I. Yu. Pyshmintsev

Structural and mechanical properties of nanocrystalleve titanium processed by severe plastic deformation

Recent investigations have demonstrated that materials with ultrafine grain (UFG) structure (nano- and submicron crystalline) can be processed by severe plastic deformation. One advantage of this method is that it can be applied to both pure metals and alloys. Moreover, it produces samples that have no residual porosity so that meaningful measurements of the physical and mechanical properties are possible. Investigations of ultrafine grain copper and aluminum alloys have revealed a number of specific features of their mechanical behavior, namely extremely high hardness and strength, the absence of strain hardening, and deviation form the Hall-Petch relationship. In this work the authors investigate the mechanical properties and thermal stability of UFG titanium.

Effect of Bainite Crystallographic Texture on Failure of Pipe Steel Sheets Made by Controlled Thermomechanical Treatment

The method of orientation microscopy (EBSD) is used to study the texture of low-carbon, low-alloy pipe steel sheets with a bainitic structure made by controlled thermomechanical processing. The specimens analyzed are inclined or not inclined towards forming separations (secondary cracks) in a fracture during mechanical testing. Formation of separations during failure of steel with a bainitic structure is connected with the presence in the material of regions with uniform orientation (001)<110> extended in the cold rolling direction. Formation of the regions is a consequence of features of γ→α shear transformation that commences at special boundaries between deformed austenite grains.

Effect of ferrite-bainite structure on the properties of high-strength pipe steel

Mechanical properties of pipe steel 07G2MFB are studied after cooling from the austenitic region at rates of 0.9–32°C/sec making it possible to obtain a ferrite-bainite structure with different ratios of structural components. It is shown that formation of a predominantly bainitic structure formed with high cooling rates provides less crack resistance with static loading than a structure in which polygonal ferrite predominates. A bainitic structure is preferable with dynamic loading. Treatment leading to formation of coarse islands of martensite-austenite (MA) component within a ferrite-bainite structure has an unfavorable effect on crack tip opening displacement CTOD, ductile-brittle transition temperature T50, and resistance to hydrogen embrittlement ∆Ψ/Ψ.

Hardening of Large Forgings in Water-Air Mixture

A double-stage mode of accelerated controlled hardening of large forgings from structural steels with relatively low hardenability in a water-air mixture with subsequent high-temperature tempering is described. Special features of the decomposition of supercooled austenite in these steels under continuous cooling are considered. The structure and properties of forgings after hardening by the recommended regime are studied.

Contributions of structural factors to the strength of K65 steels

687 Large diameter welded pipe of strength category K65 (X80), which is manufactured by numerous Rus sian and foreign companies, is used for the construc tion of gas pipelines [1, 2]. All such high strength pipe conforms to the relevant Gazprom requirements but will differ in chemical and phase composition, struc ture, and correspondingly mechanical properties. Hence, we need to identify the basic factors responsi ble for the steel’s performance and to determine their optimal values.

Microstructure and disperse phases of X80 pipe steel for gas pipelines

14 The construction of the Bovanenkovo–Ukhta gas pipeline employs large diameter welded steel pipe of strength class K65 (X80), produced by various Russian and non Russian companies [1, 2]. All the pipe meets the requirements of OAO Gazprom but there are some differences in its mechanical properties—most nota bly the crack resistance—on account of differences in the chemical composition (within the API require ments) and the sheet production technology (con trolled rolling and subsequent accelerated cooling).

Influence of microalloying with boron on the structure and properties of high-strength oil pipe

Microalloying with boron (up to 0.005%) has a considerable influence on the hardenability of steel. Four alloying systems with complete and partial replacement of molybdenum by microadditions of boron are studied. The resulting mechanical properties are satisfactory for high-strength pipe corresponding to strength groups from N80 (type Q) to Q135, according to the API 5CT, ISO 11960, and GOST R 53366 standards. The reversible tempering brittleness of Nb-B steel and Mo-B steel is considered. Overall, the strength and impact strength of Mo-B steel are greater than for steel without molybdenum.

Operation of gas pipe at working pressures up to 11.8 MPa

Full-scale hydraulic and pneumatic tests of spiral- and straight-seam gas pipe (diameter 1420 mm) produced by OAO Volzhskii Trubnyi Zavod are described. Satisfactory and equivalent resistance of different types of pipe to ductile failure is established. In terms of its operational characteristics, the pipe may be used in pipelines of working pressure up to 11.8 MPa in any Russian climatic zones, including the Far North.

Effect of High-Temperature Thermomechanical Treatment on the Brittle Fracture of Low-Carbon Steel

The effect of high-temperature thermomechanical treatment (HTMT) on the brittleness connected with deformation-induced aging and on the reversible temper brittleness of a low-carbon tube steel with a ferrite–bainite structure has been studied. When conducting an HTMT of a low-alloy steel, changes should be taken into account in the amount of ferrite in its structure and relationships between the volume fractions of the lath and the acicular bainite. It has been established that steel subjected to HTMT undergoes transcrystalline embrittlement upon deformation aging. At the same time, HTMT, which suppresses intercrystalline fracture, leads to a weakening of the development of reversible temper brittleness.

Study of Low-Carbon Pipe Steel Strain Ageing

Strain aging of pipe steels 06G2FB and 07G2MFB with ferrite-pearlite and ferrite-bainite structures is investigated. It is established that a ferrite-bainite structure is more inclined towards strain aging than a ferrite-pearlite structure. The tendency towards strain aging of steel with a ferrite-bainite structure increases with increasing austenitizing temperature. During hot plastic deformation there is development of recrystallization and the tendency towards strain aging decreases.