Quality

Used to test the transverse weld ductility on the outside surface. A specimen is flattened in a press to evaluate distance between the platens. Standard distance between the platens for A.D. Tubi is 20% greater than what prescribed by standards. Cracked samples are rejected. Testing frequency is according to production standard; however, one test is performed at least every two hours. 

This test is used to determine the ability of metallic tubes of circular cross-section to undergo plastic deformation in drift expansion. We expand the end of the specimen by a conical mandrel until the maximum outside diameter of the expanded tube reaches the value specified in the relevant product standard. A.D. Tubi standard expansion is always greater than 20% for duplex steels and nickel alloys and greater than 25% for austenitic steels. Upon customer request, for special alloys, expansion can be greater than even 40-50%. Cracked samples are rejected. Testing frequency is according to production standard; however one test is performed at least every two hours. 

Used to test the transverse weld ductility on the ID surface, thus determining properties required in the product specification. The specimen consists of a length of tubing approximately 100mm long which is slit longitudinally 90° on each side of the weld. The sample is then opened and flattened with the weld at the point of maximum bend.  Cracked samples are rejected. Testing frequency is according to production standard; however one test is performed at least every two hours. 

Used to test longitudinal weld ductility of the tubes and their ability to withstand the operation of bending into a tube sheet. A section of tube shall be capable of having a flange turned over at a right angle to the body of the tube to the width required by the applicable material specification without cracking or showing imperfections. Testing frequency is according to production standard; however, one test is performed at least every two hours. 

This test consists of driving a tapered mandrel having a slope of 60° into a section cut from the tube and thus expanding the specimen until the inside diameter has been increased to the extent required by the applicable material specifications. As per drift expanding test the A.D. Tubi standard is greater than ASTM standard. Cracked samples are rejected. Testing frequency is according to production standard, however one test is performed at least every two hours. 

Test is done to assess the welding strength of the tubes. Cracked samples are rejected. Testing frequency is according to production standard; however, one test is performed at least every two hours. 

Hardness, while technically not a material property, is used to quickly determine if the material is suitable for its intended use. Hardness test (HV10) is performed on each lot produced. One test is performed on each production beginning. Frequency of test is defined by related production standard.

From 0,3HV to 10HV both on base metal, HAZ and Welded Metal.

Microhardness test is performed upon customer request. A.D. Tubi can perform microhardness test from 0,3HV to 10HV on base metal, heat affected zone and welded metal. To see typical micro-hardness test values, see material technical sheet for further information.

A sample of tube is subjected to a controlled longitudinal tension force until it breaks, allowing us to measure ultimate tensile strength, breaking strength and maximum elongation. A tensile test is performed on each lot produced. Frequency of test is defined by related production standard. A.D. Tubi records values of Rp0,2, Rp1, Rm and elongation% for each test carried out.

By this method we test the material properties at an elevated temperature.

Burst test is a test that can be carried out upon customer request to determine the burst pressure of tube. It is a test useful to find the admissible stress (σAD), which, starting from burst pressure, can be find with the Barlow’s equation.

P = 2St /D

P = pressure
S = allowable stress
t = wall thickness
D = outside diameter

Our operators perform diameter, wall thickness and length control according to a frequency set in production standard. All measurement gauges are certified and periodically calibrated. Upon customers’ request also internal diameter can be measured using specific gauges.

Eddy current testing is performed in-line on 100% of tubes produced according to EN 10893-1/10893-2 or ASTM E426-E573-E309. Eddy current calibration and verification is performed by A.D. Tubi level II and III qualified staff according to EN473 and EN- ISO9712. Non conform tubes are automatically segregated in non-conform area.

UT can be performed on 100% of produced tubes. Test is carried out in-line on finished tubes before cutting and after eddy current. Calibration and verification is performed by A.D. Tubi level II qualified personnel according to EN ISO 9712.

A.D. Tubi can perform AUW on its tubes according to EN1779 and/or ASTM/ASME A/SA 1016. AUW can be performed on 100% of tubes upon customer request. Each tube with an internal surface clean and dry, shall be internally pressurized to 150 psi (1000 kPa) minimum with clean and dry compressed air while being submerged in clear water. After holding the pressure for not less than 5 seconds after the surface of the water has become calm, the entire external surface of the tube is inspected. Any tube showing leakage is rejected.

DPT is carried out according to ASTM A1047/1047M-05 Pr.A and EN1779.
A.D. TUBI performs leak testing using DPT obtaining an objective result.

Austenite/Ferrite balance test is carried out to verify the percentage of austenite phase and ferrite phase in duplex steels. Test is performed according to ASTM E562 (systematic manual point count) or ASTM E1245 (automatic image analysis). In A.D. Tubi's laboratory it is possible to check the correct balance of the two phases, both in base metal, heat affected zone and welded metal. A.D. Tubi's standard percentage of austenite in welded metal is between 40% and 60%, depending on the raw material percentage. 

Roughness measurement is performed upon customer request to evaluate the roughness of tubes produced. Test is carried out with calibrated profilometer. Roughness values depend strictly on raw material surface condition, so special tubes roughness values must be agreed on.
A.D. Tubi personnel can measure following surface parameter:

• Average roughness (Ra, AA, CLA)
• Root-mean square roughness (Rq, RMS)
• Maximum peak to valley height (Ry, Rmax)
• Ten point height (Rz)

Grain size determination is a test carried out to check the micro-structural grain dimension. Test is carried out according to ASTM E112. Grain dimension depends on grade and heat treatment performed. The focus of the test is determining the grain size number G corresponding to a certain average grain area. Typical A.D. Tubi tubes grain size of welded metal and heat affected zone is very close to metal base grain size.

Positive material identification is a test to verify the material grade. It is not a chemical analysis. A.D. Tubi perform PMI for every incoming strip to verify the grade. Upon customer request this test can be performed even on finished tubes.

This analysis is carried out to evaluate the shape and penetration of the weld which is evidenced by cutting a sample from the tube, polishing and etching one of its transversal sides.

Micrographic analysis is carried out to check the quality of the weld or to verify other characteristic's such as absence of intermetallic phases. A portion of tube is embedded in resin and then polished. After polishing, the sample is etched with an adequate etchant (different for every grade and scope) and then observed under the optical microscope. Microstructure, presence of micro-porosity and intermetallic phases can be verified.

A.D. Tubi can perform special analysis using its scanning electron microscope. SEM analysis is very useful to check some particular aspects out, like segregations of second phases, micro-porosity, presence of unwelcomed elements. For example, it is very useful to control the presence of molybdenum segregations in 6%Mo alloys. (However, the application field of SEM is so wide that it cannot be summarized here.)

Wall thickness can even be measured using a ultrasonic device for special applications.

Standard test method for Analysis of material by Optical Emission Spectrometry giving us the chemical composition of the product.