Specialty

Datalloy 2

Specialty - Datalloy 2

an Enhanced Corrosion Resistance Non-Magnetic Steel

Typical Analysis

C	Mn	Cr	N	Si	Mo	Ni
.03	15.1	15.3	0.4	.30	2.1	2.3

Characteristics

Datalloy 2TM is a Cr-Mn-N non-magnetic stainless steel. It has been specially developed to exhibit enhanced resistance to both pitting and galvanic corrosion. It is suitable for use in critical non-magnetic drill string components including MWD tools, LWD tools, stabilisers and compressive service drill pipe.
Datalloy 2TM has been designed to be used in place of standard Cr-Mn steels, in situations where increased corrosion resistance is required. Also the chemistry of Datalloy 2TM ensures that galvanic corrosion caused by coupling to dissimilar metals is resisted.
The increased nickel content of Datalloy 2TM does not adversely affect its resistance to Stress Corrosion Cracking or its galling performance.
Datalloy 2TM complies, as a minimum, to the mechanical property requirements of API 7.
The material is also available in a "High Strength" condition with a guaranteed minimum of 140 ksi 0.2% proof strength.

Structure

Datalloy 2TM is a highly stable, austenitic stainless steel with a maximum magnetic permeability of 1.005.
A combination of controlled hot forging and cold working generates the high proof strengths required in oilfield service. Datalloy 2TM cannot be hardened by heat treatment.
Forging parameters are carefully designed to produce optimum pitting corrosion resistance through microstructural control.

Physical Properties

Modulus of Elasticity	200 GPa
Poisson's Ratio	0.4
Coefficient of Thermal Expansion	16 x 10-6 m/m/°K
Resistivity	680 µΩmm
Thermal Conductivity	0.035 W/m°K
Density	7.65 g/cm3
Relative Magnetic Permeability	1.005 max

Fatigue Performance

Fatigue testing was performed using a Wöhler rotating bend test configuration, tested at 4000 cycles per minute. The Strength of the materials used are as below.
In rotating bend Wöhler type fatigue tests, higher strength Datalloy 2TM with 0.2% proof strengths in excess of 140 ksi, has been shown to have a fatigue endurance limit in excess of ± 70 ksi.

Specialty –Datalloy 2	Fatigue Performance
Material	0.2% Proof Strength
Datalloy 2TM	105 ksi
Staballoy AG17TM	116 ksi

Specialty –Datalloy 2

Mechanical Properties

Standard Strength

Size	< 7 inches (Min-Typical)	> 7 inches (Min-Typical)
0.2% Proof Stress (ksi)	110-125	100-115
UTS Stress (ksi)	120-148	110-135
Elongation (%)	18-33	20-35
Reduction of Area (%)	45-70	50-72
Longl. CVN at RT (J)	60-170	60-190
Hardness (HBN)	285-321	269-302

Specialty –Datalloy 2

Mechanical Properties

High Strength

Size	< 7 inches (Min-Typical)	> 7 inches (Min-Typical)
0.2% Proof Stress (ksi)	140-148	135-145
UTS Stress (ksi)	150-162	145-160
Elongation (%)	18-28	20-30
Reduction of Area (%)	45-68	50-70
Longl. CVN at RT (J)	60-130	60-150
Hardness (HBN)	302-350	203-304

Specialty –Datalloy 2

Mechanical Properties

Corrosion

Pitting Corrosion

Pitting is caused by adverse localized conditions. Corrosion rate is dependent on the differential between oxidants in the pit and the supply of oxidants to the area around the pit. Thus highly oxidized muds, or stagnant muds which form deposits that deprive localized area of oxidant, generate more aggressive environments. One widely adopted indicator of pitting resistance is the PREN or pitting resistance equivalent number. This number is a calculation based on chemical analysis, and is commonly accepted as providing a good indication of pitting resistance. Higher values indicate increased resistance to pitting corrosion.

Specialty –Datalloy 2	Mechanical Properties Corrosion
Galvanic Corrosion	When two dissimilar material come into contact it is possible that a galvanic cell will be set up, promoting corrosion in the least noble element of the couple. The resulting corrosion will usually be localized to the contact area and may be potentially catastrophic. Datalloy 2TM has been specifically designed to counteract this problem and, as the following graph shows, will resist attack even when coupled to pure copper.
Stress Corrosion Cracking	Stress corrosion cracking (SCC) is caused by the combined action of stress and a corrosive medium. The stress can be externally applied or can anise from residual stresses introduced during manufacture. It is also possible for loading and residual stresses to combine, giving a larger actual stress than is applied externally. There are two types of SCC: intergranular and transgranular. a) Intergranular SCC is caused by microstructural, sensitisation of the steel. It has been largely eliminated in modem NMDC manufacture by strict analytical control during ste Material from all Allvac Ltd (Jessop Saville Oilfield Products) collars is tested to ASTM A262 practice E to ensure freedom from sensitisanion. b) Transgranular SCC can occur in the presence of chloride ions when the steel surface is subjected to a tensile stress. Good engineering practice can help to reduce the occurrence of this type of SCC, as can surface treatments which introduce compressive stresses. Hammer peening is an optional treatment available at Allvac Ltd (Jessop Saville Oilfield, Products). It can introduce compressive stresses into the surface of our collars to a depth greater than 0.100". A 3 year warranty against stress corrosion cracking is offered on products treated in this way. The peening treatment also has the benefit of improving fatigue resistance.The possibility of cracking increases as stress approaches yield point and for the most arduous conditions, bore surface treatment by the "XL" procedure is recommended to farther resist initiation of stress corrosion cracking.

Specialty –Datalloy 2

Galling Resistance

Galling in the oil industry is defined as the seizure of, and damage to, threaded connections on tightening or untightening. Tests performed by Jessop Saville have shown that the intrinsic galling resistance of Datalloy 2TM is superior to that of other Cr-Mn steels.

Standard A.S.T.M. G98 test conditions, contact area = 123mm2, no lubricant 4-1/2" IF connections. Torque applied without lubrication.

Specialty –Datalloy 2
Galling Resistance	Furthermore, on full-scale make and break tests using a typical proprietary lubricant, galling was prevented at stresses over 50% greater than the recommended make up stress.
Quality Assurance	All collars meet API 7 specified properties and conditions as a minimum standard Each collar is mechanically tested Each collar is tested for magnetic 'hotspots' using a Foerster EC Probe. Maximum deflection guaranteed less than ±0.5µT/100mm Each collar is ultrasonically examined along its entire length Certification includes all relevant physical, chemical, mechanical, magnetic and ultrasonic results
Supply Forms	Lengths of up to 35 feet and diameters from 4 to 9-1/2" inches are supplied as standard, although longer lengths and other diameters may be ordered by arrangement. Material can be supplied solid, bored, semi-finished or fully machined to drawing. Datalloy 2TM is usually supplied in the strain hardened condition. Arrangements can be made to supply an annealed product, but at reduced strength levels. Components up to 9-1/2" diameter can be supplied on request with guaranteed minimum 0.2% proof strengths of 140 ksi. Impact toughness levels remain high and corrosion properties are similar to that of standard strength material.
Machinability	Datalloy 2 exhibits comparable machinability to Allvac Ltd (Jessop Saville Oilfield Products) grade Staballoy AG 17TM. The following graph relates measured tool wear to cutting time. Tests were performed at a cutting speed of 90m/min without lubrication, using a Sandvik CG235 insert. Austenitic steels are very ductile when compared to carbon and low alloy steels, so chip formation is far more difficult. Austenitic grades also work harden much more readily. These properties mean that cutting should be very positive and tools should not be allowed to dwell on the surface.

Specialty –Datalloy 2

Machinability

The following carbide tools are recommended, although high-speed steel tooling can be used at a lower cutting speed.

Operation	Tool Grade	Cutting Geometry	Cutting Speed	Feed Rate
Rough Turning	GC415 GC435	QR QR	400 ft/min 200 ft/min	0.018-0.024 in/rev 0.018-0.024 in/rev
Self-Finish	GC415 GC435	QM QM	200 ft/min 200 ft/min	0.008-0.018 in/rev 0.008-0.018 in/rev
Milling & Drilling Using Inserts	GCA GC235	145 and 190 145 and 190	300 ft/min 200 ft/min	0.006-0.008 in/rev 0.006-0.008 in/rev

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