PRODUCT STANDARD
Cast iron threaded fittings are defined by the European product standard EN 10242 and by the international standard ISO 49.
The EN 10242 standard has been adopted by many countries of the European Union as a national standard (UNE 19491, DIN 10242, DIN EN 10242, UNI EN 10242 ...) replacing the previous national standards UNE 19491, DIN 2950
BASIC MATERIAL
Cast iron is basically an alloy of iron and carbon in which graphite appears during the solidification processes and subsequent cooling. In this way, the properties of the designated molten iron are obtained in terms of tensile strength and percentage elongation. This material has good impact resistance and adequate ductility at low temperatures as well as interesting weldability properties.
The initial molten iron (white malleable iron with free graphite structure) has a high hardness, making mechanization difficult. For this reason, in order to obtain the final structure with good mechanization, good ductility and adequate mechanical properties, an annealing or malleability heat treatment is carried out, in order to obtain two distinct types of malleable cast iron:
- White heart malleable cast iron : obtained by decarburizing white cast iron at high temperature (approx. 1060oC) in an oxidizing atmosphere for long time cycles. The resulting material undergoes a significant reduction of carbon, even in thin pieces, obtaining a totally ferritic structure without graphite. In very thick pieces, however, there may be graphite in the central areas. Any remaining graphite is in the form of "tempered carbon".
- Black heart malleable cast iron : obtained by annealing in an inert atmosphere (vacuum, inert gas) in different phases, at temperatures of 750-950 C during time sequences lower than those required for white heart cast iron. The material obtained has a uniform microstructure with graphite nodules in the shape of "carbon temper".
As a consequence of the different heat treatment undergone, white heart malleable cast iron has some important advantages compared to black heart, such as:
- Better galvanizing (Fe-Zn alloy) given that the microstructure of the white core is ferritic on the surface (presence of pure iron).
- Better mechanical properties (greater tensile strength for elongations).
- Possibility of obtaining a weldable material after carrying out additional heat treatments.
ATUSA mainly produces White Heart Malleable Iron of EN-GJMW-400-05 quality, on standard 12 mm test tube:
- Minimum tensile strength (Rm): 400 MPa. - Minimum percentage elongation (A 3/4): 5%. - Elastic limit (Rp 0.2): 220 MPa.
- Maximum Brinell hardness: 220 HB.
The malleability achieved for our fittings ensures that no cracks appear after squeezing the cylindrical sections. In this way, after the crushing of:
- Pieces up to 2”: a 10% decrease in diameter is guaranteed without the appearance of cracks.
- Pieces larger than 2”: a reduction of 5% of the diameter is guaranteed without the appearance of cracks.
Note: Some fittings may be supplied in steel as they may exhibit similar properties to malleable iron.
SURFACE FINISHES
The fittings can be supplied with two types of finishes:
- Black finish: for those fittings without post annealing or malleability surface treatment.
- Galvanized finish: after the heat treatment, the fittings are subjected to hot-dip galvanizing by immersion in a molten zinc bath. In this way a continuous surface is obtained, free from grains, burrs and non-metallic residues.
In all cases, the fittings, after mechanization and unitary control of the seal, are subjected to a degreasing process, in order to eliminate the remains of shavings and dirt. They are thus provided with an antioxidant temporal protection layer. This ensures that their final surface is free from polycyclic aromatic hydrocarbons (PAH).
Note: Exceptions are steel fittings which may be given a black or electrogalvanized finish. GALVANIZING
The galvanizing of the fittings is carried out by means of a hot immersion process, fulfilling the requirements of the EN 10242 standard.
The base metal in white heart fittings forms an alloy (Fe-Zn) with zinc in different layers, as shown in the figure below:
Mycography (cross cut of a hot dip galvanized white heart fitting):
LAYER 1: (eta) Pure zinc, external surface
LAYER 2: (zeta) Fe-Zn (content 5.8% – 6.8% in Fe) LAYER 3: (delta) Fe-Zn (content 7 % – 12% in Fe) LAYER 4: (gamma) Fe-Zn (content 21 % – 28% en Fe)
NÚCLEO 5: Base material, internal
In this way, the galvanized instead of being just "a simple layer or external covering" applied to the surface of the fittings, represents the adhesion that forms part of the material. In this way, a very high anti-corrosion protection is provided and the complete functionality of the product in drinking water circuits is guaranteed.
The mass of the alloy is greater than 500 g/m2 and consists of a minimum thickness of 70 microns, extremely high if compared with other protection systems (electro-galvanizing).
The alloy is harder than steel, and with the external zinc (softer) it causes the joint to form a "shock-absorbing" system that is highly resistant to impact and abrasion.
1.3. CERTIFICATIONS
ER-076/2/95
Quality Management System according to UNE-EN ISO- 9001:2008 issued by AENOR.
Implementation and Maintenance for the Production of Malleable Iron Fittings.
Manufacture of Malleable Iron Fittings compliant with the UNE-EN 10242 standard (drawing symbol “A”) in the Salvatierra plant (Spain) issued by AENOR.
Certification as per Malleable Cast Iron Threaded Fittings in accordance with the DIN-EN 10242 standard (drawing symbol “A”) for the use and supply of water and gas issued by DVGW.
Certification for Malleable Cast Iron Threaded Fittings in accordance with DIN-EN 10242 (drawing symbol “A”) for use in water and gas distribution issued by SVGW .
Certification for Malleable Iron Threaded Fittings in accordance with FM Approvals Standard 1920 for use in Fire Fighting installations.
Certification of Conformity in the Production of Galvanized Cast Iron parts according to UNE-EN 10242 EO brand for use in the distribution of fluids and gases according to the provisions of Royal Decree 2531/1985 and the Ministerial Order of 13.01.1999 issued by the Ministry of INDUSTRY.
Sanitary Register for Malleable Cast Iron Threaded Fittings according to Annex IX of Royal Decree 140/2003 issued by the Spanish Ministry of HEALTH and CONSUMER.
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