Stainless Steel Strip Research Articles

Development of a Stainless Austenitic Nitrogen-Alloyed CrMnNiMo Spring Steel

The generation of a nickel-reduced, stainless spring steel strip with a thickness of 0.2 mm, producible under industrial conditions, is the aim of a transfer project together with the Institute of Metal Forming/TU BAF and the Auerhammer Metallwerk GmbH within the DFG Collaborative Research Centre (CRC) 799. The spring steel strip should exhibit a tensile strength of ≥1700 MPa in work-hardened and partitioned state. The mechanical and corrosive properties of the steel strip should be equal or better than those given for 1.4310 steel (AISI 301). The article presents the results of laboratory alloys focused on the design of steel strips, which meet the requirements for a cost-effective production. The results presented relate to steel design, microstructure formation, temperature-dependent mechanical properties, and corrosion resistance. Four alloys of the type X5CrMnNiMoN16-x-4 with manganese contents of approximately 2 to 6 wt.-percent were investigated. The austenitic steel X5CrMnNiMoN16-4-4 with TRIP/TWIP effect was selected for deformation and partitioning treatments. Its deformation-induced α’-martensite formation significantly contributes to the work hardening of the steel. A short-time annealing treatment (partitioning) further increases the strength properties.

The Impact of the Gas Inlet Position, Flow Rate, and Strip Velocity on the Temperature Distribution of a Stainless-Steel Strips during the Hardening Process

A non-uniform temperature across the width of martensitic stainless-steel strips is considered to be one of the main reasons why the strip exhibits un-flatness defects during the hardening process. Therefore, the effect of the gas inlet position in this process, on the temperature distribution of the steel strip was investigated numerically. Furthermore, an infrared thermal imaging camera was used to compare the model predictions and the actual process data. The results showed that the temperature difference across the width of the strip decreased by 9% and 14% relative to the calculated temperature and measured values, respectively, when the gas inlet position was changed. This temperature investigation was performed at a position about 63 mm from the bath interface. Moreover, a more symmetrical temperature distribution was observed across the width of the strip. In addition, this study showed that by increasing the amount of the hydrogen flow rate by 2 Nm3/h, a 20% reduction of temperature difference across the width of strip was predicted. Meanwhile, the results show that the effect of the strip velocity on the strip temperature is very small.

Clean, flawless and thinner stainless steel valves by strip casting

Compressor valves are made of hardened and tempered martensitic stainless steels. They were first produced from ingot cast material. Later continuous casting technology largely replaced this process, which led to improved, more uniform, properties and higher yields in the production of hot strip. A further development was made around the turn of the millennium, when strip casting was first used for the production of stainless steel strip, directly from the melt. In this paper the steel grade Zapp 1.4028MO produced via both production routes: a) Continuous casting - hot rolling - cold rolling and b) Strip casting - cold rolling, are compared with respect to their microstructure evolution and static/dynamic mechanical properties. It is shown that strip cast material can not only substitute that of the traditional continuous casting route, but moreover deliver performance advantages with thin stainless steel valves used within air conditioning units and household refrigerators.

Enhancement of Graphene Oxide Deposition on Stainless Steel in Presence of Iodine

In this study, Graphene Oxide (GO) was prepared by modified Hummers method and characterized by X-ray diffraction technique (XRD). The characteristic peak of GO was observed at 2=10.94° compared to graphite’s peak at 2 = 26.4°. Aqueous stable suspension of GO was prepared, and its stability was confirmed using Zeta potential and found to be-28.9 mV. Electrophoretic Deposition (EPD) process of GO on stainless steel strips was investigated. The EPD process was optimized to obtain a large amount of deposited GO layer. The optimal applied voltage was found to be 30 V and optimal deposition time was 480 seconds. At the optimum conditions, the effect of the addition of iodine was investigated for its effect on the deposited layer homogeneity. Visual investigation of samples indicated that the homogeneity of the GO coated layer was enhanced in the presence of iodine and confirmed by scanning electron microscope (SEM).

Stainless steel strip – A proposed shear reinforcement for masonry wall panels

Abstract Earthquakes can cause serious damage to historic masonry structures. Masonry reinforcement has been widely studied by proposing different retrofitting methods. However it is sometimes difficult to combine the need for effective retrofitting, with high reversibility and low impact. The use of compatible-to-masonry, chemically stable and durable reinforcement materials in another difficult task. In this area, the use of stainless steel strips, as a method for reinforcing existing masonry by increasing its tensile strength and ductility, is proposed in this paper. With the aim at reproducing the in-plane seismic loading, 10 wall panels were tested in one-sense cyclic shear in the laboratory. Stainless steel strips were mechanically attached on both panel’s sides using metal anchor bolts to the masonry substrate along the stretched diagonal and panel’s structural response was recorded and studied. The reinforcement installation procedures, the panel’s structural behavior in terms of stiffness, ductility and strength were described in detail in the paper. It is demonstrated that this retrofitting technique can enhance the mechanical behavior of the wall panels. Finally, an analysis of the features of the proposed technique indicates that it is likely to offer some advantages over some commonly-used retrofitting methods. A design procedure is also proposed and discussed in the paper.

Hybrid electroslag cladding (H-ESC): an innovation in high speed electroslag strip cladding

Application of strip cladding using electroslag welding process to cover large surface areas of vessels for oil and gas industries has been a common weld cladding method in last few decades. There has been continuous development by welding consumable suppliers to improve this method further through introduction of high-speed ESW flux and specially designed over-alloyed welding strips to achieve required weld metal chemistry in single layer for some of the alloys. However, the conventional method had limitations in achieving desired chemistry with single layer for certain alloys—Ni-625 alloy with max. 5% Fe is one among them. A new variant of electroslag cladding technique (Hybrid Electro Slag Cladding or H-ESC) has successfully been developed and introduced in the market, wherein a 3rd dimension has been added to the conventional ESW strip cladding method of using strip and flux in the form of addition of multiple hot metal cored wires into the molten electroslag weld pool. Addition of multiple hot MCW wires with a particular proportion into the molten weld pool by a uniquely designed digital weld control system helps in controlling the dilution level, thereby achieving clean undiluted cladding chemistry coupled with at least 50% higher welding speed and nearly double the weld deposition rate as compared to conventional ESW cladding technique. In this new high-speed single-layer cladding technique using neutral flux, it is possible to achieve Fe content 40% Ni for Ni-825 cladding in single layer. Similarly, this new technique offers unique solution in case of high-speed single-layer austenitic stainless steel cladding, wherein only one standard stainless steel strip type is used along with neutral flux and desired AWS clean weld metal chemistry is easily achieved for SS 308L, SS 316L, SS 347, and SS 317L by using suitably designed MCW wires. Such solution would immensely help fabricators to minimize their working capital and faster delivery of weld consumables in addition to reaching desired 3.0 mm undiluted weld chemistry in high-speed single-layer cladding of 3.5-mm thick.

Augmentation of Heat Transfer in Pipe Flow Using Plain Twisted Tape Inserts for Different Twist Ratios

The heat transfer augmentation of plain twisted tape inserts for different twist ratios has been studied in this study. The data are conducted using the plain twisted tape insert with five different twist ratios respectively. The range of Reynolds number is considered under a uniform heat flux condition. In the case of simulation, the tapes are made from a stainless steel strip with a thickness of 2 mm. A tubular pipe with 850mm U-loop length and twist length of 800 mm each is considered in our study for simulation. Water is used as working fluids inside the tube for our simulation. The simulation results demonstrate that the important heat transfer parameters including Nusselt number (Nu), friction factor (f) and thermal performance index (η) are gradually increased with the increment of the twist ratio and reached at the saturated level while twist ratio is 3.5, afterward the thermal properties are decreased.

An online quality monitoring tool for information acquisition and sharing in manufacturing: requirements and solutions for the steel industry

The purpose of this study was to develop an innovative online supervisor system to assist the operators of an industrial manufacturing process in discovering new solutions for improving both the products and the manufacturing process itself. In this paper, we discuss the requirements and practical aspects of building such a system and demonstrate its use and functioning with different types of statistical modelling methods applied for quality monitoring in industrial applications. The two case studies presenting the development work were selected from the steel industry. One case study predicting the profile of a stainless steel strip tested the usability of the tool offline, while the other study predicting the risk of roughness of a steel strip had an online test period. User experiences from a test use period were collected with a system usability scale questionnaire.

Behaviour and design of spiral-welded stainless steel tubes subjected to axial compression

Spiral welded stainless steel tubes are produced by helical welding of a continuous stainless steel strip. Recently, spiral welded stainless steel tubes have found increasing application in the construction industry due to their ease of fabrication and aesthetic appeal. However, an in-depth understanding of the behaviour of these types of structural elements is still needed due to the insufficient experimental evidence and lack of rational design guidance. In the present paper, an extensive experimental program was carried out to investigate the behaviour of axially loaded hollow and concrete-filled spiral welded stainless steel tubes. The effects of various design parameters were investigated throughout the test program. In addition to the experiments, this paper presents a finite element model for the prediction of these columns. Specifically, the proposed finite element models take into account the effects of material and geometric nonlinearities. The helical welding is modelled as an independent part that is further tied to the stainless steel tube. Moreover, the initial imperfections of the stainless steel tube and the residual stresses resulting from helical welding are included. Enhancement of the understanding of the experimental results can be achieved by extending the parametric studies based on the developed finite element model. Furthermore, a comparison of the ultimate strength between the experimental results and those obtained from existing codes of practice is conducted.

A comparison of deformation, microstructure, mechanical properties and formability of SUS436L stainless steel in tandem and reversible cold rolling processes

A comparison was made for the deformation, microstructure, mechanical properties and formability of SUS436L stainless steel in tandem and reversible cold rolling processes. At first, the thermophysical parameters and stress–strain curves of SUS436L steel were measured in temperature range of 293–573 K and a flow stress model was regressed from the data of these curves. An analytical model based on the elasto-plastic finite element method was then established to simulate the tandem and the reversible cold rolling processes of SUS436L stainless steel strip where the flow stress model was introduced. The difference in shear strain distribution, microstructure, mechanical properties and formability of SUS436L steel strip in the two rolling processes was analyzed. The results showed that the larger shear strain, the enhanced intensity of γ fiber texture and the excellent formability of the strip can be easily obtained in the tandem rolling process with the larger work roll rather than the reversible rolling process with the smaller work roll.

Interface Structure and Elements Diffusion of As-Cast and Annealed Ductile Iron/Stainless Steel Bimetal Castings

Bimetal casting is considered to a promising technique for the production of high performance function materials. Heat treatment process for bimetal castings became an essential tool for improving interface structure and metallurgical diffusion bond. Molten iron alloy with carbon equivalent of 4.40 is poured into sand mold cavities containing solid 304 stainless steel strips insert. Specimens are heated to 7200C in an electrical heating furnace and holded at 720 0C for 60min and 180min. For as-cast specimens, a good coherent interface structure of ductile cast iron/304 stainless bimetal with four layers interfacial microstructure are obtained. Low temperature annealing at 720oC has a significat effect on the interface layers structure, where, three layers of interface structure are obtained after 180min annealing time because of the complete dissolving of thin layer of ferrite and multi carbides (Layer 2). Low temperature annealing shows a significant effect on the diffusion of C and otherwise shows slightly effect on the diffusion of Cr and Ni. Plearlite phase of Layer 3 is trsformed to spheroidal shape instead of lamallar shape in as-cast bimetals by low tempeature annealing at 720oC. The percent of the performed spheroidal cementit increases by increasing anneaaling time. Hardness of interface layers is changed by low temperauture annealing due to the significant carbon deffussion.

Analysis of Springback Behaviour in Micro Flexible Rolling of Crystalline Materials

This paper presents a constitutive modelling of the polycrystalline thin metal strip under a state of combined loading in microflexible rolling. The concept of grained inhomogeneity is incorporated into the classic Chaboche hardening model that accounts for the Bauschinger effect, in order to provide more precise description and analysis of the springback mechanism in the particular forming operation. The model is first implemented in the finite element program ABAQUS to numerically predict the stress‐strain relationship of 304 stainless steel specimens over a range of average grain sizes. After validation of the developed model by comparison of predicted curves and actual stress‐strain data points, it is further applied to predict the thickness directional springback in microflexible rolling of 304 stainless steel strips with initial thickness of 250 µm and reduction changing from 5 to 10%. The model predictions show a reasonable agreement with the experimental measurements and have proven to be more accurate than those obtained from the conventional multilinear isotropic hardening model in combination with the Voronoi tessellation technique. In addition, the variation of thickness directional springback along with the scatter effect is compared and analysed in regard to the average grain size utilising both qualitative and quantitative approaches in respect of distinct types of data at different reductions.

Variations of Chemical Composition and Effects of Welding Parameters on the Overlay Welding Behaviors and Fluxes in Electroslag Cladding by using a New 420-series Stainless Steel Strip

Variations of Chemical Composition and Effects of Welding Parameters on the Overlay Welding Behaviors and Fluxes in Electroslag Cladding by using a New 420-series Stainless Steel Strip

The Effects of Nitrogen Content and Cold Rolling Reduction on the Mechanical Properties of New 420-series Stainless Steel Strip having a Mesh As-Welded Structure by the Electroslag Cladding

The Effects of Nitrogen Content and Cold Rolling Reduction on the Mechanical Properties of New 420-series Stainless Steel Strip having a Mesh As-Welded Structure by the Electroslag Cladding

Computer modelling for thin strip twin-roll casting

In twin-roll casting, the influence of the heat-transfer rate at the metal–mold boundary on the thickness and the proportion of solidifying metal at the exit from the water-cooled roller mold is analyzed. The corresponding analytical curves are plotted for the production of moderate-carbon and stainless steel strip (thickness 1–6 mm). The proposed method may be used in the development of twin-roll technology and equipment.

Analysis and Comparison Between No-Insulation and Metallic Insulation REBCO Magnet for the Engineering Design of a 1-MW DC Induction Heater

A 1-MW industrial-scale high-temperature superconductor (HTS) dc induction heater is being designed and manufactured in Shanghai Jiao Tong University, China. This paper is to present the design and engineering analysis of a HTS magnet with iron yoke for this heater. This magnet is to generate a 0.5-T dc magnetic field in the iron's air gap, where the billet is rotated. To enhance the thermal stability, the no-insulation (NI) coil and metallic insulation (MI) coil (co-wind with stainless steel strips) is introduced to the magnet. The influence of the NI&MI technique on the magnet's ramping process is analyzed. A significant ramping delay occurs on both the NI and MI magnet. Joules losses are generated by the current “bypassing” through turn-to-turn contacts, which may lead to significant temperature rise on the coils. Higher ramping rate often means faster ramping process and higher temperature rise induced by ramping loss. The MI magnet shows a much shorter ramping time and lower ramping loss than its NI counterpart, due to higher turn-to-turn resistivity. The MI coil is more suitable than the NI coil for this large-scale magnet.

Test of an 8.66-T REBCO Insert Coil with Overbanding Radial Build for a 1.3-GHz LTS/HTS NMR Magnet.

A 1.3-GHz/54-mm LTS/HTS NMR magnet, assembled with a 3-coil (Coils 1-3) 800-MHz HTS insert in a 500-MHz LTS NMR magnet, is under construction. The innermost HTS insert Coil 1 has a stack of 26 no-insulation (NI) double pancake (DP) coils wound of 6-mm wide and 75-μm thick REBCO tapes. In order to keep the hoop strains on REBCO tape < 0.6% at an operating current Iop of 250 A and in a field of 30.5 T, we overbanded each pancake in Coil 1 with a 6-mm wide, 76-μm thick 304 stainless steel strip: 7-mm thick radial build for the central 18 pancakes, while 6-mm thick for the outer 2×17 pancakes. In this paper, Coil 1 was successfully tested at 77K and 4.2 K. In the 77-K test, the measured critical current was 35.7 A, determined by an E-field criterion of 0.1 μV/cm. The center field magnet constant decreased from 34.2 mT/A to 29.3 mT/A, when Iop increased from 5 A to 40 A. The field distribution at different Iop along the z-axis was measured. The residual field distributions discharged from 10 A and 20 A were recorded. In the 4.2-K test, Coil 1 successfully generated a central field of 8.78 T at 255 A. The magnet constant is 34.4 mT/A, which is same as our designed value. The field homogeneity at the coil center within a ±15-mm region is around 1700 ppm. This large error field must be reduced before field shimming is applied.

Experimental and Numerical Study on the Effect of ZDDP Films on Sticking During Hot Rolling of Ferritic Stainless Steel Strip

The aim of this study is to investigate the effect of zinc dialkyl dithio phosphate (ZDDP) films on sticking during hot rolling of a ferritic stainless steel strip. The surface characterization and crack propagation of the oxide scale are very important for understanding the mechanism of the sticking. The high-temperature oxidation of one typical ferritic stainless was conducted at 1373 K (1100 °C) for understanding its microstructure and surface morphology. Hot-rolling tests of a ferritic stainless steel strip show that no obvious cracks among the oxide scale were observed with the application of ZDDP. A finite element method model was constructed with taking into consideration different crack size ratios among the oxide scale, surface profile, and ZDDP films. The simulation results show that the width of the crack tends to be reduced with the introduction of ZDDP films, which is beneficial for improving sticking.

Analysis of ZDDP Films on Sticking Defects by FEM during Hot Rolling of Ferritic Stainless Steel Strips

The aim of this study is to understand the effect of zinc dialkyl dithio phosphate (ZDDP) films on sticking defects during the hot rolling of ferritic stainless steel strips. The surface characterisation and crack propagation are very important for the sticking defects of ferritic stainless steel strip. A finite element method (FEM) model is constructed with different crack size ratios, in which the profile of the strip roughness and ZDDP films are taken into consideration. Simulation results show that the widths of cracks tend to be reduced with the introduction of ZDDP films, improving the sticking defects, which is confirmed by the hot rolling trials.

Influence of turn-to-turn resistivity and coil geometrical size on charging characteristics of no-electrical-insulation REBCO pancake coils

High temperature superconductor (HTS) no-electrical-insulation (NEI) coils demonstrate great advantages in thermal stability and self-protection features. However, an intrinsic delay is observed in the charging process and as a result there maybe a possible settle-out problem. It becomes more critical for large HTS coils with more turns, such as the magnets for the accelerator system and DC induction heater applications. This paper presents detailed studies on the charging characteristics of NEI coils. Firstly, two different no-electrical-insulation coils are wound: the first is directly wound using only REBCO tapes with brass lamination, which is called a no-insulation (NI) coil. The other one is co-wound with stainless steel (SS) strips and REBCO tapes whose copper stabilizer is electroplated, which is called a metallic insulation (MI) coil. Fast discharging tests are performed on the two coils and their equivalent turn-to-turn resistivity is calculated. A similar discharging delay is observed on both coils, but the turn-to-turn resistivity of the SS co-wound coil is much higher than that of the first coil. Then the resistivity data is directly applied to an equivalent circuit network model which is developed to predict the charging behaviours. The model calculates coil voltage, currents along the azimuthal and radial directions, as well as the induced magnetic field. A practical charging time is defined to characterize the field ramping process considering the charging delay between field ramping and current charging. The charging behaviours are extensively analyzed and compared in terms of three primary factors: equivalent turn-to-turn resistivity, coil size and ramping rate. The results show that the charging time increases dramatically with the coil size and may be too long to be practical for large-scale applications using HTS coils with low turn-to-turn resistivity. Increasing the turn-to-turn resistivity enables one to accelerate the charging process effectively. Therefore, the SS co-wound coil with higher turn-to-turn resistivity shows a much shorter charging time, which indicates that it may be more suitable for large-scale HTS magnets.