scholarly journals Evaluation of Fatigue Damage in 304 Stainless Steel by Measuring Residual Magnetic Field

2020 ◽  
Author(s):  
Yi Liu ◽  
Xiwang Lan ◽  
Bo Hu
Keyword(s):  
Magnetic Field ◽  
Stainless Steel ◽  
Fatigue Damage ◽  
304 Stainless Steel ◽  
Magnetic Characteristics ◽  
Fluxgate Sensor ◽  
Residual Magnetic Field ◽  
304 Austenitic Stainless Steel ◽  
Magnetic Field Change ◽  
Field Measuring

To demonstrate the feasibility of the passive magnetic NDT method for damage assessment of 304 austenitic stainless steel, the residual magnetic field change of the 304 stainless steel specimens under fatigue loads was investigated. The measurement was carried out using a fluxgate sensor and the magnetic characteristics were extracted for analysis of fatigue state. Then, the XRD test was carried out to investigate the mechanism of magnetic field changes and verify the reliability of the proposed method. The results show that the variation of the maximum gradient is consistent with the process of fatigue crack growth, which indicates that the fatigue damage can be estimated by residual magnetic field measuring. In future stage, how to distinguish the magnetic field changes derived from martensite transformation or stress magnetization effect will be investigated.

Effective hydrogen diffusivities of AISI 304 stainless steel with Ni or Au coating

2020 ◽  
Vol 62 (6) ◽  
pp. 593-596
Author(s):  
Krittayot Wannapoklang ◽  
Sirichai Leelachao ◽  
Anchaleeporn W. Lothongkum ◽  
Gobboon Lothongkum
Keyword(s):  
Stainless Steel ◽  
Hydrogen Diffusion ◽  
304 Stainless Steel ◽  
Phase Identification ◽  
Aisi 304 Stainless Steel ◽  
Aisi 304 ◽  
304 Austenitic Stainless Steel ◽  
Hydrogen Assisted Cracking ◽  
Stainless Steel Coupon ◽  
Effective Hydrogen

AbstractMetallic coatings which provide a hydrogen diffusion barrier are thought to reduce hydrogen assisted cracking on stainless steel. The influence of a metallic layer on the hydrogen migration of AISI 304 stainless steel was investigated using a commercial electroplating layer of Ni and Au on a thin stainless steel coupon. Phase identification was performed using an X-ray diffractometer to determine the average thicknesses, measured from back-scattered scanning electron images. Regarding the ASTM G148-97 practice, the effective hydrogen diffusivities of AISI 304 austenitic stainless steel, nickel and gold were measured as 7.07 × 10-13, 2.72 × 10-14 and 9.64 × 10-16 m2 × s-1, respectively. In this work, a gold layer was found to be most effective for the prevention of hydrogen diffusion when compared with untreated and Ni-plated 304 stainless steel.

Numerical Simulation and Experimental Analysis of Laser Surface Remelting of AISI 304 Stainless Steel Samples

2010 ◽  
Vol 636-637 ◽  
pp. 1119-1124
Author(s):  
Noé Cheung ◽  
M.A. Larosa ◽  
Wislei R.R. Osório ◽  
M.S.F Lima ◽  
Maria Clara F. Lerardi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Stainless Steel ◽  
Laser Surface ◽  
Temperature Fields ◽  
304 Stainless Steel ◽  
Operating Parameters ◽  
Aisi 304 ◽  
Laser Surface Remelting ◽  
304 Austenitic Stainless Steel

The aim of this work is to develop a heat transfer mathematical model based on the finite difference method in order to simulate temperature fields in the laser surface remelting process. Convective heat transfer in the remelted pool is taken into account by using the effective thermal conductivity approach. Experiments of laser surface remelting of AISI 304 austenitic stainless steel samples were carried out in the present investigation, and numerical simulations were applied for the CO2 laser machine operating parameters. The work also encompasses the analysis of microstructural and microhardness variations throughout the resulting treated and unmolten zones. This study permits to conclude that numerical simulation is a useful tool in setting the laser operating parameters, enabling pre-programming of the extent of the treated area.

Investigations on the Microstructure and the Fracture Surface of Pulsed Nd: YAG Laser Welding of AISI 304 Stainless Steel

2012 ◽  
Vol 445 ◽  
pp. 418-423
Author(s):  
Seyed Ali Asghar Akbari Mousavi ◽  
A. Garehdaghi
Keyword(s):  
Stainless Steel ◽  
Laser Welding ◽  
Cooling Rate ◽  
304 Stainless Steel ◽  
Chemical Compositions ◽  
Operational Parameters ◽  
Δ Ferrite ◽  
Higher Power ◽  
304 Austenitic Stainless Steel ◽  
Pulsed Nd:Yag Laser Welding

The paper presents pulsed Nd:YAG laser welding of the 304 stainless steels. The welding tests were carried out with various operational parameters. The effects of laser welding variables on the geometry, microstructure and solidification of the weld are considered. The austenitic or ferritic solidification is produced in the 304 austenitic stainless steel depended upon the cooling rate and its chemical compositions. The possiblity of austenitic solidification compared with the ferritic solidification decreases with the chromium to nickel equivalent ratio and that increases with cooling rates. Moreover, more δ ferrite is obtained if the cooling rate is increased or the higher power laser is used. The surface of fracture samples was considered and the reason for failure was investigated. The study shows that the fracture is in ductile type.

Formation of Ultrafine Grained Structure in SUS 304 Stainless Steel Produced by High Pressure Torsion (HPT)

2007 ◽  
Vol 561-565 ◽  
pp. 847-852 ◽  
Author(s):  
Jin Guo Li ◽  
Minoru Umemoto ◽  
Yoshikazu Todaka ◽  
Koichi Tsuchiya
Keyword(s):  
Stainless Steel ◽  
Strain Rate ◽  
High Strain ◽  
Rotation Speed ◽  
High Pressure Torsion ◽  
304 Stainless Steel ◽  
Ultrafine Grained Structure ◽  
Ultrafine Grained ◽  
304 Austenitic Stainless Steel ◽  
High Rotation Speed

SUS 304 austenitic stainless steel was processed by HPT at room temperature with different rotation speed. It was found that the microstructure evolution and composed phases along the progress of HPT were sensitive to the strain rate (rotation speed). During deforming with the low strain rate, the deformation-induced dynamic phase transformation (DPT) from austenite (γ) to martensite (α’) occurred and the microstructure is characterized by elongated submicron α’ grains after 10 revolutions. While the euqiaxed nanocrystalline α’ grains were produced after HPT at the continuously alternative low and high strain rate. XRD analyses showed that multiple DPT of γ→α’→γ→α’ took place during HPT at the continuously alternative low and high rotation speed. Based on the experimental results, it was proposed that the euqiaxed ultrafine grained structure were produced by multiple DPT under the high strain and strain gradient.

Contrast Effects at Grain Boundary Ledges in 304 Austenitic Stainless Steel

1972 ◽  
Vol 30 ◽  
pp. 650-651
Author(s):  
R. C. McDonald ◽  
A. J. Ardell
Keyword(s):  
Stainless Steel ◽  
Grain Boundary ◽  
304 Stainless Steel ◽  
Contrast Effects ◽  
Transmission Electron ◽  
304 Austenitic Stainless Steel ◽  
Cold Worked ◽  
Type 304 ◽  
Type 304 Stainless Steel ◽  
Strong Contrast

Grain boundary ledges and/or dislocations have been observed in a wide variety of materials by a number of investigators using transmission electron microscopy (TEM) techniques. These defects can be expected to have interesting implications in terms of grain boundary precipitation reactions and creep behavior. In this paper we describe some of our TEM observations of grain boundary ledges in a specimen of type 304 stainless steel which was solution treated at 1040°C, quenched, cold worked 2%, and aged for 15 minutes at 850°C.The configuration of the ledges can be observed in Fig. 1. For the diffracting conditions in Fig. 1 both bright and dark contrast effects are associated with many of the ledges. Strong contrast of this sort has been observed by other investigators. This strong contrast is not typical, however, as can be seen on comparison with Figs. 2 and 3, which show the same grain boundary under different diffracting conditions.

scholarly journals Study on Effect of Electromagnetic Characteristics of Deformed 304 Stainless Steel on Eddy Current Testing

2020 ◽  
Author(s):  
Benli Wan ◽  
Bin Hu ◽  
Yuntao Li ◽  
Yuhong Zhu
Keyword(s):  
Stainless Steel ◽  
Eddy Current ◽  
Magnetic Permeability ◽  
Excitation Frequency ◽  
Eddy Current Testing ◽  
304 Stainless Steel ◽  
Electromagnetic Response ◽  
Element Analysis ◽  
Current Testing ◽  
304 Austenitic Stainless Steel

The induced ferrite and other high magnetic microstructures content changes are studied when 304 austenitic stainless steel stripe specimens are tested under different uniaxial tension deformation, namely its deformation less than 50%. Furtherly, the correlation is plotted between the resulting magnetic permeability or coercivity caused by these microstructures and deformation. Meanwhile, the optimal eddy current excitation frequency under different deformation was obtained, which was consistent with 3-D finite element analysis (FEA). Besides, other various factors affecting the quality of eddy current testing (ECT), such as temperature and conductivity, are also considered comprehensively during the tensile test. The results of the experiment and simulation calculation show that when the deformation is within 50% that necking deformation has occurred, the magnetic permeability of specimens increases with deformation, and gradually begin to have the magnetic properties of weak ferromagnetic materials, which also changes the optimal excitation frequency, which varies from 60 kHz to 110 kHz. Because of the electromagnetic response noise increase, the impedance plane diagrams of defects distort simultaneously, which leads to the quantitative evaluation error of defects.

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