US1815691A - Method of heat treating metal parts - Google Patents

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July 21, 1931- R. v. wlLsoN v 1,815,691

.METHOD-,OF l'EA'ZI TREATING METAL PARTS Y Filed oct. s1, 1928 Patented July 2l, 1931 ROGER WILSON, 0F LA GRANGE,

COMPANY, INCORPORATED, OF NEW ILLINOIS, ASSIGNOR T0 WESTERN ELECTRIC YORK, N. Y., A. CORPORATION OF NEW YORK METHOD OF. HEAT TREATIN G METAL PARTS Application mea oetoberei, 192s. serial No.l 316,149.

This invention relates to a methodof heat treating metal parts and more particularly to the bright annealingl of iron parts.

In the heat treating of iron articles, it has lbeen customary to store the articles in a sealed container, place the -container in a heating chamber and gradually raise the temperature to the desired maximum, after which the container is withdrawn from the furnace and placed under a cooling hood `Wherein the cooling of the container and contents is effected slowly. Before placing in the furnace, the container issealed with a material designed to permit escape of oxygen therefrom as the temperature is raised and the air therewithin expands, and which material will harden and prevent vingress of oxygen to the interior due tov atmospheric pressure when the temperature issubsequently lowered. A large percentage of the oxygen contained in the container is ejected in this manner, but in some'cases a sufcient quantity of the ox gen remains within the container during t e entire process to oxidize the iron parts somewhat and thus discolor them.

The object of the present invention is to provide a simple and inexpensive method 'for heat treating parts wherein predetermined atmospheric conditions are' insured throughout the process.

According to the features of the'invention, a quantity'of materialoxidizableat a considerably lower temperature thanthe parts and having a relatively large area, such as copper tinsel, is placed adjacent to'but not in direct contact with the parts in an annealing container. y

A material having a higher ailinity for oxygen at high temperatures, such as magnesium powder, maybe added with the copper tinsel to insure that the atmosphere Within the container shall be free of oxygen throughout the annealingprocess,l and to reduce the .articles within the container to the extent in which they may have previously become oxidized.

It is believed that the invention will be more clearly understood by'reference to the accompanying drawing in which the figure represents a vertical section of a loaded annealing container-prepared for heating.

In the drawing an annealing container generally denoted by the numeral 10, comprises'vertical side walls 11, the up er portion of which consists of an upwardly rojecting lip 12 and an inner portion 13. uitably arranged within the container are a desired number of-articles such as iron parts,

generallydenoted by the numeral 14. Rest ing upon the inner portions 13 is a tray 15 upon which is placed a quantity of a material which by reason of its large surface area as compared to its weight is capable of absorbing a large portion of the oxygen remaining in the container after the oxygen content is materially reduced by heat expansion, and also such oxygen as may be drawn into the container during the cooling process. On the tray is placed also a quantity of material such as magnesium, aluminum or 'other of the metals comprising the class which are capablel of combining vigorously with oxygen at the higher of the temperatures Within the range reached during the heat treating process. The drawing illustrates the use respec# tively of a desired 17 and a lesser rials indicated' above. The copper tinsel referred to is copper in fine ribbon form such as is commonly used in the flexible conductors comprising telephone cords and similar types of electrical conductors, which has been gathered into a bundle and matted to cause it to. fit in the tray 15. It should be understood that the invention may be satisfactorily practiced through the substitution of such other materials in each of the respective classes .as will-meetthe requirements laid downabove for those classes of materialsi Should the material of the first class which quantity of copper tinsel l quantity of magnesium powder 16 as examples of the classes of mateis used be copper tinsel, and should the ma-l terial of the second class which is used be magnesium powder, it is sucient that 25 grams of copper tinsel and 10 grams of magnesium powder be used in an annealing container having a capacity of about 15 liters and'designed to receive about 200 pounds of material, although the quantities may be ingroove creased or decreased to accommodate the size bf the container used, A lid 18 having a de- A pending rim 19 covers the container, tray and contents the depending rim fitting within a 20 between the inner portions 13 and ythe lip groove 22 is filled with a stiff clay-composed of cupola loam 21, the upper surface being troweled flat. A suitable quantity of sealing mixture 22, preferably ofthe' type described in theapplication of B. J. Babbitt, for Annealing seals, Serial No. 316,146, iled October 31,- 1928, is sprinkled on the loam around the circumference of the lid. l I

After preparation in the above indicated manner, the container is placed in a furnace (not shown) and heat is applied thereto. Assume that the customary maximum tempera-l ture for annealing iron parts is 900 C. As heat is applied to the container the temperature within is slowly and steadily increased from the initial room temperature, and a substantial portion' of the oxygen is driven out through the loam seals by heat expansion of .the air remaining within the container. Being of a material and in such form as to be more readily oxidizable at lower temperature than the iron articles stored in the container,

\ the copper tinsel will absorb a large portion of the oxygen remaining in the container after the temperature has been raised to approximately 600 C., and the combination of the copperl tinsel with oxygen will continue until a point is reached commensurate with the oxidationpoint of the more energetically combustible magnesium. Experiments have shown that the magnesium combines with oxygen at a point somewhat lower than that at which the iron parts -would become materially oxidized. Owing to the great. 4natural affinity of magnesium, and other metals in its class, for oxygen the combination between the oxygen remaining in the container and thev magnesium powder has been found to take place with such energy that not only is all trace of oxygen removed from contact with the iron parts, but themagnesium has been found to act as a reducing agent on those portions of the parts which may have previously become oxidized. The remainder of the annealing process is carried on with the metal parts being heated in an atmosphere entirely free, from oxygen, no traces of oxidation will remain .upon the surfaces of the parts at the completion of the process and subsequent cooling steps and the articles will be found to possess the de'- siredA bright anneal.

' By the employment of the above method it may lbe seenv that a very small additional amount of labor beyond that which is ordinarily required to load and seal an annealing containervwill be required. Since copper tinsel in a form suitable for the practice of this method may bey produced as a by-product 12 of the vertical side walls. The` of the manufacture of telephone cords and since a comparatively small amount of-magnesium powder is required, it will be observed that the cost of bright annealing parts is not materially increased in spite of the fact that much better results are procured tainer copper tinsel and a combustible metal ,v

of. the group including magnesium and .alummum in powder form, sealing the container,

vand applying heat.

3. A method of annealing parts which consists of associating with the parts in a container a quantity of copper tinsel and a lesser quantity of magnesium powder, sealing. the container, and applying heat.

4. A method of annealing parts which consists of associating with the parts in a container copper tinsel'and magnesium powder in the proportions of 2.5 to 1.0 by weight, sealing the container, and applying heat.

5. A method of annealing parts which consists of associating with the parts in a container of 15 liters capacity 25 grams ofI cop-v per tinsel and 10 grams of powdered magnesium, sealing the container,l heat. Y,

6. A method of annealing parts which consists of associating with the parts in a container copper tinsel and an'easily oxidizable metal of the group which includes magnesium and aluminum in powder form, sealing the container, and applying heat.-

7 A method of annealing parts which consists in associating with the parts in a container a quantity of copper tinsel and a lesser quantity of powdered aluminum, sealing the container and applying heat.

8. A method of annealmg parts which con- -sists in associating with the parts in a conand applying In witness whereof, I hereunto subscribe my name this 12th dav of October, A. D. 1928.

' ROGER VERDEN WILSON,

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