MANDATORY PHYSICAL AND CHEMICAL TESTING DURING MANUFACTURING

Why should the quality of the material be checked before its usage?

Product quality is of the greatest importance to every manufacturer.

– High-quality products mean satisfied customers, a smooth manufacturing process and a healthy bottom line.

– Saving time and hence economy.

– On-time delivery to customers.

– It helps to control the inventory.

– And the most important factor is SAFETY.

What is Material Testing?

Materials testing is a broad term that refers to the use of analytical testing techniques to identify the chemical composition and physical and mechanical characteristics of a material. When it comes to quality control, manufacturers often use material testing to find the cause of defects or product failures that can lead to quality and safety issues. One very common material test are:

– Tensile Test.

– Hardness Test.

– Impact Test.

– Flattening, Flaring & Bend Test.

– Macro & Microstructure Characterisation etc.

Let’s move to IBR requirements:

In this session, we will cover the Mechanical & Chemical Testing requirements of Materials / Component as per Indian Boiler Regulations – 1950. (Nineteenth Edition, 2021)

The following Regulation has been covered in this session.

  1. Steel plates, Rivets, Sections and Bars in carbon steel.
  2. Cold Drawn Seamless Carbon Steel Boiler, Superheater And Heat Exchanger Tubes For Design Metal Temperature Not Exceeding 454 °C.
  3. Forged product.
  4. General Grey Iron Castings (Grade A)
  5. Tests on Welded Seams.
    1. Class I Boilers – Plates.
    2. Class II Boilers – Plates.
  6. Periodic Check Test

Steel plates, Rivets, Sections and Bars in carbon steel.

Branding:

a. Every plate, section and bar shall be clearly and distinctly marked by the maker in two places with the number of identification marks by which they can be traced to the charge from which the material was made. As an alternative the rivet bars may be bundled and tabbed to enable the material to be traced to the cast of steel from which they are made.

b. Every plate shall also be stamped by the steel maker as provided in IS: 2002. The following information shall necessarily be provided:

  1. Name of the manufacturer.
  2. Specification:
  3. Heat No.
  4. Plate No.
  5. Stamp.

A. Steel plates, Rivets, Sections and Bars in carbon steel.

Chemical Analysis:

a. The steel shall not contain more than 0.05 per cent of Sulphur or Phosphorus.

b. When the material is required for flame cutting and/or welding, the carbon content shall not exceed 0.30% and special precautions shall be taken when the carbon content exceeds 0.26%.

c. When steels are intended for service temperatures over 700°F the silicon content shall be not less than 0.10% or the material shall pass the proof test for creep quality of carbon steel plates of boiler quality.

d. Material shall comply with the basic chemical composition as recommended in the product specification.
For example: Chemical & Mechanical properties requirements as per IS 2002 as below.

IS 2002: Steel plates for pressure vessels for intermediate and high-temperature service including boilers. 

 

Selection of test pieces (Reg.14)

All test pieces shall be selected by the Inspecting Officer and tested in his presence, and he shall satisfy himself that the conditions herein described are fulfilled.

Tensile Test pieces (Reg.15)

The tensile strength and percentage elongation shall be determined from test pieces of gauge lengths preferably equal to Lo=5.6 √A0. Alternatively, another gauge length may be used, provided the %Elongation is expressed as the equivalent value on a gauge length of Lo=5.6 √A0.

For round specimens, gauge length shall be 5d0.

For plate thickness exceeding 60mm, test pieces shall be taken from the exterior third of the plate cross-section. Wherever practicable, the rolled surface shall be retained on two opposite sides of the test piece.

Number of Tensile Tests (Reg.17)

a) Plates: One tensile test piece shall be cut from each plate as rolled.

b) Sections (Angle, tee, rivet, and stay bars): One tensile test shall be made from each 15 or part of 15 bars rolled of each section or diameter from the same charge, but not less than two tensile tests shall be made unless the total number of bars rolled from the same charge is 8 or less than 8 and the bars of the same section or diameter, in which case one tensile test shall suffice.

Tensile Test Specified Requirements (Chapter II):

Plates of carbon steel shall conform to one of the following four grades of tensile strength:-

(i) 37 to 45 kgf/mm²

(ii) 42 to 50 kgf/mm²

(iii) 47 to 56 kgf/mm²

(iv) 52 to 62 kgf/mm²

Bend Test (Reg.19):

Number of Bend Tests (Reg.20):

(a) Plates: A bend test shall be taken from each plate as rolled. The bend test from shell plates, butt straps and other plates which have not to be flanged or worked in the fire or which when in use are not to be exposed to flame shall be the cold bend test.

(b) Angle Bars: A cold bend test shall be made from each angle bar rolled, provided that the cold bend test need not be carried out if the basic material specification does not call for it.

(c) Stay Bars: A cold bend test shall be made for every 15 stay bars as rolled from each charge.

Bend Test (Reg.19):

a) Test pieces shall be sheared lengthwise or crosswise from plates or bars and shall not be less than 1½ inches (≈ 38 mm) wide, but for small bars the whole section may be used. For rivet bars bend tests are not required.

b) For cold bend tests the test of plates of all grades of steel, the test piece shall withstand, without fracture, being cold through 180° around a mandrel, the internal radius is equal to that shown in the table below:

Tensile Strength
Internal Radius/Mandrel Radius
36 to 49 kgf/mm2 1T
41 to 57 kgf/mm2 1T
45 to 64 kgf/mm2 1.5T

‘T’ is the thickness of the bent specimen.

Bend Test Specimen:

B) Cold Drawn Seamless carbon steel boiler, superheater and heat exchanger tubes for design metal temperature not exceeding 454°c.

  1. Chemical Analysis:(Reg. 36 b)

Steel shall confirm the following limits of Chemical composition ():

Grade
%C
%Mn
%Si
%S
%P
TA 0.06-0.18 0.27-0.63 0.25 max. 0.035 max. 0.035 max.
TB 0.27 max*. 0.93 max 0.10 min. 0.035 max. 0.035 max.
TC 0.35 max*. 0.29 – 1.06 0.10 min. 0.035 max. 0.035 max.

*For TB and TC for each reduction of 0.01% below the specified Carbon maximum, an increase of 0.06% Manganese above the specified maximum will be permitted up to a maximum of 1.35

Selection of Tubes for Test (Reg.37):

Two per cent of the tubes of each thickness and diameter and only one for every 100 or part there of above 400 tubes of such similar size shall be made available to the Inspecting Officer for testing to the extent of such numbers.

(a) The tensile strength of the material cut from finished tubes shall conform to one of the following five grades namely,

(i)   31 to 41 kgf/mm²

(ii)  36 to 46 kgf/mm²

(iii) 41 to 51 kgf/mm²

(iv) 46 to 56 kgf/mm²

(v)  50 to 62 kgf/mm²

(b) Tensile test may be carried out on a full section of the tubes up to the capacity of the machine.

(c) All specimens shall be tested at room temperature.

(d) Minimum 2 tubes for first 100 tubes and 1 per 100 or part thereof for tubes over 100 numbers.

Identification and marking of the Tube/Pipe sample:

All test pieces shall be selected by the Inspecting Officer and tested in his presence, and he shall satisfy himself that the conditions herein described are fulfilled. To avoid the delay in testing the sample drawn by the Inspecting Officer shall be identified with hard stamping as suggested in the below sketch. Sample size required: Full section x 700 mm.

Tensile and Hardness Tests (Reg.38):

The test specimen shall comply with the following requirements. The hardness test may be carried out on the wall cross-section or on a flat outside surface of the tube sample.

Grade
Yield Strength Mpa
(kg/mm²) min.
Tensile Strength Mpa
(kg/mm²) min.
%Elongation on
GL = 50 mm, min.
Hardness (Max.)
HB
HRB HB
TA 180 (18.5) 325 (33.1) 35
137
TB 255 (26.1) 415 (42.2) 30 79 143
TC 275 (28.2) 485 (49.3) 30 89 179

Tensile and Hardness Tests (Reg.38):

a. The upper yield point at room temperature shall be not less than 50 per cent of the specified minimum tensile strength at room temperature.

b.   (b) The minimum values of the stress at the proof limit 0.2 per cent at elevated temperature Et of the material may be calculated by multiplying the specified minimum tensile strength at room temperature R20 by the ratio Et/R20.

c. Minimum values for the ratio of the stress at the proof limit 0.2 per cent at elevated temperature Et to the minimum specified tensile strength at room temperature R20 of carbon steel tubes.

Temperature
250 °C
275 °C
300 °C
325 °C
350 °C
375 °C
400 °C
425 °C
Et/R20 0.40 0.38 0.36 0.34 0.33 0.32 0.31 0.30

The breaking elongation in % shall be not less than (100-Rm) /C

where C = 2.2 for only gauge length of L=5 do or 5.65 (Ao)1/2

do = original diameter of the round test piece.

Ao = original cross-section of the rectangular test piece.

NOTE: C=1.9 for gauge lengths of 4 Ao 

Flattening Tests (Reg.39):

A ring not less than 63 mm in length cut from one end of each selected tube shall be flattened

between two parallel flat surfaces to a distance between the plates (H) as calculated by the formula given below without showing any sign of a crack or flaw:

Where a = thickness of tube (mm)

D = outside diameter of the tube (mm)

C = a constant as given below

C = 0.09 for steel having a specified minimum tensile strength from 31 kgf/mm² up to and including 35 kgf/mm².

C = 0.07 for steel having a specified minimum tensile strength over 35 kgf/mm² up to and including 42 kgf/mm²

C = 0.05 for steel having a specified minimum tensile strength over 42 kgf/mm² up to and including 50 kgf/mm².

C = 0.03 for steel having a specified minimum tensile strength over 50 kgf/mm² up to and including 62 kgf/mm².

Bend Test (Reg.44 b):

For pipes of outside diameter 60.3 mm and under, a bend test shall be conducted. A sufficient length of pipe shall stand being bent cold through 90° around a cylindrical mandrel, the diameter of which is 12 times the nominal diameter of the pipe without developing cracks.

Flanging & Drift Expanding Test (Reg.40):

a. The tube shall withstand either the flanging test or the drift expanding test, at the option of the manufacturer.

b. Flanging test:- A test piece cut from the end of a tube in a plane perpendicular to the axis of the tube shall show no crack or flaw after flanging to the specified outside diameter as given in the table below.

c. Drift Expanding / Flaring test: – A test piece cut approximately 100 mm from the end of a tube in a plane perpendicular to the axis of the tube shall show no crack after expanding by a mandrel having an included angle of 30°, 45° or 60° at the option of the manufacturer to increase the outside diameter.

Additional Test before rejection (Reg.41):

If any one or more tests specified in these regulations (Reg. 38, 39 & 40) fail, two further tests of the same kind may be made on TWO other tubes of the same batch. If the repeat tests are satisfactory the tubes shall be accepted. Should either of the tubes fail in any test, the batch of tubes represented may be reheat-treated. If any failure in repeat tests, the batch of tubes which the test pieces represent shall be rejected.

Flanging & Drift Expanding Test (Reg.40):

The Mouth of the flare has been expanded to the percentages given below, without cracking:

The ratio of inside diameter to the outside diameter
Minimum expansion of inside diameter %
0.9 21
0.8 22
0.7 25
0.6 30
0.4 39
0.5 51
0.3 68

C) Seamless Forged Drums (Reg.235):

I) Forging: The forging shall be made from a solid cast ingot, punched, bored trepanned, or hollow, cast ingots may be used. The resultant wall in the case of the solid cast ingot, or the wall of hollow ingot as cast shall be reduced in thickness by at least one-half in the process of forging.

  1. Chemical Analysis (Reg.236): The steel shall not contain more than 0.050 per cent of sulphur or phosphorus.
  2. Mechanical Tests

Selection of test pieces (Reg.240):

A. All test pieces shall be selected by the Inspecting Officer and shall be tested in his presence, and he shall satisfy himself that the conditions herein prescribed are fulfilled.

B. Tensile Test Pieces: The tensile strength and percentage elongation shall be determined from round test pieces with gauge lengths of 5 do.

C. Tensile Test: The tensile strength and percentage elongation shall be determined from round test pieces with gauge lengths of 5 do.

(I) The tensile strength of different grades of material shall be within the limits specified as below

(i) 37 to 45 kgf/mm2

(ii) 42 to 50 kgf/mm2

(iii) 47 to 56 kgf/mm2

(iv) 52 to 62 kgf/mm2

(II) The upper yield point at room temperature shall be not less than 50% of the specified minimum tensile strength at room temperature.

III) The breaking elongation in percentage shall be not less than as per (N-Rm)/C

Where Rm: Tensile strength at room temperature in kgf/mm²

N:  a quality index of 100 for plate thickness up to 50 mm or 95 for plate thickness over 50mm.

C:  2.2 for only gauge lengths of L=5 do or L=5.65/ √Aο

Where Lο:  gauge length

Aο: Original diameter of the round test piece.

NOTE: C is 1.9 for gauge lengths of 4 √Aο for the test piece.

Bend test pieces (Reg.240 D)

 d) Bend Test (Reg. 240 E)

Bend test pieces shall be of rectangular section 1 inch wide by ¾ inch thick. The edges shall be rounded to a radius of 1/16 inch. The test pieces shall be bent over the thinner section.

The test pieces shall, when cold, be capable of being bent without fracture, through an angle of 180°, the internal radius of the bend is not greater than that specified in the table below :

Blank size
Internal Radius of bend (in inches)
Up to 32
Above 32 and up to 36 ½
Above 36 and up to 38 ¾

Additional tests before rejection (Reg. 241):

Should either a tensile or bend test fail, two further tests of the type which failed may be made on test pieces cut from the same test rings. If the results obtained from these retests are satisfactory, the drum shall be accepted, provided that in other respects it fulfils the conditions of this Chapter. If these re-tests do not give satisfactory results the drum represented may be re-heat-treated together with the remainder of the test rings and presented for further testing. In all cases where final re-tests do not give satisfactory results, the drum represented by the test pieces which fail shall be rejected.

Discard (Reg.242):

Sufficient discard shall be made from the top and bottom of each ingot to ensure soundness in the portion for forging.

Forging (Reg.243):

The forging shall be made from a solid cast ingot, punched, bored or trepanned, or alternatively, hollow, cast ingots may be used. The resultant wall in the case of the solid cast ingot, or the wall of hollow ingot as cast shall be reduced in thickness by at least one-half in the process of forging.

D) General Grey Iron Castings – Grade A (Reg.86) 

A) Process of manufacture:

The castings shall be cast from metal melted or refined in any metallurgical plant other than an iron ore smelting furnace, for the use of which furnace permission in writing must be received from the Inspecting Authority.

B) Chemical Composition.

The composition of the iron as cast shall be left to the discretion of the manufacturer but the maximum percentage of phosphorus or sulphur or both may be specified by the Inspecting Authority if he so desires.

Provision of test bars (Reg.87):

a) The Inspecting Authority shall state at the time of enquiry whether he requires tensile or transverse tests, or both, and he may also specify cast-on bars where the design of the casting and method of running permit.

b) When the test bars are cast separately, they shall be poured at the same time and from the same ladle, or metal as the casting or castings they represent. The number of test bars specified in Regulation 92 shall be applicable to all castings of each melt.

c) When the bars are cast on, the mould for the casting and the mould for the test piece shall be joined together in such a manner that the liquid metal fills both moulds at the same operation.

d) All test bars shall be cast in green sand or dry sand or in loam moulds according as to whether the casting or castings they represent are moulded in green sand, or in loam or dry sand, respectively. The test bars shall not be subjected to any heat treatment after leaving the moulds.

Dimensions of Test Bar (Reg.88)

(a) Transverse Test Bars: The transverse test bars of the diameter specified by the Inspecting Authority according to the main cross-sectional thickness of the casting represented, shall conform to the following dimensions:

Diameter of Test Bar
(in inch)
Limits of Diameter
(in inch)
Overall Length
(in inches)
Main cross-sectional thickness of castings
Represented (in inches)
0.6 +0.045 10 Not exceeding 3/8
0.785 +0.065 15 Over 3/8 and not exceeding ¾
1.2 +0.090 21 Over 3/4 and not exceeding 1 ⅛
1.6 +0.10 21 Over 1 1/8 and not exceeding 1 ⅝
2.1 +0.10 27 Over 1  ⅝

Mechanical test:

Transverse test (Reg.90):

A transverse test bar cast by Regulation 88(a) must when placed on supports set at the distance shown in column 2 of the following table sustain a load applied at the centre of not less than that shown in column 3 and must show before rupturing a deflection not less than that shown in column 4. The supports and the point of application of the load shall be rounded to a radius of not less than ⅛ inch.

Diameter of Test Bar
(in inches)
Distance between supports
(in inches)
Minimum braking Load   Grade A
(in lbs)
Minimum deflection
Grade A
(in inches)
0.6 9 530 0.07
0.875 12 1,185 0.10
1.2 18 1,950 0.15
1.6 18 4,280 0.12
2.1 24 6,660 0.15

Dimensions of Test Bar (Reg.88)

(b) Tensile Test Bars: The tensile test bars of the diameter specified by the Inspecting Authority, according to the main cross-sectional thickness of the casting represented shall conform to the dimensions shown in the following table.  Bars may be tested with either plain or screwed ends.

Mechanical test:

Tensile test (Reg.91).

A tensile test bar machined to the dimensions shown in Regulation 88 (b) and tested with either plain or screwed ends must show a breaking strength of not less than that shown in the following table:

Diameter of Test Bar (in inches)
Minimum Ultimate Tensile Stress(in Tons/in²)
0.6 12.5
0.875 12.0
1.2 11.0
1.6 10.5
2.1 10.0
Screwed end Tensile Specimen

Mechanical test:

Number of Transverse & Tensile Tests (Reg.92):

The number of tests required for each batch of castings shall be in accordance with the following Table:

Group
Weight of Casting
No. of the test specimen.
1 Up to 28 lbs One test for each 30 cwt of castings or part thereof
2 Over 28 lbs to and up to 1 cwt. One test for every 2 tons of castings or part thereof
3 Over 1 cwt to and up to 1 ton One test for every 4 tons of castings or part thereof
4 Over 1 ton to and up to important castings, where mutually agreed upon. One test for every 4 tons of castings or part thereof or for each casting weighing 4 tons or more

Mechanical test:

Additional tests (Reg.93):

 The additional tests to be carried out before a casting or batch of castings is rejected shall be by the following table

Test Piece
Event
Conditions
1st If this fails The second

test piece shall be tested.

2nd If this passes The batch or separate casting represented shall be accepted
If this fails The batch or separate casting represented shall be rejected

Provided always that in the case of failure of both test pieces if either shows obvious defects a third test piece may be taken from a broken casting or a piece may be cut from a usable casting for further testing as follows:

Test Piece
Event
Conditions
3rd If this passes The batch or separate casting represented shall be accepted
If this fails The batch or separate casting represented shall be rejected

E) Tests on Welded Seams (Reg.561):

      Test Plates (Reg 561 a):

Test plates to represent all welded seams shall be attached at each end of each longitudinal seam in tension. These shall be of a size sufficient for the preparation of the test pieces specified. In the case of shell plates up to 16 feet in length the test plate may be located at one end only (see Figure XII/58). Where the shell is formed in two or more rings, the staggered longitudinal seam shall be regarded as a continuous longitudinal seam provided the welding is effected in one reasonably continuous operation and by the same operator or operators. The material for the test plates shall be cut from the respective plate or plates forming the appropriate seam.

Where there are circumferential seams only or where the method of welding the circumferential seams differs from that employed for the longitudinal seams, the method of providing the test plates shall be decided by the Inspecting Authority.

Test Plate Welded Coupon

Tests on Welded Seams (Reg.561):

Test Plates (Reg 561 a):

FIG.XII/58 – Details of Test Plates

Tests for Class I Boilers: (Reg 561 B):

I) Specimens for the following tests shall be selected from the test plate or plates and stamped by the Inspecting Officer for identification (see Figures XII/58 and XII/59):

  1. One tensile test specimen for the welded seam.
  2. One all-weld metal tensile test specimen.
  3. Two bend test specimens.
  4. Two impact test specimens.
  5. One specimen from each test plate for macro and micro examinations.
  6. Additional tests before Rejection.

 

1.) One tensile test specimen for the welded seam: (Reg 561 B):

 

a) Welded Joint:

(i)The dimensions of the reduced tensile section shall be as shown in FIG.XII/60 (A). The width of the reduced section shall be at least 25 mm

(ii) If the thickness of the plate does not exceed 30 millimetres, the thickness of the specimen shall be equal to the plate thickness and the plate surface of the specimen shall be machined to take away the surface irregularities of the plate and the weld.

(iii) If the plate thickness exceeds 30 millimetres, the tensile test shall be carried out on several reduced section specimens, each having a thickness of at least 30 millimetres and width at the effective cross-section of at least 25 millimetres. These specimens shall be taken out of the test piece in such a way that the tensile test covers the whole thickness of the weld joints as shown in FIG.XII/60 (B). The tensile strength shall not be less than the lower limit specified for the plate.

2.) One weld metal tensile test specimen:

The dimensions of the weld metal tensile test specimen shall be those given in FIG.XII/63. The diameter shall be the maximum possible consistent with the cross-section of the weld but in no case more than 20 millimeters, the gauge length shall be equal to five times the diameter. The tensile strength shall not be less than the lower limit specified for the plate. The elongation shall not be less than 20 per cent on a gauge length of four times the square root of the cross-sectional area of the specimen, and the reduction in area not less than 35 per cent.

3.) Two bend test specimens:

Cold Bend Tests:

One specimen shall be tested with the outer surface of the weld in tension, and the other with the inner surface in tension. The specimens shall be rectangular in section and shall be cut out transversely to the weld to have a width not less than one-and-a-half times the thickness of the plates. The sharp corners of the specimens shall be rounded to a radius not exceeding 10% of the thickness of the specimen.

Where the plate thickness does not exceed 1 ¼ inches, the thickness of the specimen shall be equal to the full thickness of the test plate. Where the plate thickness exceeds 1 ¼ inches, the specimen shall in all cases have a thickness of at least 1 ¼ inches. The specimen to be tested with the outer surface of the weld in tension shall be prepared by cutting to waste the metal local to the inner surface of the weld so that the desired specimen thickness is obtained.

The specimen to be tested with the inner surface in tension shall be prepared by cutting to waste the metal local to the outer surface of the weld so that the desired specimen thickness is obtained (see Figure XII/64). Where the thickness of the plate permits, both specimens may be cut from the same piece of plate, the specimens being in the plate one above the other (FIG.XII/64). Each specimen shall be mounted with the weld midway between the supports set apart at a distance not more than 5.2 times the thickness of the specimen and pushed through the supports with a former having a diameter equal to three times the thickness of the specimen.

Cold Bend Tests:

On completion of the test no crack or defect at the outer surface of the specimen shall be greater than 1/16 inch measured across the specimen or 1/8 inch measured along the length of the specimen. Premature failure at corners of the specimen shall not be considered a cause for rejection.

4.) Two Impact Test Specimens: (Reg 561 B):

Impact Test:

The impact test specimens are to be one of the two types and dimensions are one of two types and dimensions are shown in FIG.21A and 21B, the notch shall be contained in the weld metal at approximately the axis of the weld and the axis of the notch is to be perpendicular to the surface of the plate.

The test shall be carried out as follows:

For V-Notch as well as U-Notch specimens at a temperature of 20 ± 2 °C. In the case of a V-notch specimen, the machining of the bottom of the notch shall be done very carefully. The choice between U-Notch and V-Notch specimens shall be at the discretion of the Inspecting Authority.

Two Impact Test Specimens: (Reg 561 B):

Impact Test:

The minimum result to be obtained from the impact test pieces shall be:

Type of notch
Specified minimum requirement
U-Notch specimen 5.50kgfm/cm²
V-Notch 3.46kgfm/cm²

Note: above values are equivalent to 2.76 kgfm divided by sectional area below the notch.

5.) Macro and Micro examination:

Specimen of the full thickness of the plate and not less than 13 mm wide shall be provided from each set of test plates for the purpose of macro and micro examinations.

Micro-etching of a complete cross-section of the weld including the heat-affected zone, should show satisfactory penetration, fusion and absence of significant inclusions or other defects.

Should there be any doubt as to the condition of the weld as shown by macro-etching, the area concerned is to be microscopically examined for defect investigation.

6.) Additional tests before rejection:

If any of the test specimens taken in accordance with this Regulation fail to meet the specified requirements, retests shall be allowed for each specimen that fails as follows: Where any result of the tensile test is not less than 90% of the specified figure, one retest shall be made. Where any result falls below 90%, two retests shall be made.

Where the bend specimen fails to meet the specified requirements, two retests shall be made.

If an impact test fails to meet the specified requirements, two retests shall be taken from the test plate, one on each side of the final specimen and separate from it by not more than 5 millimetres.

If it is found there is insufficient metal to permit the preparation of specimens for retesting from the remainder of the test plate from which the original specimen was taken, the specimen for retest may be cut from the test plate relating to the opposite end of the same longitudinal seam.

should any of the additional tests fail to meet the specified requirements the welded seams represented by these tests shall be rejected.

Tests for Class II Boilers: (Reg 561 C):

I) From each longitudinal seam test pieces shall be selected for the following tests and stamped by the Inspector for identification.

  1. One tensile test specimen for the welded seam.
  2. One bend / One Reverse bend test specimen.
  3. One nick-break test specimen.
  4. Additional tests before Rejection.
FIG. XII/65

The disposition of the specimen shall be in accordance with the sketches in FIG. XII/65. The remainder of each test plate shall be retained for retests if required.

  1. One tensile test specimen for the welded seam:

The dimensions of the test specimen shall be in accordance with the sketch in FIG. XII/60. Specimen 1a, and the specimen shall be cut out transversely to the welded seam. When the capacity of the available testing machine does not allow the full specimen to be tested, two narrower tensile specimens shall be substituted. These specimens shall be the full thickness of the plate at the welded joint and their breadth shall be as great as the testing machine will reasonably allow, provided the effective cross-sectional area of the test piece is not less than 1 ½ square inches (see Figure XII/60 Specimen 1b). The tensile strength of the welded joint specimen shall be not less than the lower limit specified for the plate.

  1. One bend / One Reverse bend test specimen:

One specimen shall be tested with the outer surface of the weld in tension, and the other with the inner surface in tension. The specimens shall be rectangular in section and shall be cut out transversely to the weld so as to have a width not less than one-and-a-half times the thickness of the plate. The specimen to be tested with the outer surface of the weld in tension shall be prepared by cutting to waste the metal local to the inner surface of the weld so that the desired specimen thickness is obtained (see A. Figure XII/64). The specimen to be tested with inner surface in tension shall be prepared by cutting to waste the metal local to the outer surface of the weld so that the desired specimen thickness is obtained (see B. Figure XII/64). Where the thickness of the plate permits both specimens may be cut from the same piece of plate, the specimens being located in the plate one above the other (see C. Figure XII/64).

Each specimen shall be mounted with the weld midway between the supports set apart at not more than 5.2 times the thickness of the specimen and pushed through the supports with a former having a diameter equal to three times the thickness of the specimen. One completion of the test no crack or defect at the outer surface of the specimen shall be greater than 1/16 inch measured across the specimen, or 1/8 inch measured along the length of the specimen. Premature failure at corners of the specimen shall not be considered cause for rejection.

  1. One nick-break test specimen:

This specimen shall have a width not less than one-and-a-half times its thickness and the slot shall be cut in each side of the specimen through the centre of the weld and perpendicular to the outer face of the boiler.

The specimen shall then be broken in the weld and the fracture shall reveal a sound homogeneous weld substantially free from slag inclusions, porosity, and coarse crystallinity.

  1. Additional tests before Rejections:

If any of the test specimens should fail, two retests shall be made, and both shall meet the specified requirements.

F) Periodic Check Test (Reg.98).

The following Periodic Check Tests on each brand of electrodes shall be carried out:-

(a) Periodic check tests consist of a selection of the tests prescribed under Reg.95 and 97 and they shall be repeated at intervals of not more than 6 months to provide evidence that the electrodes currently produced continue to possess the properties recorded in the initial tests.

(1) All-weld tensile test with any two sizes of electrodes within the limits prescribed in clause (a) of Reg.95.

(2) One Tee joint fillet weld hot cracking test as prescribed in clause (b) of Reg.95.

(b) For deep penetration butt-welding electrodes, one transverse tensile test specimen and two transverse bend test specimens shall be prepared and tested as prescribed in Reg.96 and the specimens shall show that a complete penetration has been achieved.

(c) For deep penetration fillet welding electrodes one cruciform fillet weld tensile test shall be taken as prescribed in Regulation 97(1) and the two outer discards from the test pieces shall show a minimum penetration beyond the root as required under Reg.97(2).

F) Periodic Check Test (Reg.98).

The following initial tests on each brand of electrodes shall be carried out:

  1. Parent metal for test plates:

The parent metal used in preparing test pieces and test specimens shall be mild steel of welding quality in the normalised condition (this condition is optional in the case of all-weld metal tests) with ultimate tensile stress of not less than 28 and not more than 32 tons per square inch and an elongation of not less than 20 percent on standard test piece.

  1. All-weld metal test:

The method of preparation of test pieces shall be described in Reg.98 (2) & All-weld test pieces shall be prepared as shown in FIG. 1 (Reg.98 (2)). The test specimen shall not be subjected to any mechanical or thermal treatment other than that required herein.

  1. Impact Test Specimen:

The Izod impact test specimens shall be machined from the weld metal test pieces to the dimensions given in FIG. 2 care is taken that the longitudinal axis of the test piece coincides with the centre line of the weld and mid-thickness of the plate. The temperature of the test specimen at the time of testing shall not be less than 50°F (10°C).

  1. Hot Cracking Test:

A 6 inches x 4 inches x ½ inch plate shall be welded to a second plate 6 inches x 6 inches x ½ inch in the form of a close square Tee joint as shown in FIG.3. The edge of the first plate abutting the surface of the second shall be prepared by machining or grinding. The gaps between parts after tack welding at the ends shall not exceed 0.01 inch.

Two fillet welds 5 inches long and ¼ inch in leg length shall be deposited in the flat position with a single 6 S.W.G. (or 0.2 inch) electrode, using the maximum current of the range recommended by the manufacturer. The test piece shall be so positioned that the slope and the rotation of the weld are zero. The second weld shall be started at that end where the first run was finished after time interval of 4 to 5 seconds. The slag shall be removed after the test piece is cooled in still air to the room temperature. The surfaces of the weld shall be visually examined for cracks.

The second plate shall be slit and the welds broken open as shown in FIG.4. The weld shall not show any evidence of hot cracking as indicated by oxidation or temper colouring of the surface of the fractures.

Hot Cracking Test:

(5) Transverse Tensile & Bend Tests:

The transverse tensile and bend test pieces shall be made as shown in FIG.5 by butt-welding together two ½ inch plates of suitable length and not less than 6 inches in width. The Plate edges shall be prepared to form a single Vee joint the details of which shall be as follows: (see FIG.5(a))

Angle between fusion faces 60° – 70°.

Root face 1/8 inch.

Maximum gap 1/8 inch.

The welding procedure in making out the test pieces shall be according to the position of welding as in Table 1: Welding procedure for preparation of Transverse tensile test & Bend Test pieces. (Reg.98 Table 1)

Transverse Tensile & Bend Tests

(6) Transverse Tensile Tests:

Transverse tensile test specimens shall conform to the dimensions given in Figure 6*. The upper and lower surfaces of the weld shall be filed, ground or machined level with the respective original surfaces of the plates. Where the surfaces of the plates are not level with each other the metal may be cut away to bring them approximately level, provided that the thickness of the plate is not reduced by more than a total of 0.04 inch.

The test specimens shall then be tested for tensile test.

(7) Transverse Bend Tests:

The bend test specimens shall be 1½ inches in width. The upper and lower surfaces of the weld shall be filed, ground or machined level with the respective original surfaces of the plates, with the proviso as in item (6) above. Tool marks should be avoided as they lead to location of stress and may cause premature failure. For this reason, the direction of machining of the surfaces should be along the specimens and transverse to the weld. The sharp corners of test specimens shall be rounded to a radius not exceeding 1/20 inch. The test specimens shall be bent through an angle of 180° over former having a diameter equal to three times the thickness of the specimen, as shown in FIG.7. One test specimen shall be tested with the face of the weld in tension and one with the root of the weld in tension.

(8) Cruciform Fillet Weld Tensile Test:

Normal Penetration Electrodes:

The specimens shall be prepared as shown in Figure 8*. Care shall be taken that the centre lines of two vertical plates are in the same plane. The parent metal used shall be at a temperature between 50° – 100°F (10° – 38°C) immediately before depositing the first run of weld metal. The test specimens shall not be subjected to any mechanical or thermal treatment, other than what is given in this appendix. The plates shall be so placed that each weld shall be deposited in the appropriate welding position, using the procedure specified in Table 2: Welding procedure for preparation of cruciform fillet weld Tensile Test pieces for Normal penetration electrodes. As per Reg. 98 Table 2

Author

Avinash Shankarrao Tambewagh

TCR Engineering Service Pvt. Ltd.

Technical Head

    Leave Your Comment

    Your email address will not be published.*

    three × 3 =