US1485635A - Manufacture of ferrous alloys and of weatherproof articles therefrom - Google Patents

Description

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JQHN MURDOCH smnnr, DE LONDON ENG-IlZtALhTD, ASSIGNOR TO THE CONTINUOUS v REAC'IIQN COMPANY, LIMITED, OF LONDON, ENGLAND.

MANUFACTURE @F FEBRD'US ALLOYS l lo Drawing.

To all whom it may concern Be it known that 1, Joan MURDOGH Srcrranr, a subject of the King of Great Britain, residing at 155 Ghurch Road, Bat- Cl tersea, London, England, have invented new and useful Improvements in the Manufacture of Ferrous Alloys and of Weatherroof Articles Therefrom, of which the folowing is a specification.

This invention relates to the manufacture of certain ferrous alloys and to the production from such alloys of manufacturedartiples the use of which involves their expost re to alternate wetting and drying, to to damp and varying atmos heric conditions,

or to like influences whic cause the rusting ]&of articles .made of ordinary iron or stee As is'wellknown, polished hardened artiac cles; such as cutlery, of the kind commonly called stainless are manufactured from iron-chromium alloys containing about 12 to 15 per cent of chromium and small percentages of carbon, silicon and other constituents. In my experience such alloys, although serving for the production of articles which are sufiiciently untarnishable under the conditions of domestic use, are of somewhat limited applicability. They cannot be successfully used for the manufacture of unpolished, weatherproof articles, such as imple ments, fittings, plates, castings, and the like, which have to withstand for long periods exposure to alternate wetting and drying, to damp and varying atmospheric COIldltions, or to like influences. Moreover, it is necessary both to harden by heat-treatment and to impart a polished surface to articles of that composition in order to render them reasonably untarnishable under the conditions of use for which they are intended. So far as I am aware, n article of such alloys has hitherto been made which, when exposed in a clean but unpolished condition, (for example, after drilling, machining, rough bufing or grinding) to the action of rain and sunshine would not become rusted in the course of a few days.

This invention relates to the manufacture of the iron-chromium alloys hereinafter described and the production from these a1- lo s of manufactured articles, hereinafter ca led for brevity weatherproof articles the use of which involves their exposure to AND or .wnarnnnrnoor .elnrrcnns THERE- rnonr.

Application nlcd June 11, 1928. Serial No. 644,751.

alternate wetting and drying, to damp and varying atmospheric conditions, or to like influences, and which in a polished or unpolished condition, and whether. hardened or not, are capable of withstanding such exposure for prolonged periods without rustmg. Examples of such articles are plates, rails, girders, cast objects, automobile parts, iitensils, implements and tools for out-d'oor use; ships fittings; bathroom fittings; burnished fenders; cooking stoves andthe like which are liable to have liquid spil-t on them.

It is known that iron and chromium can be alloyed with one another in widely different, and probably in all, proportions. It is also known that the alloys rich in chromium are comparatively resistant to the action of acids, but are of littlepractical in terest for the production of manufactured articles owing to their high cost, the difficulty of Working them, and their defective -physical and mechanical properties. We

higher the percentage of carbon, the higher the percentage of chromium) can be readily cast or Worked and that articles -manufactured of it are highly resistant to rusting when used in the rain or otherwise exposed to damp and varying atmospheric influences. l have also found that, the usual minor constituents of commercial steels have little or no prejudicial effect upon the weatherproof properties of articles made of the alloy. It is not necessary either to harden or to polish such articles in order to render them weatherproof, although they may be so treated if desired. \Vhen polished they possess the advantageous property that if accidentally scratched or roughened they remain weatherproof The invention consists in the manufacture of ferrous alloys containing from 12 to 24 per cent of chromium, from 0.4 to 3 per cent of molybdenum, from 0.5 to 0.85 per cent of carbon and from 0.1 to 1.3 per cent of silicon (the higher the percentage of carbon, the higher the percentage of chromium), with or without the usual minorconstituents of commercial steels, and in the the said alloys. Preferably the percentage of carbon in the alloy does not exceed a certain maximum, which depends upon the percentages of chromium and molybdenum resent, the rule for determining the preferred composition (herein termed the rule of maximum carbon percentage) being as follows With 0.4 to 0.5% Mo the'maximum' percentage of C corresponding to a given percentage Cr should be as stated in the following table (from which intermediate percentages can be deduced) Alloy containing 0.40.5% Mo.

(PC/0 (I '1 12 0. l 14 O. 3 16 0. 4 18 O. 55 20 0. 65 22 0. 7 5 24: 0. 85

- for example, by melting steel, chromium or ferrochromium and molybdenum or ferromolybdenum in the requisite proportions together in an electric furnace, care being taken to avoid as far as possible any inclusion of chromium oxide, which might otherwise injure the weather-resisting properties of the alloy. Weatherproof articles are then made of the alloy by the following usual methodsl If wrought articles'are to be produced, the molten metal is cast into ingots and afterwards hammered, rolled or otherwise worked and treated according to known methods, care being taken at all stages to avoid working oxide'into the metal, as the presence of particles of oxide on the surface tends to set up rusting. It is not necessary, in order to render the article rustless, to finish the manufacture by polishing the surface; a simple cleaning by grind I ing, bufing or the like is suflicient. If the 1,4.eaeae object in view is to produce castings, the molten metal is castin moulds in the usual way and the dark, oxidized skin may afterwards, if desired, be left on the casting without undue risk of rusting occurring.

E xample 1.

and then hammering and rolling into sheets,

which are cleaned by bufiing and formed into drums in the usual manner. The alloy can be readily cut and drilled.

Plates made of this alloy, either polished or unpolished and drilled partly through at various points to ofl'er shallow depressions in which rainwater might lodge, have been openly exposed during some weeks of rainy weather and have not rusted.

' Example 2.

' An alloy containing 17 .46 per cent of chromium, 0.47 per cent of carbon, 1.2 percent of silicon and 1.1 per centof molybdenum is prepared as in Example 1.

Range-finder parts to be used in an exposed-situation are manufactured from the alloy by casting it into ingots and workin it'by usual methods into the desired articles.

What I claim is 1. A ferrous alloy containing from 12.

to 24: per cent of chromium, from 0.4 to 3 per cent of molybdenum, from 0.05 to 0.85

per cent of carbon and from 0.1 to 1.3 per cent of silicon.

- 2. Weatherproof articles manufactured from a ferrous alloy containing from 12 to 24 per cent of chromium, from 0.4 to 3 per cent of molybdenum, from 0.05 to 0.85 per cent of carbon and from 0.1 to 1.3 per cent of silicon. I v

lin testimony that I claim the foregomg as my invention 1 have signed my name this v 28th day of May 1923.

JOHN itinianocn SKJELILEY;