Showing papers on "Maraging steel published in 1989"

Fabrication of 18% Ni maraging steel laminates by roll bonding

Abstract: A method of fabricating 18% Ni maraging steel laminates of varying alloy compositions by roll bonding. Laminates composed of a plurality of different grades of Cobalt-containing or Cobalt-free maraging steels are disclosed.

Crack propagation of secondary hardened alloy steels in gaseous hydrogen atmosphere

Abstract: The crack propagation behaviour of secondary hardened alloy steels having various Ni contents and a 18%Ni maraging steel was studied using modified compact tension specimens under 98–784 kPa hydrogen gas pressure pH2 . The effect of Ni content and retained austenite was examined by comparing oil quenched specimens with those cooled to liquid nitrogen temperature. It was estimated from the effect of pH2 on the crack propagation rate da/dt that the permeation of hydrogen from the crack tip surface decreased with increasing Ni content in the order 6 or 9, 13, then 18%Ni. It was also estimated that the hydrogen induced embrittlement of grain boundaries decreased with increasing Ni content in the order 6, 9, then 13%Ni and that the embrittlement was greater for the steel containing 18%Ni than for the steel containing 13%Ni. The effect of retained austenite was expected to suppress not the permeation of hydrogen, but the embrittlement of grain boundaries.MST/757

Fracture toughness of maraging steel from Charpy “V” notch specimens

Abstract: Compact tension (CT) and Charpy “V” notch (CVN) (impact and three-point bend) specimens of 18 Ni 1800 MPa maraging steel (parent metal and weldment) were used to determine plane strain fracture toughness (K IC) and CVN impact energy (CVNIE), respectively. Using an empirical equation,K IC-CVNIE correlation is attempted which could be advantageously utilized for routine quality control of inward material to effect savings in cost and time. Investigations reveal betterK IC-CVNIE correlation for tests using the precracked CVN specimens. Scanning electron microscopic (SEM) observations reveal good correlation between fractographic features and fracture toughness.

A field–ion microscopy and atom probe study of ageing behaviour of a Co–bearing maraging steel

Abstract: This paper reports the first atom probe field-ion microscopy (APFIM) study of the ageing reactions in a Co-bearing (C-300) maraging steel (Fe-l85%Ni-90%Co-48%Mo-06%Ti-O l%Al-OI%Si-003%C (wt%)), using both the conventional APFIM and the position-sensitive atom probe (POSAP) Two families of intermetallic phases (Fe7M06 and Ni3(Mo,Ti) types) have been found to contribute to age-hardening The com~osition and morphology of these precipitates were studied for different ageing times (05- 128 hours at 510 C) to investigate the ageing sequence The observation of the (Fe,Ni,Co)7Mog p-phase is of interest since this is contrary to most published electron diffraction work, but is supported by thermodynamic calculations Austenite reversion has been found to start after ageing for 4 hours and the reverted austenite approaches the predicted equilibrium composition after ageing for 8 hours

Residual strength of maraging steel

Abstract: Surface crack tension (SCT) specimens of 18 Ni 1800 MPa grade maraging steel (parent metal and welded) were used to evaluate the residual strength in 0.015 and 0.03m wide panels. For 0.03 m wide panels which satisfy infinite plate condition up to 0.006 m surface crack length, the residual strength variation between minimum and maximum crack sizes lie within 5% of the ultimate tensile strength (UTS) of weldments. Also for larger crack sizes both 0.015 and 0.03 m wide panels yields comparable values for residual strength. The results have significant bearing on flaw detection by non destructive testing (NDT) method which could be used for quality and reliability check on the fabricated component. Stress intensity values for these data makes an interesting observation on failure mode.

Effect of alloying and of the austenizing temperature on the phase composition and properties of corrosion-resistant maraging steels

Abstract: 1. The optimal molybdenum content of steels based on Fe−0.03% C−12.5% Cr−(0–1)% Ti−(0–12)% Ni−(0–20)% Co is 3%. It is permissible to increase the amount of molybdenum to 5%, but then the ratio between the other alloying elements has to be maintained very accurately so as to attain a single-phase martensitic structure as a result of hardening. It is inexpedient to add more than 5% Mo to corrosion-resistant maraging steel. 2. Alloying with a combined amount of not more than 0.8–1.0% of titanium and/or aluminum is justified only when the steel contains more than 3% Ni. 3. Nickel and cobalt have to be added at such a ratio that the formation of X-phase and/or δ-ferrite is suppressed and that the formation of a single-phase structure of martensite as a result of hardening is guaranteed. 4. The broadest region of existence of a single-phase structure of martensite for corrosion-resistant maraging steels based on Fe-0.03% C-12.5% Cr−(0–1)% Ti−(3–7)% Mo−(0–12)% Ni−(0–20)% Co is attained with quenching temperatures of about 1100°C.

Fe-ni-ti maraging steel having excellent high toughness and delayed fracture resistance

Abstract: PURPOSE:To improve the strength, ductility, fracture toughness and delayed fracture of the titled steel by incorporating specific amounts of Ni and Ti to the steel and compositely incorporating specific amounts of Nb and B into the same, thereby permitting the industrial application of a nonrecrystallization solution heat treatment in the steel. CONSTITUTION:The steel contg., by weight, 17-26% Ni, furthermore contg. compositely 0.05-0.7% Nb and 0.0005-0.0050% B and consisting of the balance Fe with inevitable components pertaining to steel manufacturing is prepd. By this constitution, the recrystallization temp. is risen and the industrial application of a noncrystallization solution heat treatment is permitted to obtain the Fe-Ni- Ti maraging steel. Said steel is useful in the field of the outer shell material such as a rocket motor case and a pressure container, rollers and shafts.

Mechanical Property Characterization of VascoMax T-300

Abstract: : This report addresses a mechanical property characterization of 18% Nickel 300 grade cobalt-free maraging steel (T-300). Hardness, tensile, Charpy V-notch impact energy, and fracture toughness data were obtained for a 2-3/8- inch-diameter forged bar. These data are presented along with existing data on stress corrosion, microstructure, and ballistic performance for this and other maraging steels. The results indicated that the mechanical properties are more dependent on the aging temperature than on the aging time for the temperatures of 900 F and 950 F, and times of 3 and 4 hours. Both hardness and Charpy impact energy were unaffected by varying the aging temperatures and times, while the tensile properties and fracture toughness increased in response to the increase in aging temperature. Based on the information obtained in this study and the existing information available on this alloy, the recommended aging treatment is 950 F for 4 hours.

Manufacture of cold rolled 18%ni maraging steel sheet

Abstract: PURPOSE:To refine the grains of maraging steel contg. a specified amt. of Ni and to obtain superior strength, ductility and toughness in an aged state by cold rolling the steel and exposing the resulting sheet to an atmosphere at a specified temp. for a proper time. CONSTITUTION:18%Ni maraging steel is hot rolled and cold rolled. The resulting thin steel sheet is subjected to post-treatment such as degreasing and exposed to an atmosphere kept at a constant temp. of 900-1150 deg.C for a time satisfying relation represented by the equality [where T is the temp. of the atmosphere and t is exposure time (min)]. The steel sheet is then cooled. Superfine grains of <=10mum grain size are formed and a steel sheet having superior strength, ductility and toughness in an aged state is obtd.

Corrosion behaviour of pulsed laser treated maraging steel: Möussbauer spectroscopy and scanning electron microscopy study

Abstract: The changes occurring upon pulsed laser irradiation on maraging steel of 69Fe-18Ni-8Co-5Mo composition have been studied using Conversion Electron Mossbauer Spectroscopy (CEMS), Scanning Electron Microscopy (SEM), Internal Friction (IF) and aqueous corrosion It is observed that an austenitic phase in the upper layer is retained without much change in chemical composition for the pulsed laser treated sample Mechanical bulk properties are not affected by this treatment, however betterment in corrosion resistance is achieved

Effects of Cold Rolling and Annealing on the Anisotropies and Texture Formations in an 18 % Ni (350) Maraging Steel

Abstract: Synopsis : The effects of cold rolling on anisotropies in tensile properties and the second formability have been investigated on an 18%Ni (350) maraging steel. The following results were obtained. (1) The rate of strain hardening was different among the rolling directions. That is, the plot of the tensile strengths against the longitudinal, 45 degree-declined, and transverse directions, showed a V-shape. This shape almost remained unchanged after aging treatment. (2) The origin of the anisotropies was considerd to be the increase in the density of {113} <110 > orientation. (3) Recrystallization texture was formed by solution annealing after cold rolling. This recrystallization texture was similar to that of a -iron, in spite that the maraging steel had experienced the martensite to austenite reverse, and austenite to martensite transformation. This phenomenon suggested that the specified variants were preferred in the transformations. (4) The second formability measured by Erichsen test was increased by the development of {111} <112 > texture.

Crack growth characteristics of maraging steel

Abstract: Compact tension (CT) and surface crack tension (SCT) specimens of 18 Ni 1800 MPa grade maraging steel (parent metal and welded) were studied for the cyclic crack growth rate applying in sinusoidal (SL) and block loading (BL) conditions. The BL cycle was designed to simulate the stress intensity levels experienced during proof pressure and static test of a fabricated rocket motor. The threshold stress intensity for stage II crack growth for weldment is found to be about 0.6 that for the parent metal. For a given stress intensity, the crack growth rate for weldment and parent metal are in the same range under SL or BL. Through-thickness cracks (laboratory condition) in CT specimens and part-through thickness cracks (service condition) in SCT specimens show good correlation for cyclic crack growth rate. The results are of great significance for considering the reuse of the maraging steel rocket motor case.

Surface treatment for maraging steel

Abstract: PURPOSE:To provide high fatigue strength to a maraging steel by applying fluidized bed gas soft nitriding treatment to the maraging steel by using an atmospheric gas prepared by adding specific amounts of CO2 to an NH3-N2-C3 H8-type gas. CONSTITUTION:A maraging steel is subjected to soft nitriding treatment in a fluidized bed furnace by using, as a fluidizing gas, a gas prepared by adding a CO2 gas to an NH3-N2-C3H8-type gas by 0.2-5vol.%. It is preferable that the NH3-N2-C3H8-type gas has a composition consisting of 50% NH3, 35% N2, and 15% C3H8. At the time of the above treatment, the infiltration of carbon atoms and nitrogen atoms into the steel is activated by the addition of the CO2 gas, and large amounts of carbon atoms and nitrogen atoms are allowed to enter into solid solution in the outermost surface of the steel. As a result, surface residual compression stress is increased and high fatigue strength can be obtained. This method can be applied to endless metallic belt, etc.

High performance screw head

Abstract: PURPOSE:To increase corrosion resistance, wear resistance, toughness and strength by making a screw head section of high Co, or high C high Cr alloy steel and a shaft with a hot-rolled tool steel of superior toughness strength or a maraging steel and bonding and combining the both sections. CONSTITUTION:A screw head section is made of composite structure with a high Co or a high C high Cr alloy steel material, and a shaft section is made of composite structure with a hot-rolled steel tool of superior toughness strength or a maraging steel respectively by, for instance, the friction welding method. It is further useful to carry out the coating 1c of a hard material such as VC, TiC, TiN or the like by ion plating, the molten salt method or the like. Wear gets slower than articles subjected to nitriding treatment heretofore available by using a material of same hardness for the head section in firm contact with etching all through from the surface of a matrix to a center, and the wear resistance life can be longer to a large extent. On the other hand, a shaft section is made of a selected material of selected toughness strength, and breakage can be prevented in the shaft section and its vicinity.

Production of cylindrical blank made of maraging steel

Abstract: PURPOSE:To obtain the title cylindrical blank having fine crystal grains and suitable to spinning by hot-extruding a maraging billet, cold-drawing the material at a specified draft, and then applying solution treatment. CONSTITUTION:A maraging billet of Ni-Co-Mo-Ti, etc., is hot-extruded, and then air-cooled to room temp. The number of the crystal grain size is then measured. The measured value is substituted for the G.S in the inequality to obtain the draft (Rd), cold drawing is carried out at the draft, and solution treatment is then applied. The Cold drawing consists of spreading, reduction, and madrel drawing. By this method, the cylindrical blank having <=about No.7.5 crystal grain size and highly suitable to spinning can be obtained. Accordingly, the working yield is enhanced, the product precision is improved, a long- sized cylindrical blank can be produced, and productivity is also ameliorated.