Proceedings of the 3rd International Conference on Manufacturing Engineering (ICMEN), 1-3 October 2008, Chalkidiki, GreeceEdited by Prof. K.-D. Bouzakis, Director of the Laboratory for Machine Tools and Manufacturing Engineering (),

Aristoteles University of Thessaloniki and of the Fraunhofer Project Center Coatings in Manufacturing (PCCM),a joint initiative by Fraunhofer-Gesellschaft and Centre for Research and Technology Hellas, Published by: and PCCM

341

HEAVY WEIGHT DRILL PIPE HARDFACING BY USING

WELDING TECHNOLOGIES

V. Ulmanu 1, M. Bdicioiu1, M. Claru 1, Gh. Zecheru 1,

Gh. Drghici 1, M. Minescu 1, C. Preda 1

1. Petroleum-Gas University of Ploieti, Romania

ABSTRACT During the open hole drilling process, the drill string components are exposed to an intensive wear process, that leads to a drastically reduction of their durability. In or-der to increase the drill pipe wear resistance in the area frequently exposed to an abrasive wear process hardfacing wear alloys are applied using welding technolo-gies. The present paper brings forward the experimental researches regarding the heavy weight drill pipe hardfacing by using welding technology, in order to increase their wear resistance. KEYWORDS: Hardfacing, Welding, Heavy weight drill pipe

1. INTRODUCTION The heavy weight drill pipes are the most expensive elements of the drill string and their durabil-ity is essential for the economical drill work efficiency. In the exploration work, abrasion wear occurs and the durability of the heavy weight drill pipe is decreased. The abrasion wear is the result of the friction between the heavy weight drill pipe with the inner surface of the casing or the open hole wall. In order to improve the heavy weight drill pipes wear resistance the hardfac-ing technology is worldwide applied, /1/, /2/, /3/.

The heavy weight drill pipes are pipes with thick walls having De = 90168 mm outer diameter and L 9000 mm length, manufactured from full forged blanks. The hardfacing alloy is applied on the external surface of the pin and box (Figure 1), /7/, /10/.

Figure1: The hardfacing area of the heavy weight drill pipe. The hardfacing technology applied on the heavy weight drill pipes has a lot of advantages, such as: it increases the durability of the heavy weight drill pipes hardbanded with hardfacing alloys by im-proving the resistance to abrasion wear, it increases the functionality of the heavy weight drill pipes hardbanded with hardfacing alloys, it reduces the accidents and the following expensive interven-

3

1

34

760 100 20

342 3rd ICMEN 2008

tions in the drilling process, it increases the demand on the international market of the heavy weight drill pipes hardbanded with hardfacing alloys, /4/, /5/, /6/]. The present paper present the experimental researches regarding the heavy weight drill pipe hardfacing by using welding technology, in order to increase the their wear resistance. 2. EXPERIMENTAL PROCEDURE

2.1. Material (Specimen)

The experimentally researches regarding the heavy weight drill pipes hardfacing with resisting wear alloy by using welding process, were performed on specimens having 80 mm length, 134 mm outer diameter and 76 mm inner diameter, manufactured by steel AISI 4145H (utilized in heavy weight drill pipes construction). The chemical composition and the mechanical charac-teristics of the AISI 4145H steel are presented in table 1 and table 2.

Table 1: Chemical characteristics of AISI 4145H alloy steel.

C,% Mn,% Si,% P,% S,% Cr,% Mo,% Al,% Ni,% Cu,%

0.43 0.97 0.31 0.022 0.012 0.99 0.21 0.028 0.11 0.14 Table 2: Mechanical characteristics of AISI 4145H alloy steel.

HB Rm,N/mm2 A, % Z, %

336 1124.7 14 51

A recess grove with 50 mm width and 1.5 mm depth was machined onto the specimens and filled flush with hardfacing alloy in order to avoid the wear of casing inner diameter. 2.2. Hardfacing material In the experimental work it was used a wear resistant flux core tubular wire of 1.6 mm diameter, /8/, /9/. The deposit characteristics are presented in table 3. The deposit hardness is very impor-tant in the drilling process because a value higher than 57-62 HRC will cause an excessive wear of the casing. In this condition is very important to choose the most suitable hardfacing materials, /8/, /9/.

Table 3: The deposit characteristics.

Chemical composition of the deposit Hardness

C, %

Mn, %

Si, %

P, %

S, %

Cr, %

Mo, %

Nb, %

Ni, %

B, %

Fe, %

HRC

0.45 - 0.85

1.5 - 2.1

0.50 - 0.85 0.020 0.020

5.0- 7.0

0.35-0.85 - - - rest 57-62

The metal active gas welding process (MAG) was used to hardfacing the heavy weight drill pipe. The shielding gas was 80 % Ar and 20 % CO2.

2.3. Welding equipment For the experimental research a welding equipment was designed and manufactured which al-lowed, from the cinematic point of view, the following movements: continuous rotation of the specimen; axial feed of the welding torch; oscillate the welding torch. Figure 2 shows a scheme of the welding equipment used in the experimental work.

Casting, Thixo - Forming, Welding 343

Figure 2: The welding equipment scheme.

The welding equipment has the following components:

- constant direct current (DC) power supply capable of furnishing a current of 180400 Am-peres and 2030 Volts, with the wire positive (DCEP);

- griping and rotating device able to grip and rotate the heavy weight drill pipe at a constant rotating speed of between 0.2 to 1.2 rotations per minute;

- grip and oscillate device able to oscillate the welding torch parallel to the pipe surface with the amplitude of 15 to 25 mm and at approximately 60 to 90 oscillations per minute, and to incline the welding torch, in the direction of the rotation, between 1719 degrees as meas-ured from the centre-line of the heavy weight drill pipe.

2.4. Hardfacing research methodology In order to hardfacing the surface of the heavy weight drill pipe the following specific welding procedure were applied:

a) Material preparation. After turning the specimen by using a lathe machine a visual inspection of the weld surface was performed to ensure it is clean and without rust, dirt, grease, oil etc.

b) Griping the specimen in the griping and rotating device.

c) Preheating the specimen. Before to starts the hardfacing process, the specimen was pre-heated at 100 degree Celsius during the rotation. Inadequate preheating of the parent steel may cause undesirable cracking in the parent metal.

d) Hardbanding the specimen. Three welding beads were intermittently hardfaced on specimen by using the technological parameters presented in table 4. To avoid the superheating of the parent metal it was necessary to wait until the temperature of the specimen decreases below 300 oC, before proceeding to the next welding bead.

e) Controlled cooling of the specimen. When the hardfacing process was finished the hardfaced specimen was slowly cooled to avoid the cracks in the weld beads.

Table

Specimen

Y=1825 mm

X = 1238 mm

170190 Welding torch

Grip and oscillate device

344 3rd ICMEN 2008

Table 4: Technological parameters of the hardfacing regimes.

Technological parameters Values

Polarity reverse Amperage, A 260 10 Voltage, V 24 1 Shielding gas, l/min 13.5 Filler metal speed, m/min 4.5 X distance (from figure 2), mm 20 Y distance (from figure 2), mm 20 Rotating speed of the specimen,rot/min 0.6 Welding speed, m/h 14.5 Oscillating the welding torch: - oscillating speed, oscillation/min - oscillation amplitude, mm

60 25

Preheat temperature, oC 100 Interpass temperature, oC 350

2.5. Research regarding the tribological behavior of the hardfaced layer After the cooling, the harfaced specimens were analyzed and tested in order to verify the influ-ence of the hardfacing technology to the heavy weight drill pipe wear resistance. From the hard-faced specimens was cut the test sample used in the tribological testing facility (Figure 3).

Figure 3: Hardfaced specimen. In order to investigate the wear resistance, at micro scale, was utilized the Baroid Lubricity Tester modified (Figure 4) that allowed to appreciate the wear protecting materials behavior based on the test samples weight loss, U in g.

Figure 4: The Baroid Lubricity Tester modified.

Casting, Thixo - Forming, Welding 345

The tribological tests were carried out in drilling mud on barite basis with the characteristics pre-sented in table 5.

Table 5: Characteristics of the drilling mud.

Physical caharacteristics Value

Density (a), Kg/m3 1090

Plastic viscosity (p), cP 13 Apparent viscosity (a), cP 15 Shearing dynamic stress (0), N/mm

2 1,92

Shearing static stress (i), N/mm2

4,8 (i =1) 8,6 (i =10)

Filtered volume (Vf), cm3 9,8

Mud cake thickness (t), mm 2,3

The tribological testing conditions are presented in table 6. Table 6: Tribological testing conditions.

Friction couple 1 Friction couple 2

Work conditions Sabot-Heavy

weight drill pipe Ring-Casing

Sabot-Heavy weight drill pipe hardfaced with wear resisting

alloy

Ring-Casing

Sample

Sample dimensions 20 x 30 x 16 mm 35 x 8.5 mm 20 x 30 x 16 mm 35 x 8.5 mm Material AISI 4145H

sorbitic structure OLT 65

ferito-pearlitic structure

dendritic struc-ture

OLT 65 ferito-pearlitic

structure Rockwell hardness, HRC 34.6 20.3 56.9 20.3 Load force, N 350 350 Rotation speed, rot/min 72 72 Testing time, min 10 10 Friction coefficient (dry fric-tion conditions)

0.94 0.56

The wear of the test samples appreciated by the weight loss are presented in figure 5.

26.2

6.4

14

0.88

0

5

10

15

20

25

30

U *

10-3

, g

1 2Friction couple

Figure 5: The wear of the test samples.

Sabot

Ring

Ring

Sabot

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3. CONCLUSIONS

Based on experimental researches, the technology and the equipment for heavy weight drill pipe hardfacing were developed. The tribological behavior of the deposit was analyzed by performing wear tests using the two following friction couples: - couple 1: ring - casing, sabot - heavy weight drill pipe; - couple 2: ring casing, sabot - heavy weight drill pipe hardfaced with resisting wear alloy. From the experimental researches performed on the friction couples investigated (ring - casing; sabot - heavy weight drill pipe and ring - casing; sabot - heavy weight drill pipe hardfaced with resisting wear alloy) the following conclusions were results: - Friction couple 1 (ring - casing; sabot - heavy weight drill pipe) present an adhesive and

abrasive wear, characterized by the important deeps appears on the both sliding contact surfaces;

- Friction couple 2 (ring - casing; sabot - heavy weight drill pipe hardfaced with resisting wear alloy) present an spare adhesive wear, without no important deeps on the both sliding con-tact surfaces;

- Due to the wear process the weight losses in the case of friction couple 1 (ring - casing; sa-bot - heavy weight drill pipe) is practically double comparatively with the weight loses in the case of couple 2 (ring - casing; sabot - heavy weight drill pipe hardfaced with resisting wear alloy);

- The friction coefficient (dry) in the case of couple 1 (ring - casing; sabot - heavy weight drill pipe) is 0.94 and in the case of couple 2 (ring - casing; sabot - heavy weight drill pipe hard-faced with wear alloy) is 0.56; this indicate that the couple 1 present a better behavior to the friction than the couple 2.

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