Showing papers on "Maraging steel published in 1978"
TL;DR: In this paper, the authors applied the austenite ⇆ martensite cylcic heat treatment on Fe-15Ni-5−30Co−5−10Mo-0−2Ti alloys with initial coarse austenitic grain size.
38 citations
TL;DR: In this article, the microstructure and fracture toughness of AISI 4340 steel in the direct and in the step quenched and tempered condition has been studied, and the observed facts are consistent with segregation effects during the austenitizing treatment.
Abstract: The microstructure and fracture toughness of AISI 4340 steel in the direct and in the step quenched and tempered condition has been studied. Austenitizing temperatures of 1473 K followed by step quenching to either 1373 or 1143 K prior to oil quenching have been employed. A consistent drop in the fracture toughness values was observed as the intermediate holding temperature decreased or the holding time at this temperature in-creased. A concurrent increase in the amount of twinning was seen without any change in the amount and/or distribution of retained austenite. While direct evidence for segre-gation has not been found, the observed facts are consistent with segregation effects during the austenitizing treatment.
30 citations
TL;DR: In this paper, the authors examined the relationship between prior austenite grain size and age hardening in 18Ni maraging steels and showed that the Hall-Petch relationship is obeyed independently of the heat-treatment condition or alloy content.
29 citations
TL;DR: In this paper, the mechanical properties of an eighteen percent nickel, solution-annealed 300-grade maraging steel were measured to assist in the evaluation of this material for low-temperature structural applications.
Abstract: The mechanical properties of an eighteen percent nickel, solution-annealed 300-grade maraging steel were measured to assist in the evaluation of this material for low-temperature structural applications. Tensile, fatigue-crack growth rate, and fracture toughness tests were performed in ambient air (295 K), liquid nitrogen (76 K), and liquid helium (4 K), with the following results: the yield strength of this material increases from 831 MPa at room temperature to 1596 MPa at 4 K; the tensile ductility is moderate with elongation decreasing from 15.5 to 6.7 percent for this temperature region; the estimated values of fracture toughness (K/sub Ic/) decrease from 165 MPa.m/sup /sup 1///sub 2// at room temperature to 83 MPa.m/sup /sup 1///sub 2// at 4 K; and the fatigue-crack propagation resistance at intermediate stress intensity ranges is relatively insensitive to temperature. These results are compared with similar data for other cryogenic alloys.
20 citations
01 Jan 1978
TL;DR: In this paper, several compositional, processing, and testing variables that influence this austenite stability are discussed. But the authors focus on the deformation-induced phase transformation and do not consider the non-thermally activated phase transformation.
Abstract: Microstructural changes in alloys can be induced by phase transformations. While many phase transformations are thermally activated, some are not. An important example of the nonthermally activated type is the deformation-induced phase transformation. Deformation-induced phase transformations are known to cause unusual changes in the mechanical properties of ferrous and nonferrous alloys. In the past several years it has been shown that this type of transformation can considerably enhance the mechanical properties of high-strength austenitic alloys— these alloys are now known as “TRIP” steels. Useful combinations of toughness, strength, and ductility can be obtained in these steels by control of the composition and the processing. TRIP steels are thermomechanically processed in the austenitic state. During this thermomechanical processing, changes occur in both chemistry and substructure, and these alter the stability of austenite with respect to deformation during subsequent mechanical testing. The present chapter discusses the several compositional, processing, and testing variables that influence this austenite stability. It is shown that the strength, ductility, stress-strain behavior, fracture toughness, fatigue properties, and corrosion resistance of TRIP steels are strongly affected by austenite stability. The considerations involved in designing TRIP Steels, their limitations, and some of the steps that have been taken to overcome these limitations, are reviewed. Recent studies are described in which attempts were made to incorporate the TRIP phenomenon in other classes of steels. These include nonnickel cryogenic steels and low and medium alloy quenched and tempered ultrahigh-strength steels.
17 citations
TL;DR: Cylindrical steel pressure vessels are described that can be used for hydrostatic pressures up to 50 kilobars, and are much easier to use than the more usual compound vessels with a tungsten carbide inner and steel outer vessel.
Abstract: Cylindrical steel pressure vessels are described that can be used for hydrostatic pressures up to 50 kilobars. Monoblock vessels of 350 maraging steel can be used to 40 kilobars and compound vessels with an inner vessel of 350 maraging steel and an outer vessel of 300 maraging steel to 50 kilobars. Neither requires the cylinder to be end loaded, and so they are much easier to use than the more usual compound vessels with a tungsten carbide inner and steel outer vessel.
12 citations
TL;DR: In this article, electron microscope fractographic analysis supplemented an extensive study of the kinetics of gaseous hydrogen assisted cracking in 18Ni maraging steel was performed, and it was concluded that hydrogen segregation to prior austenite and lath martensite boundaries must be considered as a significant factor in developing mechanisms for gas embrittlement of high strength steels.
Abstract: Electron microscope fractographic analysis supplemented an extensive study of the kinetics of gaseous hydrogen assisted cracking in 18Ni maraging steel Temperature determined the crack path morphology in each steel which, in turn, was directly related to the temperature dependence of the crack growth rate Crack growth in the low temperature regime proceeded along prior austenite grain boundaries Increasing the temperature above a critical value produced a continuously increasing proportion of transgranular quasi-cleavage associated with lath martensite boundaries The amount of transgranular cracking was qualitatively correlated with the degree of temperature-induced deviation from Arrhenius behavior Fractographic observations are interpreted in terms of hypothesized mechanisms for gaseous hydrogen embrittlement It is concluded that hydrogen segregation to prior austenite and lath martensite boundaries must be considered as a significant factor in developing mechanisms for gaseous embrittlement of high strength steels
11 citations
TL;DR: In this article, a pre-alloyed 250-grade maraging steel powder formed by inert gas atomization was hot isostatically pressed (HIP) at five different temperatures ranging from 1285 to 1535 K. Both conventional and nonconventional aging treatments were applied to the resulting compacts.
8 citations
7 citations
TL;DR: In this article, the formation of a titanium intermetallic at the prior particle boundaries during aging caused failure at low plastic strains and resulted in a significant ductility recovery for the HIP material.
Abstract: Prealloyed 250-grade maraging steel powder produced by the rotating electrode process was fully consolidated by hot isostatic pressing (HIP) at 1100 and 1200°C. The strength following aging (3 h at 480°C) equalled that of wrought material; however, ductility was negligible. This lack of ductility in the powder metallurgy product was traced to titanium segregation which occurred at the powder surface during powder production. The formation of a titanium intermetallic at the prior particle boundaries during aging caused failure at low plastic strains. Altered aging treatments successfully broke up the embrittling film and resulted in a significant ductility recovery for the HIP material. Analysis of the fracture process indicates that further ductility gains are possible by reducing the titanium content, refining the particle size, and optimizing the thermal cycles.
5 citations
Patent•
04 Mar 1978
TL;DR: In this paper, a rotor material of high strength and very high square ratio used for hysteresis motors by subjecting Ni maraging steel of middle effective coercivity to solution heat treatment, cold working and aging is presented.
Abstract: PURPOSE:To produce a rotor material of high strength and very high square ratio used for hysteresis motors by subjecting Ni maraging steel of middle effective coercivity to solution heat treatment, cold working and aging
TL;DR: A periodicity in the changes in the strength of austenite was observed in steel 03Kh12N7YuM in relation to the number ofγ⇄α cycles.
Abstract: 1.
A periodicity in the changes in the strength of austenite was observed in steel 03Kh12N7YuM in relation to the number ofγ⇄α cycles—the strength increases with increasing numbers of cycles but drops periodically.
2.
The periodic drop of the strength of austenite during thermal cycling is due to recrystallization of phase strain hardened austenite after a certain number ofα⇄γ transformations. The periodic change in the strength of the steel is also accompanied by a periodic change in the amount of retained austenite.
3.
The change in the strength of austenite under the influence of thermal cycling has almost no effect on the strength of martensite formed from it during the following γ → α transformation.
Patent•
10 May 1978
TL;DR: In this article, the authors improve the toughness of a 280kg/mm class maraging steel by carrying out solution heat treatment, cold working, and aging of the steel, which is applied to the steel.
Abstract: PURPOSE:To improve the toughness of a 280kg/mm class maraging steel by carrying out solution heat treatment, cold working, and aging.
Patent•
18 Mar 1978
TL;DR: In this article, a rough tube made of super high tensile steel having excellent toughness and tenisile strength of 255 kg/mm and above by decreasing the amt of Mo and increasing that of Ni-Co-Mo maraging steel and carrying out slight cold working and heat treatment.
Abstract: PURPOSE:To produce a rough tube made of super high tensile steel having excellent toughness and tenisile strength of 255 kg/mm and above by decreasing the amt. of Mo and increasing that of Ni-Co-Mo maraging steel and carrying out slight cold working and heat treatment.
TL;DR: In this paper, the effects of Mo, Ti, and Al contents and thermomechanical treatments on the strength, ductility, and toughness of Fe-16•`17Ni-15Co4•`7Mo-1.0•`4.5Ti-0.05•`2.0Al alloys have been investigated.
Abstract: Synopsis: In order to develop ultrahigh strength maraging steels of over 280 kg/mm2, effects of Mo, Ti, and Al contents and thermomechanical treatments on the strength, ductility, and toughness of Fe-16•`17Ni-15Co4•`7Mo-1.0•`4.5Ti-0.05•`2.0Al alloys have been investigated. The peak-aged hardness increased in proportion to the amount of strengthening elements shown as (Mo+2Ti+1.75Al)%. The increases in the amounts of those elements, however, led to the unstable fractures in low stress level during tensile tests, and this meant that the strength corresponding to the aged hardness could not be achieved. This tendency was more pronounced in the alloys with higher Al and Ti contents than in the alloys with higher Mo contents. The combination of the superior KIC and fine grain size can prevent the low stress unstable fracture up to higher strength levels. It has been shown that, by the combination of appropriate alloy compositions and thermomechanical treatments, the ultrahigh tensile strength up to 330 kg/mm2 with the excellent ductility and toughness could be achieved in maraging steel.
TL;DR: In this paper, the effect of aging treatment on the fatigue crack propagation of 18% Ni maraging steel sheets was investigated, and an exponential relation holds between the crack propagation rate and the stress intensity factor range for the specimens heat-treated under each condition, and no significant difference in the values m and C is observed among the specimens under various conditions involving the solution annealing.
Abstract: In this study, the effect of aging treatment on the fatigue crack propagation of 18% Ni maraging steel sheets was investigated. Main results are summarized as follows. An exponential relation holds between the crack propagation rate and the stress intensity factor range for the specimens heat-treated under each condition, and no significant difference in the values m and C is observed among the specimens heat-treated under various conditions involving the solution annealing. This means that aging treatment has no favourable effect to retard the fatigue crack propagation, even if the static strength of this steel is exceedingly elevated by the aging treatment. Although the fatigue strength is increased by aging treatment, the degree of increase depends upon the loading level and the aging condition. Namely, the underaging treatment is more preferable when this material is subjected to high cycle fatigue load.
TL;DR: The change in the straight section of the fracture in relation to the severity of the stress concentrator, the development of V-shaped fracture, and a step in the fracture indicate the conditional determination of the specific work of impact bending and its components for the steel tested as mentioned in this paper.
Abstract: 1.
Hot rolling stabilizes austenite, which weakens steel 04Kh14K13N4M3T. Subsequent quenching from 1050° before aging destabilizes the austenite, and the amount of retained austenite becomes practically the same in the heats tested.
2.
Destabilization of austenite in hot rolled steel is controlled by thermally activated processes. With increasing development of these processes by increasing the time at high temperatures the strength is increased and the fracture toughness remains at practically the same level. Retention of austenite (15±5%) ensures σb > 150 kgf/mm2 anda1≥5 kgf-m/cm2 at −196° for transverse samples.
3.
Cold deformation (40%) before aging leads to an increase in strength (σb ≥ 200 kg/mm2,a1=3 kgf-m/cm2) and sharp embrittlement at −196° due to the transformation of austenite to martensite in the process of rolling.
4.
The change in the structure of the straight section of the fracture in relation to the severity of the stress concentrator, the development of V-shaped fracture, and a step in the fracture indicate the conditional determination of the specific work of impact bending and its components for the steel tested.
Patent•
22 Sep 1978
TL;DR: In this paper, a high tensile rotary cylinder with excellent mechanical properties such as strength and superior surface quality made of maraging steel consisting of Ni, Co, Mo and Mn of each specified amt.
Abstract: PURPOSE:To provide a high tensile rotary cylinder with excellent mechanical properties such as strength and superior surface quality made of maraging steel consisting of Ni, Co, Mo and Mn of each specified amt. and the balance Fe and impurities.
01 Jan 1978
Abstract: Nickel-containing steels are frequently selected for use at cryogenic temperatures because of their excellent toughness or strengths. For example, 304 stainless steel containing 8% Ni is characterized by very high toughness at cryogenic temperatures, but has relatively low strength. In contrast, 18% Ni, 200 grade, maraging steel is characterized by very high strengths at cryogenic temperatures, but with a penalty of reduced toughness. Similarly, 9% Ni steel is characterized by good toughness and moderate strength at cryogenic temperatures, while 9Ni-4Co steel has greater strength, but substantially lower toughness in the same temperature range.
TL;DR: In this article, Nitriding is recommended for surface hardening of heavily stressed machine parts of steel N18K9M5T, which does not change the ductile character of the fracture of the core observed after aging.
Abstract: 1.
With nitriding of high-strength maraging steel N18K9M5T the high resistance to fracture is retained to a considerable extent.
2.
Nitriding does not change the ductile character of the fracture of the core observed after aging.
3.
Nitriding can be recommended for surface hardening of heavily stressed machine parts of steel N18K9M5T. In this case it is necessary to impose more severe requirements with regard to defects as compared with machine parts subjected to quenching and aging.
TL;DR: The temperature for complete solution of intermetallic hardening phases should be 1100-1150° as mentioned in this paper, and steel of the 0Kh6N8M7S type has high heat resistance and can be used for pressing tools operating at elevated temperatures.
Abstract: 1.
Addition alloying of steel of the 0Kh6N8M7S type with nickel and molybdenum (1%) lowers MS by 30°, and alloying with chromium 40°.
2.
The temperature for complete solution of intermetallic hardening phases should be 1100–1150°.
3.
Steel of the 0Kh6N8M7S type has high heat resistance and can be used for pressing tools operating at elevated temperatures.
TL;DR: In this article, the effects of combined additions of Co and Mo, and strain aging have been investigated in order to strengthen 25Ni maraging steel containing Be, Ti and Al.
Abstract: Synopsis: In order to strengthen 25Ni maraging steel containing Be, Ti and Al, effects of combined additions of Co and Mo, and strain aging have been investigated. For 23.5Ni-9.1Co-5.3Mo-0.68Be-0.30Ti-0.25Al alloy, 295 kg/mmm2 tensile strength and 1.7% elongation are obtained by aging treatment at 450•Ž for 1 hr after cold working with 64% reduction of area. Dilation, electrical resistance and specific heat measurements reveal that there is no essential difference in the aging behavior between conventional aging and strain aging. But precipitation and austenite reversion can occur in strain aging at a temperature lower than 30•Ž in conventional aging.
01 Jan 1978
TL;DR: In this article, HOSOMI et al. investigated the effect of intermetallic compounds of Fe2Mo or (Fe, Co)7Mo6 on the toughness of 13%Ni maraging steel.
Abstract: Precipitation of Intermetallic Compounds in Austenite and Its Effects on Toughness of As-Quenched Martensite in 130Ni Maraging Steel Koji HOSOMI, Yoshio ASHIDA, Hiroshi HATO, Kazunori ISHIHARA, and Hitoshi NAKAMURA Synopsis: The precipitation of intermetallic ompounds in austenite and its effects on the toughness of as-quenched martensite in 13%Ni maraging steel have been studied by means of Charpy impact tests and structural observations. The heat-treatment process investigated comprises intermediate isothermal holding in the temperature range from 800°C to 1100°C after homogenization at 1200°C reheating of the martensite to the austenite region below 1100°C after quenching to room temperature from 1200°C. Not only the intermediate holding but also the reheating introduced a drastic decrease in Charpy impact energy of the as-quenched martensite. Structural observations revealed the coarse precipitates on prior austenite grain boundaries and within the grains for both heat-treatments. Prolonged intermediate isothermal holding was necessary to cause the precipitation within the grains. However, when the martenisite was reheated to the range between Af and the austenite recrystallization temperature, the precipitation within the grains was promoted in short time, due to the presence of the nucleation sites formed in martensite on the heating up to the austenitic region, or probably to the internal strains of the reverted austenite. These precipitates were considered to be intermetallic compounds of Fe2Mo or (Fe, Co)7Mo6. The major loss in the toughness of as-quenched martensite of 13%Ni maraging steel was associated with the precipitation of intermetallic compound containning Mo during holing in the austenite regions.