US1599435A - Ferrous alloy - Google Patents

Description

Patented Sept. 14, 1926.

UNITED STATES- IBYIBAMJI D.. SAKLATWALLA, OF GRAFTON, PENNSYLVANIA.

rnnnous ALLoY.

No Drawing.

1 The present invention relates to ferrous allys and particularly to a ferrous alloy contaimng chromium and copper. The addition-of chromium -to ferrous metal contain- 5 ing carbon imparts to it great hardness. To

combine increased ductility and d namic strength with this property several alloying elements, such as nickel and molybdenum,-

either singly or in combination are at prescut added to steel together with the chromium. All such elements are costly and consequently unduly raise the manufacturing cost of the steel by their addition.

The disadvantage of high cost is obviated and chromium steels combining high tensile strength with remarkable ductility areproduced by the addition of copper to them; The

percentages of copper necessary to produce this result are low, so that the reduction of y cost is attained, not only owing to the comparatively chea price of copper, but also to the verysma 1 amount of copper used per ton of'finished steel.

It has been found that an addition of copper, ranging from .15 to .-5()% to steel contaiiiing .3 to. 3.50% chromium increases its ductility and toughness to a very remarkable extent. The presence of copper also does not interfere with any properties imparted to 80 the steel by reason of its carbon and chromium contents. On the contrary, the copper content acts in an additive manner towards augmenting the tensile strength derived from the carbon and chromium contents, also 'in- 85 creasing the ratio of elastic limit to tensile strength. Consequently, it is possible to obtain steels of widely different physicalproperties suitable for a wide range of purposes, by varying the combinations ofpercentages 40 of carbon, chromium and copper in them.

Also the presence of copper does not interfere in any way with the possibilities of" heat treatment, thus allowing a latitude in the production of a variation of physical 4 properties.

Such combinations of chromium and copper are useful in ferrous alloys, not only of the steel range, that is, containing carbon up to about 2%, but also in the cast iron ranges of carbon between 2 and 3.50%. Com binations of copper from .15 to .50% and "chromium from .3 to 3.50% impart to cast iron properties of great hardness and strength, also the remarkable property of possessing this hardness and strength t Application filed August 28, 1922'. Serial No. 584,552.

higher temperatures,- at the same time withstanding the action of oxidation at such temperatures.

The ferrous alloys of these chromium copper compositions besides showing the described physical properties, possess an extremely high degree of resistance to corrosion, not onl in the hardened, but also in the anneale and natural states as cast, forged or rolled. Their resistance to mineral acid corrosion is especially remarkable. Also it is possible to produce the resistance necessary for a particular case by varying the chromium and copper contents. For instance, in the case of sulphuric and hydrochloric acids, the higher the copper content, the more resistive the alloy is to-sulphuric and less to hydrochloric, and the higher the chromium content, the more resistive it is to hydrochloric and less to sulphuric acids. Also the resistance to corrosion is influenced by the carbon content, the higher the carbon, the less resistive is the alloy to corrosion. This disadvantage of the high carbon content can, however, be obviated by an increased silicon content up to about 1%, the

effect of such a content of silicon being the same as though the high percentage of carbon'were absent. I

'The silicon not only affects the non-corrosive properties of the alloy, but also its mechanical properties, suchv as hardness. The presencev of silicon in the chromiumcopper-ferrous alloy allows it to be more easily rolled and fabricated and imparts ductilityto the metal.

Claims directed specifically to the inclusion of silicon in the applicants chromiumcopper-ferrous alloy are presented in applicants copending application, Serial No. 704,633, filed April 7, 1924.

It is thus obvious that by the variation of percentages of chromium, copper, carbon and with the help of silicon a variety of ferrous alloys can be produced, which are non-corrosive to particular agencies in question,

such as organic and mineral acids, vmine waters, sea and fresh waters, atmospheric I influences, and which are of the desired malleability, etc.

It has been found that steels' containing from .3 to 1.25% of chromium and only. .15 to .50% copper have very remarkable allround non-corrosive properties, suitable for several purposes. This fact makes this chromium and copper specified, namely, that the alloy is more reliable than when larger amounts of chromium and copper are employed. It is a generally recognized rule that the smaller the alloying elementsjn steel, the more reliable is the steel, and I have found this to be true of a copper and chromium alloy steel. For the usual steels, I prefer to use about from .4 to 1% of chromium and from .2 to .4% of copper. These percentages are suflicient to give high tensile strength, considerable ductility and resistance to corrosion. These amounts of copper and chromium are low enough so that the alloy is very reliable. These comparatively small amounts of copper and chromium give to the steelsubstantially the same resistance to corrosion as higher amounts of copper and chromium and a considerably greater resistance to corrosion than considerably greater amounts of copper andchromium used alone. They also give better physical. properties than 'larger amounts of copper and chromium mixed or larger amounts of copper alone or chromium alone. There is apparently a critical limit of about one-half of 1% for copper when added to a low chrome steel, that is, a chrome steel having not more than about 2 or 3% of chromium. If more than about one-half of 1% of copper be added to such a chrome steel, the copper has a tendency to segregate, and to adversely affect the physical properties of the metal, especially its dynamic strength and resistance to impact. In steels of a higher chromium content, more than one-half of 1% of copper may be added without this tendency, but apparently one-half of 1% of copper is a critical limit for steels having not over 2 or 3% of chromium.

While the amount of chromium may be increased above 1 or 1 4% and the amount of copper increased above .4 or'.5% such additional amounts do not increase the beneficial effects sought for in ordinary steels.

For example, .7- or .8% of copper does not apparently give any more beneficial results than about .4% of copper, the extra copper apparently being more or less inert, and its addition involving needless expense. The extra copper is, if anything, deleterious, particularly for 10y; chromium contents, on acinterfere with the strength is meant the resistance of the steel Y to repeated shocks, small stresses and vibrations. The addition of the copper increases the ductility and the dynamic strength of the steel, while still preserving the increased tensile strength and hardness due to the chromium. The addition of the copper and chromium to steel, as herein specified, also increases the ratio of the elastic limit to the ultimate strength. I have found that with the amounts of copper and chromium which I employ for ordinary steels, the chromium tends to make the steel less malleable, while the copper increases its malleability and the two combined give a steel which has great tensile strength and hardness, but which can be rolled and forged.

In forming the alloy, suflicient carbon (should be present to give the desired tensile strength and hardness in combination with the chromium and copper. The carbon should in general be over .1% to be effective in imparting high tensile strength and hardness to the steel. The chromium and copper apparently react with the carbon and tend to maintain the carbon as hardening carbon and prevent its segregation This permits mium hold the carbon in its combined hard-- ening form at an increased temperature. This is of considerable advantage in the making of tool or roll steel, which is subjected 'to heat, because the steel will not soften in use at a temperature. which would soften the plain carbon steel. The ability of the copper and chromium to holdthe carbon in its hardening state is particularly valuable in high carbon steels or high. car.- bon cast iron, in that a high. percentage of carbon may be kept in the hardening state so as to form a very hard article. I

The addition of the copper to the chromium steel makes the steel non-corrodible in all states, whether hardened or annealed or polished or rough. thus being a great improvement over the usual chromium steels which, while showin reat resistance to corrosion, when polis e will be corroded if the surface is rough. i

In the above described ferrous alloys no reference is made to the presence of other elements, such as manganese, sulphur, etc., always present in steels and cast irons, as their presence to the usual extent does not hysical properties or non-corrosiveness of t e described ferrous al- I loys.

The present invention is not limited to the exact proportions set forth, as its preferred embodiment, but may be otherwise embodied within the scope of the following claims.

I claim:

1. A ferrous allov contaimng about .2 to .4%-copper and .4 to 1% chromium together with carbon. A

2. A ferrous alloy containing over .15% but less than .5% copper and between .3% and 3.5% chromium.

3. A ferrous alloy containing copper in appreciable amounts but less than .5% and chromium in appreciable amounts but not over 3.5%.

4. A ferrous alloy consisting principally of iron and containing chromium in an appreciable amount, but less than 8% and copper over 15% but less than .5%.

5. A ferrous alloy containing about .2' to .4% copper and about .3 to 3.5% chromium together with carbon.

'In testimony whereof I have hereunto set my hand.

I BYRAMJ I D. SAKLATWALLA.