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Reg. 129-A
FURNACES

 

Welded Joints in Copper Fire Boxes

(i) Scope

All welding of Copper plates shall be carried out by the oxy-acetylene process. The Inspecting Authority may at his discretion also permit the use of propane, butane or other suitable fuel gases.

(ii) Parent Metal Phosphorus deoxidized arsenical copper in the fully annealed condition shall only be used for welded copper fire boxes.

The composition of the copper shall be within the following limits :-

Phosphorus Deoxidized Arsenical Copper –

- Copper (silver being counted as copper) not less than 99.20 per cent.
- Antimony not more than 0.01 per cent.
- Arsenic not more than 0.50 per cent and not less than 0.30 per cent. -
- Bismuth not more than 0.003 per cent.
- Iron not more than 0.01 per cent.
- Lead not more than 0.01 per cent.
- Nickel not more than 0.15 per cent.
- Phosphorus not more than 0.10 per cent and not less than 0.015 per cent
- Selenium not more than 0.02 per cent.
- Tellurium not more than 0.02 per cent.
- Tin not more than 0.01 per cent.

Pieces cut from the parent material after being heated in hydrogen for ½ hour at 800°C and subsequently cooled, must show no edge or surface cracking when subjected to a close bend test as described below.

The test piece AB is bent by steadily applied pressure or a succession of blows at right angles to the length AC and flattened close until A assumes the position indicated by D (see Fig 5A).

TEST PIECE A FOR OXYACETYLENE WELDING OF COPPER

NOMINAL THICKNESS OF TEST PIECE (i) (iI) (iii) (iv)
UPTO BUT NOT INCLUDING 3/8 INCH 3/8 INCH AND THICKER
  INCH INCH INCH INCH
WIDTH W ½ 1 1½ (Max.) 1½ (Max.)
GAUGE LENGTH G
2 4 8 8
PARALLEL LENGTH (MIN.) P 9 9
RADIUS AT SHOULDER (MAX) R 1 1 1 1
APPROX. TOTAL LENGTH 8 12 18 18

WHEN THE WIDTH OF THE MATERIAL TO BE TESTED IS INSUFFICIENT TO PERMIT OF THE PREPARATION OF THE STANDARD TENSILE TEST PIECE, A PIECE OF THE FULL WIDTH OF THE MATERIAL MAY BE USED.
(iii) Filler Rod The filler rod shall be phosphorus deoxidized non-arsenical copper and shall contain not more than 0.15 per cent and not less than 0.04 per cent phosphorus with the optional addition of silicon upto 0.15 per cent and with the optional addition of silver.

The basic copper used for the manufacture of the filler rods shall either be cathode copper or electrolytic tough pitch high conductivity copper conforming to the following chemical compositions respectively.

Chemical Composition of Cathode Copper –

-
Copper (silver being counted as copper) not less than 99.90 per cent.
- Bismuth not more than 0.001 per cent.
- Lead not more than 0.005 per cent.

Total of metallic impurities (excluding silicon, phosphorus and silver) not more than 0.03 per cent.

Chemical Composition of electrolytic tough pitch high conductivity Copper –

- Copper (silver being counted as copper) not less than 99.90 per cent.
- Bismuth not more than 0.001 per cent.
- Lead not more than 0.005 per cent.

Total of all impurities (excluding silicon, phosphorus, oxygen and silver) not more than 0.03 per cent.

Where silicon has been added in the manufacture of the filler rods the amount present in the filler rod shall be stated by the supplier.

Test pieces cut from the filler rod after being heated in Hydrogen for ½ hour at 800°C and subsequently cooled must not show any surface cracking when subjected to a close bend test as described in clause (ii) above.
(iv) Mechanical Test The welding technique shall be tested as follows:-

Three test pieces shall be cut from the welded test specimen and shall be prepared to conform to the dimensions of test piece A. The weld shall be left in the unhammered state and shall be made transverse to the test Plate. The test piece shall be machined, filled or ground to remove excess weld metal and a maximum of 5 per cent of the thickness of the plate from each side.

Each of the three test pieces shall be tested and shall show a tensile strength not less than 9 tons per sq. inch for plates upto and including ½ inch in thickness and not less than 8 tons per sq. inch for plates over ½ inch upto and including 1 inch in thickness.
(v) Number of Tests One test plate not less than 6 inches long shall be welded by each operator (or pair of operators) employed on the work to represent each 15 ft. of welding or part thereof. The test plate shall be welded, using the same form of joint and welding technique as that employed on the work and wherever practicable shall be directly attached to the welded seam or other welded joint it represents.
 
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