Installation instructions

Welding instruction

1. Equipment
2. General welding conditions
3. Filler metal
4. Preparation of joints
5. Cleaning
6. Internal protection
7. Tacking
8. Welding

Bending instruction

1. Types of bending
2. Bending by means of a rotary bending machine
3. Stretch bending
4. Roll extrusion forming
5. Compression bending
6. Roll bending
7. Heat treatment after forming

Welding instruction

Providing that certain precautions are taken, NITON 10 and NITON 30 welding does not present major difficulty. Inert shielded are processes (TIG) are particularly appropriate to the welding of these alloys.
The following procedure has been established for NITON/NITON assemblies in tubes and accessories with a thickness of 1.5 to 10 mm welded by the TIG process.

1. Equipment

To weld under proper working conditions, the welding set should be equiped with a pre-gas, pre-arc and arc fall system.

2. General welding conditions

• Direct current with direct polarity (the electrode is connected to the negative pole).
• Electrode : it is made of thorium tungsten or zirconium tungsten.
  Its state of cleanliness is most important, influencing the quality of the weld and the stability of the arc.
  The diameter of the electrode is dependent on the welding current :

Diameter mm	Current A
1	25/70
1.6	60/150
2	100/200
3	200/300

To achieve a perfectly stable arc and obtain a maximum heat concentration it is advisable to work the electrode as close as possible to the maximum supportable current.

• Protective gas : neutral argon protection is generally sufficient. Torch flow 8 to 12 l/mn.

3. Filler metal

The filler metal generally has a grade identical to that of the parent metal :
Cu Ni10 Fe (for NITON 10) - Doga UTP A 389 is recommended.
Cu Ni30 Fe (for NITON 30) - Doga UTP A 387 is recommended.
The parent metal filler rods should always be perfectly degreased.

4. Preparation of joints

In general, all types of joints can be used.
For tubes and accessories with a thickness less than or equal to 2 mm, it is not necessary to make a chamfer but it is desirable to break the internal square corner to favour penetration.
For tubes and accessories with a thickness greater than 2 mm, a chamfer of around 30 degrees to 40 degrees is recommended.

5. Cleaning

This is a most important operation : welding can only be carried out under correct conditions if the parts to be joined together are perfectly clean and free from grease and oxidation.
Cleaning can be carried out by mechanical or chemical means.

6. Internal protection

To avoid oxidation and fluxing on the inside of the joint, it is necessary to ensure internal protection by circulation of neutral gas.

7. Tacking

The parts to be joined together are placed edge to edge and tacked. The spot tacks should be carried out with a lower current than for spot welds. Care should be taken to let the spot tack cool under the jet of argon after breaking of the arc.

8. Welding

• Welding position
  NITON can be welded in any position. Welding to a celling is the most delicate. In this case, the pulsed are gives the best results. The pulse times remain at the operator's initiative.
• Welding conditions

Thickness mm	Current A	Number of passes*	Rod diameter mm	Argon flow L/mm
1	70/60	1	1.5	6
1.5	80/65	1	1.5	6
2	90/80	1	1.5	7
2.5	100/90	2	1.5/2	8
3	125/100	2	1.5/2	8
4	150/125	2	1.5/2	8
5	150/125	3	1.5/2.5	8

* The number of passes is important : it is necessary to folow this data in order to avoid local overheating which risks causing collapse of the bead.

Bending instruction

The excellent cold properties of these alloys enable them to be formed without difficulty provided that certain elementary precautions inherent in the cold deforming process are taken.
As the achievement of a bend becomes more delicate the thinner the tube and the shorter the radius of bending, it will be necessary to adapt the tooling to the difficulties of bending and to the character of the materials to be formed. We give hereafter a few general rules regarding the bending of NITON 10 and NITON 30.

1. Types of bending

There are 5 types of bending :

• Rotary bending : by winding the tube over a turning former, this involves industrial bending machines such as "Curving", "Bonnamy", "Perfect"...
• Stretch bending : on a bending machine of the "Mingori type" for small diameters.
• Roll extrusion forming : by internal rolling of the tube, "Coupe-Hugot machine".
• Compression bending : using a press.
• Roll bending : using 3 rollers.

2. Bending by means of a rotary bending machine

In general, for this type of machine the tooling is composed of a mandrel, a bending former, a clamping shoe (or jaws), a mobile slide guide and sometimes a wiper die.

• Mandrel : the job of the mandrel is to support the tube internally in the course of deformation so as to avoid flattening of the outer surface and folding of the inner surface by obliging the metal to elongate itself. For the alloys in question, the mandrels are made from treated steel. These parts are carefully machined and are given a final polish to avoid marking of the internal wall of the tubes.
• Bending form and slide guide : made from the same materials as the mandrels, thse parts must likewise have an even surface. Here again polishing of the surfaces in contact with the tubes (grooves) is desirable. The "bending form" groove will be sufficiently deep so as to give a slightly protruding lip (1 mm approximately). Sharp edges should be eliminated to avoid pinching of the tube.
• Wiper dies : for short bending radii and thin wall tubes, the use of a wiper die is recommended. it will be made preferably from a friction alloy.
• Tool settings : the clearance between the mandrel and the inside of the tube must be a few tenths of a millimeter (3/10 mm approximately).

Setting of the mandrel lead in relation to the former axis (bending axis) must be performed accurately. It may lie between -15 and +25 mm for tube diameters 38 to 140 mm.
It must be established that the clamping shoe (or jaws) axis is parallel to the mandrels axis. If this condition is not met, clamping will be inefficient ; the tube may slip during forming and bring about defects such as flattening of the outer surface or "folding" of the inner surface.

In the same way, a check should be made that the longitudinal axis of the slide guide (or the guiding counter-former) is in the same plane as the former axis.
Besides these precautions, work should be carried out slowly, avoiding any jolting which may have the effect of marking the tube.

• Lubrication is most important : to avoid seizure, the mandrel and the interior of the tube, and the wiper die must perfectly lubricated.
• Speed : the speed during bending is not an essential element for making the operation successfull.

3. Stretch bending

This process may be called upon when small batches or special bending is involved which does not justify the purchase of tooling required for forming.
In the absence of a mandrel, it is essential to fill the tube with pitch or sand to avoid flattening and ovalization of the tube.

4. Roll extrusion forming

This type of forming is reserved for marge diameter tubes necessitating large bending radii.

5. Compression bending

The method is mainly used for limited bendings on large diameter tubes.

6. Roll bending

This process is adopted for making large radii bending on small or medium diameter tubes.

7. Heat treatment after forming

After degreading the bends, annealing at 600 degrees C is necessary when the parts have to be welded to other components. To avoid pickling, this treatment can be carried out in a protective atmosphere.