Usability Testing of Ultra High-Strength Steels

2012 ◽  
Author(s):  
Jouko A. Heikkala ◽  
Anu J. Väisänen
Keyword(s):  
Tensile Strength ◽  
Plate Thickness ◽  
Rolling Direction ◽  
High Strength Steels ◽  
High Strength ◽  
Structural Steels ◽  
Test Material ◽  
Material Strength ◽  
Machining Parameters ◽  
Usability Tests

New ultra high strength (UHS) steels have been developed in order to get advantages in machine design and construction. Following benefits can be obtained for example: - less material usage due to lighter constructions; - better payload and less fuel consumption in vehicle industry; - energy saving in material production. A rough distinction of structural steels can be defined to ductile steels, with tensile strength less than 300 MPa, and high strength steels, up to 700 Mpa. A steel material can be defined as UHS steel when the tensile strength exceeds 700 MPa. Steels with yield strength of 1500 Mpa have been developed so far. UHS steels can also be divided into structural steels and wear resistant steels. With the tensile strength also the hardness increases and the tensile strain decreases. That causes several difficulties when the material is processed into products. Especially mechanical processing like bending, machining and shearing gets difficult as the material strength increases. That causes problems for the construction material users to find the proper manufacturing methods in production. In Oulu University Production Technology Laboratory material processing tests have been performed during several years in co-operation with the local steel manufacturer. The usability tests comprise mainly of bending and machining tests. Shearing and welding tests have been made to a smaller extent. Also laser treatment has been used for local heat conditioning in order to improve the bending and shearing properties, but these techniques are not yet widely used in production. The bending tests are carried out with standard bending tools and test steel plates with standard dimensions. The plate thickness varies depending on the test material. The target is to determine the reliable minimum bending radiuses whereby the plate can be bent without failure, from both sides and along the rolling direction and orthogonally to that. Also the springback angle is measured and the bent surfaces are evaluated according to several criteria. When necessary, also the mechanical testing of the formed material is carried out. The machining tests are made mainly by drilling. Also some milling tests have been performed. Drilling is a convenient way of machining testing because a substantial amount of holes can be drilled in one test plate. The drilling power can be observed precisely by monitoring the spindle power. Also a variety of different tool types can be used, from uncoated HSS drills to boring tools with indexable inserts. The optimal machining parameters (feed and speed) will be defined according to maximum tool life and minimum machining costs.

Development of a Damage Prediction System for Bending and Cutting of High Strength Steels

2013 ◽  
Vol 554-557 ◽  
pp. 2479-2486
Author(s):  
Peter Horst Vatter ◽  
Sven Hildering ◽  
Ioannis Tsoupis ◽  
Marion Merklein
Keyword(s):  
Industrial Application ◽  
Early Stage ◽  
Rolling Direction ◽  
High Strength Steels ◽  
Software Tool ◽  
High Strength ◽  
Material Strength ◽  
Punch Force ◽  
Steel Grades ◽  
Cutting Operation

Abstract. The application of modern high strength low alloyed steels (HSLA) and advanced high strength steels (AHSS) for structural and safety relevant components in the automotive industry offers the advantage of combining low specific weight with high material strength. Typical manufacturing processes for these steel grades are bending and cutting operations. The forming and cutting potential of these innovative steel grades is different to conventional steels as the process and the damage behaviour is changing. In bending operations cracks occur at the outer bending edge, whereas in cutting operations delamination can appear at the sheared edge. These damages, even though they are small, can initiate the component to fail. For a reliable use of such materials in industrial application a method for the process design is essentially needed. In particular, damages have to be predicted at an early stage. In industrial application damage is detected by a trial-and-error approach causing significant work and a high failure rate. A system for an offline assessment of the risk of failure is unknown so far. In the scope of this work, a method is presented to describe the damaging behaviour of both, bending and cutting operations, by theoretical metamodels. In order to generate a database experiments were carried out using different high strength steels. The main influence factors have been varied, such as the rolling direction, the punch-to-die clearance and the cutting contour in the cutting operation. The bending was investigated using an air-bending process varying the bending angle, the bending radius and the rolling direction. To calculate further sampling points a finite element model has been developed and validated against the experimental data. The damage criterion of Lemaître has been applied. The necessary parameters were determined by reverse identification by means of the major strain for the bending operation and by the punch force-punch stroke curve for the cutting operation. To build up a system for the prediction of the damage the gained data basis was approximated by mathematical functions. An error analysis was carried out showing good accordance. In doing so, a metamodel for the occurrence of damages could be established. The functions are implemented in a software tool which allows the user to determine the failure probability for a given parameter set.

DOGAL 600 and 800 DP

Alloy Digest ◽  
2010 ◽  
Vol 59 (12) ◽  
Keyword(s):  
Tensile Strength ◽  
Physical Properties ◽  
Surface Treatment ◽  
Tensile Properties ◽  
High Strength Steels ◽  
High Strength

Abstract Dogal 600 and 800 DP are high-strength steels with a microstructure that contains ferrite, which is soft and formable, and martensite, which is hard and contributes to the strength of the steel. The designation relates to the lowest tensile strength. This datasheet provides information on composition, physical properties, hardness, and tensile properties. It also includes information on forming, joining, and surface treatment. Filing Code: CS-160. Producer or source: SSAB Swedish Steel Inc. and SSAB Swedish Steel.

scholarly journals Effect of Quenching and Partitioning Temperatures in the Q-P Process on the Properties of AHSS with Various Amounts of Manganese and Silicon

2012 ◽  
Vol 706-709 ◽  
pp. 2734-2739 ◽  
Author(s):  
Hana Jirková ◽  
Ludmila Kučerová ◽  
Bohuslav Mašek
Keyword(s):  
Tensile Strength ◽  
Retained Austenite ◽  
Isothermal Holding ◽  
Bainitic Ferrite ◽  
High Strength Steels ◽  
High Strength ◽  
Experimental Program ◽  
Quenching Temperature ◽  
Quenching And Partitioning ◽  
Advanced High Strength Steels

The use of the combined influence of retained austenite and bainitic ferrite to improve strength and ductility has been known for many years from the treatment of multiphase steels. Recently, the very fine films of retained austenite along the martensitic laths have also become the centre of attention. This treatment is called the Q-P process (quenching and partitioning). In this experimental program the quenching temperature and the isothermal holding temperature for diffusion carbon distribution for three advanced high strength steels with carbon content of 0.43 % was examined. The alloying strategies have a different content of manganese and silicon, which leads to various martensite start and finish temperatures. The model treatment was carried out using a thermomechanical simulator. Tested regimes resulted in a tensile strength of over 2000MPa with a ductility of above 14 %. The increase of the partitioning temperature influenced the intensity of martensite tempering and caused the decrease of tensile strength by 400MPa down to 1600MPa and at the same time more than 10 % growth of ductility occurred, increasing it to more than 20%.

DESIGN PARAMETERS SELECTION OF SPRINGBACK EFFECT IN AIR-V BENDING USING TAGUCHI APPROACH ON ADVANCE HIGH STRENGTH STEEL-DP590

2015 ◽  
Vol 76 (3) ◽  
Author(s):  
Shahrul Azam Abdullah ◽  
Muhamad Sani Buang ◽  
Juri Saedon ◽  
Hashim Abdullah
Keyword(s):  
Plate Thickness ◽  
High Strength Steels ◽  
High Strength ◽  
Design Parameters ◽  
Optimum Level ◽  
Advanced High Strength Steels ◽  
Parameters Selection ◽  
Bending Process ◽  
Punch Radius ◽  
Evaluation Problem

Advanced High Strength Steels (AHSS) are increasingly utilized especially in automotive industry. However, forming of AHSS is challenging particularly in prediction of springback effect caused by material properties, tools and dies parameters, work material and bending technique factors. An air V-bending process was chosen as an evaluation problem because it showed larger springback effect. This paper presents an optimization to predict the influence of various parameters on springback of sheet metal in air V-bending process using Taguchi method (TM). The experimental study was conducted on DP590 sheets with plate thickness of 1 and 2 mm under different process parameters such as punch radius, die radius, die gap and punch travel. A significant level of springback parameters was further described by using the analysis of variance (ANOVA). It showed that the contribution percentage of each factor to springback was calculated to optimum level and the significant levels of entire factor were observed. The thickness of material, die width, punch travel and punch radius were found to be the most significant factor affecting springback while die radius is insignificant. 

Expulsion Intensity Monitoring and Modeling in Resistance Spot Welding Based on Electrode Displacement Signals

2020 ◽  
Author(s):  
Yu-Jun Xia ◽  
Yan Shen ◽  
Lang Zhou ◽  
Yong-Bing Li
Keyword(s):  
Resistance Spot Welding ◽  
Spot Welding ◽  
Low Carbon Steel ◽  
Sheet Thickness ◽  
High Strength Steels ◽  
High Strength ◽  
Material Strength ◽  
Low Carbon ◽  
Resistance Spot ◽  
Electrode Displacement

Abstract Weld expulsion is one of the most common welding defects during resistance spot welding (RSW) process especially for high strength steels (HSS). In order to control and eventually eliminate weld expulsion in production, accurate assessment of the expulsion severity should be the first step and is urgently required. Among the existing methods, real-time monitoring of RSW-related process signals has become a promising approach to actualize the online evaluation of weld expulsion. However, the inherent correlation between the process signals and the expulsion intensity is still unclear. In this work, a commonly used process signal, namely the electrode displacement and its instantaneous behavior when expulsion occurs are systematically studied. Based upon experiments with various electrodes and workpieces, a nonlinear relation between the weight of expelled metal and the sudden displacement drop accompanied by the occurrence of weld expulsion is observed, which is mainly influenced by electrode tip geometry but not by material strength or sheet thickness. The intrinsic relationship between this specific signal feature and the magnitude of expulsion is further explored through geometrical analysis, and a modified analytical model for online expulsion evaluation is finally proposed. It is shown that the improved model could be applied to domed electrodes with different tip geometries and varying workpieces ranging from low carbon steel to HSS. The error of expulsion estimation could be limited within ±20.4 mg (±2σ) at a 95% confidence level. This study may contribute to the online control of weld expulsion to the minimum level.

Structural Performance Evaluation of Built-Up Stub Steel Column with Various Steel Grades under Concentric Loading

2015 ◽  
Vol 764-765 ◽  
pp. 127-131
Author(s):  
Yang Yang ◽  
Kang Min Lee ◽  
Keun Yeong Oh ◽  
Sung Bin Hong
Keyword(s):  
Tensile Strength ◽  
High Strength Steel ◽  
Local Stability ◽  
Experimental Studies ◽  
High Strength Steels ◽  
High Strength ◽  
Design Criteria ◽  
Stability Criteria ◽  
Steel Grades ◽  
Concentric Loading

The current local stability criteria (KBC2009, AISC2010) are enacted through theoretical and experimental studies of ordinary steels, but the mechanical properties of high strength steels are different from ordinary steels. The high strength steel in the applicability of design criteria should be needed to review because of increasing market demanding for high strength steel in the high-rise and long span buildings. In this study, stub columns of H-shaped and box section with various steel grades subjected to concentric loading were investigated, and these steels were checked to the applicability of current local stability criteria. The difference between the ordinary steel and high strength steel was compared. As a result of comparison with various steel grades, most specimens were satisfied with the design criteria, but some specimens with lower tensile strength were not reached the required strength. It is considered that the uncertainty of material was the higher when the tensile strength of material was the lower.

Incremental Bending of Ultra-High-Strength Steels

2011 ◽  
Vol 473 ◽  
pp. 53-60 ◽  
Author(s):  
Antti Määttä ◽  
Kari Mäntyjärvi ◽  
Jussi A. Karjalainen
Keyword(s):  
Automotive Industry ◽  
Rolling Direction ◽  
High Strength Steels ◽  
High Strength ◽  
Roll Forming ◽  
Complex Phase ◽  
Bending Angle ◽  
Bending Radius ◽  
Ultra High Strength Steels ◽  
Traditional Manner

Utilisation of ultra-high-strength steels (UHS) has increased, particularly in the automotive industry. By using these materials vehicle structures can be lightened. However, one of the problems of UHS is weak formability. Materials fracture easily with small bending radii and the minimum bending radii are rather large. In this study, the tested materials were complex phase (CP) bainitic-martensitic UHS steels (YS/TS 960/1000 and 1100/1250). The steels were incrementally bent with a press brake in the rolling direction and perpendicular to it, and the final bending angle was 90 degrees. The incremental bending angles were 150°, 130°, 110° and 90°. The punch was unloaded after every incremental bending step. The test materials were bent with different bending radii. The aim was to find the minimum bending radius which produces an acceptable bend. Every incremental bend was compared with a bending performed in the traditional manner. The aim of this study was to examine how well the results of incremental bending compare to roll forming. In addition, clarification studies of when the bend started to fracture were made. It is well known that steels are more efficiently bent by roll forming compared with traditional bending. The results presented in this study demonstrate that incremental bending does not produce better results than traditional bending. Nevertheless, it has been shown that the examined steels can be bent incrementally against manufacturer’s recommendations.

Fatigue Assessment of Tubular Automotive Components in Presence of Inhomogeneities

2004 ◽  
Author(s):  
Stefano Beretta ◽  
Herna´n Juan Desimone ◽  
Andrea Poli
Keyword(s):  
Fatigue Limit ◽  
Detrimental Effect ◽  
Fatigue Behavior ◽  
High Strength Steels ◽  
High Strength ◽  
Probability Of Failure ◽  
Integral Approach ◽  
Material Strength ◽  
Automotive Components ◽  
Tubular Components

Tubular automotive components, e.g. stabilizers and half shafts, are components subjected to fatigue. In order to assess fatigue behavior of such components, it is important to know both the real load conditions as well as the material strength against multi-axial fatigue. For the second point, a detrimental effect in the fatigue limit of high strength steels is given by the defects present in the component, coming from the material (such as microinclusions, microvoids, etc) or for the process (e.g. handling marks). An integral approach in order to assess fatigue limit of tubular components is proposed. The attention is focused onto planar inhomogeneities, which are the most common in tubular products, though the methodology can be extended to different defect-shapes. The method is applied together with a probabilistic model, in order to analyze the probability of failure. In particular, two different processes (in terms of inhomogeneities present in the final component) are compared, and the results allow to evaluate, for example, the admissible load for the desired (or design) level of failure probability for the component.

Optimisation of V/N Ratios and Stelmor Cooling for Electric Arc Furnace Steels Used in Galvanised High Tensile Strength Wire Applications

2005 ◽  
Vol 500-501 ◽  
pp. 745-752
Author(s):  
Andrew Wallace ◽  
Allan Brownrigg ◽  
Peter D. Hodgson ◽  
Leo Frawley ◽  
Warwick Heath
Keyword(s):  
Tensile Strength ◽  
High Strength Steels ◽  
High Strength ◽  
Electric Arc Furnace ◽  
Electric Arc ◽  
Vanadium Nitride ◽  
Arc Furnace ◽  
High Tensile Strength ◽  
Major Factors ◽  
High Level

The high level of residual nitrogen in Electric Arc Furnace (EAF) steels is one of the major factors influencing the performance of the finished product. For high tensile strength galvanised wire applications, nitrogen in interstitial solid solution can severely limit drawability and formability. This problem can be controlled simply and effectively by adding nitride-forming elements to the molten steel so that the nitrogen is removed from solution. Vanadium additions are especially beneficial in high strength steels because the removal of nitrogen as vanadium-nitride can cause extensive precipitation strengthening. This investigation concerns commercial grade steels microalloyed with vanadium and rolled to 5.5mm rod, under controlled Stelmor cooling conditions. This rod is used to produce 2.5mm high tensile strength galvanised wire. The aim of the research was to determine the optimum vanadium/nitrogen (V/N) ratio and Stelmor cooling profile for the vanadium steel rod. This was achieved by extensive production and laboratory trials followed by mechanical and microstructural analyses of the product.

scholarly journals STUDYING THE IMPROVEMENT OF TENSILE STRENGTH OF LOW ALLOY HIGH STRENGTH STEEL WELDS USING AN ECONOMICAL TECHNIQUE

2018 ◽  
Vol 18 (3) ◽  
pp. 498-505
Author(s):  
Abdul Sameea J Jilabi
Keyword(s):  
Tensile Strength ◽  
Weld Joint ◽  
Copper Wire ◽  
High Strength Steels ◽  
High Strength ◽  
Low Alloy Steels ◽  
Joint Efficiency ◽  
Comparison Results ◽  
Alloy Steels ◽  
Welding Processes

Low alloy steels are particularly used in manufacturing several parts in the heavyengineering industries, agricultural equipment and dies which may be subject to servicefailure, and thus may need to be repaired by one of the welding processes. The weldabilityof steels is determined by their sensitivity to cracks that can be prevented by the use ofspecial welding procedures which are often expensive and difficult to use. Manual metal arcwelding of low alloy high strength steels was done firstly, using a cheap electrode (OK46.00), followed by the use of an economical technique which depends on coiling copperwires with different diameters around the cheap electrode. The expensive electrode (OK73.68) was also used for comparison. Results showed an increase in the tensile strength (712MPa) and weld joint efficiency (83.8%) when the expensive iron powder low hydrogencovering electrode (OK 73.68) was used. On the other hand, the tensile strength wasdecreased to (206 MPa) and the weld joint efficiency to (24.2%) when the cheap electrode(OK 46.00) was used. Coiling a (0.6 mm) dia. copper wire around the (OK 46.00) electrodeincreased the tensile strength and weld joint efficiency to (510 MPa) and (60%) respectively.

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