US2280796A - Phosphorus titanium steel - Google Patents

Description

Patented Apr. 28, 1942 UNITED STATES PATENT OFFICE rnosrnonns TITANIUM STEEL George F. Comstock, Niagara Falls, N. Y., assignor to The Titanium Alloy Manufacturing Company, New York, N. Y., a corporation of Maine No Drawing. Application December 18,1940, Serial No. 370,683

2 Claims.

contributes to these desirable qualities and can be used safely if the carbon content is not too high. However, for steels which are fabricatedby welding, the property of maintaining toughness when rapidly cooled from high temperatures, or absence of air-hardening, also becomes of great importance. Many of the low-alloy high-strength steels, which are now in use and which rely on phosphorus as a strengthening and anti-corrosion agent, are not specially. desirable for welded structures because they are apt to crack, harden and lose too much ductility when rapidly cooled in air from the welding temperature.

These difliculties can be overcome by providing a new alloy steel containing carbon, phosphorus, titanium, silicon, manganese and copper in certain well defined and limited percentages.

As in the case of many alloys, greater tolerance is permitted in the case of some of these alloying elements than with others. quantity of carbon should be most strictly limited, followed by phosphorus, titanium. silicon, manganeseand copper in order of importance. If the carbon is allowed to drop too low, the strength of the resulting steel will be impaired. If it is allowed to rise too high, the steel becomes much too brittle when rapidly cooled from high temperatures, as in welding. 'With low phosphorus, the steel will not be sufiiciently anti-corrosive; with high phosphorus, the steel becomes brittle as with high carbon. Low amounts of titanium can be permitted only if the carbon and phosphorus are also low, while excessive amounts of titanium should be avoided from the standpoint of expense. High silicon tends to 'make the steel brittle. High copper causes precipitation hardening on slow cooling, and creates difiiculty in maintaining smooth surfaces in rolling.

Thus the,

In accordance with this invention the broad and preferred quantities of these alloying 'elements are as follows:

Broad Perlcrrcd Percent Carbon 0. 12 0.08 to 0. 11 Phosphorus 0.20 0.10 to 0. 16 Titanium 0. O. 40 to 0. 60 S,i1icon L 0. 0.30 0.15 to 0.25 Manganese 0. 1.50 0. to 1.25 pper 0 to 1.20 o. 45 to 0.60

Most of the balance of the alloy is iron, but small amounts of chromium, nickel, molybdenum, vanadium, zirconium and/or columbium, and perhaps also other elements, may be incorporated without detracting from the desirable characteristics of the present alloy. ments, such as chromium, may in fact enhance these characteristics slightly, but-any improvement attained does not usually justify the expense of these elements. 25

The present alloy is characterized by its resistance to corrosion, a high yield point of at least 50,000 pounds when cooled in still air (normalized) from 1650 F., high tensile strength, high ductility and'high resistance to impact, with an Izod impact value of at least 20 when quenched in water from 2000 F.

The following Table I illustrates various alloys according to this invention. In each case substantially the balance of the alloy is iron.

Table I Example 0 P Ti 1 Si Mn Cu .145 585 l6 1. 34 07 147 57 21 87' 58 147 54 .18 33 1.01 .142 .48 20 1. 22 .44 128 42 24 1. 12 5 12 315 15 .99 5 080 442 22 1. ll 5 .083 315 .19 1.15 .53

In the following Table II, some of the physical characteristics of these alloys are indicated:

Some of these ele-' Quenched in water from 2,000 F. Example Yield Tensile Reduction Brinell Impact strength of area hardness value Percent The yield point and tensile strengthare given in pounds per square inch, and the impact value is the Izod impact resistance in toot-pounds.

The inferior nature of alloys resulting when some of the alloy constituents fall outside the ranges indicated are shown from similar tests made on such alloys. For example, an alloy containing 0.094% carbon, 0.15% phosphorus, 0.45% titanium, 0.50% silicon, 0.88% manganese, and 0.47% copper, with the remainder. iron, showed an impact value of only 5 when quenched in water from 2000 F., showing the effect of high silicon. An alloy containing 0.095% carbon, 0.791% phosphorus, 0.60% titanium, 0.21% silicon, and 0.38% manganese, with the remainder iron, shows the eflect of high phosphorus. A sample of this alloy, when quenched in water from 2000 F., was so brittle that it broke in machining prior to testing. The efi'ect of low titanium is shown by an alloy containing 0.07% carbon, 0.127% phosphorus, 0.218% titanium, 0.18% silicon, 1.09% manganese, and 0.52% copper, with the remainder iron. When quenched in water from 2000 F., this alloy had an impact value of only 11. Finally, the effect of too high carbon is shown As with the other alloys discussed, the remainder is substantially iron.

As is well known in steel making practice, titanium and carbon combine to form titanium carbide. (TiC), and in this respect titanium is similar to zirconium, columbium and vanadium. However, titanium is cheaper and more readily available than these metals' In addition, titanium has a marked effect on the phosphorus in the alloy, in particular reducing the tendency of the latter to make the steel brittle. The titanium may be added to the steel in the form of lowcarbon or medium-carbon ferro-titanium. The latter, being less expensive, is preferred whenever the carbon content of the steel will not be 7 unduly raised by its addition.

By the practice of the present invention structural steels or high yield point and good weldability may be obtained. They may be quenched in water from high temperatures without great increase in hardness or loss in resistance to impact. They have excellent resistance to corrosion.

As many variations are possible within the scope of this invention, it is not intended to be limited except as defined by the appended claims. It is understood, for example, that the present invention contemplates the addition of small amounts of chromium, nickel, molybdenum, vanadium, zirconium and/or columbium, where such additions do not change the fundamental characteristics of the alloy.

Iclaim:

1. An iron-base alloyor steel consisting of 0.06% to 0.12% carbon, 0.08% to 0.2% phosphorus, 0.2% to 0.7% titanium, 0.1% to 0.3%

silicon, 0.3% to 1.5% manganese, an appreciable amount up to 1.2% copper, and the balance iron,

characterized by its resistance to corrosion, a yield point of at least 50,000 pounds per square inch when normalized at 1650 F., high tensile strength, high ductility, and an Izod impact resistance value of at least 20 foot-pounds when quenched in water from 2000 F.

2. An iron-base alloy or steel consisting of 0.08% to 0.11% carbon, 0.1% to 0.15% phosphorus, 0.4% to 0.6% titanium, 0.15% to 0.25% silicon, 0.85% to 1.25% manganese, 0.45% to 0.6% copper, and the balance iron, characterized by its resistance to corrosion, a yield point of at least 50,000 pounds per square inch when normalized at 1650 F., high tensile strength, high ductility, and an Izod impact resistance value of at least 20 foot-pounds when quench in water from 2000 F.

GEORGE F. COMSTOCK.