US2893115A

US2893115A - Method of coating and working metal

Info

Publication number: US2893115A
Application number: US668771A
Authority: US
Inventors: Frank X Mccawley
Original assignee: Chicago Dev Corp
Current assignee: Chicago Dev Corp
Priority date: 1957-06-28
Filing date: 1957-06-28
Publication date: 1959-07-07
Anticipated expiration: 1976-07-07

Description

July 7, 1959 F. x. MCCAWLEY METHOD OF COATING AND WORKING METAL Filed June 28, 1957 mufimnw 20E 3: N w m o. N.

QmPOuhOmaZD 7 INVENTOR .FRANK x. MSCAWLEY BY w ATTORNEY inert atmosphere.

United States Patent METHOD OF COATING AND WORKING METAL Frank X. McCawley, Cheverly, Md., assignor to Chicago Development Corporation, Riverdale, Md., a corporation of Delaware Application June 28,1957, Serial No. 668,771

' 1 Claim. ores-424 "electrolytic process. For this purpose, I provide a molten bath of strontium, barium, sodium, potassium, lithium or calcium chloride. The bath may contain a mixture of these chlorides. I prefer a mixture of alkaline earth and alkali chlorides. I particularly prefer to use a bath containing 65% SrCl 35% NaCl, because such a bath is molten at relatively low temperatures and 810% titanium can be dissolved in it as lower chlorides together with one of the alkali or alkaline earth metals.

When the metal to be coated with TiC is coated with graphite and made a cathode in such a bath, a layer of titanium carbide is formed on its surface. The thickness of this layer depends on the thickness of the adherent graphite layer Which can be applied. In most cases, this is on the order of 1 mil.

The extent of protection afforded for a titanium surface during hot working is illustrated in the sole figure which shows the oxygen penetration for unprotected titanium, for titanium protected by a salt layer and for titanium protected by a layer of titanium carbide.

I have used other procedures for producing a layer of titanium carbide on titanium such as heating to a high temperature in argon containing a small percentage of hydrocarbon gas. I have found, however, that titanium carbide layers produced in this manner are less adherent and protective.

Having now described my invention in its more general terms, I will illustrate it by examples.

Example I I take an ingot 4" x 4" x of titanium-vanadium alloy containing 4% V, 01% oxygen, balance substantially titanium. I split this lengthwise to obtain two identical portions each 2" x 4" x 10". I coat one of these with graphite and make it a cathode in a cell having a particulate titanium anode contained in an annular perforate iron basket and the cathode disposed in the center of the cell surrounded by the perforate basket. The cell is provided With an inert atmosphere and means for raising the cathode out of the bath and cooling it in an The cell bath consisted of 65% strontium chloride 35% sodium chloride in which was dissolved 8% titanium as chloride, average valence 2.4 and 3% alkalinous metal calculated as sodium. A di- 2,893,115 Patented July 7, 1959 rect current of amperes was passed for minutes at 750 C.

After cooling in an inert atmosphere, the portion of the ingot with adhering salt, fine titanium crystals and titanium carbide layer is placed in a furnace at 900 C. along with the untreated portion. Heating is continued for 1 hour and both pieces are hot rolled to A" thickness without reheating. They are then reheated for 15 minutes and hot rolled to A" thickness. Both pieces are then scalped to remove 4 mils of the original metal on both sides. The piece protected by the plating operation then analyzed .014 oxygen and the other piece .071

oxygen. Example I! I take a bar Mt" x 12" x 3' steel and treat it in the same manner as the titanium alloy ingot in Example I to produce a coating of titanium carbide on the bar. I hot roll this bar at 750 C. to 40 gauge strip. The resulting strip has a coating of titanium carbide which protects the steel from surface contamination. I take several portions of the sheet and galvanize it by hot dripping. The adherence of the zinc is good and the brittle layer of iron zinc alloy common in hot galvanizing is absent.

Example 111 I proceed as in Example I except that the cell bath is NaCl in which is dissolved 4.5% titanium as chloride, average valence 2.4 and .3% sodium. The bath temperature is 850 C. The metal treated is highly pure zirconium. The results are identical with those of Example I.

Example IV I proceed as in Example I except that I use a cell bath of KCl 10% BaCl in which is dissolved 2% titanium as chloride, valence 2.15 and 2.5% alkalinous metal (calculated as K). The metal to be treated is a zirconium alloy containing .2% iron. The results as to oxygen absorption on hot rolling are the same as in Example I.

Example V I proceed as in Example I except that the cell bath is 50% CaCl 50% LiCl and the metal to be treated is pure titanium. The temperature of the cell bath is 800 C. The results obtained are identical with those in Example I.

Example VI I take a strip 4" thick of pure titanium containing .0l% oxygen and substantially no other impurities. I heat this strip in a mixture of CH, and TiCL, at 800 C. whereby to coat it with TiC. I but roll the so-coated strip at 850 C. to reduce it to one-half its thickness. I scalp .004 inch from each side. The resulting strip analyzes .02% oxygen.

Example VII In this example I apply the procedure of my invention to the protection of titanium-aluminum alloys during hot working. Such alloys of usual purity containing 10% aluminum have been found to break up when hot rolled at 1650 F. I have found that this is due to very rapid oxygen absorption. In this example I make an ingot of aluminum-titanium alloy containing 10% aluminum, .02% oxygen, and substantially no other impurity. I cast this ingot by rubbing with flake graphite and then provide a further carbon coating by exposing the ingot to a smoky acetylene flame. I make this ingot a cathode in a bath consisting of calcium chloride having dissolved therein 10% titanium chloride, average valence 2.4, and 3% metallic calcium, the anode is particulate titanium. I employ a cathode current density of amperes/sq.

ft. for 15 minutes. A titanium carbide layer is formed on the ingot which layer is covered with salt and finely divided titanium. The so protected ingot is heated to 165.0 Ftvin air. and hot rolled. The hot rolling proceeds smoothly, and an analysis of the hot rolled bar aftenremoving. .005. inch from the surface shows 10,1%- aluminum,f .025% oxygen, balance substantially titanium.

whatisiclaimed-is: 5 The method of. fabricating a metalselected from the group consisting of titanium, and zirconium, and alloys consisting principally bf these metals which consists in coating said metal with carbon and making it a cathode in anelectrolyticcellshaving a fused electrolyte of at least onechloride; selected from the group consisting of calciurn, strontium, barium, sodium, potassium and lithium chlorides and dissolved therein 140% titanium aslower chlorides and .1-5 of a metal corresponding to the chlorides of the fused electrolyte, and passing a direct current from a particulate titanium anode to said cathode whereby to form a coating on the cathode surface and then fabricating the metal by subjecting it to working at temperatures from 750-900 C., whereby to limit oxygen absorption to .02'% when a surface layer about 5 mils: thick is removed.

References Cited in the file of this patent UNITED STATES PATENTS