US2034181A - Carburizing box - Google Patents

Description

Marc 1933. H, HARRiS 2,034,18

CARBURIZING B Patented Mar. 17, 1936 UNTED STATES PATENT oFFicE 3 Claims.

This invention relates to carburizing boxes and is an improvement on the invention of my Patent No. 1,882,580.

It is an object of my invention to provide a carburizing box which will stand up better and longer under the severe usage which such bo-xes receive.

It is a further object of my invention to provide a carburizing box which will have a longer service life in proportion to the diiiiculty and expense of making same.

Other objects will appear in the course of this speciiication.

When carburizing boxes are to be used in heat treating furnaces, metal articles to be carburized are placed in the boxes, together with a carburizing agent such as bone dust. Trays are placed over the boxes, the boxes with their trays are then usually inverted, and in this position subjected to heat suppliedfrom beneath in a heat treating furnace.

The boxes must stand up under rough handling, extremely high temperatures, sudden changes in temperature, and the pressure of a heavy load of contents while softened by heat, all with attendant warping and buckling, producing cracks in the course of time and. ultimately breaking the box down.

As a result, if the boxes were not made so as to have great durability under such treatment they would have to be replaced constantly at great expense, and it becomes a problem of some nicety and importance to devise a box having the longest life in proportion to the cost of producing same.

I have found that the ordinary rectilinear box breaks down first along the open edges at about the centers of the longer sides, this principal locus of failure being indicated by arrow l in Fig. 3 of the drawing.

While the form shown in my prior patent above referred to is an advance over former practice, I have now devised a construction which is an improvement thereon, greatly increasing the life of carburizing boxes without greatly increasing the amount of high grade alloy required, and which at the same time is easier to make.

In the drawing, Fig. 1 is a perspective View of a box constructed in accordance with my invention;

Fig. 2 is a plan view thereof; and

Fig. 3 is a side view thereof with a portion broken away.

The carburizing box of this invention consists of three sections A, B and C, united together as at i l and I2, preferably by welding with welding stick material. The end sections A and C are preferably formed of relatively inexpensive metal, such as low-grade iron-nickel-chromium alloy, preferably cast. The center section or gusset B is formed, cast or in sheet, of a high grade heat resistant ductile alloy, such as Q-alloy which has a high nickel chromium content. This gusset B is located midway of the length of the box, extending down one side, across the bottom, and up the other side. The portion in the bottom is relatively narrow, being shown for example as about one-iifth the length of the box. As the gusset strip starts up each side it flares out, until at the top edge it is shown for example as comprising about half of the length ol the box.

A thickened edge or bead I8 is formed along the top edge of all the sections.

Making the end and center parts as separate sections provides an accommodating and equaliZing-of-strain effect, which is increased by making the center section of higher grade alloy better adapted to withstand and absorb strains.

By this construction the part of the box at the principal locus of failure is strengthened by provision thereat of an adequate width oi' highly resistant flexible material to take up strains, and at the same time a continuous strip of this material capable of absorbing and withstanding strains is provided all the way around the center part of the box to take up the strains oi the box as a whole with a minimum of the expensive alloy material.

With this construction the end sections A and C are easier to cast, or should they be made oi sheet material are easier to form therefrom. These sections are generally cast about a solid core. Since with the present construction each end piece approaches more nearly a simple saucer shape rather than a deep cup shape it is easier to cast, has fewer casting strains, and can be cast thinner. The bead I3 around the top edge becomes feasible with this shape end section, because it is now possible to cast the main body of the end section no thicker than necessary, while the top edge is left thicker to meet localized strains.

It will be seen that by this invention I have achieved a carburizing box of longer life with minimum expense and weight. While I have shown one specific form to illustrate the invention, it will be apparent that variations thereof may be made within the spirit of the invention,

and hence I wish to be limited only by the scope of the appended claims.

I claim:

1. A metallic receptacle for use in heat treating furnaces comprising a shell having a rectangular open top', the top edges being formed thicker than the Walls of the box to provide a reinforcing bead, and a gusset set in and extending around the shell -transverse toy its longer dimension, said gusset at the edges of the open top comprising substantially the central half of the side walls, and at the bottoms of the side walls and across ber widens gradually and smoothly from its nar- 10 row bottom portion to its wide side edge portions.

HENRY H. HARRIS.

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