S. Yu. Zhukova

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.

Ensuring complete scale removal from wire rod before drawing

Low-temperature coiling in the Stelmor line (∼850°C) is best for chemical scale removal. In that case, thin, dense scale is formed, without peeling, spots, or blisters. For low-carbon wire rod, the plasticity declines monotonically, while the strength increases. For high-carbon wire rod, the microstructure is unsatisfactory: tempering sorbite and also bainite and pearlite of reduced dispersity. (The optimum scale consists of wustite.) With increase in coiling temperature (950–1000°C), mechanical scale removal is best, on account of the difference in thermal expansion of the scale and the metal. In storage and prolonged transportation, blisters and scale-free sections may lead to corrosion and, on etching, to overetching of the metal.

Reversible tempering brittleness of structural steel

415 In the theoretical analysis of reversible tempering brittleness, most attention has been paid to the segre gation of harmful impurities—phosphorus and its chemical analogs (As, Sn, Sb)—along the grain boundaries, which weakens the binding of the grains [1–3]. Since industrial steel contains more phospho rus than As, Sn, and Sb, it plays the greatest role in grain boundary embrittlement. The harmful effect of phosphorus depends not only on its concentration but also on the alloying and final structure of the steel and the total area of the grain boundaries.

Martensitic steel with 13% Cr for corrosion-resistant oil pipe

The temperature ranges corresponding to phase transitions in the heating and cooling of L80 steel of 13Cr type according to the API 5CT/ISO 11961 standard are determined (the Russian analog is 20X13 steel). The influence of the heat treatment on the structure and mechanical properties of the steel is investigated. It proves expedient to reduce the initial temperature in quenching from 1030–1040°C to 930–960°C, so as to improve the impact strength of the steel at negative temperatures. The influence of additional alloying of L80-13Cr steel with manganese and molybdenum on its strength and plasticity is studied. The use of steel with 13% Cr and with 1–2% nickel and manganese is promising for low-temperature pipe resistant to carbondioxide corrosion.

Structure and mechanical properties of low-carbon steel for oil and gas pipelines

The structure and mechanical properties of low-carbon microalloyed pipe steel are studied. Different heat-treatment systems permit the regulation of microstructure formation and modification of the strength. A complex structure with minimal content of acicular components is observed in the steel after quenching from the austenite region at the cooling rate typical of pipe treatment and high tempering. The best combination of structure and mechanical and corrosion properties is obtained after heat treatment that includes double quenching (first from the austenite region and then from the intercritical range) and high tempering.

Structure formation in the accelerated cooling of rolled reinforcement

The structure and metallic properties of hot-rolled rolled reinforcement (strength class 400) made from moderate-carbon Si-Mn and manganese steel are analyzed. Thermomechanical treatment is proposed for improvement in these characteristics.

Production of wire rod for high-strength reinforcing cord

Improvement in the microstructure and performance of wire rod for the production of high-strength reinforcing cord is considered, To suppress undesirable structures (structure-free cementite and martensite), the use of high-carbon steel microalloyed with vanadium and/or chromium is recommended, as well as thermomechanical treatment of the wire rod.

Decomposition kinetics of supercooled austenite in moderate-carbon pipe steel

The mechanical properties of hot-rolled pump, compressor, and casing pipe made from moderate-carbon steel are largely determined by the content of various decomposition products of supercooled austenite (pearlite, excess ferrite, bainite) in the structure and by their morphology [1‐4]. The type and quantity of structural components depends on the composition of the steel (specifically, on the stability of the supercooled austenite), which, in turn, is affected by the rolling conditions, especially in the final stages of pipe production (the initial and final temperatures of reduction, the postdeformation cooling rate, etc.). In recent years, a group of dispersion-hardening Cr‐Mn‐Mo steels has been developed for the production of high-strength hotrolled pump and compressor pipe at OAO Sinarskii Trubnyi Zavod (SinTZ), in collaboration with the Russian Research Institute of the Pipe Industry and Ural State Technical University [4]. To this end, thermokinetic decomposition diagrams of supercooled austenite must be plotted both for the 37 E2e and 48 E2Aa steel traditionally used at SinTZ and for new steel. The influence of the austenitization temperature and hot plastic deformation on this diagram must be investigated. We consider the group of moderate-carbon pipe steels based on the compositions Mn‐Si and Mn‐Cr, microalloyed with vanadium (0.05‐0.10%), niobium (around 0.04%), and molybdenum (0.10‐0.20%). The thermokinetic decomposition diagrams of supercooled austenite are plotted from dilatometric, microstructural, and durometric data. To study the influence of various technological factors on the decomposition kinetics of supercooled austenite, 13 × 13 mm rods of the given steels are subjected to hot rolling on a laboratory mill, with 15% reduction. The laboratory conditions approximate the final operations in the production of hotrolled pipe. As is evident from Fig. 1, the decomposition of supercooled austenite in the given steels is characterized by clear separation of both decomposition stages and increased stability of the supercooled austenite in the region of diffusional transformations. It follows from direct measurements in the SinTZ shop [3] and from combined analysis of the microstructure and hard