Ironmaking & Steelmaking Processes, Products and Applications
ISSN: 0301-9233 (Print) 1743-2812 (Online) Journal homepage: http://iom3.tandfonline.com/loi/yirs20
Titanium microalloyed steels T. N. Baker To cite this article: T. N. Baker (2018): Titanium microalloyed steels, Ironmaking & Steelmaking, DOI: 10.1080/03019233.2018.1446496 To link to this article: https://doi.org/10.1080/03019233.2018.1446496
Published online: 05 Apr 2018.
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IRONMAKING & STEELMAKING, 2018 https://doi.org/10.1080/03019233.2018.1446496
REVIEW
Titanium microalloyed steels T. N. Baker Metallurgy and Engineering Materials Research Group, Department of Mechanical and Aerospace Engineering, University of Strathclyde, Glasgow, UK
ABSTRACT
ARTICLE HISTORY
Compared with niobium and vanadium, titanium has been regarded as a relative minor element in microalloyed (MA) steels. More recently, titanium compounds in MA steels have been recognised as having a wider role than just involved in austenite grain refinement. A brief history is followed by considering the physical state of titanium and its compounds characterized in MA steels. Their solubility in iron and the morphology of the precipitates they form, lead to their functions in controlling mechanical and toughness properties of MA steels often involving the multiple alloying with niobium, vanadium, carbon and nitrogen. Titanium has become an important element in the development of linepipe steels, which can develop bainite/acicular ferrite (AF) microstructures. The influence of Ti on nucleation of AF is an active research area, particularly in welding of MA steels. Finally, the influence of titanium on hot ductility, continuous casting and thin slab direct-charging processes is discussed.
Received 7 February 2018 Accepted 24 February 2018
L LWS M pre-exponential factor MA austenite M–A acicular ferrite Ms abnormal grain growth MDZ atom probe NWOR atom probe tomography P bainite PEELS bainite-martensite PSOR Baker–Nutting orientation relationship Q solubility of the particle material Q&T conventional bainite R carbon equivalent RA crack tip opening displacement Rc diffusion coefficient of the particle material 2r deformation-induced-ferrite transformation REM dual phase RT Gibbs free energy SAED activation energy SEM energy-dispersive X-ray spectroscopy SIP volume fraction SSC ferrite SSS field emission gun STEM Fray Farthing Chen T field ion microscope Tc finish rolling temperature TRZ oxide coarse grain heat-affected zone t Guinier–Preston t8/5 heat-affected zone TEM hydrogen embrittlement TRIP hydrogen induced cracking TMP high-resolution transmission electron microscopy TSDR high-strength low alloy Vm intercritical coarse grained heat-affected zone X intergranular ferrite Greek letters isothermal heat treatment α Joint Committee Powder Diffraction–International γ Center for powder diffraction data σc solubility product σy Kurdjumov–Sachs orientation relationship σo
Nomenclature Symbols A A AF AGG AP APT B B–M BNOR Cα CB CE CTOD D DIFT DP ΔG Ea EDX f F FEG FFC FIM FRT CGHAZ GP HAZ HE HIC HRTEM HSLA ICCGHAZ IGF IHT JCPDS K KSOR
KEYWORDS
Titanium; microalloyed steels; niobium; vanadium; carbon; nitrogen; crystallography; solubility; processing; microstructure; properties
interaction parameter Lifshitz Wagner Slyozov metal microalloyed martensite–austenite martensite start temperature manganese depleted zone Nishiyama–Wassermann orientation relationship pearlite parallel electron energy loss spectroscopy Pitsch–Schrader orientation relationship heat of dissolution quenched and tempered universal or ideal gas constant retained austenite critical maximum grain radius average particle diameter rare earth metal room temperature selected area electron diffraction scanning electron microscopy strain-induced precipitate sulphide stress cracking solid solution strengthening scanning transmission electron microscopy absolute temperature in degrees Kelvin impact transition temperature REM-rich and Zr-rich oxide phases time time to cool between 800°C and 500°C transmission electron microscopy transformation-induced-plasticity-assisted (steels) thermomechanical processing thin slab direct rolled molar volume of the particle material interstitial element ferrite austenite cleavage strength lower yield stress experimental constant
CONTACT T. N. Baker
[email protected] Metallurgy and Engineering Materials Research Group, Department of Mechanical and Aerospace Engineering, University of Strathclyde, Glasgow G1 1XJ, UK © 2018 Institute of Materials, Minerals and Mining
2
T. N. BAKER
σp σs: ky ρ vE−20
contribution to yield strength from precipitates giving dispersion strengthening contribution to yield strength from solid solution strengthening experimental constant particle surface tension or energy solubility of the particle material impact absorption energy at −20°C
Table 1. Microalloyed additions, country, year and yield strength [4,13]. Element V V Nb Nb Ti Zr Zr
wt-%
Country
Date
Yield strength (Nmm−2)
0.10–0.20 0.10 0.02–0.03 0.005–0.05 0.10–0.20 0.10–0.20 0.05–0.10
USA Germany USA UK Germany Germany USA
1916 1945 Pre1959 1959 1921 1914 1918
275–342 >390 325–445 350–425 260–550 250–400 260–450
Introduction Microalloyed (MA) steels, also known as high-strength lowalloy (HSLA) steels, have become an indispensable class for a range of applications such as in the construction of large ships, oil and gas transmission lines, offshore oil drilling platforms, pressure vessels, building construction, bridges, storage tanks and automotives. In 1997, Pickering [1] published what was probably the first review of titanium-containing MA steels. In the intervening years, much has been written on the effect of titanium in low carbon steels, as additions of titanium, often with niobium and or vanadium have become more common practice, particularly in steels for line pipe applications. The present review attempts to fill the gap mentioned by Cochrane [2] in a wide-ranging review of ‘phase transformations in microalloyed high-strength low alloy (HSLA) steels’ through the consolidation of many of the pertinent publications considering titanium in MA steels. It follows the format used by the author in previous reviews which dealt with the role of vanadium [3] and with zirconium [4] in MA steels. Parts of the present review were also discussed in an invited review on Microalloyed Steels [5]. Titanium and its alloys have many applications in the aerospace, petrochemical energy-producing industries and in prosthetic devices. Titanium, which weighs 40% less than carbon steels, can be strengthened by alloying with elements such as aluminium and vanadium [6,7]. The most widely used titanium alloy, Ti-6Al-4V, is present in 45% of titanium alloy industrial applications. The unique combination of this alloy's physical and mechanical properties with workability, fabricability, production experience and commercial availability allows it to be economically useful [8,9]. However, only 5% of the titanium mined today is used in its metallic form. Some of the remainder is used to manufacture titanium dioxide (TiO2), an ingredient in paper, paint, plastics and white food colouring, while a large percentage of the world annual tonnage is used in the steel industries as an alloying element. Titanium additions of 0.02% were known to reduce the segregation of carbon, sulphur and phosphorus in rail steels as long ago as 1914 [10,11], and by 1921 it was being used as an alloying element in steel [12]. Table 1, taken from Baker [4] and Morrison [12], lists data on the main microalloying additions, and it is noticeable that titanium was the earliest, and niobium the most recent. An examination of the literature shows that nearly all the elements now used as deliberate additions in MA steels were used in low alloy and stainless steels for what was described as precipitation strengthening, but was thought to be due to the precipitation of intermetallics such as Ni3Ti and TiSi [11]. To achieve this, larger additions were made than in current MA steels. However, stainless steels are not discussed further in this review.
Initially, the role of titanium added to steel as ferrotitanium, was mainly to reduce grain size and as a deoxidiser. Small additions of titanium,
