Wyniki wyszukiwania - BazTech

1

Processing routes, resulting microstructures, and strain rate dependent deformation behaviour of advanced high strength steels for automotive applications

Nanda Tarun, Singh Vishal, Singh Gurpreet, Singh Manpreet, Kumar B. Ravi

Archives of Civil and Mechanical Engineering

|

2021

|

Vol. 21, no. 1

112--135

EN

Automobile industry is continuously striving to obtain light body-in-white structures to meet tightened regulations on flue-gas emissions/crash-testing parameters. ‘Advanced high strength steels (AHSS)’ find increased applications in the automotive industry because of improved crashworthiness/formability at reasonably low costs. AHSS category mainly includes transformation induced plasticity (TRIP) steels, twinning induced plasticity (TWIP) steels, dual phase (DP) steels, complex-phase (CP) steels, and quenching-partitioning (Q&P) steels. AHSSs provide superior strength-ductility combination than conventional high-strength steels by virtue of their multi-phase microstructures. Mechanical properties of AHSSs are greatly influenced by processing routes/derived microstructures. Furthermore, mechanical properties/tensile deformation behavior are also strain rate dependent. During an automobile crash, deformation occurs at strain rates which are exceedingly higher than quasi-static conditions. So, investigation of AHSS properties under both quasi-static as well as high strain rates conditions is important to check applicability for superior crash-resistance. The present work critically reviews details of processing routes, room temperature microstructures, mechanical properties, and finally strain rate dependence of tensile deformation behaviour of AHSSs. Finally, main gaps in existing literature/scope for future research with regards to high strain rate deformation dependent properties of this steel category are presented.

2

Welding of mobile elevating work platforms

Silva Abilio, Szczucka-Lasota Bożena, Węgrzyn Tomasz, Jurek Adam

Welding Technology Review

|

2019

|

R. 91, nr 6

15--20

EN

The demand for new welding technologies in civil engineering and transport is increasing. An example of this is the tendency to increase the operating range of a mobile platform mounted on motor vehicles while maintaining the weight of the vehicle. The most commonly used material in the production of mobile platforms are AHSS steels due to their high tensile strength at the level of 1400 MPa. However, the joints created with their use are characterized by much lower strength than the native material. In this article, the most appropriate parameters for welding elements of a mobile platform from difficult-to-use steel AHSS were selected.

PL

Wzrasta zapotrzebowanie na powstawanie nowych technologii spawalniczych w inżynierii lądowej i w transporcie. Przykładem tego może być tendencja zwiększenia zasięgu operacyjnego podestu ruchomego montowanych w pojazdach samochodowych przy jednoczesnym zachowaniu masy pojazdu. Ostatnio stosowanym materiałem w produkcji podestów ruchomych są stale AHSS z uwagi na ich dużą wytrzymałość na rozciąganie na poziomie 1400 MPa. Powstałe przy ich wykorzystaniu złącza cechują się jednak dużo niższą wytrzymałością od materiału rodzimego. W niniejszym artykule opisano proces doboru parametrów do spawania elementów podestu ruchomego z trudnospawalnej stali AHSS w celu osiągnięcia połączeń spawanych o wytrzymałości na poziomie 700 MPa lub wyższej.

3

The effect of selected spot resistance welding parameters on properties of martensite-structured AHSS

Górka Jacek, Ozgowicz Andrzej, Matusek Kamil

Biuletyn Instytutu Spawalnictwa w Gliwicach

|

2019

|

Vol. 63, No. 5

15--21

EN

The paper presents the effect of welding current and clamping force on the properties of spot resistance-welded joints made of 1.8 mm thick steel DOCOL 1200M. Because of the fact that martensite-structured steel DOCOL 1200M is hardened when exposed to deforming force, it is used to make energy absorbers or car header panels. Test joints, made using a robotic welding station, were subjected to macro and microscopic metallographic tests, hardness measurements and strength tests. The obtained test joints were subjected to strength verification performed in accordance with PN-EN ISO 14273:2016. The tests demonstrated that excessively high clamping force combined with relatively low welding current do not guarantee the obtainment of a joint characterised.

PL

Przedstawiono wpływ natężenia prądu zgrzewania oraz siły docisku na własności złączy zgrzewanych oporowo punktowo stali DOCOL 1200M o grubości 1,8 mm. Stal DOCOL 1200M o strukturze martenzytycznej umacnia się pod wpływem działania siły odkształcającej i w związku z tym jest ona stosowana na absorbery energii lub pasy przednie samochodów osobowych. Złącza próbne, wykonane na stanowisku zrobotyzowanym, zostały poddane badaniom metalograficznym makro i mikroskopowym, pomiarowi twardości oraz badaniom wytrzymałościowym. Złącza poddano weryfikacji wytrzymałościowej zgodnie z PN-EN ISO 14273:2016. Wykazano, że zbyt duża siła docisku przy stosunkowo niskim prądzie zgrzewania nie gwarantuje uzyskania połączenia o wymaganej wytrzymałości. Natomiast zwiększenie natężenia prądu przy obniżeniu siły docisku zwiększa wytrzymałość połączenia zgrzewanego. Zastosowanie odpowiednich parametrów cyklu zgrzewania punktowego oporowego pozwala na uzyskanie złączy stali DOCOL 1200M o zadowalającym poziomie wytrzymałościowym.

4

Verification of Properties of Joints Made of Advances High Strength Steels in the Conditions of the Complex Thermal Cycles of the HPAW Process

Nowacki J., Sajek A.

Biuletyn Instytutu Spawalnictwa w Gliwicach

|

2018

|

Vol. 62, No. 5

167--173

EN

The article discusses the primary issue related to the verification of properties of joints made in AHSS in relation to conventional structural steels and based on the identification of cooling time t8/5. The solution suggested in the study involving the application of the Finite Element Method is based on two computational models. In addition the article presents a material model allowing for properties of single metallic phases and their interaction during the welding cycle. The study also describes the numerical model of the HPAW (plasma + MAG) heat source composed of two models predefined in the Simufact.Welding software programme corresponding to the nature of constituent processes. The research-related tests also involved welding simulations and experimental verification. The tests demonstrated the conformity of simulation results and the high usability of simulation when verifying properties of joints.

PL

Scharakteryzowano podstawowy problem kontroli właściwości złączy wykonanych ze stali AHSS w odniesieniu do konwencjonalnych stali konstrukcyjnych, bazujący na wyznaczaniu czasu stygnięcia t8/5. Zaproponowane rozwiązanie w postaci zastosowania metody elementów skończonych bazuje na dwóch modelach obliczeniowych. Przedstawiono model materiałowy, który uwzględnia właściwości pojedynczych faz metalicznych oraz ich interakcje w trakcie cyklu spawania. Jako drugi, opisano numeryczny model hybrydowego źródła ciepła HPAW (plazma + MAG) składający się z dwóch predefiniowanych w oprogramowaniu Simufact.Welding modeli, adekwatnych do charakterów procesów składowych. Przeprowadzono symulację spawania oraz eksperyment weryfikujący. Wykazano zgodność wyników symulacji i jej wysoką przydatność w zakresie kontroli właściwości analizowanych złączy.

5

Comparative evaluation of various experimental and numerical simulation methods for determination of t8/5 cooling times in HPAW process weldments

Sajek A., Nowacki J.

Archives of Civil and Mechanical Engineering

|

2018

|

Vol. 18, no. 2

583--591

EN

The aim of this article is to provide a quantitative comparison and efficiency verification of the methods of estimating t8/5 cooling time in the process of HPAW of S960QL steel. The measurements of t8/5 welding time were conducted at the face of weld with the use of thermoelectric, pyrometric and thermovision methods. A FEM model of the joint was made, and welding simulation was done. The results of the calculations were then confronted with experimental data, and measuring methods were evaluated. Differences in the results of t8/5 time measurements were determined for the analysed methods and arranged according to the precision of results presented; the applicability of FEM for predicting the value of t8/5 time was investigated. The usability of temperature measuring methods for determining cooling time was determined, the weaknesses of non-contact measurement in terms of diversification of cooling time in a section of a welded joint were shown, and the advantages of numerical method were demonstrated. It was established that joining experimental methods for measuring cooling time of a joint with FEM analysis allows to obtain a desired resolution of prediction. In this way, the technology for hybrid welding of advanced high-strength steels can be designed more efficiently.

6

Some aspects of the determination of retained austenite using the Rietveld refinement

Morawiec M.

Journal of Achievements in Materials and Manufacturing Engineering

|

2017

|

Vol. 80, nr 1

11--17

EN

Purpose: The aim of the paper is to show the advantage of the application of the Rietveld refinement for determination of retained austenite amount in multiphase microstructure steels. Design/methodology/approach: The steels used for the investigation were thermomechanically rolled and controlled cooled to room temperature. The investigation of the microstructure was carried out using light microscopy. X-ray diffraction investigations of analyzed steel were a major part of the research. The phase identification and quantitative analysis of retained austenite were done using the HighScore Plus software that includes the Rietveld refinement method. The Rietveld analysis takes into account the preferred orientation that occurs during thermo-mechanical processing of steel. Findings: It was found that after the thermo-mechanical processing the microstructure of steel is composed of fine-grained bainitic matrix which includes bainite-austenite constituents, martensite blocks and some fraction of retained austenite. The X-ray diffraction showed that this steel includes phases of Feα (bainite and martensite) and Feγ (retained austenite). The Rietveld analysis showed that the volume fraction of retained austenite is 14.1%. Research limitations/implications: To confirm that Rietveld refinement method is a good tool for the quantitative analysis of retained austenite volume fraction EBSD measurements should be done for comparison purposes. Practical implications: The obtained results can be used for determination of retained austenite fraction in AHSS steels. It is important because the retained austenite content and its mechanical stability decide about a formability level of these steel grades. Originality/value: Some methodological aspects are concerned affecting the final quantitative results of retained austenite volume fraction is AHSS.

7

Modelowanie procesu tłoczenia części nadwozia samochodu ze stali superwysoko wytrzymałej

Wyrobek K.

Inżynieria Maszyn

|

2017

|

R. 22, z. 1

76--84

PL

W artykule przedstawiono model procesu tłoczenia przykładowej części nadwozia samochodu z superwysoko wytrzymałej blachy stalowej typu AHSS (Advanced High-Strength Steels). W tym celu zostały przeprowadzono badania materiałowe stali DP600, na podstawie których wykonano symulacje procesu tłoczenia. Opracowany proces może stanowić ekonomicznie uzasadnioną alternatywę dla kosztownych procesów obróbki plastycznej na gorąco czy hydroformowania.

EN

The article presents process of sample car body part made from advanced high strength steel sheet (AHSS). For this purpose conducted research tensile strength of DP600 steel and based on them simulations of forming process. Developed process may constitute an economically viable alternative to the costly hot forming and hydroforming processes.

8

Microstructural Aspects of Bifocal Laser Welding of TRIP Steels

Grajcar A., Grzegorczyk B., Różański M., Stano S., Morawiec M.

Archives of Metallurgy and Materials

|

2017

|

Vol. 62, iss. 2A

611--618

EN

This work is concerned with comparative tests involving single-spot and twin-spot laser welding of thermomechanically rolled TRIP steel. The welding tests were carried out using keyhole welding and a solid state laser. In the case of twin-spot laser beam welding, the power distribution of beams was 50%:50%. The changes in macro- and microstructures were investigated using light and scanning electron microscopy. Three main zones subjected to the tests included the fusion zone, the heat affected zone and the intercritical heat affected zone (transition zone between the base material and the HAZ). Special attention was paid to the effect of various thermal cycles on the microstructure of each zone and on martensite morphology. The tests involved hardness measurements carried out in order to investigate the effect of different microstructures on mechanical properties of welds.

9

Analysis of chattering phenomenon in industrial S6-high rolling mill. Part 2: Experimental study

Papini S., Valigi M. C.

Diagnostyka

|

2016

|

Vol. 17, No. 4

27--32

EN

The paper represents an extension of a previous work where the problem of chatter in a rolling mill producing advanced high-strength steels (AHSS) was investigated by a combination of a linear lumped parameter model and the slab analysis. In this paper the authors show the detailed experimental study of the problem with a complete description of all the phases related to the vibrational investigation that lead to the solution of the problem. Furthermore, a different model based on the Orowan’s method together with a nonlinear model of the rolling mill is presented and simulations are performed.

10

Wpływ energii liniowej spawania wiązką laserową na mikrostrukturę i wybrane właściwości połączeń ze stali AHSS na przykładzie CPW 800

Różański M., Grajcar A., Stano S

Przegląd Spawalnictwa

|

2015

|

R. 87, nr 2

23--29

PL

Praca dotyczy problematyki spawania laserowego stali typu CPW 800 z mikrododatkami Ti i Nb. Próby spawania laserowego blach walcowanych termomechanicznie prowadzono techniką głębokiego przetopienia z wykorzystaniem lasera na ciele stałym. Przeprowadzono próby przy różnej energii liniowej procesu, a następnie wykonano badania metalograficzne makroskopowe i mikroskopowe oraz oceniono twardość materiału rodzimego, strefy wpływu ciepła i spoiny. Określono wpływ energii liniowej spawania na szerokość spoiny. Twardość spoiny wynosi około 400 HV1 niezależnie od energii liniowej spawania, a dominującym składnikiem strukturalnym złącza jest martenzyt niskowęglowy. Przedstawiono wyniki badania wytrzymałości na rozciąganie połączeń spawanych.

EN

This study discusses issues related to laser welding of the CPW 800 steel with Ti and Nb microadditions. The tests of laser welding of thermomechanically rolled sheet sampies were carried out using keyhole welding and a solid-state laser. The test s performed for the various values of linear energy were folIowed by macro- and microscopic metallographic investigations as well as by the hardness measurements of base metal, heat-affected zone and fusion weld. The effect of welding linear energy on a weld width has been determined. The weld hardness is approximately 400 HV1 independent on the welding linear energy applied. Low-carbon martensite is a dominant microstructural constituent of the joint. Results of tensile strength test of welded joint were presented.

11

Numeryczna symulacja testu zderzeniowego z uwzględnieniem umocnienia odkształceniowego w procesie wytwarzania energochłonnego elementu samochodu

Ambroziński M., Polak S., Gronostajski Z., Kuziak R., Chorzępa W., Pietrzyk M.

Mechanik

|

2015

|

R. 88, nr 2

92--97

PL

Przedmiotem artykułu jest ocena możliwości numerycznej symulacji zachowania się elementów nadwozia samochodu w czasie kolizji. Opisano problematykę związaną z wytwarzaniem elementów pochłaniających energię oraz doborem materiału na te elementy. Do analizy wybrano stal z mikrododatkami, stal dwufazową i stal z efektem umocnienia (TRIP). Przeprowadzono symulacje wytwarzania oraz eksploatacji, tj. test zderzeniowy (crash test), elementu karoserii samochodowej wykonanego z tych stali. W teście zderzeniowym przyjęto dwa modele materiału. W pierwszym pominięto odkształcenia materiału podczas wytwarzania elementu, natomiast w drugim uwzględniono lokalną niejednorodność odkształceń powstałych w trakcie tłoczenia. Wyniki obliczeń porównano z fizycznymi symulacjami testu zderzeniowego. Wykazano, że drugie podejście daje znacznie lepsze oszacowanie właściwości produktu dla stali z mikrododatkami i stali dwufazowej. Takiej poprawy dokładności nie uzyskano dla stali z efektem TRIP.

EN

Paper deals with an evaluation of possibilities of numerical simulations of car body parts during collision. Problem of manufacturing of the crash box and selection of materials for this part was described. Microalloyed steel, Dual Phase (DP) steel and TRIP (Transformation Induced Plasticity) steel were selected for the analysis. Numerical simulations of manufacturing of crash box and crash tests were performed for element made of the three selected steels. Two variants of material model were used in the simulations of the crash test. In the first variant earlier deformation of the material during manufacturing was neglected. In the second variant strains calculated in simulations of the stamping process were transferred to the crash box. Results of calculations were compared with physical simulations of the crash test. It was shown that the second variant gives improvement of the results for microalloyed and DP steels. This improvement was not observed for the TRIP steel.

12

Robust Multiscale Modelling of Two-Phase Steels on Heterogeneous Hardware Infrastructures by Using Statistically Similar Representative Volume Element

Rauch Ł., Bzowski K., Bachniak D., Pietrzyk M.

Archives of Metallurgy and Materials

|

2015

|

Vol. 60, iss. 3A

1973--1979

EN

The coupled finite element multiscale simulations (FE2) require costly numerical procedures in both macro and micro scales. Attempts to improve numerical efficiency are focused mainly on two areas of development, i.e. parallelization/distribution of numerical procedures and simplification of virtual material representation. One of the representatives of both mentioned areas is the idea of Statistically Similar Representative Volume Element (SSRVE). It aims at the reduction of the number of finite elements in micro scale as well as at parallelization of the calculations in micro scale which can be performed without barriers. The simplification of computational domain is realized by transformation of sophisticated images of material microstructure into artificially created simple objects being characterized by similar features as their original equivalents. In existing solutions for two-phase steels SSRVE is created on the basis of the analysis of shape coefficients of hard phase in real microstructure and searching for a representative simple structure with similar shape coefficients. Optimization techniques were used to solve this task. In the present paper local strains and stresses are added to the cost function in optimization. Various forms of the objective function composed of different elements were investigated and used in the optimization procedure for the creation of the final SSRVE. The results are compared as far as the efficiency of the procedure and uniqueness of the solution are considered. The best objective function composed of shape coefficients, as well as of strains and stresses, was proposed. Examples of SSRVEs determined for the investigated two-phase steel using that objective function are demonstrated in the paper. Each step of SSRVE creation is investigated from computational efficiency point of view. The proposition of implementation of the whole computational procedure on modern High Performance Computing (HPC) infrastructures is described. It includes software architecture of the solution as well as presentation of the middleware applied for data farming purposes.

PL

Symulacje wieloskalowe z wykorzystaniem sprzężonej metody elementów skończonych wymagają kosztownych numerycznie procedur zarówno w skali makro jak i mikro. Próby poprawy efektywności numerycznej skupione są przede wszystkim na dwóch obszarach rozwoju tj. zrównoleglenie/rozproszenie procedur numerycznych oraz uproszczenie wirtualnej reprezentacji materiału. Jedną z metod reprezentującą obydwa obszary jest podejście Statystycznie Podobnego Reprezentatywnego Elementu Objętościowego. Głównym celem tej metody jest redukcja ilości elementów dyskretyzujących przestrzeń obliczeniową, ale również możliwość zrównoleglenia obliczeń w skali mikro, które mogą być realizowane niezależnie od siebie. Uproszczenie domeny obliczeniowej poprzez tworzenie elementu SSRVE realizowane jest za pomocą metod optymalizacji umożliwiających tworzenie elementu najbardziej podobnego do rzeczywistego materiału na podstawie wybranych cech charakterystycznych. W rozwiązaniu dla stali dwufazowych cechy opisujące podobieństwo są tworzone na podstawie analizy współczynników kształtu ziaren martenzytu na zdjęciu rzeczywistej mikrostruktury. Natomiast podejście przedstawione w niniejszym artykule zostało rozbudowane dodatkowo o lokalne wartości naprężeń i odkształceń tak, aby w pełni odzwierciedlić podobieństwo zarówno wizualne jak i behawioralne. Różne formy funkcji celu zostały poddane analizie w procesie optymalizacji, a uzyskane wyniki zostały porównane pod względem jakości, a także efektywności i unikalności rozwiązania. Ostatecznie zaproponowana została najlepsza funkcja celu obejmująca współczynniki kształtu oraz wartości naprężeń i odkształceń. Przykłady SSRVE wyznaczone dla analizowanych stali dwufazowych zostały przedstawione w artykule. Natomiast każdy krok procedury tworzenia elementu SSRVE został poddany analizie wydajności obliczeniowe, na podstawie której zaproponowane zostało podejście wykorzystujące nowoczesne architektury sprzętowe wysokiej wydajności. Opis podejścia zawiera zarówno architekturę rozwiązania jak i prezentację oprogramowania warstwy pośredniczącej.

13

Joining of Advanced High Strength Steels

Ivarson A.

Biuletyn Instytutu Spawalnictwa w Gliwicach

|

2014

|

Vol. 58, No. 5

58--61

EN

This paper describes joining of Advanced High Strength Steels (AHSS). Over the past 2 to 3 decades the usage of AHSS has increased constantly, and will continue. In order to succeed with the overall design it is of importance to know how to design AHSS from e.g. fatigue, bending and welding point of view. As presented in this paper, AHSS has to be treated differently than mild steel regarding welding.

PL

Przedstawiono zagadnienia związane ze spawaniem stali wysokowytrzymałych AHSS (Advanced High Strength Steel). Przedstawiono zasady doboru materiału dodatkowego do spawania, wartości energii liniowej spawania oraz temperatury podgrzewania wstępnego. Przedstawiono warunki technologiczne spawania dla stali Weldox, Hardox i Domex.

14

Optimization of the Q-P Process Parameters for Low Alloyed Steels with 0.2% C

Jirková H., Kučerová L., Aišman D., Mašek B.

Archives of Metallurgy and Materials

|

2014

|

Vol. 59, iss. 3

1205--1210

EN

In steels which are treated by the quenching and partitioning (Q&P) process, carbon content is one of the crucial parameters because carbon contributes greatly to stabilization of retained austenite and strengthens the material. In the present study, the Q&P process was gradually optimised for two low-alloyed steels with 0.2 % carbon content and with and without Cr addition. The results show that the cooling rate, as well as the austenitizing temperature, has a pronounced effect on microstructure evolution. The strength and elongation in the Mn, Si and Cr-alloyed steel was approx. 900 MPa and more than 30 %, respectively.

PL

W stalach poddanych obróbce hartowania i partycjonowania (Quenching and Partitioning – Q&P), zawartość węgla jest jednym z kluczowych parametrów, ponieważ węgiel znacząco wpływa na stabilizacje austenitu szczątkowego i umacnia materiał. W niniejszych badaniach obróbka Q&P była stopniowo optymalizowana dla dwóch niskostopniowych stali o zawartości węgla 0, 2% zawierających dodatek chromu oraz bez tego dodatku. Wyniki pokazują wyraźny wpływ szybkości chłodzeniaoraz temperatury austenityzacji na ewolucje mikrostruktury. Wytrzymałość na rozciąganie oraz wydłużenie do zerwania w manganowo-krzemowo-chromowej stali wyniosły odpowiednio ok.900 MPa oraz ponad 30%.

15

High-strength martensitic steels with low Ms temperature

Bublikova D., Masek B., Jirkova H., Jenicek S., Ibrahim K., Cubrova J.

Archives of Materials Science and Engineering

|

2014

|

Vol. 65, nr 2

53--57

EN

Purpose: Various novel heat treatments and thermomechanical treatment procedures have been developed recently in order to enhance mechanical properties of high-strength steels. Design/methodology/approach: The new heat treatment process was tested on newly designed low alloy AHSS steels alloyed with manganese, silicon, chromium and alternatively molybdenum and nickel. Two different cooling rates of 16°C/s and 1°C/s showed that over a wide interval of cooling rates a hardened structure based on martensite and retained austenite can be achieved with an average hardness from 538 to 716 HV10 and ultimate strength in the range between 1837 and 2354 MPa. Findings: The main aim of these steels was to decrease the temperature Mf to below 100°C by quenching in a water or oil bath and use common industrial techniques. Manganese alloying was used for the required decrease of temperatures Ms and Mf. Silicon and chromium were used to increase the ultimate strength, silicon was used to eliminate the carbide formation and to support sufficient oversaturation of martensite. Practical implications: The industrial application of this process is complicated by the need for quenching in the range between Ms and Mf. The Ms temperature normally lies in the 200-250 °C interval. This is why new steels with low Ms temperature were selected for the experimental programme. Thanks to this feature, the steels could be quenched in water or polymer-based baths. The primary alloying elements of these four selected steels were manganese, silicon, molybdenum and chromium. Originality/value: The experimental heat treatment led to microstructures of martensite with retained austenite in all steels. Their strengths were in the range of 1750-2400 MPa and their A5 mm elongation levels were up to 10%. The morphology and distribution of retained austenite dictate the resulting mechanical properties of the material.

16

Wpływ prędkości stempla na wielkość sprężynowania powrotnego w procesie gięcia blachy wysokowytrzymałej martenzytycznej

Krupa R.

Przegląd Mechaniczny

|

2013

|

nr 11

29--33

PL

Artykuł prezentuje wyniki prac eksperymentalnych, których celem była analiza wpływu prędkości suwaka prasy mechanicznej na wielkość sprężynowania powrotnego blachy w procesie gięcia. Do badań wykorzystano wysokowytrzymałą stal martenzytyczną MS-W 1200 z grupy AHSS (Advanced High Strength Steel). W celach porównawczych przeprowadzono również analizę dla stali mikrostopowej o podwyższonej wytrzymałości HX340LAD. Przedstawione wyniki wskazują na wzrost wielkości (kąta) sprężynowania wraz ze wzrostem prędkości stempla.

EN

This paper presents experimental investigation of the influence of press side velocity on the springback amount in sheet metal bending process conducted by using a mechanical press. Tested part was made of martensitic high strength steel MS-W 1200 which belongs to AHSS (Advanced High Strength Steel). The experimental test was carried out aIso for micro-alloyed high strength steel HX340LAD for comparative purposes. The obtained results show the increase of springback amount (angle) with increasing the punch velocity.

17

Segregation behaviour of third generation advanced high-strength Mn-Al steels

Grajcar A.

Archives of Foundry Engineering

|

2012

|

Vol. 12, iss. 2

123-128

EN

The paper addresses the macro- and microsegregation of alloying elements in the new-developed Mn-Al TRIP steels, which belong to the third generation of advanced high-strength steels (AHSS) used in the automotive industry. The segregation behaviour both in the as-cast state and after hot forging was assessed in the macro scale by OES and by EDS measurements in different structural constituents. The structural investigations were carried out using light and scanning electron microscopy. A special attention was paid to the effect of Nb microaddition on the structure and the segregation of alloying elements. The tendency of Mn and Al to macrosegregation was found. It is difficult to remove in Nb-free steels. Microsegregation of Mn and Al between austenite and ferritic structural constituents can be removed.

18

Third generation of AHSS with increased fraction of retained austenite for the automotive industry

Grajcar A., Kuziak R., Zalecki W.

Archives of Civil and Mechanical Engineering

|

2012

|

Vol. 12, no. 3

334--341

EN

Third generation of advanced high-strength steels for the automotive industry contains a high volume fraction of fine-grained ferrite, carbide-free bainite, martensite and retained austenite. The level of strength and ductility is highly dependent on the fraction and mechanical stability of austenitic phase. One of the methods to obtain an increased fraction of γ phase is trough its chemical stabilization by Mn. Two 0.17C–3Mn–1.5Al–0.2Si–0.2Mo steels with and without Nb microaddition were developed in the present study. The steels were subjected to the thermomechanical processing designed on the basis of the DCCT diagram (deformation – continuous cooling transformation). The paper presents the results of the multi-stage compression tests and multiphase microstructures obtained as a result of the controlled multi-stage cooling. It was found that the hot workability of a new generation of AHSS is very challenging due to high values of flow stresses required. However, the thermomechanical processing enables to obtain very fine-grained bainite-based microstructures with a fraction of retained austenite up to 20%. The highest fraction of fine grains and interlath austenite was obtained for the temperature range between 400 and 450 °C. The effect of Nb results in higher flow stresses and better distribution of all the microstructural constituents.

19

Application of statistically similar representative volume element in numerical simulations of crash box stamping

Ambrozinski M., Bzowski K., Rauch L., Pietrzyk M.

Archives of Civil and Mechanical Engineering

|

2012

|

Vol. 12, no. 2

126--132

EN

The paper presents multiscale simulations of the crash box, which is being widely used in automotive industry, because of its high influence on improvement of passengers safety. The multiscale simulations are presented with application of statistically similar representative volume element (SSRVE), which besides offering the reliability of conventional representative volume element (RVE), gives much shorter computational time. At first, the idea of SSRVE with examples obtained for HCT600 steel, used for crash box production, is presented. Then macroscale model of crash box is described in details, as well as the results obtained for macroscale simulations. Finally, the introduction of SSRVE into the multiscale simulations is shown. The results for the created multiscale approach prove that the proposed solution offers the possibility of better estimation of final product properties on the basis of microstructural information and that it can be efficiently used in industrial conditions.

20

Mikrostruktura i właściwości stali o wysokiej wytrzymałości AHSS

Krajewski S., Nowacki J.

Przegląd Spawalnictwa

|

2011

|

R. 83, nr 7

22-27

PL

Przedstawiono nowe stale o wysokiej wytrzymałości AHSS na podstawie analizy danych żródłowych. Zaprezentowano składy chemiczne i właściwości mechaniczne wybranych gatunków tych stali. Stale o wysokiej wytrzymałości coraz częściej używane są w przemyśle motoryzacyjnym oraz w budowie ciężkich maszyn. Właściwości mechaniczne i ciągliwość tych stali pozwalają na projektowanie lżejszych i bardziej wytrzymałych konstrukcji o dotąd nieosiągalnych możliwościach. Spawalność stali AHSS jest dobra. Dzięki prostemu składowi chemicznemu i małej liczbie dodatków stopowych możliwość doboru metody i parametrów spawania jest szeroka i dotyczy zarówno zgrzewania, jak i spawania metodami MMA, GTA i GMA.

EN

The characteristic of this novel group of steels is done on literature source bases. Chemical composition and mechanical properties of representatives of different groups of these steels is presented. Advanced High-Strength Steels are increasingly used in the automotive industry and in the construction of heavy machines. The mechanical properties and toughness of these steel permit to design lighter and high strength structures with previously unattainable possibilities. Weldability of these steels is defined as a good. Due to a plain chemical composition and small amount of alloying elements, possibility of welding method and parameters selection is large and allow use well known resistance spot welding as well as MMA, GTA and GMA methods.