gen content of the steel showed that the hydrogen content of samples taken during the tilting and during teeming increases with an increase in the consumption of lime per heat (Fig. i), with overheating of the metal and cooling by lime at the end of the heat (Fig. 2), after the addition of a large quantity of carbonizing additions (Fig. 3), and with the use of screened lime to thicken the slag in the ladle. After we limited the recarbonization of the metal (to no more than 0.1%) and eliminated the addition of lime to the ladle, the hydrogen content de- creased by an average of 1.8 cmS/100 g steel. Despite these measures, however, the hydrogen content of the steel after deoxidation fluctuated within a broad range and reached 6.1 cm~/ i00 g steel on some heats.

We deoxidized the rail steel with silicomanganese, ferrosilicon, and aluminum in the ladle. The metal was blown with argon for 10-15 min to average out its chemical composition and temperature. The hydrogen content of the metal decreased from 3.2-6.1 cm3/100 g steel before the blowing to 1.0-1.6 cm3/100 g steel during the blow. Given such a fluctuation in hydrogen content, the production of steel which will not be susceptible to flaking cannot be guaranteed. In connection with this, the combine has begun construction of a section to sub- ject rails to an antiflaking treatment after rolling.

The quality of the rails obtained from the converter steel corresponds to the quality of rails made of open-hearth steel and meets the requirements of GOST 24182-80. Tensile strength is 890-1050 N/mm ~, the yield point is 405-630 N/mm 2, elongation is 5-9.7%, and re- duction of area is 7-14%. Impact toughness at +20~ is 5-10 J/cm 2 higher than that of rails made of OH steel.

Thus, the technology developed provides for the production of quality oxygen-converter rail steel which meets all of the requirements of the standard.

PRODUCTION OF STEEL 32KhG2SAF FOR DRILL PIPE

Yu. Z. Babaskin, S. M. Kutishchev, I. F. Kirchu, L. V. Dubenko, I. P. Aliev, B. I. Podzharskii, Yu. G. Isaev, V. K. Laptev, and G. M. Aliev

UDC 669.183.23:669.14.018.295

Most high-strength drill pipe of strength groups "E" and "L," for oil-field service, are made of steel 38KhNM. The steel is normalized and then tempered in this case. The production of pipes of steel 30G2SF in the quenched-and-tempered state has also been mastered, but this method involves a 20-30% reduction in the output of first-grade pipe. Also, in the normalized state, the necessary strength properties are not achieved without nitriding. In view of this, it is important to develop an economically alloyed steel for high-strength drill pipe in the normalized state.

Fig. I. Microstructure of steel 32KhG2SAF in the hot-rolled tempered state (a) and normalized state (b). •

Institute of Casting Problems, Academy of Sciences of the Ukrainian SSR, Azerbaidzhan Pipe Plant. Translated from Metallurg, No. 3, pp. 21-22, March, 1987.

0026-0894/87/0304-0049 $12.50 �9 1987 Plenum Publishing Corporation 49

~,o ~ ~_....... ~"

42 i -6O -~0 -20 0 20

Test temp., ~

Fig. 2. Dependence of impact tough- ness (an) , crack nucleation work (au) , and crack growth work (ag) on test temperature,

The Azerbaidzhan Pipe Plant worked with the Institute of Casting Problems of the Ukrain- ian Academy of Sciences to master the production of a high-strength chromium--vanadium-man- ganese steel strengthened by nitriding (0.8-1.6% Mn, 0.4-0.9% Si. 0.3-0.6% Cr, 0.013-0.017% N, 0.08-0.12% V, 0.28-0.36% C).

The steel is made in open-hearth furnaces by the pig-and-scrap process. Nitrogen is in- troduced in the form of cast nitrided ferrochromium in the metal bath after preliminary deoxi- dation; it is almost completely assimilated. Ferrovanadium is added to the ladle simultaneously with the deoxidizers after the ladle is filled one-third with metal. The steel is bottom-poured into 4.45-ton ingots which are then used to make 127-mm-diameter high-strength drill pipe of improved reliability.

During all of these stages of the pipe production process, the microstructure of the steel during the numerous heatings and deformations remains for the most part pearlitic-ferritic, with there being some change in the ratio of the structural constituents.

In the hot-rolled state without subsequent tempering and in the hot-rolled tempered state, grain size corresponds to 4-5 points under GOST 5639--65 (Fig. la). This grain size is retained after the ends are upset and the pipe wall is thickened twice. After normalization from 880- 950~ the structure consists of finely dispersed sorbitic pearlite and sections of bainite and ferrite with grain refinement up to 9-10 points (Fig. ib).

The metal subjected to vanadium-nitride strengthening has good weldability. In resist- ance butt welding, the heat-affected zone propagates as much as 30-40 mm into the body of the pipe, and the grains coarsen to 5 points. After normalization of the weld and heat-affected zone from 880-950~ grain size is restored to 9-10 points.

Experience in the production of high-strength pipes for steel 32KhG2SAF shows that their properties meets the requirements for strength classes "E" and "L" in the normalized state.

Normalized steel 32KhG2SAF is characterized by a favorable combination of strength and ductility characteristics and good impact toughness at room the minus temperatures. Even in the case of maximum or high contents of carbon, silicon, manganese, and chromium and a high level of strength properties, the ductility properties of the metal remain within the speci- fied ranges. The mechanical properties of steels 32KhG2SAF and 38KhNM are as follows: o u = 890 and 860 MPa; Oy = 690 and 670 MPa, ~ = 20 and 19%, ~ = 52 and 50%, a n = 0.95 and 0.90 MJ/m 2.

Figure 2 shows results of tests of the metal for impact toughness at different tempera- ture and determinations of the crack nucleation work and crack growth work.

In the temperature range from +20 to --20~ the steel fractures in a ductile manner. The fracture is fibrous in this case. At--40~ 20% of the fracture is brittle. At --60~ the amount of this component increases to 40%. Thus, steel 32KhG2SAF has a sufficient margin of ductility at the test temperatures used.

The residual stresses in the normalized pipes do not exceed 20 MPa (200 kgf/cm). At these values, the stresses will not promote cracking, and the pipes do not require tempering after normalization.

Thus, steel 32KhG2SAF is comparable to steel 38KhNM in terms of the level of its proper- ties and can be successfully used in the production of different types and grades of pipe.

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