US1992039A - Method of producing high silicon steel articles - Google Patents

Description

Patented Feb. 19, 1935 nm'rnon or PRODUCING HIGH SILICON STEEL ARTICLES Gustav A. Reinhardt, Youngstown, Ohio, assignor to The Youngstown Sheet and Tube Company, Youngstown, Ohio, a corporation of Ohio No Drawing. Application February 15, 1932, Serial N0. 593,202

7 Claims. (Cl. 175-21) The present-invention relates to the manufacture from high silicon steel of articles especially adapted to be built to form a laminated body having a high degree of magnetic permeability accompanied with relatively low hysteresis losses and thus suitable for use in electrical apparatus such as transformers, motor and generator armatures and the like, the invention being more particularly directed to an improved method of 10 manufacturing the individual pieces or articles preparatory to their being assembled to form the laminated body.

In the ordinary manufacture of articles or pieces of this character, steel having up to l to 5% silicon is usually employed, being hot rolled into sheets or strips of about 28 to 29 U. S. standard gage, that is, to a thickness of about 0.0156" to-0.0141" from which the shapes or pieces are formed by stamping, but ithas heretofore been extremely diflicult, if not impossible, to satisfactorily produce the latter from this and like materials for the reason that when the sheets or strips are hot rolled, annealing is thereafter reguired to produce the large grain structure necessary to impart suitable magnetic and other properties thereto, but such annealing produces also an increased brittleness in the sheets or strips which is highly inimical to the subsequent stamping or like operations by which the pieces 30 are individually formed.

If the hot rolling of silicon steel sheets is completed below the thermocritical range in accordance with the usual sheet rolling practice, the

( material lacks the magnetic and other properties desired when the parts made therefrom'are to be used in electrical apparatus requiring high magnetic permeability so that, so far as I am aware, no method has heretofore been devised for manufacturing high silicon steel articles of the 40 character described at a relatively low cost, without relatively large and extravagant losses from breakage in stamping or otherwise or without depriving the resultant articles of the magnetic and other properties sought for and substantially necessary to enable the articles to be satisfactorily employed for their intended purpose.

On the other hand, it has been observed when rolling sheets or strips with the use of severe cold rolling, that is, with about 75% cold reduction in thickness, such as results from rolling while under tension on a backed up or cluster mill of the Coryell type, followed by annealing, a higher degree of ductility is produced than would result when the same gage of sheet is rolled with moderate cold working in the customary manner as generally practiced in sheet mills, followed by annealing.

' A principal object of the present invention,

therefore, is to provide an improved method for of relatively high magnetic permeability and subject to only relatively low hysteresis losses may be readilyand cheaply manufactured with a minimum number of operations and undue brittleness and hardness in the ultimate articles avoided.

"Other objects, purposes and advantages of the invention will hereinafter more fully appear or will be understood from the following description of a preferred manner of performing the invention in the manufacture of stamped shapes adapted to be built into transformer cores, armature cores, and the like.

It will be understood that the material-usually supplied for manufacture into the ultimate articles of the class described is in the form of ingots or bars such as are ordinarily termed sheet v bars or pairs in the trade which may be made in any usual way from steel having a high silicon content, for example, from l to 5%. In accordance with the present method these bars, after being heated to a suitable hot-rolling temperature, are first progressively hot rolled in a suitable mill or mills to reduce them to sheets, desirably about 16 U. S.standard gage, i. e.,'about 0.0625" in thickness. The attenuation of the metal which takes place during this hot rolling results in a sheet having a grain structure and electrical properties rendering it distinctly unsuitable for electrical work of the character heretofore mentioned, but in accordance with my method, the hot rolled sheets or strips are allowed to cool and, when cold, are subjected to great pressure such, for example, as that which may be produced on a cluster mill having relatively large backing up rolls-providing support for working rolls of comparatively small diameter, or on a 4-high mill or the like preferably provided with rolls of the character just mentioned so as to secure a large angle of bite in the metal while under tension,

to further reduce the thickness of the metal to- 28 or 29 U. S. standard gage while subjecting it to very severe cold. working which rearranges the grain structure and produces a sheet or strip of suitable thickness and of suflicient ductility and malleability for relatively easy stamping. The now relatively thin material is thereafter delivered to a stamping press or other mechanism suitable for cutting it into the desired shapes, for example, into small pieces the outlines of which conform generally to the several transverse sections of the body to be made of the shapes, whereby whena number of the latter are laid together with their edges in superposed alignment, a laminated article for use as a transformercore, armature core or the like willemployed in electrical apparatus in such way as to serve as conductors of a magnetic field, this annealing also operating to relieve internal strains produced by the stamping operation.

It will thus be understood that my improved method as hereinabove described does not require any special machinery for its performance, as each of the several steps may be effected. with the aid of apparatus ordinarily found in many sheet and/or strip mills and other factories in which hot and cold rolling and stamping of steel plates, strips and sheets are performed. Moreover, my method, of producing articles of the character to which the invention relates involves no greater complication than the methods heretofore employed for like purposes, while the desired properties are imparted to the resultant product to a greater degree and undesirable properties such as excessive brittleness substantially eliminated.

It will furthermore be understood that while I have herein described with some particularity one manner of performing the method of my invention with the aid of the apparatus to which specific reference has been made, changes in andmodification of the specific operations incident to the method may be made if desired and any suitable apparatus utilized in the practice of the invention, without departing from the spirit and scope thereof as defined in the appended claims.

Having thus described my invention, I claim and desire to protect by Letters Patent of the United States:

1. The method of producing steel articles having a high degree of magnetic permeability and not readily subject to material hysteresis, which comprises the steps of hot rolling a bar of high silicon steel to thereby form a relatively attenuated sheet or strip of substantial thickness, thereafter cold rolling said sheet or strip to substantially decrease its thickness, then cutting the arfrom a plurality ticles therefrom, and finally annealing the articles to produce therein a predetermined grain structure.

2. The method .of producing articles of the character described which comprises the steps of hot rolling a body of high silicon steel, there-.

standard, thereafter cold rolling said reduced bar until its thickness approximates 29 gage U. S.

standard, then stamping the articles to shape therefrom, and finally annealing the stamping: to produce a relatively large grain structure therein.

4. The method of producing a metal article having a relatively large grain structure and consequent high magnetic permeability, which comprises the steps of reducing by hot rolling to a sheet or strip of predetermined thickness a bar of high silicon steel, next subjecting the rolled sheet or strip to severe cold working to further materially reduce its thickness to a predetermined point, then stamping from the material articles of the desired shape, and finally subjecting the stamped articles to an annealing treatment adapted to enlarge their grain structure to the desired point and also relieve internal strains.

5. In a method of producing thin steel articles of high magnetic permeability,.the steps of hot rolling a stefl shape containing a relatively large amount of s licon into a sheet or strip of predetermined thickness, and then cold working said sheet or strip to effect a further and material reduction in its thickness and render the sheet or strip suitable for a subsequent stamping op- I eration.

6. In a method of producing thin steel articles of high, magneticlpermeability, the steps of hot rolling a steel shape containing from 4% to 5% of silicon into a sheet of approximately 16 gage U. S. standard thickness, and then subjecting the sheet while cold to severe pressure to effect is further reduction to approximately 29 gage U. S. standard thickness.

'7. The method of producing high silicon thin steel articles which comprises the steps of hot rolling a steel shape having the desired analysis into a sheet or strip of predetermined thickness, then cold working the sheet or strip to reduce its thickness to that desired in the finished articles, stamping the articles from the cold worked metal, and finally enlarging the grain structure of the stamped articles to enhance their magnetic permeability.

GUSTAV A. REINHARDT.