Browse Topic: Hardening
The current ASTM A653 standard for determining the bake hardening index (BHI) of sheet metals can lead to premature fracture at the transition radius of the tensile specimen in high strength steel grades. In this study, a new test procedure to characterize the BHI was developed and applied to 980 and 1180 MPa third generation advanced high strength steels (3G-AHSS). The so-called KS-1B methodology involves pre-straining over-sized tensile specimens followed by the extraction of an ASTM E8 sample, paint baking and re-testing to determine the BHI. Various pre-strain levels in the range of 2 to 10% were considered to evaluate the KS-1B procedure with select comparisons with the ASTM A653 methodology for pre-strain levels of 2 and 8%. Finally, to characterize the influence of paint baking at large strain levels, sheared edge conical hole expansion tests were conducted. The tensile mechanical properties of the 3G steels after paint baking were observed to be sensitive to the pre-strain with
Alloy steel possesses high strength, hardenability, fatigue strength, and good impact toughness. It is widely used for making various machine parts, automobile components, shafts, gears, connecting rods, and more. Hardening and tempering develop the optimum combination of hardness, strength, and toughness in engineering steel, thereby providing components with high mechanical properties. Hardening and tempering temperatures are crucial factors that affect the mechanical and metallurgical properties of 42Cr4Mo steel. In this research work, 42Cr4Mo alloy steel samples were subjected to hardening and tempering processes. The hardening temperatures were set at 830°C, 850°C, and 870°C, while the tempering temperatures were maintained at 590°C and 650°C. The test results show that hardening at 830°C and tempering at 590°C achieve high tensile strength, which decreases as the temperature increases. Different hardening temperatures and constant tempering temperatures will be optimized to
Magnesium (Mg) alloys are becoming ever more ubiquitous as the need for lighter and stronger alloys has increased significantly in the past decades. Mg alloy grade AZ91D is embedded in 0.5 of cerium have a high strength-to-weight ratio and lower specific density, which is useful in the case of automobile applications. An inconclusive study by Lagowski has shown that interrupted age hardening of AZ magnesium alloy increases the yield strength by around 10%. An investigation on the developed AZ91D+0.5Ce alloy subjected to various ageing treatments was carried out in this present study. The various aged samples were investigated by optical microscopy and scanning electron microscopy analysis. The yield strength was also evaluated quantitatively as a function of ageing parameters. A significant increase in yield strength and hardness values was observed in the artificially aged samples due to the precipitation of Mg17Al12 phases.
The figures in this SAE Information Report illustrate the principle that, regardless of composition, steels of the same cross-sectional hardness produced by tempering after through hardening will have approximately the same longitudinal1 tensile strength at room temperature. Figure 1 shows the relation between hardness and longitudinal tensile strength of 0.30 to 0.50% carbon steels in the fully hardened and tempered, as rolled, normalized, and annealed conditions. Figure 2 showing the relation between longitudinal tensile strength and yield strength, and Figure 3 illustrating longitudinal tensile strength versus reduction of area, are typical of steels in the quenched and tempered condition. Figure 3 shows the direct relationship between ductility and hardness and illustrates the fact that the reduction of area decreases as hardness increases, and that, for a given hardness, the reduction of area is generally higher for alloy steels than for plain carbon steels. It is evident from
This recommended practice provides recommendations for minimizing high temperature oxidation (HTO) during the heat treatment of aluminum alloy products and parts. HTO leads to deterioration of properties.
This specification covers an aluminum alloy in the form of sheet and plate 0.017 to 2.000 inches (0.43 to 50.80 mm), inclusive, in nominal thickness (see 8.6).
At the dawn of battery electric vehicles (BEVs), protection of automotive battery systems as well as passengers, especially from severe side impact, has become one of the latest and most challenging topics in the BEV crashworthiness designs. Accordingly, two material-selection concepts are being justified by the automotive industry: either heavy-gauge extruded aluminum alloys or light-gauge advanced high-strength steels (AHSSs) shall be the optimal materials to fabricate the reinforcement structures to satisfy both the safety and lightweight requirements. In the meantime, such a justification also motivated an ongoing C-STARTM (Cliffs Steel Tube as Reinforcement) Protection project, in which a series of modularized steel tube assemblies, were demonstrated to be more cost-efficient, sustainable, design-flexible, and manufacturable than the equivalent extruded aluminum alloy beams as BEV reinforcement structures. Tangent to this comparative study, the present work shed some light on the
This specification defines the requirements for locally hardening steel parts by the induction hardening method.
This SAE Standard prescribes the procedure for making hardenability tests and recording results on shallow and medium hardening steels, but not deep hardening steels that will normally air harden. Included are procedures using the 25 mm (1 in) standard hardenability end-quench specimen for both medium and shallow hardening steels and subsize method for bars less than 32 mm (1-1/4 in) in diameter. Methods for determining case hardenability of carburized steels are given in SAE J1975. Any hardenability test made under other conditions than those given in this document will not be deemed standard and will be subject to agreement between supplier and user. Whenever check tests are made, all laboratories concerned must arrange to use the same alternate procedure with reference to test specimen and method of grinding for hardness testing. For routine testing of the hardenability of successive heats of steel required to have hardenability within certain limits, it is sufficient to designate
This specification covers an aircraft-quality, low-alloy steel in the form of heat-treated bars and forgings, and of forging stock.
Precipitation Hardened Stainless Steel (PHSS) is one of the martensitic steels that possess exceptional strength and corrosion resistance. Because of its characteristics, this PHSS is exclusively adopted in numerous engineering uses such as nuclear, chemical and marine industries. Welding is one of the important methods of joining that helps to make weldments with better performance characteristics. Corrosion behaviour is one of the important characteristics that contribute hugely to marine and other corrosion-related environments and also this is the most common problem for most of the manufacturing industries. The goal of this study was to analyze the PHSS weldments’ corrosive behavior and compare it with that of the two commonly used welding processes, namely MIG and TIG. The corrosive properties of the weldments were evaluated using various mediums, such as nitric acid, ferric chloride, and Oxalic acid. The weight loss procedure was utilized to calculate the PHSS weldments
This specification covers an aircraft-quality, low-alloy steel in the form of heat-treated bars 1.50 inches (38.1 mm) and less in diameter or least distance between parallel sides.
Surface engineering is becoming increasingly crucial for several automotive and aerospace components that involve intense surface interactions. Friction stir processing (FSP) has emerged as an effective surface modification and hardening technique in recent days. The technique also allows the incorporation of reinforcement into the modified surface to enhance the strength and hardness further. This work applied FSP to develop a pure Ti particulate reinforced AA6061 metal matrix composite (MMC). Six different strategies were adapted (in the form of micro grooves, micro drills on the surface) to effectively infuse reinforcement on the alloy surface. Microstructural changes before and after FSP were studied using SEM and EBSD. Other tests such as post-mortem EDS, XRD, hardness, and compression were also done to examine the performance of developed composite. Microstructural lineaments revealed a more uniform dispersion of reinforcement particles in the matrix when the particles were
In most cases, the properties of a metal are evaluated in their as rolled condition, prior to any work hardening or bake hardening. But in the Automotive World, these steels get work hardened during the forming process and bake hardened in the paint shop. The goal of this paper is to evaluate the variations in the performance of Dual Phase (DP) steels and understand the most optimized method of testing and property generation. This method can then be used to extrapolate to real automotive components. Dual Phase Steels or DP Steels contain a mixture of Ferrite & Martensite from which they derive their name. They are a part of the advanced high strength and ultra-high strength steels steel family according to World Auto Steels. The Ferrite phase, with its iron content contributes to the material displaying an increased level of ductility whilst, the martensitic phase provides the steel with increased mechanical strength. These two properties together enable the steel to be highly
Case hardening may be defined as a process for hardening a ferrous material in such a manner that the surface layer, known as the case, is substantially harder than the remaining material, known as the core. The process embraces carburizing, nitriding, carbonitriding, cyaniding, induction, and flame hardening. In every instance, chemical composition, mechanical properties, or both are affected by such practice. This testing procedure describes various methods for measuring the depth to which change has been made in either chemical composition or mechanical properties. Each procedure has its own area of application established through proved practice, and no single method is advocated for all purposes. Methods employed for determining the depth of case are either chemical, mechanical, or visual, and the specimens or parts may be subjected to the described test either in the soft or hardened condition. The measured case depth may then be reported as either effective or total case depth
Prediction of the surface finish of hardened bearing steels was estimated in machining with ceramic uncoated cutting tools under various process parameters using two statistical approaches. A second-order (quadratic) regression model (MQR, multiple quantile regression) for the surface finish was developed and then compared with the artificial neural network (ANN) method based on the coefficient determination (R 2), root mean square error (RMSE), and percentage error (PE). The experimental results exhibited that cutting speed was the dominant parameter, but feed rate and depth of cut were insignificant in terms of the Pareto chart and analysis of variance (ANOVA). The optimum surface finish in machining bearing steel was achieved at 100 m/min speed, 0.1 mm/revolution (rev) feed rate, and 0.6 mm depth of cut. In addition, the ANN model revealed a better performance than that of MQR for predicting the surface finish when machining the hardened bearing steels because R 2 was about 0.787
The characterization of sheet metals under in-plane uniaxial bending is challenging due to the aspect ratios involved that can cause buckling. Anti-buckling plates can be employed but require compensation for contact pressure and friction effects. Recently, a novel in-plane bending fixture was developed to allow for unconstrained sample rotation that does not require an anti-buckling device. The objective of the present study is to design the sample geometry for sheared edge fracture characterization under in-plane bending along with a methodology to resolve the strains exactly at the edge. A series of virtual experiments were conducted for a 1.0 mm thick model material with different hardening rates to identify the influence of gage section length, height, and the radius of the transition region on the bend ratio and potential for buckling. Two specimen geometries are proposed with one suited for constitutive characterization and the other for sheared edge fracture. It is shown that
Light weighting has been one of major driver in automotive industry for few decades. Today when automobile industry is in the transition from internal combustion engine to electric vehicles it becomes even more dominant driver. Many high strength or advanced high strength steels are used in different parts of automotive body for down-gauging and light weighting. BH 220 steel is used in automotive skin panels for its bake hardening property. BH220 provides excellent combination of formability during stamping process and dent resistance in skin panel parts post painting and baking cycle. This material uses CED oven temperature for baking and provide bake hardening effect (BH effect/BH Index) in parts due to increase in yield strength by 35-70 MPa. Current national and international standards specify requirement on BH Index at 170°C for 20 minutes with 2% pre-strain. In order to optimize paint shop CED oven baking temperature, study carried out to know baking temperature effect on BH
This SAE Recommended Practice provides procedures for determining shot peening coverage and relating coverage to part exposure to the media stream. Effectiveness of shot peening is directly dependent on coverage. Inadequate or excessive coverage can be detrimental to fatigue strength and component life.
This specification covers a premium aircraft-quality, low-alloy steel in the form of sheet, strip, and plate.
This specification covers a low-alloy steel in the form of investment castings.
This specification covers a low-alloy steel in the form of investment castings.
This specification defines the requirements for locally hardening steel parts by the induction hardening method.
This specification covers a low-alloy steel in the form of investment castings.
An aftertreatment system is the back-end component of an automotive exhaust system, used mainly to reduce pollutant emissions. This system is exposed to high thermal loads which can exceed temperatures of 900 oC, usually they operate at temperatures under 600 oC - 700 oC, depending on the engine application. The durability assessment of a system under thermomechanical loads can be challenging due to the complexity of the technical problem, which involves complex material behavior at high temperatures and results in high thermomechanical strains and stresses. This study presents a computational approach for the lifetime assessment of an exhaust aftertreatment system subjected to thermomechanical loading. The method is composed of a fluid flow analysis to compute the temperature fields which are mapped to a mechanical analysis combined with a nonlinear elasto-viscoplastic material behavior. Lastly, the lifetime of the overall assembly is assessed through a fatigue analysis. The elasto
For cold gas Inflator, high refinement of ultimate pressure load forecast of inflator housing is one key of Inflator development. For inflator housing hydro-burst test ultimate load calculation, nonlinear finite element software for high precision results. At beginning, the material parameters of inflator housing for simulation is correlated. The FEA material model adopts the stress-strain data from uniaxial tensile experiments. Considering the geometrical nonlinearity resulting from large deformation as well as material nonlinearity from plastic hardening, the whole tensile process from tensile deformation to failure of the specimen is simulated. Numerical results show that the simulation is appropriate to predict the entire deformation process, and simulation results of ultimate tensile load, X-shape distribution of concentrated instability zone, the fracture location and inclined angle all agrees with that of test results. After finishing the correlation of uniaxial tensile test and
During deep drawing processes, the metal blank is radially drawn by mechanical action of the punch forcing the metal into a forming die. As a result, the workpiece goes through some work hardening where some residual energy is released in final stage which results in further deformation of the part (so called “springback”). This research paper is focused on development of a real-time control strategy to reduce springback effects in deep drawing. It reports on the results of the experimental study of springback in drawing and the parameters involved. In this regard, an experimental setup is designed and developed that is used for design of experiment study and simulation validation of the process. Design of experiment technique is utilized to systematically analyze the effects of the process parameters and their relative contribution in springback phenomenon. It is also used to validate process simulation model utilized to study performance of a control strategy developed to reduce
Limited room temperature formability hinders the wide-spread use of high strength aluminum alloys in body parts. Forming at warm temperatures or from softer tempers are the current solutions. In this work, our approach is to start with age-hardened sheets from 7xxx and 6xxx family of alloys and improve their formability using local thermomechanical processing only in the regions demanding highest ductility in the forming processes. We achieved local formability improvements with friction stir processing and introduce another process named roller bending-unbending as a concept and showed its feasibility through finite element simulations. Initial results from FSP indicated significant deformation in the processed zones with minimal sheet distortion. FSP also resulted in dynamically recrystallized, fine grained (d < 5 μm) microstructures in the processed regions with textures significantly different from the base material. This resulted in formability improvements of > 30% in 7085-T76
In automotive body manufacturing the dies for blanking/trimming/piercing are under most severe loading condition involving high contact stress at high impact loading and large number of cycles. With continuous increase in sheet metal strength, the trim die service life becomes a great concern for industries. In this study, competing trim die manufacturing routes were compared, including die raw materials produced by hot-working (wrought) vs. casting, edge-welding (as repaired condition) vs. bulk base metals (representing new tools), and the heat treatment method by induction hardening vs. furnace through-heating. CaldieTM, a Uddeholm trademarked grade was used as trim die material. The mechanical tests are performed using a WSU developed trimming simulator, with fatigue loading applied at cubic die specimen’s cutting edges through a tungsten carbide rod to accelerate the trim edge damage. The tests are periodically interrupted at specified cycles for measurement of die edge damage. The
This specification covers a corrosion-resistant steel product 8 inches (203 mm) and under in nominal diameter, thickness or for hexagons least distance between parallel sides, and having a maximum cross-sectional area of 64 in2 (413 cm2) in the solution and precipitation heat treated (H1025) condition.
This specification covers a corrosion-resistant steel product 8 inches (203 mm) and under in nominal diameter, thickness or for hexagons, least distance between parallel sides, and having a maximum cross-sectional area of 64 in2 (413 cm2) in the solution and precipitation heat treated (H1150) condition.
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