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High strength seamless steel pipes


Structure Forming Control from Initial Crystallization till Obtaining of High Strength Seamless Pipes According to AP1SCT N80, Realized by Chemical Composition of Steel 40NMnVTi

Tech Area / Field

  • MAT-ALL/High Performance Metals and Alloys/Materials
  • MAT-SYN/Materials Synthesis and Processing/Materials

3 Approved without Funding

Registration date

Leading Institute
Georgian Technical University, Georgia, Tbilisi


  • Bakhtiyarov & Associates Consulting Corporation, USA, AL, Auburn

Project summary

The aim of the project is improvement of the quality of round billet metal and reduction of second rate while achieving high strength state of seamless oil pipes according to AP1SCT N80 without complication of technological route of seamless tube rolling sets “140” and “400”.

The second set (furnace - ladle) for refining of steel noticeably improved the quality of metal (e.g. plasticity). But melting and refining in two electroarc furnaces has its influence as amount of dissolved atomic nitrogen in steel is increased. Without protective measures uncontrollable aging process (especially in AlN compound) may cause undesirable phenomena. This undesirable effect is used by us for regulating (controlling) of structure forming process in the technological cycle “steel – end product” in the presence of other specially introduced elements.

40NMnVTi steel is the result of our elaborated pipe steels (40MnTi – certificate N1381190, 38Mn1Ti – certificate N1381191, 40MnV – certificate N1381190, 45Ti – certificate N1242541, 20Ti – certificate N1544833).

In these elaborations were established influence limits of titanium and vanadium microadditions for the base of 40Mn steel. At the content of Ti = 0.010 – 0.020 % in the 40Mn titanium acts as midificator (inoculant) (40MnTi) and at higher content - Ti = 0.030 – 0.045 % - as microalloying element (38Mn1Ti). Till the content of 0.05 % vanadium acts as modificator and at content (V 0.06 %) as microalloying element (40MnV). The developed composition of 40MnV steel allowed to obtain T 560 N/mm2 for rolled billet. Besides, the experiments for achieving higher strength (T 660 N/mm2, T 760 N/mm2 and above) were carried out on this composition. These tasks were settled in laboratory conditions by choosing thermomechanical parameters (tC, %, V m/s) of rolling process, accelerated cooling (Vcool = 2 – 4 C/s) after normalization of casting pipe material, using HTMT, etc.

It is supposed that elaborated composition (40NMnVTi) at V = 0.01 – 0.04 % content will allow to obtain on both tube rolling sets T 500 N/mm2 for continuous casting in hot rolled condition and at V = 0.07 – 0.14 % T 560 N/mm2. According to existing data insignificant improvement of technology on tube rolling sets will allow to obtain T 560 N/mm2 and that would be the excellent scientific – technical results. Besides, presented project as also interesting (valuable) from the commercial point of view, e.g. cost of one ton tubing’s by group of strength “D” is 600$ and by the group of strength “E” is 800 – 1 000 $.

The project fully meets STCU objectives.

Former arm scientists are involved in the project; subject is very urgent and significant not only for our republic; methodology is original and the work is perspective.

1. Thorough investigation of 40MnTi, 38Mn1Ti, 40MnV, 45Ti, 20Ti steels;

1.1. Thorough investigation of 40MnTi steel;
1.2. Thorough investigation of 38Mn1Ti steel;
1.3. Thorough investigation of 40MnV steel;
1.4. Thorough investigation of 45Ti steel;
1.5. Thorough investigation of 20Ti steel,
2. Laboratory analyses of 40NMnVTi steel;
2.1. Melting of 40NMnVTi steel, extraction of round billets trough quartz tubes. Investigation of the obtained metal;
2.2. Research of hot plastic deformation (HPD) influence (tC, %, V m/s) on 40NMnVTi steel properties without forced cooling after deformation at the rate 2 – 4 C/s in HTMT regime (conditions);
2.3. Analysis of the data obtained after detailed research of the metal,
3. Realizing of industrial tests on 40NMnVTi steel;
3.1. obtaining of high strength seamless pipes from rolled billets;
3.2. Obtaining of high strength seamless pipes from continuous casting billets;
3.3. undertaking of comparative (profound) research enlisting collaborator’s laboratories (Germany – TU Freiberg, USA – Auburn University, Alabama). Mutual discussion of the obtained results with the professors J.Bast and D.Marghitu will assist to make scientifically proved conclusion on the issue.
4. The analysis of the obtained results and preparation of the report.

Compilation of technological directives.

Preparation of patent application to take out the Georgian patent.

All basic investigations are conducting in “The Laboratory of Properties of Materials” Georgian Technical University, in which following researches can be realized:

1. Mechanical tests of metals covering wide range of properties (SK, SB, B, S (0.2) 0.05, (1+2), (1+2), A, D; a0.25 (a1+a2), a, T50, J – integral; -1; macro- and micro hardness, etc.);

2. Metallographic, fractographic, X – rey analyses;
3. Kinetic research of phase transformation under usual conditions and under the influence of HPD;
4. Investigation of solid solution supersaturation (studying of thermal cycling under stress below A1), etc.;

Determining experimentally constituents 1, 1, a1 (deformability of metal, static and dynamics before the beginning of fracture) and 2, 2, a2 (deformability of metal, after beginning of fracture process), T50 (cold brittleness threshold), J – integral (crack resistance of material), -1 (fatigue) and other indices of mechanical properties, we establish structural strength of the end product – “durability” of metal.

Reliability of the obtained results is ensured by original, verified methodology.

Technical equipment of the project:

1. Induction melting units (5, 10, 50, 60 Kg);

2. Mechanical shop:
3. Test machines FPZ – 100; EU – 40;
4. Impact testing machine MK – 30 with recorder of loading process and impact testing machine IO 5003 – 03 – 01;
5. High temperature microscope IMASh 20 – 78;
6. Dozdovski’s vibrator and cycling loading machine VP 107;
7. Hardness testers (HB, HR, HV, H);
8. Metallographic microscopes Neophot – 21; Epiquant;
9. X – rey difractometer DRON – 3M;
10. Electronic microscopes REM 200, EMMA – 2;
11. Vacuum electron beam installations;
12. Heating furnaces, Tamman vacuum furnace;
13. Magnetometer with the rolling mill;
14. Foundry, welding, chemical laboratories;
15. Installation for defining of hydrogen content in metals;

Flaw detector DSK – 1, ferrosonde sorter, mills, “Neris”, calorimeter, photolaboratory, abrasive tester.