High Strength Steel Forgings

THIS REPORT IS MAINLY CONCERNED WITH FORGINGS MADE FROM MARTENSITIC STEELS HEAT TREATED TO STRENGTHS RANGING FROM 240,000 TO 300,000 PSI. FORGING CHARACTERISTICS, DESIGN LIMITATIONS, DIMENSIONAL TOLERANCES, AND QUALITY-CONTROL PROBLEMS ARE DISCUSSED. A CONSIDERABLE AMOUNT OF DATA ON MECHANICAL PROPERTIES IS ALSO PRESENTED. IN ADDITION, THE REPORT SUMMARIZES THE AVAILABLE INFORMATION ON FORGED, SEMIAUSTENITIAL STEELS. THIS COMPILATION IS BASED ON PUBLISHED ARTICLES, GOVERNMENT REPORTS, AND INTERVIEWS WITH PRODUCERS AND USERS OF STEEL FORGINGS.

This paper describes the existing state-of-the-art for production forgings manufactured from steels treatable to strengths in excess of 200,000 psi. The need for increasing cleanliness with an increasing strength requirement is emphasized, particularly for those applications where design criteria require high transverse ductility. Economical vacuum arc melting has been largely responsible for bringing reliable, reproducible high-strength steel forgings to a production level of activity. Experience in forging a variety of alloys has highlighted relative levels of uniformity and reliability. Some of the more often selected high-strength steels are discussed from the standpoint of ease of forging, uniformity of strength response, and general quality. Data are given on cleanliness, transverse ductility, and other important properties for such alloys as Ladish D-6ac, AMS 6427, and AISI 4340. Methods for achieving high strengths vary from the standard quench and draw to the more complex thermal-mechanical treatments. The latter treatments, while readily applied to flat products, are difficult to impart to most forgings because complex shapes do not lend themselves to uniform levels of reduction. Mechanical property values obtainable in forgings produced from maraging steel are discussed. These steels represent a potential for the highest strengths obtainable in the steel family. The highest ductilities, however, are obtained by forging sequences that require added manufacturing steps. Since this represents added cost, data useful for specifying practical levels of properties are presented.

Comprises 25 papers from the November 1996 symposium in New Orleans. The papers explore four subject areas: pressure vessel and nuclear forgings, general industrial forgings, test methods, and turbine and generator forgings. Specific paper topics include: new materials and forgings used for pressure

Steels, Forgings, Pressure equipment, Fine-grain material, Strength of materials, Proof stress, Chemical composition, Compositional tolerances, Mechanical properties of materials, Thickness, Yield strength, Tensile strength, Elongation at fracture, Heat treatment, Tempering, Impact strength, Delivery

The Memorandum discusses the current situation on the inclusion of fracture-toughness testing requirements in specifications for high-strength steels used for military applications. The Memorandum was prepared at the request of The Technical Cooperation Program (TTCP), and contains information from Canadian and British members of that program, as well as U.S. information. Military applications discussed include missile motor cases, aircraft landing gear, gun tubes, armor plate, and hydrofoils. (Author).

Since the combination of tensile properties and toughness that can be obtained with the maraging steels is higher than can be achieved with other steels by simple heat treatments, there is considerable interest in using the maraging steels for critical components such as rocket motor cases, pressure vessels, and aircraft forgings. This report includes information on the tensile, compressive, shear, bearing, dynamic modulus, impact, bend, fatigue, creep, and rupture properties of the 18 per cent nickel maraging steels and on the effect of temperature on these properties. Data for the properties of sheet, bar, and forgings, as well as data illustrating the effect of cold rolling, variation in the heat treatment, and elevated-temperature exposure also are presented. Data on the effect of specimen orientation, which are also included, indicate that the ductility and toughness of specimens designed to evaluate the properties in the short transverse direction are somewhat lower than in the other directions. The high strength and toughness that can be obtained in the 18 per cent nickel maraging steels make them attractive for certain critical applications that require these properties. The fabrication characteristics, weldability, and simple heat treatment are other advantages of these steels. (Author).