in its production without decarburization. When the carbon content is less than 0.020%, the strength properties of steel are below an acceptable level, just as steel has high heterogeneity, heterogeneity, stamping of steel with high speed stamps (number of strokes up to 300 beats per minute) is impossible. An increase in carbon content of more than 0.045% leads to a strong decrease in the ductility of steel, an excessive increase in strength, which is unacceptable.

Silicon in steel is used as an alloying element that determines magnetic and mechanical properties. When the silicon content is less than 0.50%, the steel is ductile, during stamping, burrs can form on the products, a low silicon content leads to an increase in electromagnetic losses. When the silicon content in the steel is more than 2.10%, ductility decreases, steel embrittlement occurs, and this silicon content also leads to a decrease in magnetic induction.

Manganese is introduced into steel in order to bind sulfur and provide the desired mechanical properties of rolled products. If the manganese content is less than 0.10% during hot rolling, edge defects may occur. An increase in the manganese content of more than 0.80% excessively strengthens the steel, worsens its ductility.

Aluminum is introduced into steel as an alloying element that provides nitrogen bonding and determines magnetic and mechanical properties. If the aluminum content is less than 0.10%, unbound nitrogen may remain in the ferrite solution, which negatively affects the magnetic properties, and the steel may become prone to aging. An increase in the aluminum content of more than 0.60% leads to contamination of the steel with non-metallic inclusions and a decrease in magnetic induction.

Sulfur adversely affects the magnetic properties of steel, and can also lead to edge defects during hot rolling. Therefore, its content is limited - not more than 0.015%.

Chromium, nickel, and copper as a whole at high contents can cause deterioration of the electromagnetic properties of steel: an increase in specific electromagnetic losses, a decrease in magnetic induction. The content of these elements is limited to chrome - not more than 0.10; nickel - not more than 0.15%; copper - not more than 0.15%.

Phosphorus is added to steel as an alloying element. The increased phosphorus content favorably affects the mechanical and magnetic properties: the strength of steel increases, the ratio of yield strength to tensile strength increases, elongation decreases, the level of electromagnetic losses decreases, and magnetic induction increases. The phosphorus content is limited - not more than 0.15%, since its increase above this value can lead to excessive embrittlement of steel.

Hot rolling with a rolling start temperature in the finishing group of stands of not more than 1070 ° C and subsequent finishing rolling at a rolling end temperature of 780-880 ° C / s, cooling of the strip on the discharge roller at a speed of 20-45 ° C / s, winding of the strip into a roll with a temperature of 480-640 ° C provide the formation of an optimal microstructure with high stability and uniformity of grains, this structure is preserved (inherited) even after cold rolling and annealing (provided that the annealing is accompanied by a partial decarburization operation and I). The technical result was not achieved above the stated temperature limits, namely, steel acquired a structure with a high heterogeneity by the heterogeneity of ferrite grains, which was unfavorable for stamping and did not provide the required magnetic properties.

Carrying out recrystallization annealing with partial decarburization, to a carbon content of 0.012-0.030%, at a temperature of 780-820 ° C, followed by tempering at a temperature of 450-550 ° C for 150-250 seconds, provides a fine-grained fully recrystallized structure, the ferrite grain is not less than 7 points, the inherited structure of hot-rolled steel, with the absence of internal stresses. This structure provides the required values of the mechanical properties listed in table 1, while maintaining the required magnetic properties of steel. The complex of these mechanical properties ensures a high speed of the dies during the manufacture of blanks (stator and rotor plates), as well as the absence of edge and burr defects after stamping.

If necessary, after heat treatment of cold-rolled steel, training is carried out with a compression of 0.5-5%. Training is carried out in order to give the rolled product the required roughness in order to prevent possible adhesion of the plates during annealing at the consumer. Compression within the selected limits leads to the optimal formation of the size of the micrograin during annealing of the metal at the consumer, after the manufacture of the magnetic circuit.

Examples of the method. In the oxygen converter, 4 pilot melts were smelted, the chemical composition of which is shown in Table 2 (including steel grade M450-50E).

table 2 The chemical composition of experimental swimming trunks Composition number C% Si,% Mn,% P% Cr,% S,% Ni,% Cu,% Al,% N% one 0,026 1,57 0.223 0.056 0.024 0.0029 0.019 0,026 0.37 0.006 2 0,031 1,56 0.28 0,053 0,037 0.006 0.02 0,039 0.45 0.005 3 0,040 1,54 0.291 0.051 0,038 0.003 0,025 0.058 0.4 0.004 four 0,033 1,54 0.249 0.058 0,046 0.0033 0,035 0,061 0.44 0.006

Cast iron used for the production of this steel was pretreated at a desulfurization unit to ensure that the steel had a sulfur content of not more than 0.015%. Smelted steel was cast on a continuous casting machine into slabs with a cross section of 250 × 1070 mm. The slabs were heated in a heating furnace with walking beams to a temperature of 1200-1250 ° C for 2.5-3.5 hours and rolled on a continuous broadband mill 2000 in strips 2.0 mm thick. Hot rolled strips on the discharge roller table were cooled with water to certain temperatures and wound into rolls. The cooled rolls were subjected to sulfuric acid pickling in a continuous pickling unit and dressing in a bending-stretching machine. Then, the etched strips were rolled on a 5 stand mill to a final thickness of 0.5 mm. Cold rolled coils were processed on a continuous combination unit.

The deformation-thermal processing conditions and the properties of the rental are presented in table 3.

From tables 2-3 it is seen that in the case of implementing the proposed method (options No. 1-No. 4 mode a), the mechanical properties of rolled products are achieved, which are characterized by the further ability of the steel to be processed (stamping, cutting) at high speeds of the stamp.

In the case of transcendental values of the declared parameters (option No. 4 mode c), as well as in the implementation of the known method (option No. 4 mode b), it was not possible to obtain a technical result due to the low ratio of yield strength to tensile strength.

The proposed technology for the production of cold-rolled semi-processed alloyed electrical steel also ensures the absence of edge defects and burrs on manufactured products after the stamping (punching) operation.

Table 3 Technological parameters of production and indicators of mechanical properties Composition number The temperature of the start of rolling in the finishing group of stands TNP, ° C The temperature of the end of rolling Tkp, ° C Cooling rate at the discharge roller table, ° C Winding temperature Tcm, ° C Annealing temperature, ° C Temp. ° C Compression during training,% Strength σ _B , N / mm ² σ _T / σ _B Elongation δ,% Hardness, hv Specific magnetic losses at 1.5 T (50 Hz), W / kg one 957 820 25 600 790 580 500 0.80 26 156 4.1 2 961 841 31 603 780 540 1,5 530 0.86 28 167 3.8 3 985 835 32 601 785 460 540 0.81 27 170 4.2 4 mode a 964 846 28 596 795 510 530 0.85 25 160 4.1 4 mode b 970 832 thirty 610 754 without decarburization without vacation 580 0.75 26 171 4.2 4 mode in 970 836 29th 603 795 without decarburization without vacation 570 0.76 28 168 4.1

Claims (2)

1. Method for the production of cold rolled semi-processed alloyed electrical steel, including steel smelting, casting, hot rolling, water cooling, winding strips into coils, pickling, cold rolling and heat treatment in a continuous combined unit, characterized in that the steel containing components in the following is smelted ratio, wt.%:
carbon 0,020-0,045 silicon 0.50-2.10 manganese 0.10-0.80 sulfur no more than 0.015 phosphorus no more than 0.015 chromium no more than 0.10 nickel no more than 0,15 copper no more than 0,15 aluminum 0.10-0.60 nitrogen 0.002-0.010 iron and inevitable impurities rest,
in this case, the final deformation of the strip in the finishing group of the continuous broadband mill is carried out at an inlet temperature of the roll no more than 1070 ° C, the temperature of the end of rolling is maintained at 780-880 ° C, accelerated cooling is carried out at a speed of 20-45 ° C / s, the temperature of the strip winding into rolls set 480-640 ° C, conduct recrystallization annealing of cold rolled steel with a temperature of 780-820 ° C in a continuous combined unit with partial decarburization to a carbon content of 0.012-0.030%, after which steel is tempered at a temperature of 450-600 ° C for 150-250 seconds. 2. The method according to claim 1, characterized in that after the heat treatment of the cold rolled metal, metal training is performed with a compression of 0.5-5%.