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BS 3504:1962 – Specification for Magnesium activated nickel cathodes of electronic tubes and valves

This standard makes reference to the following British Standards:

BS 1499, Sampling non-ferrous metals.
BS 3073, Nickel and nickel alloys: strip.
BS 3074, Nickel and nickel alloys: tube.

1 Scope

This British Standard specifies the composition, mechanical properties and finish of two grades of magnesium-activated nickel (0.075 and 0.050 per cent magnesium) in the form of tube, strip, tape or wire used in the manufacture of oxide-coated cathodes for electronic tubes and valves.

2 Chemical composition

Magnesium-activated nickel shall be made by melting from virgin electrolytic nickel or carbonyl nickel pellets, or by other approved methods, and the chemical composition shall be within the following limits:

Nickel and cobalt	not less than 99.5 per cent
Cobalt	not more than 0.90 per cent
Iron	not more than 0.10 per cent
Magnesium	a) 0.075 ± 0.015 per cent b) 0.050 ± 0.015 per centª
Manganese	not more than 0.020 per cent
Silicon	not more than 0.010 per cent
Copper	not more than 0.10 per cent
Carbon	not more than 0.04 per cent
Sulphur	not more than 0.005 per cent
Chromium	not more than 0.02 per cent
Titanium	not more than 0.005 per cent
Aluminium	not more than 0.01 per cent
Zinc	not more than 0.005 per cent
Boron	not more than 0.0005 per cent
Calcium	not more than 0.005 per cent

ªTwo grades of nickel are defined by the different magnesium contents.
No other material shall be deliberately introduced.
Methods of sampling for analysis shall be agreed between supplier and user but whenever possible these should be in conformity with BS 1499, “Sampling non-ferrous metals”. The total gas content shall be in the category “low gas content” the actual level to be fixed where necessary by mutual agreement by the supplier and user.
Suitable methods of chemical and spectrographic analysis will be given in a separate British Standard. These methods shall be used in all cases of dispute.

3 Processing and surface finish

Processing shall be controlled to avoid changes in composition, either in the bulk or on the surface of the finished parts. The material shall be uniform in composition and properties.

The surfaces of the tube, strip, tape and wire shall. in the finished condition, be clean and bright and from defects, inclusions and lubricants.

4 Mechanical testing

a) Strip. The properties shall be those agreed between the user and the supplier. The hardness shall be assessed in the manner specified in BS 3073 (Nickel and nickel alloys: strip) or by the spring test described in Appendix A.
b) Tubing and sleeves. The properties shall be tested by an elongation method to be agreed between the user and the supplier.

5 Packaging and marking

Strip, tube, sleeves tape and wire shall be suitably packed to prevent chemical or other contamination or mechanical damage either in transit or during storage. Each package shall be marked with the following:
Name of manufacturer.
Details of product.
Any reference number.
Quantity.
Date.
Cast number of material.
Number and date of this British Standard, BS 3504: 1962.

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