US1610567A

US1610567A - Annealing of sheet steel

Info

Publication number: US1610567A
Application number: US60978A
Authority: US
Inventors: Henry S Marsh; Ralf S Cochran
Original assignee: Individual
Current assignee: Individual
Priority date: 1925-10-07
Filing date: 1925-10-07
Publication date: 1926-12-14
Anticipated expiration: 1943-12-14

Description

Dec. 14 1926.

H. S. M'ARSH ET AL ANNEALING 0F SHEET STEEL F'iled Oct. '7, 1925 2 Sheets-Sheet s n W w Dec. 14 1926. 1,610,567

H. s. MARSH ET AL ANNEALING OF SHEET STEEL Filed Oct. 7, 1925 2 Sheets-Sheet 2 /N VEN TORS W l TNE'SSES "fum Pezenas Dec. 14,1926,

UNITE-.D STATES HENRY s.

PjA'rlzN'r oFFficE. A

BALB' B, OOUHBAN, 0F YOUNGBTOWN, OHIO.

"mamme 4on' sanar srnnr..

Application med Uetobor?, 1925. Serial No. 30,978.

ylow temperature. that the crystals or grains are badly distorted, and consell qliliently it becomes necessary to anneal the eets after they have 4been rolled, in order to restore the normal grain structure, and render the sheets suitable for the .drawing operations which at the, present day are widely practiced. Some" years ago rolled, steelsheets were ordinarily box annealed: 'But box annealing gives widely varying resultrs; sometimes the annealed sheets are very sti and sometimes they are of loaden y softness. and the product'yvhich approaches eitherof-these extremes is unsuitablefor-the drawin trade. A later practice has been to-blu anneal sheets, which are intended to be used in drawing operations, and some- 3 timesto bei: anaiealafterwards. But still the resultsI are erratic and not to be depend- 5ed on: box annealing causes gram growth, 'and sheets which are blue annealed are sub- I ject toscalingl The consequent roughness of 'surface cannot be entirely eliminated in subt F sequent cold rolling.

Such, however, are the limitations 'under t lwhich the art has prolgressed4 hithertoi and the trade is constant v demanding o f the l steel makerl better-and 4better sheets. Our

process overcomes these limitations. -V

We ,iirst heat the rolled sheet material in a non-oxidizingatmosphere to the requisite high temperature, which for ordinary comvmereial.steels is 'fro1n 17509....to 1800 F., preferably to the "higher figure; and then, while'still maintaining the non-oxidizing at- Inosplmre, we .coolit again through a range of 290 to 300do'wnward from. the maxiindicated. Having accomplished this,

method whereby' we allow thev cooling Vto proceed with no further concern tomamtan a non-oxidizing atmosphere, and preferably in the lopen air, until the material comes to. a dull red heat. At this .tenperature we pass the sheets through a'ro er leveler. which attens them, and incidentally cools them through another hundred degrees, more or less.' Vlfe then make the sheets up into packs of from three to six inches thick; they are then of just visible redness. And we then set 4the packs aside tov cooLto atmospheric 'tem rature.

The initial steps of heating an cooling in a non-oxidizing atmosphere ma be carried out in a continuous furnaceof he ordinary open-type, modified to serve the ends described. Thron h the furnace shown in the drawings the sheets advance .from left to right. V.The furnace toward .the intake end is provided with burners 1, through which flame-has ingress, and in the proper'operation of the furnace the llame ywill be of non-oxidizing character, or substantially so,4

and under ordinary conditions of 4operation such ingress of air as occurs still leaves the atmosp ere within the furnace substantially neutral., Thefurnace stack 2 is to the right, and the flow of flame and hot gases is in the direction of the ladvance of the material,

from ,left to right.

The furnace is made much lon r than such furnaces ordinarily are, an toward the delivery end there is no inflow of llame. Toward the delivery end accordingly the stream of gases, non-oxidizing in character, is. cooling ing up their'heat and becoming cooler.

Furnace strpcture and operation will vary in detail, to suit .the character of the material which is habitually'or .occasionally run through it. For instance, when thick sheets are being annealed -ent-high speed, relativel large quantities of heat are given up to an absorbed bv the walls at the cold end of the furnace. To meet such a condition, 'the furand the advancing sheets are giv.

.nace walls may be made thin, and pipes of familiar construction may be provided withy in the furnace walls, for the circulation `of water, to carry away the excess heat, perhaps regularly, perhaps whenspecially required. With like ends in view, a bridge wall, such as is indicated at 3, Fig. II, ma be provided within the furnace, to absor and reflect heat,-and render the cold end of the furnace cooler, while operation progresses.

Temperature conditions within the furnace may be. observed by means of a radiation pyrometer, and furnace operation controlled accordingly.

Typically we so proportion the parts of the apparatus which we employ, and we drive our conveyer at such speed, that the steps of iour operation proceed as follows: heating quickly, within an interval of from 2 to 7 minutes in a nearly neutral atmosphere, to a temperature of 1700* to 1850 F.; cooling quickly, within an interval of from 1/2 minute to 2 minutes, and still in a nearly neutral atmosphere, to a temperature of 1200 to 1400* F.; continued cooling quickly (and conveniently in the open air) in about l to 2 minutes, to dull red: roller leveling; then cooling slowly in 1 to 3 hours, in packs, in the open air, to a temperature of 200 F. or less.

After performing the annealing operation described, the sheet ordinarily is pickled before use.

Certain details remain to be mr articularly mentioned. Variations in shee thickness are in ordinary practice substantially offset by varying accordingly the number of sheets which are caused to pass at once through the furnace. When we anneal 11- gauge sheets, we pass them through, one at a time. We ordinarily pass. ifi-gauge sheets through, two at a time; and 20gauge, three a't a time. Finer adjustment may be effected by varying the speed of the conveyor. Thin sheets, if run singly would heat too rapidly and would chill before they could be made up in packs. 4The cooler `the sheets when made up in packs, the thicker the packs can be made, without too much softening. y

When making up the pack, the {irstsheet alone tends'to cool rapidly, but the superposition of successive sheets arrests the fall of temperature and undue chilling is prevented. The 6-inch ,pack is the practical optimum. The more sheets in a pack, the fewer lifts of the crane required for setting them aside to cool; but, in a 12-inch pack, for instance, cooling proceeds so slowly that the sheets tend ultimately to be softer than we desire them to be. The outermost sheets are, of course, always cooler than those within the pack, but there is a permissible range within which the cooling step may proceed. And we have found, all things considered, that a 6-inch pack is best.

Our invention may be practiced with some refinement in detail, to produce a sheet of still better drawing quality, `in case the use required of it can justify the somewhat greater cost. In this case the furnace is made very tight, in order to Vkeep out all air, and a completely reducing atmosphere is maintained within the furnace. And potection in a reducing atmosphere may prolonged to the nontarnislimg degree of approximately 400 F. In this case cooling will preferably be so controlled as to be achieved in five to ten minutes. The sequence in treatment then is: hot roll roller level, ickle, cold roll, anneal. In this case, it wi be observed, ickling after annealing is not required. ickling as a. last operation (particularly when the sheets are immediately to be put on the drawing press, as when' t e customer does the pickling) sometimes renders the metal brittle. Heating removes such brittleness, supposedly by driving out .occluded hydrogen. Another reason why ultimate picklin is advantageously avoided, is that when t e sheet is under the drawing operation subjected to tensile stress, small surface depressions, such as are incident to picklin tend to weaken the metal irregularl sheet will during the rawing over the corner of the die wit less resistance than a rough one, and in that respect the danger of a break in the sheet is diminished. From this it is clear that a smooth sheet, annealed after cold rolling, is better than a rough sheet, pickled after annealing. Such is our preferred procedure, when the customers job is such as to warrant the extra expense of cold rolling, and the maintenance of a furnace with air-tight walls.

We claim as our invention:

1. The method herein described of annealing sheet steel which consists in heating the sheet material in a non-oxidizing atmosphere to a temperature of 1750 F.4 as a minimum, cooling the material whileV maintaining it still in a non-oxidizing atmosphere to a temperature of -1550" F. as a maximum, cooling it ythence to a dull red in the open air, making the material at the temperature last indicated into packs, and allowing the packs to cool in the air toy atmospheric temperature. Y 2. The method herein described of annealing sheet steel which consists in heating the sheet material within aumaximuniV time interval of seven minutes and while maintained in a non-oxidizing atmosphere to a temperature of 17 50 F. as a minimum, cooling the material within a maximum interval of two minutes and `while still maintained operation slip gain, a smoothin a non-oxidizing. atmosphere to a temperature of 1550 F. as a maximum, and then completing the cooling in the openair.

3. The method herein described of annealing sheet steel which consists in heating the sheet material within a maximum time interval of seven minutes and while maintained in a non-oxidizing atmosphere to annealing temperature, cooling the material within a maximum interval of two minutes and while still maintained in a non-oxidizing atmosphere to a temperature of 1550o F. as

a. maximum, cooling it further and within a. maxlmum time lnterval of two minutes set our hands.

HENRY S. MARSH. RALF S. COCHRAN.

i atmosphere to a temperature of 1550o F. as

to dull red, then making thc material into packs, and allowing the packs to cool in the air to atmospheric temperature.

In testimony whereof We have hereunto set our hands.

HENRY S. MARSH. RALF s. COCHRAN.

a maximum, cooling it further and Within a maxlmum tlme interval of two minutes DI 8O I Al M E R 1,610,567 .`-Henry S. Marsh and Ralf S. Cochran, Youngstown, Ohio. ANNEALING oF SHEET STEEL. APatent dated -December 14, 1926. Disclaimer filed March 28, 1935, by the asslgnee, Swface Combustion Corporation.

claim 2 of the said Lettersl Patent, except upon ordinary commercial the result. and eflectJ of gaining relatively high ductility.

[Ojicwl Gazette April 2 1.935.]

steel, and with DISCLAIMER 1,610,567.'Henry S. Marsh and Ralf S. Cochran, Youngstown, Ohio. ANNEALING or SHEET STEEL. .Patent dated December 14, 1926. Disclaimer filed March 28, 1935, by the assignee, Sudace Combustion Corporation. Therefore, enters this disclaimer to any performance of the method recited in claim 2 of the said Letters Patent, except upon ordinary commercial steel, and with the result. and effect. of gaining relatively high ductility.

[Oficial Gazetie April 23, 1935.]