The RFPL range of disc springs is intended for exacting applications where long fatigue life or repeatability of force/deflection (compression) is important. The stock range offers engineers proven spring designs to an international standard.

Group 1 Disc Springs:-

• Manufactured from high carbon steel strip specification BS 1449 pt1 CS70, equivalant to SAE/AISI 1070, DIN 17222 Ck67.
• Group 1 springs have a material thickness less than 1.25 mm and are deburred so that all edges are rounded.
• Conform to DIN 2093 dimensions and load characteristics.

Group 2 Disc Springs (Machined Edges) :-

• Manufactured from alloy steel DIN 17222 50CrV4, equivalant to EN 132 50 CrV4, SAE 6150
• Group 2 springs have a material thickness from 1.25mm up to and including 6mm and are machined on the inside and outside diameters before deburring to round all Edges.
• Conform to DIN 2093 dimensions and load characteristics.

Group 3 Disc Springs:-

• Manufactured from alloy steel DIN 17222 50CrV4, equivalant to EN 132 50 CrV4, SAE 6150.
• Group 3 springs have a material thickness over 6mm and are manufactured with contact surfaces. This range of Disc Springs are machined on all surfaces.
• Conform to DIN 2093 dimensions and load characteristics.

Standard Range pressed Edges :-

The RFPL standard range offers a reliable cost-effective alternative to the DIN 2093 range and will provide acceptable performance in all but the most orduous Applications.

• Manufactured from either BS 1449 pt1 CS70, or DIN 17222 50CrV4
• Deburred so that all edges are rounded.
• Conform to DIN 2093 dimensions and load characteristics.

Heat Treatment :- All disc springs are austempered to provide the optimum blend of ductility and hardness in the range HRC 42-52

Finish :- The standard finish for RFPL disc springs is commercial phosphate coating. Electro Zinc plating can be supplied at extra cost.

Warning :- RFPL will not be held responsible for any plating related problems if customers carry out their own plating.

Materials :-

STANDARD DISC SPRINGS ARE MANUFACTURED FROM :-

Carbon Spring Steel :-
Specification BS 1449 pt1 CS70 equivalant to SAE/AISI 1070 and DIN 17222 Ck67.

This type of material is used throughout the world in spring components and is widely available. It is capable of being heat treated to give maximum ductility, hardness and toughness.

Chrome Vanadium Steel :-
Specification DIN 1722 50CrV4 EN 132 50 CrV4, SAE 6150. Generally used on the mid to large disc springs where austempering of CS70 is unsatisfactory due to the inconsistency of hardenability of thicker sections. The functional and mechanical properties of austempered 50CrV4 Disc springs are equivalent to those of CS70.

Stainless Steel (To order only) :-
Specification are BS1449 pt2 304 equivalant to ISO A2 and AISA 304 and BS5770 Pt4 301 equivalant to DIN Werkstoff 1.4310 and AISI 301.

These specifications are austenitic stainless which offers excellent all round corrosion resistance in normal atmospheric conditions. Austenitic stainless cannot be heat treated but work hardens during stamping to give adequate mechanical properties for most applications.

Spcial Materials (To order only) :-
Our Technical Sales staff will be pleased to advise you on the suitability and availability of special materials for disc spring applications.

Material Specifications :-

Heat Treatment :-

RFPL disc springs are heat treated by austempering which is considered to be superior to the conventional hardening and tempering process. Austemering offers significant improvements in ductility, hardness and toughness when compared with oil harden and tempering.

Austempering is an isothermal transformation in hot salt to form bainite, whereas the conventional harden and tempering process is a rapid oil quench followed by tempering, to produce tempered martensite.

In quenching from austenite the steel changes to a denser atomic structure, and carbon atoms are released. In oil quench hardening these carbon atoms become trapped and distort the structure leading to high stress and brittleness, which must then be relieved by tempering.

Schematic comparison of time-temperature transformation cycles for conventional hardening and tempering and for austempering.

In austempering, the freed carbon has time to diffuse before transformation occurs, the resulting structure being less stressed and giving superior properties. Bainite has an extremely fine structure. It varies in appearance from a fine needle-like structure visually similar to martensite to a feathery appearance more like tempered martensite.

It is easily mistaken for tempered martensite. RFPL's heat treatment furnaces are fully automatic continuous lines which are strictly controlled and monitored to ensure maximum quality and consistency.

Hardness Conversion Table :- The Table is only an approximate conversion due to the different test methods. The Brinell (hardened ball) and Vickers (diamond pyramid) tests measure the spread of surface indentation under load, whereas the Rockwell (diamond cone) test measures the depth of indentation and is thus a more rapid test. The Vickers test is the most accurate at the hardness levels used on RFPL Disc Springs.

Plating and Surface Finishes :- RFPL Disc Springs are normally supplied in a Phosphated and Dry Oiled Finish, this condition adequately protects the discs from rust in normal borage and transit conditions. This process is carried out by our own in-house phosphate plant.

Additional protection against atmospheric corrosion is possible by a varity of surface finish processes which are mainly zinc based. Zinc is a excellent protective material which has a slow rate of corrosion and also provides additional exectrochemical protection for the steel, even where the coating is scratched or porous. Zinc coating usually resist normal atmospheric attack at a rate of around 5 microns or .0002" per year. The addition of a chromate passivation to prevent the initial oxidation of zinc by the atmosphere will significantly increase this protection.

Most surface tratments are available on RFPL disc springs. A general guide to the treatments most commonly requested is detailed below.

Electroplated Zinc with Clear or Yellow Passivation :- The Protection given is directly related to the thickness of the zinc plate, commercial quality zinc plate has very little thickness and is not recommended unless the plating is mainly required for decorative reasons. We recommend a minimum zinc plate thickness of 5 microns or .0002" together with chromate passivation. All electroplating process will produce hydrogen which may be absorbed and lead to embrittlement of hardened parts. Electroplated disc springs are treated immediately after plating to minimise this risk.

Austemper Range :-

Table of Protection offered :- The table gives an indication of the comparative protection given by various coatings, all the times quoted are to the start of red rusting of the base metal during accelerated salt spray test (this being the standard measurement of the corrosion resistance.)

* At extra cost to RFPL Standard Phosphat.

WARNING :- RFPL will not be held responsible for any plating related problems, if customers carry out their own plating.