Ultrafine grained dp ufgdp steel with an average grain size of about 2. Ultrafine grained steel wire and its formability scientific. Although ufg stainless steels exhibit excellent yield and tensile strength, they sometimes show poor ductility in comparison with coarse grained counterparts 6. Pdf managing both strength and ductility in ultrafine. Ultrafine grained ufg steels with grain sizes around 1 micron can be produced by. Issue 1 structural ultrafine grained steels obtained by advanced controlled rollin 63 g name s315 s355 s420 s460 s500 s550 s600 s650 s700 table 1 chemical composition of thermomechanically rolled steels material number 1. Enhanced workhardening behavior and mechanical properties. Us3178324a method of producing ultrafine grained steel. The book covers latest results on ultrafine grained titanium, aluminum and copper alloys and on ufg iron and steels and thus provides a deep insight to current research activities in the field of ultrafine grained metals.
As another route the static recrystallisation of severely coldrolled martensite srm was utilized. The unique feature of grain refinement is that it is the only strengthening mechanism which also increases toughness. For example, steel industries use enormous facilities, so that it is quite difficult to. Dynamic transformation mechanism for producing ultrafine. Nanoscale spheroidized cementite induced ultrahigh strengthductility combination in innovatively processed ultrafinegrained low alloy mediumcarbon steel n.
A laboratory processing route was designed that involves coldrolling of a tempered martensite structure followed by a second tempering step to produce a fine grained aggregate of ferrite and. A cciaio fabrication and tensile properties of ultrafine. Yag laser welding under different welding conditions. Effect of rolling reduction on ultrafine grained structure. The aim of these efforts is to increase strength and toughness of the steel product without the usage of costly alloying elements. The microhardness profile for the ultrafinegrained steels did not follow a pattern similar to the asreceived material. In the present study, an ultrafine grained ufg 304l stainless steel with the average grain size of 300 nm was produced by a combination of cold rolling and annealing. Dec 14, 2016 combination of dynamic transformation and dynamic recrystallization for realizing ultrafine grained steels with superior mechanical properties.
Ultrafine grained dualphase steels journal of ultrafine. The purpose here is to explain these contradictory observations and in the process, propose a theory for the strain to fracture for the novel bainitic steels. Mechanical properties of the ultrafine grained ufg steels having mean. E t s i m o ovied, o university, oviedo 33004, spain. Download analysis of fracture toughness mechanism in ultra. Here, the formation of ultrafine ferrite uff involves the dynamic transformation of a significant volume fraction of. However, this treatment enhances the multipotent mesenchymal stromalstem cell proliferation by 26% for 316l steel and by 17% for crniti. Because the annealing temperatures are relatively low and the recrystallized structure is twophase, grain growth is restricted. Based on systematic description of research achievements of the project of ultrafine grain steels and their engineering. Alloy design is one of the first considered issues, while designing new steel with targeted mechanical properties.
Thermal stability of the ultrafine grained structures, especially those from the dsit route, was found to be excellent. However, ferritic ufg steels have limited work hardening. Apr 19, 2015 download analysis of fracture toughness mechanism in ultrafinegrained steels ebook epub pdf fb2. Ultrafine grained ufg steels with grain sizes around 1 micron exhibit an excellent strength. Kim three types of ultrafine grained ufg low carbon steel were fabricated by equal channel angular pressing, and their microstructure and tensile properties were. Ultrafinegrained microstructures can be developed in a variety of alloy steels by coldworking followed by annealing in the. Ultrafine grained materials ii proceedings of a symposium sponsored by the shaping and forming committee of the materials processing and manufacturing division mpmd and the mechanical behavior committee jt. The formation of ultrafine grained steels is an area of intense research around the world. In contrast, ductile bainitic steels have been produced in which the controlling scale of the ferrite crystals is 2040 nm 4. We study orientation gradients and geometrically necessary dislocations gnds in two ultrafine grained dualphase steels with different martensite particle size and volume fraction 24 vol. Schoo of engineering l, panamerican university, mexico city 03920, mexico. Recent trends in producing ultrafine grained steels journal. In this study, the effect of the rolling reduction ranging from 25 to 70% equivalent strains of 0. Ultrafine grained dual phase steels fabricated by equal.
Zhang guifeng,miao huixia,zhang jianxun,pei yi institute of welding research,xian jiaotong university,xian 710049,china. Us3178324a us285121a us28512163a us3178324a us 3178324 a us3178324 a us 3178324a us 285121 a us285121 a us 285121a us 28512163 a us28512163 a us 28512163a us 3178324 a us3178324 a us 3178324a authority us united states prior art keywords steel heating austenite grain grain size prior art date 19630603 legal status the legal status is an assumption and is not a legal. Ultrafinegrained dp ufgdp steel with an average ferrite grain size of about 2. Ultrafine grained structure formation in steels using dynamic. By severe plastic deformation submicrongrained microstructure less than 1. Over the past decade a substantial body of work has been devoted to developing ultrafine grained ufg lowcarbon steels with grain sizes of the order of 1. The steel with higher martensite fraction has a lower elastic limit, a higher yield strength and a higher tensile strength. Effect of thermomechanical treatment on the microstructures and mechanical properties of an ultrafine grained steel using bainite starting microstructure. The ufg steels performed very high strength that reached to 24 times of the starting materials having conventionally coarsegrained structures. Recent trends in producing ultrafine grained steels. Nganb adepartment of materials engineering, isfahan university of technology, 8415683111, isfahan, iran bdepartment of mechanical engineering, the university of hong kong, pokfulam road, hong kong. This paper provides an overview on obtaining lowcarbon ultrafine grained dualphase steels through rapid intercritical annealing of coldrolled sheet as improved materials for automotive applications.
Ufg structures of initial grain size of 144 nm exhibited the typical threestage softening comprising recovery, recrystallization, and grain growth. The tensile strength of these ultrafine grained dualphase steels can be increased by up to 200 mpa as compared to coarsegrained dualphase steels while maintaining uniform elongation values. Ultrafine grained steels with grain sizes below about 1 um offer the prospect of high strength and high toughness with traditional steel compositions. Kim three types of ultrafine grained ufg low carbon steel were fabricated by equal channel angular pressing, and their microstructure and tensile properties were examined. Effect of ferrite grain size on dynamic tensile properties of. The regularities of the influence of hardness, strength and ductility of steels with ultrafine grained ufg structure on the rate and peculiarities of corrosion in the hydrogen sulfidecontaining medium in comparison with steels with the coarse grained cg structure were investigated. Toughness of ultrafine grained ferritic steels fabricated by.
Ultrafine grained ufg ferritemartensite dual phase steels were fabricated by equal channel angular pressing and subsequent intercritical annealing. Corrosion resistance of steels with ultrafine grained. Zhang guifeng zhang jianxun welding research institute,xian jiaotong university,xian 710049. Friction welding of ultrafine grained 316l steel welding. Ultrafine grained steels fabricated by novel processes. The steel with higher martensite fraction has a lower elastic limit, a. Based on systematic description of research achievements of the project of ultrafine grain steels and their engineering applications, new theories of microstructural refinement and the newly developed technologies in production of high strength and high toughness steels are introduced. The role of martensitic transformation on bimodal grain. Rapid austenitizing refines the austenite grain size if the initial microstructure is a fine aggregate, such as martensite or tempered martensite. Ultrafine grained steels with grain sizes below about 1. The role of martensitic transformation on bimodal grain structure in ultrafine grained aisi 304l stainless steel s. Mechanical properties of the ultrafine grained ufg steels having mean grain sizes much smaller than 1. Fabrication and tensile properties of ultrafine grained steels d. Numerical investigations on residual stress in laser.
Enhanced workhardening behavior and mechanical properties in ultrafinegrained steels. Ultrafine grained structure formation in steels using. Tensile testing revealed superior mechanical properties the ultimate tensile strength of 1267 mpa and uniform elongation of 8. Toughness of ultrafine grained ferritic steels fabricated.
Structural ultrafine grained steels b obtainey d advanced controlled rolling r gonzalez1, j garcia o 2, m barbes a 2, m quintana j 1, l verdeja f 2, j verdeja i 2 1. Enhanced workhardening behavior and mechanical properties in ultrafinegrained steels with largefractioned metastable austenite. In general, the term ultrafine grain is used for average grain sizes between 1. X80 pipeline steel produced by tmcp has high strength and high toughness with ultrafine grain microstructure. The key of the process is to start from martensite structure. The ufg steels performed very high strength that reached to 24 times of the starting materials having. Similarities and differences in prepared technologies and. Processing and stability of ultrafine grained structures. Low carbon ultrafine grained dual phase steels ubc. The effects of carbon content, alloying additions, initial starting structures and processing parameters like heating and cooling rate on the mechanical properties have. Ultrafine grained steels managing both high strength and. Nanoscale spheroidized cementite induced ultrahigh.
Ultrafinegrained microstructures and mechanical properties of alloy. Their room temperature tensile properties were examined and compared to those of coarse grained counterpart. Combination of dynamic transformation and dynamic recrystallization for realizing ultrafinegrained steels with superior mechanical properties. Formation mechanism of ultrafine grained microstructures. Strengthening mechanisms of ultrafine grained dual phase. Dobatkin et al ultrafine grained low carbon steels by severe plastic deformation tem contrast at the grain boundaries. These materials are currently the subject of extensive research efforts worldwide.
Enhanced workhardening behavior and mechanical properties in. Structural ultrafine grained steels obtained by advanced. A plain if steel and a padded if steel having various ultrafine grain sizes from 0. Grain refinement is an effective method to improve strength and toughness simultaneously without addition of alloying elements. The biocompatibility of samples with the ultrafine grain structure obtained in the ecap process did not deteriorate in comparison with an austenitic 316l stainless steel in coarse. Effect of rolling reduction on ultrafine grained structure and mechanical properties of lowcarbon steel thermomechanically processed from martensite starting structure. The possibility of making microstructures in which bands of ultra fine ferrite uff grains act as. Recent progress in new producing and welding process for ultrafinegrained steels in japanj. Strain induced dynamic transformation and ultrafine surface grained steel one of the objectives of this project was to obtain ultra fine surface grained steels for plain and microalloyed lowc steels 0. Ultrafinegrained microstructures and mechanical properties. Three milling conditions varied the microhardness strongly c4, c5 and c6, two of them affected slightly c2 and c7 and other three ones presented null influence c1, c3 and c8. This heatsoaking to above the ferriteaustenite transformation temperature and subsequent slow cooling generates a fine, regular ferriticpearlitic microstructure in the steel. However, solidification crack formation in the fusion welding process continues to be one of the major challenges in the use of laser penetration. The microstructure coarsens and the toughness worsens at the coarse grained cg haz.
Ultrafine grained steels and the n coefficient of strain. In general, the term ultrafine grain is used to define microstructures with grain sizes between 100 nm and nm, whereas the term nano structure refers to grain sizes below 100 nm. Download analysis of fracture toughness mechanism in ultrafinegrained steels ebook epub pdf fb2. Microstructure and mechanical properties of a coldrolled. There are principally two ways to obtain ultrafine grained structure in steels. Normalised fine grained structural steels are traditionally produced by means of heat treatment, socalled normalising annealing, after rolling. Managing both strength and ductility in ultrafine grained steels article pdf available in isij international 488. Dynamic transformation mechanism for producing ultrafine grained steels. May 10, 2018 the article discusses the issues of weldability of metals with ufg ultrafine grained metals. Equal channel angular pressing of lowcarbon steel produces an ultrafine grained microstructure with an average sub grain size of 325 nm and both coarse and fine carbides, a microhardness of 330. The problem was discussed on the example of 316l steel with ufg structure obtained by metal forming method of hydrostatic extrusion. Tensile testing revealed superior mechanical properties the ultimate tensile strength of 1100 mpa and elongation of % for the new dp steel in comparison with the. Ultrafine grained steels managing both high strength. The dynamic straininduced transformation dsit of ferrite from austenite in intense deformation at temperatures close to ar3 were applied to one cmn steel and several nb and nbti microalloy steels to obtain an ultrafine ferrite grain size.
Effect of strain energy and grain size on corrosion resistance of ultrafine grained ufg fe20%cr steels with extremely low c and n fabricated by equal channel angular pressing ecap was investigated. The technique of austenitizing steel by heating rapidly through the ac1 to ac3 range, limiting the maximum temperature to the minimum required for complete austenitization and quenching immediately is discussed. Low carbon ultrafine grained dual phase steels ubc library. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Effects of strain energy and grain size on corrosion. The microhardness profile for the ultrafine grained steels did not follow a pattern similar to the asreceived material. In order to obtain ultrafine grains in steels, several new concepts have. The laser penetration welding technology has potential uses in additive manufacturing of ultrafinegrained steels 2, 3. Dynamic fracture toughness of the ultrafine grained if steels was investigated as a function of grain size by miniaturized charpy impact test. Processing of ultrafine ferrite steels, journal of materials.
Surface integrity analysis when milling ultrafinegrained steels. Ultrafine grained steels can be produced either by advanced thermomechanical processes or by severe plastic deformation strategies. Dynamic transformation dt is a phenomenon that ferrite transformation occurs during the deformation of austenite. Since the end of 1980s, ultrafine grained ufg metallic materials having average. Ultrafinegrained ferrite steel with dispersed cementite. Surface integrity analysis when milling ultrafinegrained. Ultrafinegrained ferrite steel with dispersed cementite particles ultrafinegrained ferrite steel with dispersed cementite particles nagai, k. C10 and c45 were used as the materials under study. Ultrafine grained steels with relatively simple and plain chemical compositions, strengthened primarily by grain refinement, have great potential for replacing high strength low alloyed steels. Pdf recent trends in producing ultrafine grained steels. Dynamic transformation mechanism for producing ultrafine grained steels article pdf available in advanced engineering materials march 2018 with 565 reads how we measure reads. Properties of finegrained steels generated by displacive.
Ultrafine grained steels with different carbon contents from ultralow carbon to high carbon were produced through warm caliber rolling. The term submicron structure refers to grain sizes between 100 nm and nm. Processing and stability of ultrafine grained structures in. May 10, 2003 recently, the grain refinement of metallic materials has been investigated intensively.
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