Silicon Alloy Steel

Abstract

Pure silicon is a brittle insulator and, with addition of doping elements, performs as a semiconductor. It has found widespread use in computer integrated circuits as well as other semiconducting devices used in communication, electrical switching and power control. Silicon has also been used in solar collectors as active photovoltaic devices. The present application discloses formation and use of certain silicon alloys that take advantage of silicon's relatively low density near 2.33 grams per cubic centimeter and high melting temperature of 1,410° C. Alloys prepared with two to six percent boron, beryllium or mixtures thereof are strong and tough. Silicon steel containing near 2 percent alloying boron is hard while silicon alloys containing near 6 percent boron are tough and more flexible.

Description

REFERENCES CITED

U.S. Patent Documents

Pat. No.	Issue Date	Author	Comments
7,321,140	Jan. 22, 2008	Y Li, J J Chen,	Magnetron sputtered metallization of a nickel silicon alloy,
		L Yang	especially useful as solder bump barrier where the alloy
			contains at least 2 wt % silicon and preferably less than
			20 wt %. Commercially available NiSi.sub.4.5% sputter
			targets have provided a superior under-bump metallization.
6,923,935	Aug. 2, 2005	R J Donahue,	A hypoeutectic aluminum silicon casting alloy includes
		T M Cleary,	10 to 11.5% by weight silicon, 0.10 to 0.70% by weight
		K R Anderson	magnesium and also contains 0.05 to 0.07% by weight
			strontium.
6,149,862	Nov. 21, 2000	N I Gliklad,	Iron-silicon alloy product, exhibiting improved resistance
		A B Kuslitskiy,	to hydrogen embrittlement and method of making the
		L A Kuslitskiy	same. It has 1.38% to 1.63% weight Si, 0.10% to 0.25%
			weight C and 0.10% weight of at least one element from
			Be, Mg, Al, Ca, Sc, Ti, V, Cr, Mm, Co, Ni, Cu, Zn, W,
			Mo, Ge, Se, Rb, Zr, Nb, Ru, Ag, Cd, La, Ce, Pr, Nd, Gd,
			Tb, Dy, Er, Re, Os, Pb, Bi, U, N and other REM.
5,080,862	Jan. 14, 1992	K L Luthra	Iridium silicon alloy having a very high resistance to
			oxidation contains 30 to 75 atom percent silicon.
5,049,357	Sep. 17, 1991	H Matsuno, T Takaoka,	Method for manufacturing iron-boron-silicon alloy.
		Y Kikuchi, Y Kawai,
		T Nishi

BACKGROUND

Field of Invention

Common construction steel like A36 carbon steel is more than 95 percent iron, the other constituents being <2.1% carbon, <1.65% manganese, <0.4% copper and <0.6% silicon. These carbon steels have a density of 7.8 g/cm³, a yield strength of 36,000 psi (250 MPa) and an ultimate tensile strength of 58,000-80,000 psi (400-550 MPa). A500 cold-formed steel is produced by reducing the carbon content to 0.26% and maintaining minimums for phosphorous and sulfur. Iron melts at 1,538° C. and low carbon steel alloys generally corrode readily. A number of other dense, strong steel and stainless steel alloys have been produced for industry, all based on iron. Construction aluminum, like alloy 6061, is more than 96 percent aluminum, the other constituents being 0.6% silicon, 0.5% iron, 0.25% copper, 0.1% manganese, 0.2% chromium, 0.15% zinc, 0.1% titanium and other elements <0.15% total. These aluminum alloys have a density of 2.7 g/cm³, a yield strength of 8,000 psi (55 MPa), elongates 25 to 30% and has an ultimate tensile strength of 18,000 psi (125 MPa). Aluminum alloys suffer from brittle fracture and aluminum melts at 660° C. producing reduced strength at elevated temperature.

Silicon is a common element, a brittle non-metallic material thus few alloys are in wide spread use. Its advantages are a low density near 2.33 g/cm³, a high melting temperature of 1,410° C. and it is not easily corroded. The present application discloses formation of certain silicon alloys prepared with 2 to 6 percent boron or beryllium creating materials that are tough, strong and not brittle as is elemental silicon.

Description of Prior Art

Energy demands of the transportation and construction industries favor low cost, strong, light weight materials that do not degrade over time. Silicon alloys, as disclosed in this application, are needed to fill these requirements. A number of specialty materials have been described that employ silicon. U.S. Pat. No. 7,321,140, issued Jan. 22, 2008, disclose use of nickel silicon alloy for use in interconnect solder bumps. Magnetron sputtered metallization of a nickel silicon alloy was especially useful as solder bump barrier where the alloy contains at least 2% silicon and preferably less than 20%. Commercially available NiSi_4.5 sputter targets have provided a superior under-bump metallization. U.S. Pat. No. 6,923,935, issued Aug. 2, 2005, describe a hypoeutectic aluminum silicon casting alloy that includes 10 to 11.5% by weight silicon, 0.10 to 0.70% by weight magnesium and also contains 0.05 to 0.07% by weight strontium. A specialty iron-silicon alloy product exhibiting improved resistance to hydrogen embrittlement is described in U.S. Pat. No. 6,149,862, issued Nov. 21, 2000. It has 1.38% to 1.63% weight silicon, 0.10% to 0.25% weight carbon and 0.10% weight of at least one element from the list Be, Mg, Al, Ca, Sc, Ti, V, Cr, Mm, Co, Ni, Cu, Zn, W, Mo, Ge, Se, Rb, Zr, Nb, Ru, Ag, Cd, La, Ce, Pr, Nd, Gd, Tb, Dy, Er, Re, Os, Pb, Bi, U or N. U.S. Pat. No. 5,080,862, issued Jan. 14, 1992, teaches use of an exotic iridium silicon alloy having a very high resistance to oxidation contains 30 to 75 atom percent silicon. U.S. Pat. No. 5,049,357, issued Sep. 17, 1991, describes a method for economically manufacturing an iron-boron-silicon alloy through simple steps, which comprises the steps of: adding a boron raw material and a carbonaceous reducing agent to a molten iron received in a vessel; blowing oxygen gas into the molten iron to reduce the boron raw material in the molten iron by means of the carbonaceous reducing agent to prepare a boron-containing molten iron; continuing the blowing of oxygen gas to decarburize the boron-containing molten iron until the carbon content in the boron-containing molten iron decreases to 0.2 wt. %; and adding at least one of silicon and ferrosilicon to the boron-containing molten iron while stirring the boron-containing molten iron, thereby manufacturing an iron-boron-silicon alloy.

None of this prior art describes production or use of silicon alloys comprising a majority of silicon with 2 to 6 percent boron or beryllium added to produce structural alloys.

SUMMARY OF THE INVENTION

The present application discloses formation of certain silicon alloys that are quite different from aluminum and iron based steel alloys, take advantage of silicon's relatively low density and high melting temperature of 1,410° C. These alloys as prepared with 2 to 6 percent boron or beryllium are tough, strong and resist corrosion.

It is an object of this invention, therefore, to disclose boron and beryllium silicon alloys that are tough and strong with a reduced tendency toward corrosion. Other objects of this invention will be apparent from the detailed description thereof which follows, and from the claims.

DETAILED DESCRIPTION OF THE INVENTION

Pure silicon is brittle and not suitable for use as a construction material. Addition of additives comprising boron and beryllium, in a concentration range comprising 2 to 6 percent, to pure silicon form alloys with surprisingly good mechanical characteristics. These alloys are light weight in that they have densities of less than 2.7 grams per cubic centimeter. Once produced, they can be cut and formed like rigid steel.

Boron silicon alloys can be prepared by a number of methods, the simplest being from finely divided pure elements melted under an inert atmosphere. Blending a selected concentration comprising 2 to 6 percent finely divided elemental boron with a majority of finely divided elemental silicon, loading into a clean alumina crucible, moving into a furnace, carefully degassing and purging with an inert atmosphere during the entire heating process produces the desired alloy upon cooling. For example, a silicon steel alloy is formed by heating a uniform mixture containing 4.5 percent of finely divided 99% pure elemental boron and 95.5 percent of finely divided 99.5% pure elemental silicon, contained in a suitable crucible in an inert atmosphere, at 1,470° C. until completely molten. Upon cooling a strong, malleable steel alloy is evident.

Beryllium silicon alloys can be prepared by blending a selected concentration comprising 2 to 6 percent finely divided elemental beryllium with a majority of finely divided elemental silicon, loading into a clean alumina crucible, moving into a furnace, carefully degassing and purging with an inert gas atmosphere during the entire heating process produces the desired alloy upon cooling. For example, a uniform mixture containing 4.5 percent of finely divided 99% pure elemental beryllium and 95.5 percent of finely divided 99.5% pure elemental silicon, contained in a suitable crucible, is heated in an inert atmosphere at 1,350° C. until completely molten. Upon cooling a strong, malleable steel alloy is formed.

EXAMPLES OF CHEMICAL CONVERSION

Specific examples of boron or beryllium silicon alloy compositions are disclosed.

Example A: Boron Silicon Alloy Steel

A uniform mixture containing 1.125 grams of finely divided 99% pure elemental boron and 23.875 grams of finely divided 99.5% pure elemental silicon, contained in a suitable crucible, was heated in an inert atmosphere at 1,470° C. until completely molten. Upon cooling a silver-gray colored steel alloy was found to be strong and malleable but not brittle. Its density was 2.69 grams/cubic centimeter.

Example B: Beryllium Silicon Alloy Steel

A uniform mixture containing 1.075 grams of finely divided 99% pure elemental beryllium and 23.925 grams of finely divided 99.5% pure elemental silicon, contained in a suitable crucible, was heated in an inert atmosphere at 1,350° C. until completely molten. Upon cooling the steel alloy was found to be strong and malleable but not brittle.

Claims

1. A process for formation of silicon steel alloy comprising melting together silicon with selected 2 to 6 percent boron in the temperature range comprising 1,400° C. to 1,800° C. in a suitable crucible in an inert atmosphere.

2. A process for formation of silicon steel alloy comprising melting together silicon with selected 2 to 6 percent beryllium in the temperature range comprising 1,200° C. to 1,600° C. in a suitable crucible in an inert atmosphere.

3. A process for formation of silicon steel alloy comprising melting together silicon with selected 2 to 6 percent boron, up to 2 percent of manganese for toughness and up to 0.5 percent sulfur for corrosion resistance in the temperature range comprising 1,400° C. to 1,800° C. in a suitable crucible in an inert atmosphere.