Study for Performance Increase of a Extractor Device by Steel Replacement of AISI 304 Steel for AISI 420 Steel

The performance of an extractor device used in the food industry was studied from the development of structural analysis through computational modeling based on finite elements. These analyses considered the mechanical properties of AISI 304 and 420 stainless steels, in addition to the tribological aspects of the device in operation. Initially, uniaxial tensile tests were carried out according to the ABNT NBR 6892 standard and hardness tests were carried out according to ASTM E384, E92, and E18 standards. From the mechanical tests, structural analyses were carried out numerically on each of the components of the extractor device. After analyzing all the components, the device was assembled to be tested in operation. The wear and service life of devices made from these two materials were evaluated. From this study, it could be concluded that the extractor device made with AISI 420 stainless steel, in addition to having a lower manufacturing cost, suffered less wear and had an increase in service life of up to 650% compared to the extractor device made with steel stainless steel AISI 304.

Formability Prediction of Laser-Welded Stainless Steel AISI 304 and AISI 430

The effect of laser welding on the mechanical properties and the prediction of formability for austenitic stainless steel AISI 304 and ferritic steel AISI 430 when welded by a YLS-5000 fiber laser, were studied in the paper. The microstructure of the welded joint was analyzed using light microscopy. The mechanical properties were determined by static tensile testing. The forming limit diagrams were produced from notched samples at R5, R17, and R25 mm. The hardness values of the welded joint and the base material were determined using the Vickers method. Samples made of AISI 430 showed that the formability suffered due to laser welding. Longitudinal coarse ferrite grains were observed in the microstructure of the AISI 430 weld metal. The coarse-grained structure of the welded joint and the continuous interface along the centerline caused the failure of the AISI 430 laser-welded samples at significantly lower actual stress and strain values than were required to break the base material. No significant changes in the formability were observed in the AISI 304 samples after laser welding. The growth of dendrites was observed in the microstructure of the AISI 304 welded joint in a direction towards the centerline of the welded joint. A comparison of the experimentally determined FLD0 values and the values calculated from predictive equations showed that a better agreement was achieved for uniform elongation than for the strain hardening exponent. The manufacturability and economic efficiency of selected parts of an exhaust system by hydromechanical drawing were evaluated on the basis of the process capability index Cpk.

Dimensional Stability of Low Temperature Surface Hardened Stainless Steel Components*

Stainless steels are commonly used for high precision components, which often are exposed to corrosive media. However, their inferior tribological behaviour restrict the use of these materials in many technical applications. Thermochemical surface hardening is one way to overcome these weaknesses. Solution nitriding in the austenitic range above 1000 °C is mainly used for hardening martensitic and ferritic stainless grades. In austenitic and duplex stainless grades, however, the hardening effect is limited. Additionally, the high process temperatures combined with a necessary rapid cooling may lead to non-desired dimensional changes. Low temperature surface hardening processing below 500 °C here offers interesting alternatives for increasing the wear properties, while maintaining the corrosion resistance. This paper demonstrates the influence of high and low process temperatures of thermochemical surface hardening treatments on the tight dimensional tolerances of a rotationally symmetrical precision component made from cold worked AISI 304. Based on these results, current and new industrial applications, which benefit from low temperature surface hardening, will be discussed.

Non-Destructive X-ray Characterization of a Novel Joining Method Based on Laser-Melting Deposition for AISI 304 Stainless Steel

In this study, an application of the laser-melting deposition additive manufacturing technique as a welding method has been studied for the laser welding (LW) of AISI 304 stainless steel, specifically 0.4 mm and 0.5 mm thick sheets. The welding was carried out without and with filler material. Inconel 718 powder particles were used as filler material in the second case. A series of experiments were designed by changing the process parameters to identify the effect of operating conditions on the weld width, depth, and height. The welds were examined through metallographic experiments performed at various cross-sections to identify the defects and pores. All the deposited welds were passed through a customized mini-focus X-ray system to analyze the weld uniformities. The optimal operating conditions were determined for 0.4 mm and 0.5 mm sheets for the LW with and without filler material. It was found that laser power, laser scanning speed, powder flow rate, and helium to argon gases mixture-control the weld bead dimensions and quality. X-ray analyses showed that the optimal operating conditions gave the least peak value of non-uniformity in the laser welds. This study opens a new window for laser welding via additive manufacturing with X-ray monitoring.