Series A300 AUSTENITIC STEELS are those that Zamet S.p.A. uses for the metal cable trays currently in production. These steels may be divided into three groups depending on their chemical composition and characteristics:
Cr-Ni Austenitic steels
Characterised by 16-20% Cr and 7-12% Ni with the possible addition of other elements like Sulphur or Selenium that facilitate removal of shavings in machining, or Titanium or Niobium as Carbon stabilisers to prevent the formation of Chromium carbides. They possess mechanical characteristics that are of little importance at ambient temperature but remain significant at very low temperatures, and offer good resistance to corrosion in almost all aggressive environments.
Cr-Ni-Mo Austenitic steels
Their chemical composition is characterised by Cr (16-18%) and Ni (10-18%) and by Mo (2-6%), and it is the presence of this last element that gives these steels particular resistance to corrosion under tension and to corrosion due to pitting. This makes it suitable for use in the presence of strong chemical aggression and also in the presence of solutions containing Chlorine ions. As in the previous case, there are low carbon types and stabilised types with the addition of Titanium, to allow use at temperatures between 450 and 800 °C.
Austenitic steels resistant to high temperatures
Also called “refractory steels”, indicating their characteristics of high mechanical and corrosion resistance which are maintained even at rather high temperatures. Their chemical composition is characterised by higher levels of binding elements than those of the previous types. Chromium is frequently present in percentages higher than 20%. In some cases Nickel may also reach, and even exceed, 20%. Silicon is frequently present in percentages greater than 1% and Carbon is usually present at rather high levels compared to traditional stainless steels.
Depending on the type, they may be used at temperatures higher than 700 °C and up to 1150 °C, and maintain good stainless characteristics and acceptable mechanical characteristics.
| BRAND | UNI (X 5CrNi 18-10) AISI (304) (W.Nr. 1.4301) |
UNI |
UNI (X2CrNiMo17-12-2) AISI (316L) (W.Nr. 1.4404) |
|||
| State of the material | Can be solubilized at 1050° | Can be solubilized at 1075° | Can be solubilized at 1075° | |||
| Mechanical characteristics |
Rm | 540/865 | Rm | 510/660 | Rm | 490/640 |
| Rs | >195 | Rs | >215 | Rs | >275 | |
| A | >40 | A | >45 | A | >45 | |
| HBMax | 200 | HBMax | 190 | HBMax | 180 | |
| (55/70 Kgf/mm2) | (52/67 kgf/mm2) | (50/65 kgf/mm2) | ||||
|
Temperature °C |
|
1150 1100> 5mm water 950 1050 > 5mm air |
1150 1100> 5mm water 950 1050 > 5mm air |
|||
| Characteristics | - Good resistance to corrosion - Good drawability - Good weldability and can be mirror polished |
- High ductility - Good weldability and can be mirror polished High resistance to corrosion thanks to the presence of Molybdenum (in particular to pitting corrosion in environments rich in Chlorine ions). |
Steel with very low levels of Carbon that give it good intercrystalline corrosion resistance even after welding, without the need for subsequent solubilization. Resists point corrosion and corrosion under tension very well. |
|||
| Uses | Used in the manufacturing of cookware, widely used in the chemical,food, dairy and wine-making industries. | Used in highly aggressive environments, i.e.some chemical and naval industries. | Used in welded construction in the chemical and naval industries. | |||
LEGEND
Rm = Resistance to tensile strength (Unit modulus of rupture) in N/mm2 - table UNI 556
Rs = Yield point in N/mm2 - table UNI 556
A = Percentage of elongation after rupture (measured on a useful section equal to five times the diameter of specimen) - table UNI 556
HB = Brinell hardness value - 10 mm diameter sphere - load 29,400 N - time 10-15 s - table UNI 560-75
