US1017904A - Producing rolled shapes of manganese steel. - Google Patents

Description

UNITED STATES PATENT OFFICE.

WINFIELD S. POTTER, NEW YORK, N. Y.

PRODUCING ROLLED SHAPES OF MANGANESE STEEL.

No 'Drawing.

Specification of Letters Patent.

To all whom it may concern."

Be it known that I, WINFIELD S. Po'r'rnn, a citizen of the United States, residing in the city, county, and State of New York, have invented certain new and useful Improvements in Producing Rolled Shapes of Manganese Steel; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

The object of my invention is to obtain reliably a rolled manganese steel rail or bar with a continuous fine grained austenite structure throughout; that is to say with the separable constituents of the metal in solution, and also with a continuous structure free from irregularities or lamination.

A suitable method for obtaining the finished rail or bar in the desirable finegrained condition is set forth in my application for Letters Patent of the United States, Ser. No. 604,996, filed January 27th,

1911, for improvements in the heat treatment and rolling of manganese steel.

I have found, in practice, that, in some instances because of the character of the mill or particular conditions and exigencies at a partial separating out of the constituents which had been in solution throughout the metal, this separating out being particularly prominent in the thinner sections of the rail or bar. The rail or bar, in such cases, correspondingly loses the uniformity of condition which it has been the purpose of the treatment to attain, and if quenched or 'otherwise rapidly cooled in its altered condition will have these irregularities retained or made permanent in the completed product.

One' of the purposes of my present invention is to restore to the condition suitable for quenching or rapid cooling a rail or bar which after leavingthe finishing pass of the rolls, has suffered in some of its parts the separation referred to, so that thus restored and thereupon quenched or rapidly cooled, it will, as a final product, have the same continuous fine grained austenite structure free from irregularities or lammations and with its separable constituents in solution throughout substantially the same as if it had been immediately quenched or rapidly cooled upon its issuance from the finishing passes of the mill.

The method herein described further contemplates the avoidance of lamination in the rolled product by so conducting the manufacture that the ingot or bloom is prepared for' rolling without a formation of.

very large grainshaving smooth surfaces and feeble cohesion, such feeble cohering grains if present being elongated during rolling into fibers or sheets, which also have but feeble cohesion one with the other.

- In the practice of the invention, the steel, containing the desired high proportion of manganese, carbon'and other elements, as for example, containing 13% of manganese, 1.25% of carbon, is so cast as to ob tain a sound ingot free from pipes. This may be effected, for example, by using molds whose top section is of refractory material, or of chills thinner than the chills employed in the lower parts of the mold; so that the metal remains molten longest in the upper portion of the ingot. So also, the steel is preferably cast at a temperature notmuch above the freezing point of the metal so" of August 16, 1910, is also preferred so as to render the temperaturesv in the ingot higher and more uniform at the time suitable for stripping than would be the case if the ordinary heavy iron mold were used.

When the ingot is frozen and has suitably cooled, depending upon the character of the mold employed, the ingot is stripped andis placed in a furnace which, at the time, has a temperature not far removed from the surface temperature of the ingot, and more especially is caution to be observed in this partlcular if the ingot shall have retained any of its freezing structures when stripped. The ingot is then brought to a temperature of about 1200 C. and heated until in a plastic and uniform con Patented Feb. 20,1912. Application filed October 30, 1911. Serial No. 657,397.

- maximum without any long rest in its progress particularly any long rest above 1125 C. When the maximum temperature is reached this maximum temperature is continued for such time only as to bring the mass to a uniform temperature without detaining the ingot in the furnace beyond this point, as by so doin coarse, feebly cohering grains would be ormed in the ingot.

The rail or other bar to be rolled may be obtained direct from the ingot in a continuous operation, or by rolling in stages after reheating the bloom; according to the arrangement of the mill or the particular section of the rail or bar required. If conducted in stages, requiring the reheating of the bloom, the bloom is preferably taken quickly from the blooming mill to the reheating furnace while still retaining as much as possible of the initial heat in order to facilitate the reheating operation. The temperature of the reheating furnace at this time should closely approximate the intended temperature to which the reheated bloom is to be brought, so that the reheat may be of short duration, such as to avoid excessive crystal building in the bloom;

It may be here noted that-an ingot which is finely recrystallized in the mold by redistribution of the heat'of casting and which is then introduced with a high and nearly even temperature throughout into the soaking pit may be brought rapidly to a temperature and condition suitable for rolling in a short time and without the progressive building up of coarse, feebly coherent crystalline structures; and that similarly, the bloom which is placed in the reheating furnacewith a high and nearly even temperature may be brought to a temperature and condition suitable for further rolling with the smallest degree of crystal building and in thestate of substantial uniformity and continuity of. structure, whereby the characteristic lamination of manganese steel rolled from a blank, which has been either too slowly heated or which has been over-heated may thus be avoided.

The temperature for the reheated bloom will depend largely upon the character and extent of the work to which it is to be subjected in the finishing passes of the mill, and may range from as low as 1000 G. in those instances where the bar is to receive but one or two additional passes and is then to be immediately quenched, up to say 1225 C. in casethe percentage of reduction to the finished sectionis still considerable and the shape to be produced is of such design that the greatest plasticity of the bloom is requisite.-

To obtain in the finished bar a state of maximum strength and toughness, the finishing temperature, as the bar leaves the finishing pass of the mill should be as uniform as posslble and as near 950 C. as possible, provided that the bar is thereupon immediately quenched. At all events, the parts of the bar that are to be subjected in use to Wear, as, for example, the head portions of a rail should be rolled and quenched while the temperature is below 1075 C. or thereabout to. secure a fine grained dense steel, and these parts, as for example, the hotter head-portion of a rail should be speedily cooled to about 1000 C. thereby so'equalizing the temperatures as to avoid changes in the wrought state due to slow air cooling from higher temperatures; and the bar may be quickly brought 'to the water and quenched, in accordance with my application for Letters Patent of the United States, Ser. No. 604996, while still in a fine grained stiff and uniform condition. If the arrangements in the mill, or the character of the section is such that the rail or bar can not be reliably brought to the water while still having its separable constituents in solution and while still retaining throughout the desirable uniformity of temperature and condition, the finished bar should be taken as speedily as possible and with the least possible loss of temperature and change in condition to a reheating furnace (of the continuous type, for example) and therein equalized at about 1000 0. throughout and then quickly removed and quickly quenched.

The temperature at which the re-solution of the carbids of iron and manganese can be quickly eflected ranges from about 975 C. upward. The higher the temperature of the reheating furnace, the shorter is the time required to bring the steel to temperatures above 975 (1, when the carbids will be quickly taken into solution. I have found that the higher the temperature to which the steel 1s brought the more rapidly is it recrystallized, and the size of the grain registers the highest temperature at which any portion of the mass is permitted to rest even for so short a time, for examp e, as 10 mmutes; and this recrystallizing, if permitted, may even destroy entirely the fine wrought state of the bar previously obtained during the rolling operation. It is therefore very important that the finished bar shall not be reheated throughout and allowed to rest in the reheating furnace long at any high temperature, and particularly at temperatures above 1075 C. or thereabout, above which point the bar if brought to an equal heat and allowed to rest soon assumes throughout a coarse grained excessively ductile and a than as above described, the time of subweak and unreliable condition. jecting them to the action of the equalizing The reheating or equalizing furnace may furnace may be correspondingly shortenedbe of the usual type, that is to say,-a furnace or lengthened, as the case may be and as may having a hearth on which the bars are to bebe necessary to restore the coldest parts to 70 placed and having a reverberatory roof and the desirable uniform condition; whereupon a heating medium or flame below the roof, the bars will beremoved from the equalizing so that the bar is heated by radiation from furnace and quenched or rapidly, cooled to the flame and from the roof. The reheating below 420 C. q

10 of the finished bar will be best conducted sub Having thus described my invention what 75 stantially as follows: The bar to be reheated I claim is p (being for example, a T-rail or a girder 1. The method of producing rolled shapes rail), having still from the heat of rolling, of manganese steel, which consists in first a temperature in its thicker head portion heating a manganese steel ingot or bloom suflicient to retain in solution the separable until it is in a condition of substantial. uni- 30 constituents of the steel, and having so far formity of distribution of its constituents, cooled in its base as to be in an unsuitable rolling'to finished shape with finishing temstate for quenching, will be placed on the peratures below 1075 (3., transferring to anhearth of the equalizing furnace head downequalizing furnace and subjecting it to an ward, or on its side with the head inclined equalizing reheat therein at such temperag downward, so as to expose the cooler parts ture as will effect the re-solution of any carof the rail to the radiation from above. The bids that may have se arated and until such flame and roof temperature of the furnace is resolution has been e ected, terminating. the maintained preferably at about 1025 C. so equalizing reheat before any substantial loss that the bar may remain in the furnace for of-the wrought condition has occurred, and a few minutes after its temperatures have then quenching; substantially as described, become equalized without considerable alter- 2. The method of-producing rails of manation of structure other than the desiredreganese steel, which consists in first heating solution of carbids and for such time as will a manganese steel ingot or bloom until it is 30 surely effect such solution. The bar, leavin a condition-of substantial uniformity-of ing the mill at say 1025 C. in its hottest distribution. of its constituents, rolling to portions and at say 950 C. in its coolest porfinished shape with finishing temperatures tions will move to the furnace in say 30 seebelow 1075 C. in the parts of the rail that onds with a loss of about 50 C. in its averare to be subjected in use to wear, transfer- 35 age temperature. Its coldest parts may then ring to an equalizing furnace and subjecthave a temperature below 900 C. and these ing the rail therein to an equalizing reheat coldest parts willhave begun to suffer a sepat such temperatures as will effect the resoaration of carbids and a transition from a lution of any carbids that may have sepa uniform austenite structure. The bar being rated and until such re-solution has been 40 placed in the equalizing furnace without effected, terminating the equalizing reheat further loss of time is brought back to say before any substantial loss of the wrought 1000 C. in about 5 minutes and may then be condition has occurred and then quenching; quenched at once, or it may be detained in substantially as described. the furnace for say 5 additional minutes to 3, The m thod of roducing rails of man- 45 ore nearly equalize its temperatures beganese steel, which consists in first heating fore quenching. After obtaining an equal an ingot above 1125 C. until in a uniform temperature above 975 C. or thereabout no coh r nt ondition, rolling to a bloom, readditional stay in the furnace is necessary heating the bloom and equalizing for a short or advisable, inasmuch as immediately after time at temperatures between 1000 C. and

50 solution of the carbids is complete, grain 1225 C., rolling to a rail with a finished building would begin with a rapid loss of temperature below 1075 C.,equal1z1ng for a stiffness, hardness and strength of the steel. short time, and quenching; substantlally as In fact, these objectionable changes proceed described. H so rapidly at 1100 (1, for example, that as 4. The method 61 producing rails of man- 55 short a delay as one minute after the bar ,ganeses trfl, which consists in first heating has been equalized at this p irglsrefiough an ingot above 1125 0., until in a uniform to cause a c n i ljlibleq -osspf quality. The coherent condition, rolling to a rail with a bar sliguld there fore, be kept in the furnace finishing temperature below 107 5 (3., equal- .-l1nder a rapidly rising heat until its temperizing for a short time, and quenching; suboo atures are nearly or quite equalized above stantially as described. 975 C. throughout the bar, and the car- 5. The method of producing rails of manbids will then be insolution whereupon the ganese steel, which consists in first heating bar should be immediately removed and an ingot above 1125 C. until in a uniform v quenched. In those instances when the bars coherent condition, rolling to a rail wlth a 65 reach the equalizing furnace hotter or colder finishing temperature of about 950 0.,

equalizing for a short time at about 975 C. about 1000 (3., and shortly thereafter 10 to 1025 C., and quenching; substantially as quenching; substantially as described.

' described. In testimony whereof I afiix my signature,

ganese steel, which consists in first heating 6. The method of producing rails of manin presence of two witnesses.

an ingot above 1125 (1., until in a uniform WINFIELD POTTER coherent condition, rolling to a rail with a YVitnesses:

finishing temperature below 107 5 0., equal- JOHN C. PENNIE, izing the temperatures of the finished rail at M. A. BILL.