Background Utility stainless steels, typified by grades ASTM A240 UNS S41003 and EN 10088-2 1.4003 have been defined within standards since the early 1980’s. These grades were developments of products similar to 3CR12 (a registered trade mark of Columbus Stainless (Pty) Ltd) which was originally developed in the late 1970’s as a low cost grade of stainless steel possessing good fabrication properties. It was intended to provide a superior alternative to carbon steels both coated and uncoated for corrosive/abrasive material handling applications.
Since its introduction they have found wide ranging applications in the coal, concrete, electronic enclosures, agricultural, sugar and road and rail industries.
Grade 1.4003 was originally defined in German standards SEW 400 and DIN 5512 Part 3 as early as 1981. With the harmonization of European standards, grade 1.4003 was included in EN 10088-2 in 1995, and subsequently in EN 10028-7 in 2000. This latter specification covers stainless steel flat products for pressure applications.
For the USA, grade UNS S41003 was included in ASTM A240 in the late 1990’s.
PropertiesChemistrySpec C Mn Si P S Cr Ni N EN 10088-2 1.4003 Min - - - - - 10.50 0.30 - Max 0.030 1.50 1.00 0.040 0.015 12.50 1.00 0.030 EN 10028-7 1.4003 Min - - - - - 10.50 0.30 - Max 0.030 1.50 1.00 0.040 0.015 12.50 1.00 0.030 ASTM A240 UNS S41003 Min 10.50 Max 0.030 1.50 1.00 0.040 0.030 12.50 1.50 0.030
Mechanical PropertiesProperties unless otherwise stated, are transverse at room temperature.
Spec Product Form Tensile Str (MPa) 0.2% Proof Str (MPa) Elong. (%) Impact Energy (J) Hardness Brinell (BHN) EN 10088-2 1.4003 C 450-650 320 min 20 min - - H 450-650 320 min 20 min - - P 450-650 280 min 18 min - - EN 10028-7 1.4003 C 450-650 320 min 20 min 50 min - H 450-650 320 min 20 min 50 min - P 450-650 280 min 18 min 50 min - ASTM A240 UNS S41003 C,.H, P 455 min 275 min 18 min - 223 max
For material conforming to EN specifications:
· C – cold rolled strip, up to an including 6mm thick
· H – hot rolled strip, up to an including 12mm thick
· P – cold rolled plate, up to an including 25mm thick
· For thicknesses above 25mm, the mechanical properties shall be agreed.
Physical PropertiesAt 20°C unless otherwise stated.
Property Value Density 7740 kg/m3 Modulus of elasticity in tension 200 GPa Poisson’s ratio 0.32 Thermal conductivity 100°C 30.0 W/m.K 500°C 40.0 W/m.K Electrical resistivity 678 nΩm Specific thermal capacity 478 J/kg.K Co-efficient of thermal expansion 1-100°C 11.1 μm/mK 0-300°C 11.7 μm/mK 0-500°C 12.3 μm/mK Melting range 1430-1510°C Relative permeability Ferromagnetic
Atmospheric Corrosion ResistanceAtmospheric corrosion will occur when metals are exposed to the environment. Atmospheric corrosion can be classified as dry, damp or wet corrosion. For the first of these, most dry metals corrode very slowly at ambient temperatures. It is the latter two cases, when the corrosive medium of water, in the form of rain or condensation, which, combined with various salts and pollutants, can result in more severe corrosion taking place. Climate/geographical variations are therefore strong factors and the following atmospheres are generally distinguished; marine, industrial, rural and urban.
Utility stainless steels such as grades 1.4003 and UNS S41003 are both nominally 12% chromium stainless steels. Based on this, they will give similar corrosion resistance performance as other 12% chromium grades such as 409 and 3CR12.
It should be noted that utility stainless steels are not recommended for decorative purposes. In aggressive environments they will tend to form a light surface rust colored patina. However, this is superficial and does not affect the mechanical properties of the steel.
Should aesthetic qualities be of prime importance utility stainless steels can be painted with a number of paint systems.
Corrosion/AbrasionThe simultaneous abrasion and corrosion of a metal can result in significant material loss which is exacerbated through the synergistic effect. This is the case even when costly coatings are applied.
In wet or damp conditions where abrasion occurs, utility stainless steels have demonstrated excellent performance by resisting corrosive attack and so maintaining better flow and slideability characteristics compared to non- or low-alloyed steels, including abrasion resistant grades.
These steels have practically shown their advantages in a number of applications. For materials handling applications, the superior slideability can be exploited, not only to restore lost capabilities in existing plant, but also to save costs in new plant. Similarly, because of the improved slideability, they have found use in the storage, handling and transportation of coal, allowing rapid throughput of material, lower discharge angles and less problems with hang-up.
In addition, corrosion resistance allows bins that have been out of service for a length of time to be brought back into immediate mass flow service.
In general it can be shown that in dry abrasion, utility stainless steels are no better than mild steel, but in a real industrial situation where moisture is also present they have shown to be vastly superior to carbon and low alloy steels. When cost per unit volume loss is also taken into consideration, it can be shown that they are superior to all types of steel that have been tested.
FabricationCutting· A number of processes both mechanical and thermal can be used.
· Mechanical methods include guillotining, sawing, blanking and piercing.
· Thermal cutting processes most commonly used are plasma and laser cutting.
· Other thermal and abrasive cutting methods may be used but can leave a rough and uneven cut edge, which requires dressing before welding or further use.
· Oxy acetylene cutting is not suitable for cutting stainless steels.
Forming· Utility stainless steel can usually be formed on the same equipment, with the same tooling as for carbon steel.
· Recommended inner bend radius should be sought from the specific mill supplying material, as there are slight variations in advice. Reverse bending is not recommended. Bending should be carried out transverse to the rolling direction.
· Stainless steels should not be contaminated with any mild or low alloy steel during handling, storage or fabrication.
MachiningUtility stainless steels have machining characteristics similar to AISI 430 (i.e. a machinability rating of 60 compared to mild steel of 100). The reduced extent of work hardening compared to austenitic stainless steels eliminates the need for special cutting tools and lubricants. Slow speeds and heavy feed rates with sufficient emulsion lubricant will help prevent machining problems.
WeldabilityWelding processes that can be successfully used include: SMAW, GTAW, GMAW,FCAW, PAW, laser, resistance spot and seam welding.
It is recommend to use ER309L for GTAW and GMAW and E309L for SMAW
Coating and PaintingUtility stainless steels may, under mildly corrosive conditions, develop a uniform rust colored patina. This does not affect the structural integrity of the steel, but for aesthetic reasons, painting may be required. Normal preparation is necessary, such as ensuring a clean, grease and contamination free surface. A primer coat is recommended for cold rolled material due to its smoother surface, but hot rolled, pickled steel may be suitably painted in a single coat.
ApplicationsUtility grades of stainless steels such as 1.4003 and S41003 have been used in a wide range of industries including:
· Mining
· Power Generation
· Sugar
· Bulk Handling
· Water
· Transport
· Telecommunications/Electrical
· Engineering
· Rail
· Agricultural
Typical applications are-
· Bulk wet materials handling
· Vehicle frame/chassis
· Rail car hoppers
· Sweeper/gritter vehicles
· Conveyors, chutes, screens, troughs
· Bunkers, hoppers
· Tanks and containers
· Chimneys, ducting
· Enclosures, cabinets
· Walkways, stairs, railings