In this article we justify the economic feasibility of using thermos-cyclic treatment of casing from economically alloyed steel 09G2S to produce the strength group Q125, in accordance with API 5CT. It was confirmed by the experiment that using a four-fold thermal cyclic quenching followed by a low-temperature tempering from the low-alloyed pre-eutectoid steel, it is possible to produce mechanical properties at the level: tensile strength 1068 MPa, conditional yield strength 1002 MPa, elongation 11.2 % and absorbed energy 64 Joules. In addition, an economic evaluation of the application in the production of high-strength casings from steel 09G2S, which allows reducing production costs by at least 11 %, due to thermal cycling.

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This work investigates the problem of how to reduce the prime cost of Grade Q125 Group 4 casing and tubing according to API 5CT and proposes process solutions to resolve it, consisting in the enhancement of series of mechanical properties without chemical alloying of steel with expensive elements such as chromium, molybdenum, vanadium, niobium and boron. During the investigation the process parameters of 9MnSi5 low-alloy steel heat treatment were developed, which confirmed the efficiency of this technology providing high values of strength and yield strengths which are minimum 931 MPa and 862 MPa respectively; at the same time maintaining the required cold resistance and resistance to hydrogen cracking of pipe. The suggested process parameters were based on heat cycle quenching with heating in induction furnace up to 1050–1100°С, 880–900°С and 740–780°С accordingly at each cycle and cooling rate in each case equal to 50°С/sec, during which the uniform martensite grain size ranging from 5 to 10 micron was obtained.

Бас редакторы т.ғ.д., проф Мерзадинова Г.Т. (Қазақстан) Бас редактордың орынбасары Жусупбеков А.Ж., т.ғ.д, проф. (Қазақстан) Бас редактордың орынбасары Тогизбаева Б.Б., т.ғ.д., проф. (Қазақстан) Бас редактордың орынбасары Сарсембаев Б.К., т.ғ.к., доцент (Қазақстан) Редакция алқасы Акира Хашигава проф. (Жапония) Акитоши Мочизуки проф. (Жапония) Базарбаев Д.О. PhD (Қазақстан) Байдабеков А.К. т.ғ.д., проф. (Қазақстан) Дер Вэн Чанг PhD, проф. (Тайвань (ROC)) Жардемов Б.Б. т.ғ.д. (Қазақстан) Жумагулов М.Г. т.ғ.к., PhD (Қазақстан) Йошинори Ивасаки т.ғ.д., проф. (Жапония) Калякин В. т.ғ.д., проф. (АҚШ) Колчун М. PhD, проф. (Словения) Тадатсугу Танака проф. (Жапония) Талал Аввад PhD, проф. (Сирия) Хо Линг проф. (АҚШ) Чекаева Р.У. а.к., проф. (Қазақстан) Шахмов Ж.А. PhD, доцент (Қазақстан) Юн Чул Шин PhD, проф. (Оңтүстiк Корея)