US1972524A - Alloy steel spring - Google Patents

Description

Patented Sept. 4, 1934 UNITED STATES PATENT OFFICE ALLOY STEEL SPRING No Drawing. Application September 30, 1931, Serial No. 566,180

3 Claims.

My invention relates to alloy steel springs, and more particularly to alloy steel leaf springs.

The steels heretofore commonly used in the manufacture of leaf springs require quenching, usually in oil, from an elevated temperature and a subsequent draw at a moderate temperature, before they acquire satisfactory physical properties. This heat treatment not only adds appreciably to the cost of the finished springs, but also lowers the effective fatigue limit by causing the development of incipient cracks and strains within the metal. Although these incipient cracks may not be detectable in the quenched steel, and although the drawing operation may have been used to minimize strains, nevertheless the drastic quenching treatment so affects the steel as to reduce greatly the fatigue limit, and this is particularly true if the surface be left as treated and not ground and polished.

What I have discovered is that the addition of moderate amounts of certain hardening elements such as chromium, vanadium and molybdenum to a silico-manganese base steel yields an alloy steel which; upon being fabricated into a'spring and simply air-cooled fromthe forming temperature, has sufiicient strength for satisfactory operation, and is free from the incipient cracks and strains common to oil-quenched springs.

For example a steel containing from about 0.5% to about 0.7 carbon, from about 1% to about 1.5% of manganese, from about 0.5% to about 1% of silicon, from about 0.4% to about 0.6% of chromium and about 0.15% to about 0.3% of vanadium, when normalized and air-cooled from a forming temperature of about 900 C. has a tensile strength of about 200,000 pounds per square inch with a minimum elongation of about 10% in 2 inches, and has an exceptionally high effective fatigue limit.

Steels which are to be used in heavy springs may advantageously contain up to about 1.5% of chromium, about 2.25% of manganese, about 0.9% of carbon, about 2% of silicon and about 2% of vanadium, although it is not generally economical to use as high as 2% of silicon or vanadium.

The alloy steels of my invention can be fabricated into springs without the added expense of heat treatment, and when so fabricated lack the incipient cracks which quenching would develop.

Molybdenum may be substituted for the chromium in these steels wholly or in part, and other modifications may be made without departing from the essentials of my invention.

I claim:

1. A spring characterized by a high fatigue limit, a tensile .strength approximating 200,000 pounds per square inch, an elongation under tension of at least about 10% in 2 inches, and having substantially the composition: 1% to 2.25% manganese, 0.5% to 2% silicon, 0.5% to 0.7% carbon, 0.4% to 1.5% chromium, 0.15% to 0.3% vanadium, the balance iron; which spring has been hardened by air-cooling from the forming temperature. A i

2. A spring characterized by a high fatigue limit, a. tensilestrength approximating 200,000 pounds per square inch, an elongation under tension of at least about 10% in 2 inches, and having substantially the composition: 1% to 1.5% manganese. 0.5% to 1'% silicon, 0.5% to 0.7% carbon, 0.4% to 1.5% chromium, 0.15% to 0.3% vanadium, the balance iron; which spring has been hardened by air-cooling from the forming temperature.

3. A spring characterized by a high fatigue limit, a tensile strength approximating 200,000 pounds per square inch, an elongation under tension of at least about 10% in 2 inches, and having substantially the composition: 1.1% to 114% manganese, 0.8% to 1% silicon, 0.55% to 0. carbon, 0.4% to 0.6% chromium, 0.15% to 0.30% vanadium, the balance-iron; which spring has been hardened by air-cooling from the forming temperature.

AUGUSTUS B. KENZEL.