US2058582A - Forged steel roll - Google Patents

Description

Patented Oct. 27, 1936 UNITED STATES PATENT OFFICE roman STEEL non. Cliiford 1;. Fence, Pittsburgh, Pa.

No Drawing. Original application January 30,

1935, Scrlal'No. 4,093. Divided and this application Octobcr 9, 1035, Serial No. 44,208

2 Claims. (01. 80-58) This invention relates to steel forgings, and

finds practical application in the formation of rolls for rolling-mills. Its greatest value is re-' l priate manner; it involves, second, improvements of method; and, finally, it is found in a roll of new characteristics. Production is simplified; the'time factor. in production is very substantially and advantageously shortened; the loss of articles found in the course of fabrication to be defective (inthe present practice a very considerable and serious matter) is reduced to the point of disappearance; the danger to life and limb, consequent upon explosion of rolls, existent 0 both during fabrication and during use, is substantially eliminated; and the durability ofthe rolls in service is very considerably increased.

This application for Letters Patent is a division of an application filed by me January 30, 1935; Serial No. 4,093.

In the refining of steel preparatory to the productlon of forged rolls, it is the universal practice so to proportion the ingredients and so to conduct and control the refining operation that g the steel shall be hypereutectoidal; that is to say,

shall have a carbon content substantially exceeding the eutectoidal value of 0.9%. Specifically, the carbon content ranges from 0.95 to 1.2%. Additionally, and in order to gain hardness and toughness, chromium is included, in

association with another alloying metal, ordinarily modybdenum, or, alternatively, vanadium of tungsten. The chromium is present in an amount exceeding 1.85% and within the range of 1.85-2.25; and with it molybdenum, for example, may be present .in an amount ranging from 0.15 'to 0.2%. The accepted typical formula for the refined steel for forged rolls is- I have discovered that by reducing the carbon 66 content of the refined steel to eutectoidal value,

oreven less; and by reducing the chromium content to less than 1.85%; other such alloying metals as vanadium and tungsten that heretofore have been included to aiford increased hardness and toughness may be omitted,and large 5 and unanticipated gain and advantage. both in fabrication and in service may be-realized; and that by improved methods of procedure incident to and forming part of the fabricating operation superior results are realized. 10

The formula of my invention is- Per cent Carbon 0.75-0.95 Manganeseun 0.2 -0.3 Phosphorus. under 0.03 l5 Sulphur under 0.03 Silicon 0.2 -0.35 Chromium 1.3 -1.8

Remainder, iron Following are the new and distinguishing features of fabrication, and the gains and advantages in method and product:

In the usual proceudre, beginning with a steel of the composition typically given in the first formula above, it is customary, before pouring the metal into the mold, to add a small quantity of aluminum, or of that combination of aluminum, silicon, and iron, known as alsifer; in my improved practice, using the second formula given above, I find such an addition unnecessary. I reject a small quantity of metal at the beginning of the po r, because this is likely to be contaminated; but, thereafter, I pour into the mold. In the usual practice counterboring is frequently necessary, in order to remove .defects in the casting; in my improved practice there are no such defects, and counterboring is in no case requisite.

In the practice now prevalent the ingot is stripped from the mold at relatively high tem- 40 perature (typically 1550 F.I shall throughout use the Fahrenheit scale), charged into the forge furnace and brought as rapidly as possible to the forging temperature. I have found, with the steel of my improved formula, that advantageously the casting may continue in the mold until a very much lower temperature is attained (1000 or less); and that thereafter, in the forge furnace the casting may advantageously be brought very slowly to the forg g temperature.

approximately eutectoidal steel, modified as specifled with respect alloy content, Ifind thata forging temperature of 2090 need never be elceeded. The economy of this variation in pmcedure is manifest; and the structure of-the steel of the forged article I find to be, not inferior, but superior rather to that of prevalent practice.

The heat treatment of the forged roll of the usual practice includes, first, normalizing to a peak temperature of 1650-1700 and rapid cooling again to about 800'; second, spheroidizing to a Peak temperature of about 1550-1560; followed by slow cooling in the furnace; third, oil-hardening, by heating to-a peak of about 1800, followed V tively high and varies widely, according to theby cooling in oil; and, finally, a tem pering of the roll before machining. I find that the heattreatment of my forgingof essentially eutectoidal character may advantageously be reduced to the single operation of heating to a peak temperature of 1490", followed by slow cooling in the furnace.

As always in heat-treating, the time during which vthe articleis held at peak temperature varies,

according to the mass of the article; and 'I find.

that in the heat-treatment my roll should be held at the. peak for one hour for every inch of roll. diameter. My roll, cooled after the single heattreatment, is ready, without any intervening tempering step, for machining.

The roll of prevalent practice, heat-treated and tempered, when it is being machined, is relatively hard, the turnings are hard and brittle; the roll of my invention, when being machined, is relatively soft, the turnings are tough and "gummy, with tendency to'curl, rather than to break into small pieces.

After machining, the roll is hardened, by raisv ing to high temperature and cooling again under a water spray. In, the prevailing practice the peak temperature of this hardening step is rela-- size of the roll (typically, 15502 -1590); in my improved procedure the peak temperature is lower, and is the same forall rolls, regardless of size (1475'-1500).

The hardened roll of my'improved procedure has a scleroscope-hardness of 104-110, and that is somewhat greater than that of the roll of the usual practice (100-103); in consequence, the ultimate tempering step of my improved procedure involves a much higher peak temperature:

a,oss,saa

425, ascompared with Mir-300' of the usual procedure.

The roll. produced has the desired ultimate hardness (-100) it is superiorin homogeneity,

in the uniformity of its physical characteristics; it will not spell, and the reason for this is that. hu therequisitehardnms, it possuperior toughness; it is less liable to breakage under the stress of millpperation; it is less liable to burning when in service, and on that account it may be re-ground with relative ease;

the quality of hardness penetrates deeply, and

the life of the roll is correspondingly long; since a roll when in service may not safely be allowed to attain ,the temperature of its ultimate tempering,

and since in my improved procedure the tempera-' ture of ultimate tempering is much higher than is usual, it follows and is practically true that the roll of my invention is serviceable in a larger way. It need not be so carefully tended, lest it grow too hot in service; and the speedof mill operation as a whole, relieved of this ement, may be accelerated.

I claim as my invention:

1. A forged steel rolling-mill roll having a scleroscope hardness of not less than 95, whose carbon content approximates and does not substantially exceed the eutectoid value, and in which the only hardening and toughening agent is chromium, said chromium content ranging in value from 1.3 to 1.8%.

2. A forged steel rolling-mill roll having a scleroscope hardness of not less than 95, containing carbon OHS-0.95%, manganese 0.2-0.3%, phosphorus not exceeding 0.03%, sulphur not exceeding 0.03%, silicon 0.2-0.35%, chromium 1.3- 1.8%, and the rest iron.

CLIFFORD B. FERREE.