CS197209B2 - Method of production of the steel sheet metal with the low contents of carbon - Google Patents

Abstract

1393175 Making steel sheet; altering physical Structure USS ENGS & CONSULTANTS Inc 14 April 1972 [23 April 1971] 17391/72 Headings B3A and B3V Sheet of plain low carbon steel for magnetic applications and of thickness 0À05-0À10 inch is made by hot rolling, finishing at 900-1200‹ F. and, preferably being at 1430-1620‹ F. when the thickness is one inch, coiling at 900-1200‹ F., cleaning, cold rolling with a reduction of 40-80%, annealing at 1125-1300‹ F. and temper rolling with an elongation of 6-10%. After hot rolling the sheet is cooled by water sprays, coiled, pickled and cold rolled. Box annealing follows at 1125-1300‹ F. for 3À30 hours in a nitrogen atmosphere containing 10% hydrogen, before temper rolling. Test strips were cut and annealed for one hour at 1450‹ F. The steel may include, by weight per cent: c 0À1 max, e.g. 0À07 Mm 0À4-0À6, e.g. 0À57 P 0À02-0À09, e.g. 0À06 S 0À025 max, e.g. 0À021 Si 0À01 max, e.g. 0À003 Cu 0À01 Ni 0À01 Cr 0À02 Mo 0À01 Sn 0À006.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a low carbon steel sheet for articles having magnetic properties, in which the steel is hot rolled into a sheet having a thickness of 0.127 to 0.25-4 cm at a temperature of 2.54 cm, and at a temperature of 176.6 ° to 882 ° C when finishing sheet rolling and at 482.2 ° to 649 ° C when the sheet is rolled into coils, and in which the steel is cleaned, cold rolled to reduce the thickness to 40 to 80% and calcined to achieve recrystallization.

Because of its perfect magnetic properties, silicon steel sheet has wide application in the manufacture of magnetic components in electrical equipment such as motors, generators, transformers and the like. These advantageous magnetic properties, in particular high magnetic permeability, high electrical resistance and low hysteresis losses reduce the losses caused by the conversion of electrical energy to heat to a minimum and therefore allow the production of electrical devices of greater power and efficiency. In order to achieve and optimize the desired magnetic properties, the silicon steel sheet must be manufactured with carefully controlled and accurate manufacturing parameters. Silicon steel sheet is therefore considerably more expensive than other conventional flat-rolled steel products.

In the high volume production of small electrical appliances, toys and the like, the most important aspect is the cost per unit, far outweighing efficiency and performance. For these applications, electrical equipment manufacturers use the most inexpensive conventional low carbon steel sheets for magnetic circuit components. Therefore, this steel is the most important in the low carbon steel sheet market because it has acceptable magnetic properties for use on magnetic circuits.

In the production of low-carbon steel sheets for magnetic applications, economic considerations suggest that costly processing processes must be avoided and that even inexpensive processes must be reduced. Therefore, although these sophisticated processes have evolved from the production of low carbon steel sheet having exceptional magnetic properties, these processes are not elaborated commercially because the use of such processes increases the cost of the product while not improving the magnetic properties of the resulting sheet compared to such silicon. sheet metal having a comparable production price. In terms of measurement, any new method for improving the magnetic properties of low carbon steel sheets must be such that it does not increase the cost of the steel product too much. Thus, commercially low carbon steel sheet for magnetic applications is made from ordinary low carbon steel having less than 0.1 wt% carbon and the usual residual elements in normal amounts for cold rolled products. used for other cold rolled products. The manufacturing steps are typically intended for hot rolling low carbon ingots into plates; hot rolling of sheet metal plates; hot-pickled sheet pickling, cold pickled sheet rolling to reduce the thickness to 40 to 80%; annealing the steel to achieve recrystallization, usually in a chamber annealing furnace. The resulting final cold rolling at a thickness reduction of 0.5 to 2% to cure the sheet surface is sometimes used to roll the resulting sheet and is suitable for subsequent sheet shearing and stamping. In order to optimize the flatness of the surface and thus the suitability for cutting and stamping, the elongation during cold rolling must be minimized to 0.5 to 2%.

Commercially produced low carbon steel sheet for magnetic use is rolled to a thickness of 0.47 mm, has a permeability in the rolling direction of 5000 to 6000 at 1.0 T, core losses of 2.87 to 3.53 W / kg. For the same thickness at 1.5 T, the penetration in the rolling direction ranges from 2000 to 4000 with core losses of 6.64 to 8.84 W / kg. The 0.625 mm thick sheet has a permeability in the rolling direction of 4200 to 4800, a core loss of 3.97 to 4.41 W / kg at 1.0 T, or a permeability in the rolling direction of 2000 to 3000, a core loss of 9.26 to 10.6 W / kg at 1.5 T.

This relatively wide range in magnetic properties shows an established tendency in some industries not to emphasize the magnetic properties of a low carbon steel sheet, but to emphasize the low cost of the product. However, in recent times, customers are beginning to require improved magnetic properties, especially when

1.5 T, without corresponding price increase. As mentioned above, manufacturers are forced to improve the magnetic properties of these steels without correspondingly increasing product prices.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a new process for manufacturing low carbon steel sheet with improved magnetic properties without noticeably increasing the cost of products.

It is an object of the invention that after annealing with a cold finishing rolling, a further reduction in the thickness of the sheet by 6 to 10% is carried out.

The invention is based on the finding that cold rolling of low-carbon cold-rolled and annealed steel sheets with a critical elongation of 6 to 10% greatly improves the magnetic properties of steel sheets that have not yet been achieved with non-silicon steel sheets. Although the other process steps may be substantially the same as the currently commercially performed steps, the only modification of the invention, that is, the increased elongation in the final cold rolling, does not substantially increase the cost of the product.

The invention is further explained by way of example with reference to the accompanying drawings, in which the graphs depicting the result of a single heating test theist described at the end of the invention, the graphs in FIGS. 3 and 4 show permeability and the graphs in FIGS. in the core at 1.0 a

1.5 T depending on the percentage of cold rolling elongation at 1 T in Figs. 1 and 3 and at 1.5 T in Figs. 2 and 4.

In a preferred embodiment of the present invention, the starting steel may have substantially the same composition as the low carbon steel sheets produced in the conventional manner. In particular, the composition of the steel is as follows:

footprint up to 0.10 wt% carbon, 0.40 to 0.60 wt% carbon; % manganese, 0.02 to 0.09 wt.% phosphorus, trace to 0.025 wt. % sulfur, trace to 0.010 wt. % silicon, the rest iron and other impurities.

In the manufacture of a steel sheet according to a preferred method of the present invention, the steel having the above composition is poured into a casting mold and then hot rolled onto the plates in a conventional manner. The plate is then reheated and hot rolled to a sheet thickness of 0.15 cm or from 0.127 cm to 0.254 cm, the temperature of the steel having a thickness of 2.54 cm being in the range of 1038 ° to 1100 ° C and the final temperature at the end of rolling is in the range of 776.6 ° to 882.0 ° C. The sheet is then cooled with a water spray so that the temperature drops to 482.2 ° to 649.0 ° C. Preferably, the rolling temperature is from 1038 ° C to 1038 ° C

1065.5 ° C when the steel is 2.54 cm thick and from 793.3 to 876.65 ° C in the final steel processing.

After cooling, the steel is pickled and then cold rolled to reduce the sheet thickness to 40-80%. The sheet is then calcined to achieve recrystallization. The annealing is preferably carried out in an annealing chamber furnace at a temperature of 607.2 to 704.5 ° C for 3 to 30 hours.

The principle of the present invention consists in cold-rolling after recrystallization by annealing to achieve an elongation of 6 to 10%, preferably 7 to 9%, ideally 8%. As shown in the accompanying drawings, the magnetic properties are rapidly improved by cold rolling in the above range. For example, a rolled sheet of a final thickness of 0.625 mm according to the invention and tested at 1.5 T has an optimum premeability in the rolling direction of about 2,700 and a core loss of about 8.4 W per kilogram. By way of comparison, values previously obtained which were not better than about 3000 for permeability and 9.28 W / kg for core losses were reported. When tested at 1.0 T, the same 0.625 mm thick steel sheet of the present invention had an optimum rolling direction permeability of about 5200 and core losses of about 3.31 W / kg, while earlier values were generally not better than 4800 and 3.97 W / kg. The low carbon rolled sheet 0.47 mm thick according to the invention and tested at 1.5 T had an optimal permeability in the rolling direction of about 5600 and core losses of about 5.52 W / kg compared to earlier generally achieved values which were not better than 4000 and 6.63 W / kg. At the 1.0 T 0.47 mm thick steel sheet of the present invention, it has an optimal rolling direction permeability of about 7200 and core losses of about 2.43 W / kg compared to earlier generally achieved values that were not better than 6000 and 2. 89 W / kg.

Another test illustrates the critical values of the present invention. For this test, the following steel was prepared:

Carbon 0.07 weight % Manganese 0.57 weight % Phosphorus 0.06 weight % Sulfur 0,021 weight % Silicon 0.03 weight % Copper 0.01 weight O / o Nickel 0.01 weight O / o Chrome 0.02 weight O / o Molybdenum 0.01 weight · o / o Tin 0.006 weight ° / o

This melt was poured into an ingot mold and hot rolled first onto plates and then onto a 1.6 cm thick sheet. The hot rolling was controlled so that at a thickness of 2.54 cm the sheet had a temperature of 1065.5 ° C and at the completion of the rolling a temperature of 782 ° C. Prior to rolling, the hot rolled sheet was cooled with a water spray to 638 ° C.

The hot rolled sheet was then divided into five parts and cold rolled to different thicknesses, so that the final cold rolling that followed the annealing was carried out with different degrees of deformation to produce a sheet of one of the two final thicknesses. The intermediate thickness, final thickness and degree of final cold rolling are shown in the following table.

Table

Reduction scheme and magnetic Properties plate at 60 Hz Medium extend- reduction 1.0 T 1.5 T thickness getting married (%) losses permeabi- losses parmeabi (cm) (%) in the core lita in the core lita (W / kg)  (W / kg) Sheet thickness 0.47 mm 0,0477 1.6 1.5 3.36 5618 8.16 2055 0,0495 5.5 5.1 3.20 5629 6.79 5004 0.05 (08 8.0 7.8 2.47 7246 5.61 5456 0,0529 10.2 9.3 2.91 5905 6.70 4639 0,0564 20.0 16.7 3.26 5391 7.55 3409

Sheet thickness 0,625 mm

-0.0645 1.6 1.5 4.06 .4761 10.20 2679 0,0669 5.0 4.9 4.04 .4545 9.35 4054 0.01685 8.0 7.8 3.31 5155 8.35 4286 0,0’698 10.0 9.1 4.06 .4348 9.57 3661 0,0762 20.0 16.7 4.24 4348 10.35 3000

After reduction to medium thicknesses, the sheets were annealed for 12 hours at 649.0 ° C in a nitrogen atmosphere containing 10 vol% hydrogen and having a dew point of about 21 ° C. The sheets were then cold rolled as shown in the above table and cut into test strips. The test strips were annealed for 1 hour at 787.7 ° C in the above shear stress relieving environment and the magnetic properties were then measured at 60 Hz . The resulting magnetic properties are shown in the above table and graphically shown in Figures 1-4, which show permeability and losses in iron as a function of percent plastic elongation at 1.0 T and 1.5 T. cold at elongation between 6 and 10 ° / o.

Claims (1)

OBJECT OF INVENTION A method for producing low carbon steel sheet for articles having magnetic properties, in which the steel is hot rolled to a sheet thickness of 0 · 127 to 0.254 cm at a temperature of 1038 ° to 1100 ° C when the steel has a thickness of 2.54 cm, at a temperature of 176.6 ° to 882 ° C when finishing the sheet rolling and at 482.2 ° to 649 ° C when the sheet is rolled into coils, and in which the steel is cleaned, cold rolled to reduce the thickness to 40 to 80 % and anneals to achieve recrystallization, characterized in that after annealing with a cold finishing rolling, a further reduction of the sheet thickness of 6 to 10% is carried out.