High Strength Austenitic Steel Research Articles

Description of the flow behaviour of a high strength austenitic steel under biaxial loading by a constitutive equation

Uniaxial and biaxial tension-torsion tests were carried out on a high strength austenitic steel at room temperature in the strain rate range from 10 −5 to 10 2 s −1. This material shows a strong dependence of strength on strain rate. The yield loci of the combined tests are described by ellipses. The size and the shape of these ellipses are functions of strain and strain rate. The quasi-static and dynamic tension and tension-torsion behaviour of the austenitic steel is described by Perzyna's constitutive equation. There is good agreement between measured and calculated results if a yield criterion as a function of strain and strain rate, and a formula which contains the dependence of flow stress on strain rate based on thermal activation, are included.

High-strength austenitic steels with tungsten

1. The yield of austenitic high-manganese steels can be raised by 100–250 N/mm2 as a result of disperse-carbide segregation when they are alloyed with tungsten. 2. Steels with 15–20% Mn, 10% W, and more than 0.65% of C possess the best combination of mechanical properties in the initial and quenched states. 3. Cold plastic deformation makes it possible to increase the yield point to 1500–1600 N/mm2 with satisfactory plasticity.

A cumulative fatigue damage formulation for persistent slip band type materials: Cordero, L. Ahmadieh, A. and Mazumdar, P.K. Scr. Metall. Nov. 1988 22, (11), 1761–1764

Fatigue properties in high pressure gaseous hydrogen environment were investigated for pipe materials used in fuel cell vehicles and hydrogen stations. Cyclic pressurization tests were conducted using a tubular specimen filled with hydrogen pressurized up to 90MPa. Tested materials were types 316L, 304 and A286 stainless steels, low alloy steels such as JIS SCM435 (1.0Cr-0.2Mo), Cr-Mo-V steels. The fatigue life in hydrogen was compared with that in inert gas to evaluate the effect of gaseous hydrogen on fatigue properties. The fatigue life in hydrogen was slightly shorter than that in argon in the case of a stable stainless steel type 316L. In contrast, a metastable stainless steel type 304 showed a remarkable degradation of the fatigue life in the hydrogen environment. Although the fatigue lives in hydrogen of type 316L and 304 stainless steels decreased with the increase in the cycle times, the fatigue lives remained unchanged over 102 of the cycle time. The fatigue life of low alloy SCM435 steel in hydrogen extremely decreased. The fatigue life of high-strength austenitic steel A286 in hydrogen is much better than that of low alloy SCM435 steel at the same tensile strength. The Cr-Mo-V steels showed longer fatigue lives than JIS SCM 435 at same strength levels in hydrogen. Fracture surfaces revealed transgranular cracking for the Cr-Mo-V steels, while intergranular cracking was observed for SCM435 with tensile strength more than 1.2 GPa. It was assumed that the carbide precipitation affected the fracture morphology.

The influence of waveform and long hold time on the corrosion fatigue crack growth behavior of an austenitic steel

An inexpensive test set-up for conducting fatigue crack growth tests in corrosive environments under hold times of up to 24 h is described. The set-up uses modified creep machines for conducting slow cyclic tests for cyclic times up to 24 h. Corrosion fatigue crack growth rate data were generated for a high strength austenitic steel in an environment consisting of a mixture of hydrogen and air at several relative humidity levels. It was observed that frequency, waveform and load ratio had significant influence on the corrosion fatigue crack growth behavior. The level of relative humidity appeared to have no measurable influence on the corrosion fatigue crack growth behavior.

Influence of grain size and ?-phase stability on the fatigue limit of high-strength austenitic steels

1. The high fatigue strength of N26KhT1 metastable austenitic steel is caused not only by strengthening as a result of phase strain hardening and aging but also by the instability of the Fe−Ni−Ti austenite. 2. An increase in grain size leads to a reduction in the fatigue limit of N26KhT1 and 40G18Yu3F steels. The fatigue limit of 40G18Yu3F stable dispersion hardening steel is more sensitive to a change in grain size. 3. The straight-line relationship of the fatigue strength of N26KhT1 and 40G18Yu3F steels to grain size, described by the Hall-Petch equation, has a break, which is caused by a change in the character of failure in the transition from the fine- to the coarse-grained condition of the steel. 4. The low-cycle fatigue strength of N26KhT1 steel is practically independent of grain size.

Corrosion cracking of high-strength steel �I723I and austenitic steel �P33

Corrosion cracking of high-strength steel �I723I and austenitic steel �P33

Fatigue limit and durability of precipitation-hardening austenitic steels

1. Alloying with chromium raises the fatigue limit of austenitic steel in the quenched condition. In the hardened condition the presence of ∼15% Cr in austenitic steel lowers the fatigue limit due to precipitation of Cr23C6 carbides in the grain boundaries. For long-term operation under ordinary cyclic loading conditions, high-strength austenitic steel with an elevated chromium content is unsuitable. The steel can be recommended when the total number of cycles during operation does not exceed 104–105. 2. Nickel raises the fatigue limit of precipitation-hardening maraging austenitic steel. Nickel-manganese steel 40G14N9F can be recommended for long-term operation under cyclic loading conditions. 3. Electron fractographic studies showed a relationship between the durability of austenitic steel and the microrelief of the fatigue fracture. The number of cycles to failure is inversely proportional to the distance between striations on the fracture surface.