Change search
Refine search result
1 - 7 of 7
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Rehan, Arbab
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Effect of heat treatment on microstructure and mechanical properties of a 5 wt.% Cr cold work tool steel2019Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This work presents investigations related to phase transformations occurring inthe 5 wt.% Cr cold work tool steel Caldie during hardening and tempering treatments. The influence of austenitisation temperature, cooling rate, sub-zero cooling, isothermal treatment during cooling, tempering temperature and holding time on the microstructure and mechanical properties were investigated.The hardened microstructure of the investigated steel consisted of a mixture ofplate and lath martensite, minor amounts of bainite, blocky and thin retained austenite and M7C3 carbides. Increasing austenitisation temperature from 1020°Cto 1050°C was found useful as it provided higher hardness, good compressive strength and sufficient toughness. However, a further increase to 1075°C resulted in large prior austenite grains which produced coarse martensite containing somewhat increased carbon content. This was found to reduce the impacttoughness of the steel. Significant amounts of retained austenite were present after tempering for 2x2 h between 200°C and 500°C while tempering at 525°C or higher, reduced retained austenite content to below 2%. During holding at tempering temperature carbides precipitated in martensite and possibly in retained austenite. The retained austenite was thereby destabilised and transformed to martensite on cooling. This fresh martensite was tempered by following tempering treatments. It was concluded that tempering at 525°C for 2x2 h was suitable to achieve a good combination of hardness, compressive strength and impact toughness. Retained austenite was also found to transform during holding at 600°C for longer times. Initially, carbides formed in the austenite and after some time transformation of retained austenite to ferrite and carbides took place. Results were used to discuss alternative heat treatment procedures for the 5wt.% Cr cold work tool steel Caldie and some changes of current heat treatment recommendations were suggested.

  • 2.
    Rehan, Arbab
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Microstructure and mechanical properties of a 5 wt.% Cr cold work tool steel: Influence of heat treatment procedure.2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The demand for Advanced High Strength Steel (AHSS) in the automotive industry is increasing day by day. It is mainly motivated by the fact that AHSS can be used as thin sheets while having high strengths. It enables weight reduction of the automobiles which consequently increases the fuel efficiency and has proven to be less harmful to the environment. It is also expected that AHSS will have even higher strength in the near future. Cold work tools steels with 5 wt.% Cr are commonly used to process AHSS. Therefore, the tool steel must meet the challenges in the future, i.e. have even higher hardness, compressive strength and toughness. One way of increasing the mechanical properties of the tool steel is by improving the heat treatment parameters. However, it is not possible without a deeper understanding of the heat treatment process. Therefore, this work presents investigations related to phase transformations occurring in a 5 wt.% Cr cold work tool steel during heat treatment. Furthermore, the influence of austenitisation and tempering temperatures on the microstructure and mechanical properties were investigated. The studies revealed that a higher austenitisation temperature can be used to achieve a higher hardness, good compressive strength and adequate toughnessof the steel. However, too high austenitisation temperature may result inexcessive coarsening of prior austenite grains which reduced the impact toughness. It was also found that retained austenite can transform during tempering by two different mechanisms. Firstly, when tempering at 525°C, carbides precipitate in retained austenite lowering its stability and permitting a transformation to marten site on cooling. Secondly, when tempering at 600°Cfor extended holding time retained austenite isothermally transforms to ferrite and carbides. This occurs by precipitation of carbides in retained austenite followed by a final transformation to ferrite and carbides.These results were used to understand the standard tempering procedure of the 5 wt.% Cr cold work tool steel. Furthermore, alternative heat treatment procedures are discussed based on the important findings presented in this thesis. 

  • 3.
    Rehan, Arbab
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West. Dept. of Material Technology, Uddeholms AB, Hagfors, Sweden.
    Högman, B.
    Effect of microstructure on the impact toughness of a cold work tool steel2014In: Sonderbände der Praktischen Metallographie: Proceedings of 14th International Metallography Conference 2014, Montanauniversitet, Leoben, Österrike, 17-19 sept 2014, Riederer , 2014, Vol. 46, p. 307-312Conference paper (Refereed)
    Abstract [en]

    The effect of different combination of austenitization temperatures and tempering treatments on microstructure and impact toughness has been studied for the cold work tool steel -Uddeholm Caldie. This is a chromium, vanadium and molybdenum alloyed tool steel with approximately 0.7 wt.% C. It is used as a tool in industrial applications such as cutting, punching, shearing, forming, drawing and extrusion. A combination of high hardness and adequate toughness is required to withstand the common tool failure modesof chipping and cracking.Retained austenite content, hardness and prior austenite grain size were measured. The impact toughness was determined for un-notched impact test specimens. The microstructure and fracture surfaces of impact tested samples were characterized both macroscopically and microscopically. Scanning Electron Microscopy, Light Optical Microscopy and X-Ray Diffraction measurements were used. Higher austenitization temperatures resulted in larger amounts of retained austenite and higher hardness. A higher austenitization temperature also caused coarsening of austenite grains and resulted in reduced toughness. Impact specimens austenitized and tempered at lower temperatures were found to have better toughness than those at high austenitization and tempering temperatures.

  • 4.
    Rehan, Arbab
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West. Uddeholms AB, Hagfors, Sweden.
    Medvedeva, Anna
    Uddeholms AB, Hagfors, Sweden.
    Högman, Berne
    Uddeholms AB, Hagfors, Sweden.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Welding Technology.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Welding Technology.
    Effect of Austenitization and Tempering on the Microstructure and Mechanical Properties of a 5 wt% Cr Cold Work Tool Steel2016In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 12, no 1 December, p. 1609-1618Article in journal (Refereed)
    Abstract [en]

    The effects of austenitization and tempering temperatures for a 5 wt% Cr cold work tool steel are studied with an aim of understanding the influence on microstructure and mechanical properties. Microstructures are characterized with scanning electron microscopy and light optical microscopy. Retained austenite contents and martensite start temperatures are measured by X-ray diffraction and dilatometry, respectively. Hardness, impact toughness, and compressive yield strength are also determined. When the austenitization temperature is increased from 1020 or 1050 to 1075 °C, followed by tempering at 525 °C, significant hardness is gained while there is no increase in compressive yield strength. Higher austenitization temperatures also produce larger amounts of retained austenite. At the same time, the impact toughness is reduced due to coarsening of the martensitic microstructure. When the steel is tempered at 200 °C, a higher impact toughness and a higher volume fraction of retained austenite are observed. Retained austenite is not found after tempering at temperatures of 525 °C or above. It is concluded that the best combination of mechanical properties is achieved by austenitization at 1020 or 1050 °C followed by tempering at 525 °C.

  • 5.
    Rehan, Arbab
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West. Uddeholms AB, SE-683 85, Hagfors, Sweden.
    Medvedeva, Anna
    Uddeholms AB, SE-683 85, Hagfors, Sweden. .
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Welding Technology.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Welding Technology.
    Effects of Austenitisation Temperature and Multiple Tempering on the Microstructure and Impact Toughness of a 5 wt. % Cr Cold Work Tool Steel2016In: 10th TOOL Conference, Tool, conference proceedings, 10th TOOL Conference , 2016, p. 1-10Conference paper (Other academic)
    Abstract [en]

    The microstructure and properties of a 5 wt.% Cr cold work tool steel were studied after austenitisation at 1020°C, 1050°C or 1075°C followed by single, double and triple tempering treatments at 525°C. The microstructures were investigated with scanning electron microscopy and X-ray diffraction and phase transformations were studied by dilatometry. Furthermore, hardness and Charpy un-notched and V-notched impact toughness testing was performed and results were correlated to observed microstructures. With higher austenitisation temperature, the martensite and bainite start temperatures were lowered resulting in microstructures containing a higher volume fraction of retained austenite. Retained austenite transformed into martensite on cooling from the tempering temperature. Specimens that were austenitised at 1050°C or 1075°C and tempered twice contained fresh martensite. Applying a third tempering was therefore required to guarantee a fully tempered microstructure. The second tempering resulted in an increase of the un-notched impact energy while the third tempering did not have a pronounced effect. A triple tempering procedure could be preferable when austenitising at high temperatures to avoid undesirable fresh martensite in the tool microstructure.

  • 6.
    Rehan, Arbab
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Medvedeva, Anna
    Uddeholms AB, S-68385 Hagfors, Sweden.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Welding Technology.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Welding Technology.
    Retained Austenite Transformation during Heat Treatment of a 5 Wt Pct Cr Cold Work Tool Steel2017In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 48A, no 11, p. 5233-5243Article in journal (Refereed)
    Abstract [en]

    Retained austenite transformation was studied for a 5 wt pct Cr cold work tool steel tempered at 798 K and 873 K (525 degrees C and 600 degrees C) followed by cooling to room temperature. Tempering cycles with variations in holding times were conducted to observe the mechanisms involved. Phase transformations were studied with dilatometry, and the resulting microstructures were characterized with X-ray diffraction and scanning electron microscopy. Tempering treatments at 798 K (525 degrees C) resulted in retained austenite transformation to martensite on cooling. The martensite start (M-s) and martensite finish (M-f) temperatures increased with longer holding times at tempering temperature. At the same time, the lattice parameter of retained austenite decreased. Calculations from the Ms temperatures and lattice parameters suggested that there was a decrease in carbon content of retained austenite as a result of precipitation of carbides prior to transformation. This was in agreement with the resulting microstructure and the contraction of the specimen during tempering, as observed by dilatometry. Tempering at 873 K (600 degrees C) resulted in precipitation of carbides in retained austenite followed by transformation to ferrite and carbides. This was further supported by the initial contraction and later expansion of the dilatometry specimen, the resulting microstructure, and the absence of any phase transformation on cooling from the tempering treatment. It was concluded that there are two mechanisms of retained austenite transformation occurring depending on tempering temperature and time. This was found useful in understanding the standard tempering treatment, and suggestions regarding alternative tempering treatments are discussed. (C) The Author(s) 2017.

  • 7.
    Rehan, Arbab
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West. Dept. of Material Technology, Uddeholms AB, Hagfors, Sweden.
    Medvedeva, Anna
    Uddeholms AB.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Welding Technology.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Welding Technology.
    Retained austenite transformation during heat treatment of a 5wt.% Cr cold work tool steelManuscript (preprint) (Other academic)
1 - 7 of 7
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf