Showing papers on "Maraging steel published in 1970"

L'Hydrogène dans les Métaux

Abstract: J P Fidelle and M Rapin France: Commissariat a l'Energie Atomique 1969 pp 362 price FF95 This volume consists of the papers and a report on the discussion of a conference held at Valdue on 27–28 September 1967. Apart from two short papers by Troiario and his associates on hydrogen embrittlement in stainless steel, a paper on maraging steel and a final summing up, the proceedings are in French.

The effect of heat treatment on the fracture toughness and subcritical crack growth characteristics of a 350-grade maraging steel

Abstract: The heat treatment response of a 350-grade maraging steel, with the nominal composition 18.5 Ni, 12 Co, 4.6 Mo, 1.4 Ti, balance Fe, has been determined in billet and bar form. When aged at temperatures below 900°F, the material was very susceptible to subcritical crack growth, and premature brittle fracture occurred in unnotched tension specimens loaded at a slow strain rate in laboratory air. Fracture mechanics was used to interpret this behavior. The introduction of reverted austenite significantly decreased the strength level but had little effect on fracture toughness. The resistance to brittle fracture of this material is contrasted with that of high-strength steels currently used by the airplane industry.

The effects of thermal treatment on the austenitic grain size and mechanical properties of 18 Pct Ni maraging steels

Abstract: A technique has been developed for controlling the austenitic grain size of 18 pct Ni maraging steels by thermal treatment alone. This treatment has been applied to two different grades, 250 and 300, of maraging steel, and a large grain size, ASTM 2, was reduced to ASTM 7 in both cases. The process of grain size refinement requires thermal cycling from a temperature belowM f to a temperature considerably above the austenitizing temperature. The minimum austenitic grain size attainable depends on the prior strain in the material as well as the thermal treatment. While significant grain size refinement can be attained by one cycle to the proper temperature, the attainment of the minimum uniform grain size requires several cycles. The effects of austenitic grain size on tensile properties have been investigated both at room temperature and at elevated temperatures. The prior austenitic grain size has a small but measurable effect on the mechanical behavior of aged material at room temperature. The austenitic grain size has a significant effect on the ultimate tensile strength at 1600°F.

Irradiation effects on reactor structural materials.

Abstract: : The report includes the following: (1) a comparison of the response of selected structural steels to irradiation at 550 and 650F to high neutron fluences, (2) the through-thickness Charpy-V notch ductility performance of a 10-1/2-in.-thick plate of irradiated A302-B steel, (3) an investigation of the effects of oxygen and nitrogen contents on the radiation embrittlement sensitivity of 7-1/2Ni-Cr-Mo steel at 250F, (4) the notch ductility behavior of irradiated 12Ni-5Cr-3Mo maraging steel weldments, (5) the response of A350-LF1 (Modified) steel to postirradiation annealing at temperatures in the range of 550 to 590F, (6) the notch ductility behavior of A350-LF1 (Modified) steel with cyclic 430F irradiation-168 hour annealing, (7) the preirradiation mechanical properties of the MH-1A reactor pressure vessel steel, (8) the notch ductility of several reactor structural steels after irradiation in a heavy water moderated reactor, (9) the modification, installation, and initial operation of a remotely operated, tape-controlled milling machine, and (10) a description of newly acquired remotely operated precision measuring equipment. (Author)

STRESS-CORROSION CRACKING BEHAVIOR OF AN 18% Ni MARAGING STEEL

Abstract: Stress-corrosion cracking of an 18 pct Ni maraging steel in aqueous solutions was studied using precracked cantilever beam specimens. By appropriate heat treatments, six different structures having the same yield strength were obtained. Although significantly different plane strain fracture toughness values (KIc) resulted, it was found that the threshold plane strain stress intensity (KIscc) was the same for all structures.KIscc had the same value in 3 pct NaCl at various pH values, in 1N H2SO4, and in distilled water. Specimens tested in 3 pct NaCl under both anodic and cathodic applied potentials also exhibited this sameKIscc value. Fractographic inspection of the crack surfaces revealed no apparent differences due to changes in solution, pH, or applied potential. The crack path was intergranular in all cases. However, specimens austenitized at 1500°F exhibited crack branching, whereas in specimens austenized at much higher temperatures branching no longer occurred. Aging time and temperature seemed to change only the time to failure. The mechanism most consistent with all observations appears to be hydrogen cracking.

Carbide Cracking in a High-Strength Steel

Abstract: A high-carbon maraging steel has been subjected to four different heat-treatments to vary its tensile properties. The stresses necessary to initiate cracking of TiC particles in the steel were then determined. In all cases cracking began at about the point when visible necking occurred in the tensile specimens. The results are discussed in terms of the influence of the maraging precipitate particles in homogenizing flow and changing the local stresses at the carbide particles. The results show that suitable precipitate dispersions can both significantly increase the strength and minimize cracking of brittle inclusion particles.

Age-hardening iron-base alloy with improved toughness

Abstract: A MARAGING STEEL ALLOY HAVING, IN THE AGED CONDITION, A YIELD STRENGTH IN THE 200,000 TO 300,000 P.S.I. RANGE AND A SUPERIOR TOUGHNESS, EXHIBITING CHARPY V-NOTCH VALUES IN EXCESS OF 100 FT-LBS. AT 80*F. THE ALLOY ESSENTIALLY CONTAINS LESS THAN 0.005% EACH OF CARBON AND SULFUR, 1520% NICKELT, 5-10% COBALT, 3-8% MOLYBDENUM, UP TO 1.5% TITANIUM, UP TO 0.5% ALUMINUM, AND THE BALANCE IRON WITH NORMAL INCIDENTAL IMPURITIES. IN ANOTHER EMBODIMENT, TOUGHNESS CAN BE INCREASED APPRECIABLY WTH AN INSIGNIFICANT SACRIFICE IN STRENGTH BY SUBSITUTING TUNGSTEN FOR MOLYBDENUM.

The Effect of Strain Rate and Temperature on Yielding in Steels

Abstract: : The effect of elastic strain rates ranging from 0.001 to 10/sec and temperatures ranging from 200K (-100F) to 590K (600F) on the yield strength of several steels is reported. The steels utilized are a 1018 mild steel, 4340 steel, H-11 tool steel and 300 grade maraging steel. The results are interpreted in terms of the Cottrel-Bilby yielding model based on release of dislocations from locking carbon atmospheres. The results for all of the materials except the maraging steel are consistent with this model if it is modified to account for re-locking of dislocations by migration of carbon atoms. The maraging steel shows a constant strain rate sensitivity at a constant temperature, over the range of strain rates investigated. This rate sensitivity decreases with increasing temperature and at 590K (600 F) a decreasing strength with increasing strain rate is found. This is attributed to stress aging effects. (Author)

The effect of loading rate and temperature on the fracture toughness of high strength steels

Abstract: : The effect of loading rates, ranging from 10 to 100,000 ksi square root of (in/sec), and temperatures, ranging from room temperature to -100F, on the plane strain fracture toughness of several high strength alloy steels has been determined Materials investigated are a commercial 4340 steel, a modified 4330 steel from a gun tube forging having three different heat treatments and two different heats of 250 grade maraging steel Test specimens utilized are essentially ASTM 'compact tension' type specimens of one inch thickness Tests were conducted on an open loop, hydraulic, high loading rate tensile testing machine Results are presented in the form of graphs of fracture toughness versus temperature for the maximum and minimum loading rates ('dynamic' and 'static') Fracture toughness versus loading rate at -60F and yield strength versus elastic strain rate at room temperature, -60F and -100F for one heat of maraging steel are also reported

The Influence of Machining on the Performance of Ultra High Strength Steels

Abstract: During an exercise to determine the optimum conditions for metal removal and tool wear, three ultra high strength steels investigated were 18% Ni maraging steel, a Ni-Cr-Mo steel (designated REX 685), and a 5% Cr-Mo-V steel (designated H50). These were machined in the fully heat treated condition (120 tsi U.T.S.). Metallurgical etch inspection techniques were used to assess the metallurgical surface conditions created by the machining operations, which were turning, milling, drilling, reaming and grinding. Stress corrosion and fatigue tests were carried out on specimens machined under optimum and sub-optimum conditions, “sub-optimum” being used to describe machining under conditions outside those recommended but which can develop during normal workday practice.Copyright © 1970 by ASME

CHARACTERIZATION OF TIG WELDS IN 12-5-3 MARAGING STEEL PLATE WITH APPLICATION OF A NEW SCALING METHOD FOR K sub Ic PLASTICITY CORRECTIONS.

Abstract: : This report is concerned with fabricating and optimizing weld joints in the 12-5-3 maraging steel. Three weld-wire compositions, two TIG welding processes, and two heat-treating sequences were compared in all possible combinations. Welds and weld repairs were compared in tensile, impact, fracture-toughness, and metallographic evaluations. Various comparisons are presented in tables and graphs. These data show that the slightly increased yield strength obtained through the Big TIG welding process is more than offset by the reduced toughness K sub Ic values, obtained from the three-point bend test, showed slight advantages in using a weld wire with a lower percentage of titanium and in welding the plate in the aged condition. However, multiple weld repairs may cause as much as a 26-percent decrease in weld toughness. The greatest reduction in toughness was found in the plates that had three aging cycles: one before welding, one after welding, and the third after welding repairs had been made. (Author)

Fatigue crack growth studies on constant compliance specimen

Abstract: Fatigue crack growth tests in the presence of tensile cyclic stressing have been conducted on 18% Nickel Maraging steel and 70/30 Brass. The stress intensity level is restricted to values which maintain plane strain conditions at the crack tip. Crack growth has a linear relationship to maximum stress intensity and the results predicted a minimum stress intensity below which crack growth should not occur.

Mechanical properties of plates of maraging steel N18K9M5T

Abstract: The resistance to crack propagation is the decisive factor in the high strength of steel under severe load. Plates of high-strength maraging steel N18K9M5T, which has high strength and ductility, can be recommended for parts operating under severe loading conditions.