US615075A - Treating chilled cast-iron car-wheels - Google Patents

Description

UNITED STATES PATENT @EETQE.

WVILLIAM IV. LOBDELL, OF WILMINGTON, DELAWARE.

TREATING CHILLED CAST-IRON CAR-WHEELS, ROLLS, 84.0.

SPECIFICATION forming part of Letters Patent No. 615,075, dated November 29, 1898.

Ap lication filed November 28, 1892. Serial No. 453,402. (No specimens.)

T0 aZZ whom it may concern.-

Be it known that I, WILLIAM W. LOBDELL, a citizen of the United States, and a resident of Wilmington, Delaware, have invented certain Improvements in Treating Chilled Cast- Iron Car -Wheels, Rolls, &c., of which the following is a specification.

The object of my invention is to so treat chilled cast-iron wheels, rolls, and the like as to relieve them from defects which arise from the chilling operation; and this object I attain in the manner hereinafter set forth.

In casting chilled iron car-wheels the tread of the wheel is cast against a chill which is made of iron or other metal that is a good conductor of heat, the sides, plates, or spokes of the wheel being cast in sand.

Rapid transmission of heat from the molten iron through the chill against which it is cast causes the tread of the wheel to present an entirely different physical structure from that portion of the wheel which is cast against the sand, the chilled portion being crystalline in character and silvery white in color, while the other portions of the wheel are of the ordinary color and character of cast-iron.

Because of the rapid transmission of heat from the tread of the wheel that portion of the wheel cools and contracts rapidly, while the hub or centralportion still remains in a semifluid state. This causes a strain upon the wheel, which is partially relieved by removing the wheels from the molds as soon as set and covering them up in sand or placing them in air-tight pits, where they are allowed to cool slowly; but'that this strain is not entirely removed by such treatment is evidenced by the fact that if two thirty-three-inch wheels are cast from the same pattern and from the same ladle of iron, one in a chill-mold and the other in a sand mold, the one cast in the sand will be larger in diameter, probably by.

one-fourth or one-third of an inch, than the one cast in the chill-mold, and when such wheels are subjected to a breaking test the one cast in the sand mold will be much the stronger of the two. This indicates that the process of casting the chilled wheel causes.

more than a normal shrinkage of the iron.

Of course a wheel may be weak because of the use of iron of inferior quality; but chilled wheels, even if made of iron of the best qualing the chill or wearing part of the tread; in

fact, they may be permanently expanded to an extent greater than the difference between a wheel cast in a chill and one cast in sand, thus indicating that the process not only relieves the casting from its abnormal shrinkage, but from the ordinary shrinkage, or may even have the effect of permanently expandingthecastingbeyonditsnormal limits. The treatment seems to effect some change in the physical or molecular structure of the iron in the plates and hub of the wheel, the iron in these parts of the wheel being changed from a light gray to a bluish-black color and partaking more of afibrous nature than of the usual granular form of cast-iron-that is to say, the crystals or grains are enlarged and interlaced and the casting is of greater bulk, greater toughness, and of greatly-increased strength as compared with the same casting before treatmentand this is true not only of wheels cast in a chill, but also of those cast in asand mold, there being in either case a great increase in the strength of the wheel, this increase varying from one hundred to five hundred'per cent. or more and being generallyin proportion to the degree of perma .nent expansion or increase in bulk of the 2.0455 per cent, and combined carbon, 1.2008 per cent.

This analysis shows that the total carbon in specimen No. 1 was 3.1087 percent. and in specimen No. 2, 3.2523, showing an increase of total carbon of .0830 per cent, while the combined carbon has increased from 1.0265 per cent. to 1.2008 per cent, showing an increase of .1803 per cent, and in all cases the treated casting will show an increase in total and combined carbon.

lVhile in some cases a mallcableiron casting, when fractured, may show a bluish'black color, somewhat similar to that found in the unchilled portion of my castings, it should be observed that in addition to the fact that such malleable-iron castings are not composed of chilled and unehilled portions the change in total and combined carbon therein is radically different from that in my castings, because the total carbon in the malleable-iron castings is slightly decreased and the combined carbon is changed to the graphitic form.

I am aware that it has been proposed to take chilled car-wheels directly from the molds as soon as they were set and to place such hot wheels in an annealing-kiln, in which they were heated to still higher temperature or to a point a little below the point of fusion and then allowed to cool slowly; but this process is essentially different from that which I have devised, for in carrying out the latter process the wheels are first permitted to become quite cold and to have an abnormal shrinkage and are then gradually heated and gradually cooled, with the result of permanently i11- creasing their diameter and completely overcoming the objections due to such abnormal shrinkage.

I am also aware of the patent of H. V. Moore, No. 51,338, dated December 5, 1865, which describes a method of annealing chilled iron car-wheels by superposing them while hot in a soaking-pit, packing the webs with charcoal, and protecting the chilled rims from the effect of the heat due to the slow combustion of such charcoal, the intention being to cause an approximation to malleable iron in the webs of the wheels. Such treatment does not heat the wheels uniformly throughout their entire extent, as in my process, and the wheel produced is essentially different from one ma spccordance with my process that is to say, it isnot permanently expanded, and the change in therarbon contents of the metal, if any there be, is intlle direction of an increase in graphitic carbon instead of an increase in combined carbon.

The degree of temperature to which the wheels are subjected in carrying out my invention should not be so high as to inj uriously affect the chill, and the application of heat may be continued until the desired expansion of the article under treatment has been effected, the length of treatment varying, depending upon the bulk of said article and upon the depth of chill. I may say, however, that in case of ordinary car-wheels I prefer to heat them to a dark cherry red, the temperature being from 900 to 1,200 Fahrenheit, the treatment being continued for twenty-four hours or in some cases even longer in order to insure the proper permanent expansion of the casting.

The advantages of my improved process are, primarily, the very great increase in strength, and,furthcrmore,1he abilitytoproducewheels or other objects with an extra deep chill without impairment of strength, therebyinsuring greatly-increased wearing qualities and the ability to use grades of iron which will produce a very hard and lasting chilled surface, which grades of iron, because of their great shrinkage, cannot now be used with safety.

In the case of car-wheels treated in accordance with my invention the heating of the iron by friction due to long-continued action of the brake cannot have the effect of expanding the Wheel so as to crack the plates of the same, because such heating cannot possibly be as great as that which the Wheel receives in the carrying out of my improved process; hence a fruitful source of loss and danger in the use of ordinary chilled carwheels is effectually overcome.

In the case of chilled rolls or other expensive chilled castings the great increase in strength and greater depth of chill renders them 111 uoh more durable in use and decreases the risk of breakage.

Having thus described my invention, I claim and desire to secure by Letters Patent- 1. The mode herein described of treating chilled castings, said mode consistingin first permitting said castings to become cold and then subjecting them, uniformly throughout their entire extent, to a temperature from about 900 to 1,200 Fahrenheit, whereby the casting is permanently expanded without injuriously affecting the chill.

2. As a new article of manufacture, the herein-described iron casting, such as a carwheel or roll, composed of chilled and unchilled portions, possessing as physical characteristics in the unchilled portion a bluishblack color, enlarged interlaced crystals or grains, greater bulk and toughness, much greater strength, and a greater percentage both of total carbon and combined carbon, than the same casting before treatment, substantially as specified.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

XVILLIAM IV. LOBDELL.

Witnesses:

CHAS. F. WoLLAsToN, WINFIELD T. MoKAIo.