US2090408A

US2090408A - Mold coating

Info

Publication number: US2090408A
Application number: US572227A
Authority: US
Inventors: Howard C Vance
Original assignee: EATON ERB FOUNDRY Co
Current assignee: EATON ERB FOUNDRY Co; EATON-ERB FOUNDRY Co
Priority date: 1931-10-30
Filing date: 1931-10-30
Publication date: 1937-08-17
Anticipated expiration: 1954-08-17

Description

Patented Aug. 17, 1937 MOLD COATING Howard C. Vance, Detroit, Mich assignor, by

mesne assignments,

to Eaton-Erb Foundry Company, Vassar, Mich, a corporation of Michigan No Drawing. Application October 30, 1931i,

. Serial No. 572,227

. Claims.

The specific object of my invention is to increase the life of cast iron or cast iron alloy molds such as used in production of iron castings.

The general object is to increase the life of 5 metal molds. Mold coatings heretofore in use have been in two classes. (1) Refractory coatings which were applied to the surface of iron molds such as shown in Meloche's Patent No. 1,492,694. (2) Coatings consisting of volatile substance. The volatile substances gave protection for a limited number of castings but required re.- newing frequently. Neither of these two types of coatings has been altogether satisfactory. The refractory coatings were porous and permitted the oxygen of the air to penetrate to the metal in the moldand to oxidize it and thus destroy the mold.

This invention involves the protecting of the surface of a cast iron mold by providing a thin integral coating of aluminum iron alloy whichis impervious to the oxygen of the a r. In practice the coating according to this invention is employed in conjunction with a refractory coating such as described in the above-mentioned Meloche patent. The coating according to the present invention is produced by first sand blasting the surface of the cast iron mold or cleaning by other means to eliminate all grease etc., and slightly to roughen the surface, then spraying molten aluminum onto the face of a cast iron mold to form a coating having a thickness of from .007 to .011'

40 the heating process the aluminum, being protected from air, does not oxidize, but alloys with the iron to form a permanent coating which is not destroyed by the heat of the grey iron castings which may be poured repeatedly into such molds without the coating requiring to be renewed. The same method may be applied to protect a steel mold or a copper mold with which aluminum alloys freely. The object of the application of potassium silicate is to insure that when heated the aluminum is protected from the action of air,-to hold the aluminum in place until the alloying process has been completed, and to insure that the mold itself heats up before the aluminum.

In the absence of the thin coating of potassium silicate or its equivalent, when the mold is placed in the oven to be baked, not only will the aluminum be oxidized before it is alloyed with the iron, but it will melt and run off and segregate in pockets; the desired uniform coating of aluminum will not be produced and the dimensions of the mold will be changed.

The aluminum iron alloy which is formed on the surface of the mold has a higher melting point than the cast iron and increases the heat resisting qualities of the mold. As cast iron has a. relatively low melting point and poor heat resisting qualities, it is most desirable to raise both of these in order the prolong the life of the mold. The life of the mold can be still further prolonged by using this coating of aluminum iron alloy in conjunction with the Meloche coating described in the above citedv patent and also in Patent No. 1,453,593, which patents teach "that a thin solution of sodium silicate in water, having'finely divided fire clay in suspension, is applied to a heated metal mold until a thin refractory coating of fire clay bonded with silica gel forms on the surface of the metal mold. Finally during the operation of the molds a relatively thick coating of lamp black is applied, which coating is removed and renewed between each casting.

'As mentioned above, the aluminum coating can be applied to an iron mold and also to molds formed of alloys of iron and nickel, and iron and chromium.. This coating can also be applied to copper molds and'molds formed of alloys of copper and tin (bronze) because aluminum alloys with copper as freely as it does with iron.

What I claim is:

1. The method of protecting the surface of a cast iron mold by spraying on the surface of the mold a layer of'from .007 to .011 of an inch .of aluminum, then brushing the surface of the layer of aluminum with a solution in water of a soluble silicate and placing the mold in an annealing furnace at a temperature in excess of 1650 Fahrenheit.

2. The method of protecting the working surface of an iron mold, which method comprises coating the working surface of the mold with an adherent layer of aluminum, protecting the sure face of the aluminum with'a-temporary coating consisting of a solution in water of a soluble material having a melting point in excess of 1750 Fahrenheit and then heating the mold in an annealing furnace at a temperature of at least 1650 Fahrenheit.

3. The method of protecting the surface of an iron mold by spraying on the surface of the mold a layer of from .007 to .011 of an inch of aluminum, then brushing the surface of the layer of aluminum with a solution in water of a soluble silicate and placing the mold in an annealing furnace at a temperature in excess of 1650 Fahrenheit.

4. The method of protecting the surface of a metal mold by sprayingon the surface of the mold a layer of from .007 to .011 of an inch of v aluminum, then brushing the surface of the layer of aluminum with a solution in water of a soluble silicate and placing the mold in an annealing furnace at a temperature in excess of 1650 Fahrenheit.

5. The method of protecting the working surface of when mold, which method consists in: covering the working surface of the mold with aluminum; protecting the surface of the aluminum with a temporary coating of a. material having a. melting point about 1750 Fahrenheit; and heating the protected mold at a temperature of at least 1650 Fahrenheit, in such a manner that the temporary coating protects the aluminum against oxidization, holds the aluminum in place until alloyed with the iron of the mold and causes the mold itself to be heated prior to the aluminum.