US1997469A - Furnace roll and the like - Google Patents

Description

April 1935. N. B. ORNITZ FURNACE ROLL AND THE LIKE Filed April 5, 1935 INVENTOR Patented Apr. 9, 1935 UNITED STATES PATENT OFFICE The present invention relates to furnace parts, such as rolls andskids, which are intended for use under exposure ,to furnace gases at high temperature. More particularly, my invention relates to furnace parts formed of a chromiumnickel ferrous alloy having the nickel, chromium and other-elements of such absolute and relative proportions that there is imparted to such furnace parts a remarkable structural strength, re-

I sistance to abrasion and. resistance to corrosive attack of sulphurous gases at high temperatures. There has been a demand for furnace parts,

such as rolls and skids, which have high resist ance to'abrasion, resistance to corrosive attack of from about 4 to 11%, preferably 'betweeh.6, -to

.16. sulphurous gases, and structural strength at high temperatures, such furnace parts-being in particular'demand for annealing and normalizing furnaces, where the parts must have a high temperature so as not to cool the sheets or other 0 articles being annealed ornormalized. The tem- -peratures at which such parts should operate are frequently-as high asabout 2000 F. -Such furnaces are frequently fired with gases containing sulphurous compounds, and to resist such gases, it is necessary that the furnace parts resist the corrosive action of the sulphur compounds even at these elevated temperatures. The parts which support the materials being heat treated, .such for example, as the rolls or skids in an annealing or normalizing furnace, are subject to abrasion,

and it is necessary that the material have a high resistanceto abrasion at the elevated temperatures employed. y

Examples of such parts are shown in the drawing in which,

' Fig. 1 is illustrative of a u adapted to be used I in an annealing or normalizing humane, and

Figs; 2 and 3 are respectively a plan view and used in such furnaces."

1 a view in side elevation of a skid adapted to be.

The roll shown in Fig. 1 is merely one example of a great many different types of furnace mlls to which my invention may be applied. This roll comprises a shaft 4 and a plurality of 'discs 5 upon which the sheets or theJike may travel. The skid I shown in Figs. 2 and 3 is provided with lugsyB engageable with suitable supports,

such as the hollow rods 9. I I have succeeded in producing rolls, skidsand other furnace parts which meet the exacting conditions present in furnaces of thetype mentioned above, wherein such parts are called upon to resist gases containing sulphurous compounds and in which-the temperature frequently rises as high or higher than 2000 F. Such furnace parts terially' affect the heat-resisting .properties of the alloy. I

successfully meet all of the conditions required when I have formed them of a chromium-nickel ferrous alloy having the nickel, chromium, and other elements restrictedwithin certain narrow ranges of proportions.- w 5 The base of my alloy is iron usually supplied as low carbon steel scrap. '-'Ihe alloy is preferably melted in an electric furnace since this. gives good control of the alloying elements and the carbon.

The chromium in my alloy may vary from about 27 to 35%, preferably from 27.5 to 32%, and in the preferred specific formula, I use chromium from 28 to32 The nickel may vary 11%, and in the preferred specific formula, the nickel is held'to between 6 to 8%. The silicon may vary in accordance with good steel-making practice, say-between about .15 to 3%, but preferably between-1 to 2%. In thepreferred specific 20 formula, the silicon isabout 1 /2%. The mang'anese may have-the usual variations in steel-making practice, say, between about :30 to' 2%, but preferably between .50 to 1%, and in the preferred specific formula, the manganese is about 25 -terials. I preferthat the sulphur shall not-be 35 over about .10-%, and in my, preferred formula, the sulphur is not over .05%. Similarly, I prefer that the phosphorus shall not be over about'.10%, and in my preferred formula not over .04%.

The raw-material such asthe low carbon steel scrap, the low carbon ferro-chromi'uin and the metallic nickel',,arecharged and melted in an electric furnace in the usual way, andthe charge tapped out into castings or ingots as required. I Small amounts of other alloying elements may 45 be used,su'ch for example; as'tungsten, cobalt,

vanadium, titanium, aluminum, etc., which, when present in relatively 'minorquantities, do not ma- 50 Articles'made from my alloy, either cast} forged orrolled, have a novel combinationof,

desirable properties which particularly adapt them for high temperature. furnace work. Parts "made from h 11.03 have a remarkable struc- '55 Normalizing furnace rolls of my alloy have been successfully operated at temperatures as high as v tural strength and hardness at high temperatures, say 1700 to 1900" F. The parts so made are adapted for those uses which require structural strength and resistance to abrasion, such for example, as the rolls which support and feed sheets or other articles through an annealing o normalizing furnace. s

According to my best observations and tests which I'have at the present time, furnace parts made of an alloy such as the one disclosed as my preferred formula actually grow harder as the temperature is increased above 1500 F., reaching its maximum high temperature hardness at 1850 F. After this there is a gradual softening, although the parts retain good structural strength and hardness even at 2000 F.

2000" F., and may be used under no load conditions at temperatures as high as 2100 F. v

The furnace parts made of this alloy have not only remarkable hardness and structural strength as ordinarily measured, but also have a remarkable resistance to the so-called creep or slow flow which causes ultimate failure of furnace parts at high temperatures under long continued stresses, 7

At the furnace temperatures frequently employed in annealing and normalizing furnaces, say at 1700 to 2000 F., furnace parts made of my alloy have a remarkable resistance to the corrosive action of the sulphurous gases'wliih'are present in the gaseous products of combustion from sulphur-containing fuel, such for example, as producer gas, blast furnace gas or coke oven gas. There is practically no scaling or disintegration or deterioration of the furnace parts under the action of such gases. a

I have found that the optimum results have been obtained in making articles such as rolls, roll shafts, and roll disks for annealing and normalizing furnaces using an alloy having the preferred formula set forth above, although certain variations may be made in it as above indicated. There are, however, rather narrow limits to the variations in the nickel and chromium contents. If the nickel is materially increased above 11%, the alloy is attacked by the sulphurous gases at high temperatures. Indeed, if the conditions are particularly rigorous as regards sulphur content f and temperature of the furnace gases, the nickel the modern annealing and'normalizing furnaces.

If the chromium is decreased below my proportions, the chromium ceases to offer effective protection to the nickel and the alloy is attacked by the sulphurous gases as wellas by oxygen at the chromium content.

high temperatures. As the chromium content is lowered, its effectiveness in resisting the sulphurous and oxidizing gases decreases as the carbon content increases, so that unless the carbon content is held low, the chromium cannot be lowered much below that of the preferred proportions; although if the carbon content is held low, there is a little more latitude in decreasing If the chromium-content is higher than my proportions, there is a tendency to objectionable brittleness and the cost is unnecessarily increased since low carbon ferro-chromium is expensive. H

As above pointed out, my invention relates particularly to articles requiring structural strength, resistance to abrasion and resistance to corrosion at high temperatures, and especially to furnace parts, such for example, as rolls, roll disks, roll shafts, skids and other furnace parts, which must be maintained at a high temperature so as not to chill the articles which are carried thereby, such for example, as the sheets in a sheet annealing or normalizing furnace.

Rolls of my annealing or normalizing furnace may be maintained continuously at temperatures the neighborhood of 1700 to 2000 R, which are the temperatures of the furnace gases. My rolls under such conditions have been continuously and successfully employed for a considerable period of time without failure, whereas the rolls made of the best of the other alloys heretofore known for such purposes have failed under the severe furnace conditions. .The furnace referred to was a continuous pack-heating furnace in which the rolls had to be operated at a temperature of 1900 F. and where the producer gas used was made from a coal containing about 3% of sulphur.

' This application is a continuation-in-part of my copending application Ser. No. 359,428, filed April 30, 1929.

While I have specifically described the preferred embodiment of my invention' and the characteristics of the articles made from my alloy,

it is to be understood that the invention is not so limited, but may be otherwise embodied and practiced within the scope of the following claim.

I claim:

A roll for a high temperature annealing or normalizing furnace formed of a ferrous alloy containing chromium about 28% to 32%, nickel about 6% to 8%, silicon about, 1% to 2%, manganese about .5% to 1%, carbon not over about 30% sulphur not over about .05%, and phosphorous not over about .04%, the balance of the alloy being substantially iron, and characterized by its structural strength, resistance to abrasion and resistance. to corrosion by the furnace gases at high temperatures.

NATHANIEL B. ORNITZ.

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