US2357885A

US2357885A - Melting magnesium

Info

Publication number: US2357885A
Application number: US513460A
Authority: US
Inventors: Franks Russell; William O Binder
Original assignee: ELECTRO METALLURG CO
Current assignee: ELECTRO METALLURG CO; ELECTRO METALLURGICAL Co
Priority date: 1943-12-08
Filing date: 1943-12-08
Publication date: 1944-09-12
Anticipated expiration: 1961-09-12

Description

Patented 12,.

ammo MAGNESIUM Russell and William 0. Binder, Niagara Falls, N. Y., assignors to Electro Metallurgical Company, acorporation of West Virginia No'Drawing. Application December a, 1943,

Serial No. 513,460

8 Claims. This invention relates to the melting of magnesium and magnesium-base alloys and refers more particularly to containers for holding such materials in the molten condition.

A disadvantage of magnesium and its alloys which has hindered their use as structural materials for some purposes is their susceptibility to localized corrosion, generally believed to be due to impurities. Impurities are ordinarily introduced during melting operations in the manufacture of magnesium alloys or in the fabrication of useful articles from magnesium and its alloys. The impurities thought to have the most damaging effect on the corrosion resistance of magnesium alloys are iron and nickel.

It is the commercial practice to employ carbon steel containers for handling and holding molten magnesium and magnesium-base alloys during their manufacture or fabrication. It has been observed that magnesium and magnesium-base alloys so handled may have quite poor resistance to corrosion despite the fact thatmagnesium of materials which include the step of conducting such operations in containers composed of such steels.

The composition of the steel used for containem for molteni magnesium and its alloys in accordance with the invention may vary widely within the composition limits given. For example, containers may be composed of a steel containing 10% to manganese and 0.8% to 1.5% carbon. If a steel containing more manganese, say about 16% to is used, the car- 'bon content is preferably diminished and. should very high purity is used, but no commercially ments in the method of melting magnesium and magnesium-base alloys and in methods of handling such materials in the molten. condition.

The invention by which these objects are achieved is based on the discovery that molten magnesium and its alloys may be held in contact with certain steels, the principal characteristic of which is a high manganese, content, without seriously detrimentally affecting their resistance to corrosion. The invention comprises a container for molten magnesium and magnesium alloys, which container is composed of a steel-containing 10% to 30% manganese, the principal part of the remainder being iron. The steel of which the container of the invention is composed preferably also contains up to 18% chromium and may contain up to about 2% orsomewhat more silicon, up to 1.5% carbon, up to 2% columbium, up to 1% copper, up to 2% molybdenum, up to 3% nickel, and up to about 0.3% nitrogen, and the incidental impurities commonly present in steels of good quality. The invention also comprises the improved methods of melting magnot be more than about 0.5%. For containers more resistant to oxidation and loss of toughness at the elevated temperatures at which they are used, a steel containing up to 18% chromium, preferably 5% to 15% chromium, may be used. The presence of columbium up to about 2% or molybdenum up to about 2%, or both, improves the high temperature strength of the steel. Preferably, not more than 1% each of columbium 'or molybdenum is present, and steels containing these elements should contain less than 0.3% carbon. Small quantities of copper and of nickel may be present but the nickel content should not exceed about 3% nor the copper about 1%. Nitrogen in an amount not exceeding about 0.3% and preferably 0.05% to 0.15%, may be present in all of these steels as may be silicon, but the silicon content is preferably under 2%.

The corrosion-resistance of magnesium which has been melted in containers fabricated from the steels just described is markedly superior to the corrosion-resistance of magnesium, otherwise identical, which has been melted in containers composed of ordinary carbon steels. This conclusion is supported by the results of nu- 1 merous tests in which several different samples of commercially pure magnesium were melted in different containers embodying theinvention and in carbon steel containers under comparable melting conditions. Cast samples of the magnesium melted in these containers were subjected to corrosion tests in which the samples were exposed alternately to a 3% sodium chloride solution for a few minutes and to air for a few minutes, the alternate exposures being repeated and continued for a period of several days. In general, samples produced from the first one or two batches of magnesium melted in a given conftainer had poor corrosion-resistance, but -samples produced from successive batches melted in the same containers had markedly improved ourrosion-resistance-except in the case of samplesproduced from metal which had been melted in carbon steel containers. Typical test results are showninthe following tableinwhichthecorrosion rate of samples taken from successive batches of pure magnesium melted in containers having the composition indicated is expressed as loss of weight in milligrams per square centimeterperday.

tlooi aluminum: m l a ubs tanfiyaillron) number mm Mplapess-ll l The improved corrosion-resistance oi substantially pure magnesium melted in the containers of the invention, as compared with that of the same material melted in .carbon steel containers is evident from the above table. Similar resultswere obtained in tests conducted using several of the well known magnesium alloys now in commercial use containing manganese and aluminum. some with and some without zinc, such alloys exhibiting substantially the same order of improvement incorrosion-resistance when melted in the containers of the invention as that shown by the substantially pure magnesium.

To attain the benefits of theinvention, containers composed of the steel described should be employed whenever magnesium and its alloys are melted or are handled in the molten condition. By melting such materials and by handlingv canon and a' more viscous flux for others. The containers of the invention may be used for aw typeot melting procedure, with or without flux. In

the melting operations reported in ythe above table, a viscous flux containing about potassium chloride, 21% magnesium chloride, 19% calcium chloride, 12% magnesium fluoride, 7%

calcium fluoride and 7% chloride was I used.

We claim:

$1. In the art of handling molten magnesi and magnesimn-base alloys, the improvement which comprises holding such moltenmaterials in a container made of steel containing 10% to 30% manganese.

2. In the art of melting magnesium and magnesium-base alloys, the improvement which comprises melting such materials in a container composed oi a steel containing 10% to 30% manganese.

3. In the artoi melting magnesium and magnesium-base alloys, the improvement which comprises melting such materialsin a container composed of a steel containing 10% to 30% manganese and up to about 18%. chromium.

4. In the art of melting ium and magneslum-base alloys, the improvement which comprises melting such materials in a container compom of a steelcontaining 10% to '25 manganese, 12% to 15% chromium, up to about 2% each of columbium and silicon, up to about 1% of copper, up to about 2% of molybdenum, carbon in an amount not exceeding about 0.3%,

the remainder substantially all iron.

5. A container for use in contact with molten magnesium and magnesium-base alloys which container is composed of a steel containing about 10% 'to 30% manganese.

6; A container for use in contact with molte magnesium and magnesium-base alloys which container is composed of a'steel cents-lo n! about them. in the molten condition exclusively in such containers, the production of magnesium and magnesium-base alloys having greatly improved resistance to corrosion is achieved without changing substantially the composition of the materials now used commercially.

It is common practice in melting um and its alloys to conduct the melting operation under a protective flux blanket. A relatively fluid ilux is employed for some melting methods,

10% to 15% manganese, up to about 2% silicon, and 0.8% to 1.5% carbon.

7. A container for use in contact with molten magnesium and magnesium-base alloys which container is composed of a steel containing about 10% to 30% manganese, chromium'in an amount up to about 18%, and the remainder principally iron.

8. A container for use incontact with molten magnesium and magnesium-base alloys which container is composed oi a steel containing about 10% to 25% manganese, about 5% to 15%, chromium, up to about 2% silicon, up to about 2% columbium, up to about 1% copper, up to about 2% molybdenum, nitrogen in an amount not exceeding about 0.15%, the remainder substantially all iron and incidental impurities including nickel, the nickel content not exceeding 3%,.

RUSSELL FRANKS. WILLIAM O. BINDER.