1. Overview
NS112 is a fully austenitic low-carbon nickel-iron-chromium alloy in the same series as Incoloy 800. The cobalt content in the alloy can be strictly controlled. Below 0.01%. NS112 is resistant to many corrosive media. Its high nickel content makes it very resistant to stress corrosion cracking in aqueous corrosive conditions. The high chromium content gives it better resistance to pitting and crevice corrosion cracking. This alloy has good corrosion resistance to nitric acid and organic acids, but has limited corrosion resistance in sulfuric acid and hydrochloric acid. In addition to the possibility of pitting corrosion in halides, it has good corrosion resistance in oxidizing and non-oxidizing salts. It also has good corrosion resistance in water, steam and mixtures of steam, air and carbon dioxide. Used in nitric acid condensers - resistant to nitric acid corrosion, steam heating tubes - very good mechanical properties, heating element tubes - very good mechanical properties, etc. For applications in environments up to 500°C, the alloy is supplied in the annealed condition. ?
NS112 physical properties:
Density: ρ=8.0g/cm3
Melting temperature range: 1350～1400℃
NS112 Mechanical properties: (minimum value of mechanical properties detected at 20°C)
The properties listed in the table below are applicable to the specified specifications of NS112 alloy products after softening annealing (stabilization annealing). Special properties of non-standard size materials can be provided as required for specific applications.
Room temperature mechanical properties (minimum)
NS112 has the following properties:
●Excellent corrosion resistance in extremely high temperature aqueous media up to 500°C Properties
●Good stress corrosion resistance
●Good processability
NS112 grade and standard:
NS112ISO V-notch impact test:
Room temperature average: axial>=150J/cm2
radial>=100J/cm2
Time-temperature-sensitive Chemical curve
NS112 conditional stress value:
The high conditional stress value reaching 90% yield strength can be used in applications that allow a slightly larger deformation. These stresses cause permanent stresses that can lead to dimensional changes and are not recommended for flange and gasket connections.
NS112 metallographic structure:
NS112 alloy has a stable face-centered cubic structure. The chemical composition and appropriate heat treatment ensure that the corrosion resistance is not compromised by sensitization.
NS112 Corrosion Resistance:
NS112 is a general engineering alloy that is resistant to acid and alkali metal corrosion in both oxidizing and reducing environments.
The high nickel content gives the alloy effective resistance to stress corrosion cracking.
It has good corrosion resistance in various media, such as sulfuric acid, phosphoric acid, nitric acid and organic acids, alkali metals such as sodium hydroxide, potassium hydroxide and hydrochloric acid solution.
NS112's higher comprehensive performance is reflected in nuclear combustion dissolvers with various corrosive media, such as sulfuric acid, nitric acid and sodium hydroxide, all processed in the same equipment.
NS112 application scope:
NS112 is widely used in various industrial fields where the operating temperature does not exceed 550°C.
Typical applications are:
● Heating tubes, containers, baskets and chains used in sulfuric acid pickling factories.
● Seawater cooling heat exchangers, marine product pipeline systems, acid gas environment pipelines.
● Heat exchangers, evaporators, washers, dipping tubes, etc. in phosphoric acid production.
● Air heat exchangers in petroleum refining
● Food engineering
● Chemical processes
● Flame retardant for high-pressure oxygen applications alloy.
NS112 processing and heat treatment
NS112 is suitable for hot processing and cold processing, but due to its high strength, high-power processing equipment is required.
NS112 is suitable for welding with various convenient welding methods.
NS112 heating:
1. The workpiece should always be kept clean before and during heat treatment.
2. Do not come into contact with sulfur, phosphorus, lead and other low-melting point metals during the heat treatment process, otherwise the performance of the material will be damaged. Pay attention to remove marking paint, temperature indicating paint, colored crayons, lubricating oil, etc. Fuel and other dirt.
3. The lower the sulfur content in the fuel, the better. The sulfur content in natural gas should be less than 0.1%, and the sulfur content in heavy oil should be less than 0.5%. ?
4. Considering the need for temperature control and maintenance of cleanliness, it is best to perform heat treatment in a vacuum furnace or gas protection furnace.
5. It can also be heated in a box furnace or a gas furnace, but the furnace gas must be clean and neutral to slightly oxidizing, and the fluctuation of the furnace gas between oxidizing and reducing properties should be avoided. , the heating flame cannot burn directly to the workpiece.
NS112 thermal processing:
1. The thermal processing temperature range of NS112 is 1200℃～900℃, and the cooling method is water quenching or cooling as quickly as possible between 760℃～540℃.
Hot bending should be carried out between 1150℃-1000℃.
2. In order to obtain the best corrosion resistance and creep resistance, annealing treatment is required after hot processing.
3. The material can be directly fed into a furnace that has been heated to 1200°C. The heat preservation time of the material is 60 minutes per 100mm thickness. After being kept warm for a sufficient time, it is quickly released from the oven and thermally processed within the specified temperature range. When the material temperature drops below the thermal processing temperature, it needs to be reheated.
NS112 cold working:
1. The work hardening rate of NS112 is greater than that of austenitic stainless steel, so processing equipment needs to be selected. Cold worked materials should be in an annealed heat treatment state, and intermediate annealing should be performed during cold working.
2. If the amount of cold working is greater than 10%, the workpiece needs to be softened and annealed before use.
NS112 heat treatment:
1. The softening annealing treatment temperature range of NS112 is 920°C ~ 980°C, and the optimal treatment temperature is 950°C.
2. In order to obtain the best corrosion resistance, water quenching is used as the cooling method, and rapid air cooling can also be used for materials with a thickness less than 1.5mm. ?
3. During the heat treatment process, the aforementioned matters that must be kept clean during the heating process must be followed.
NS112 scale removal and pickling:
1. The surface oxide of NS112 and the adhesion of the welding slag around the weld are stronger than that of stainless steel, both mechanical and chemical methods can be used, but when choosing mechanical methods, avoid methods that can produce metal contamination or surface deformation.
2. Before pickling with HNO3/HF mixed acid, the oxide film must be carefully polished or salt bath pretreated to break up the oxide film.
Machining of NS112:
NS112 must be machined after annealing heat treatment. Due to the work hardening of the material, it is appropriate to use a lower cutting speed than when processing low-alloy standard austenitic stainless steel. Only by machining with heavy feed can the machine go under the cold work hardened surface.
NS112 welding:
NS112 is suitable for welding using any traditional welding process, such as tungsten electrode inert gas shielded welding, plasma arc welding, manual sub-arc welding, metal electrode inert gas shielded welding, Melting extremely inert gas shielded welding, shielded gas arc welding, etc.
The welding of NS112 must be carried out in the annealed state, and stains, dust and various marks must be cleaned away.
Use low heat input, and the interlayer temperature does not exceed 150°C.
No pre- or post-weld heat treatment required.
NS112 cleaning:
Remove oxide scale, oil stains and various marks and marks, and use acetone to clean the base metal and filler alloy (such as welding rod) in the welding area. Be careful not to use three Vinyl chloride TRI, perchlorethylene PER and tetrachloride TETRA.
NS112 edge preparation:
It is best to use machining, such as turning, milling, planing, or plasma cutting. If the latter is used, the cutting edge (welding surface) must be The grind is clean and flat, allowing for fine grinding without overheating. The approximately 25mm wide area of ??the base metal on both sides of the weld should be ground until bright metal is exposed.
NS112 bevel angle:
Compared with carbon steel, the physical performance characteristics of nickel-based alloys and special stainless steels are mainly low thermal conductivity and high expansion coefficient. These characteristics All must be considered when preparing the welding groove, including widening the bottom gap (1~3mm). At the same time, due to the viscosity of the molten metal, a larger groove angle (60~70°) should be used during butt welding. Counteract material shrinkage.
NS112 arc starting:
Arc cannot be started on the surface of the workpiece, but should be started on the welding surface to prevent corrosion caused by the arc starting point.
NS112 welding process:
NS112 is suitable for welding with the same material or other metals using any traditional welding process, such as tungsten electrode inert gas shielded welding, plasma arc welding, and manual sub-arc welding. , metal extremely inert gas shielded welding, melting extremely inert gas shielded welding, among which pulse arc welding is the preferred solution. When using manual arc welding, it is recommended to use a shielding gas mixed with (Ar+He+H2+CO2) multiple components.
The welding of NS112 must be carried out in the annealed state, and stains, dust and various marks must be cleaned with a stainless steel wire brush. When welding the root of the weld, in order to obtain the best quality of the root weld, the operation must be very careful (argon 99.99) so that no oxides are produced in the weld after the root welding is completed. The color produced in the welding heat affected zone should be brushed away with a stainless steel brush before the weld area is cooled.
Recommended welding materials for NS112:
GTAW/GMAW Nicrofer S 7020
W.-Nr.2.4806
SG-NiCr20Nb
AWS A 5.14 ER NiCr-3
BS 2901-NA 35
SMAW
W.-Nr.2.4648
EL-NiCr19Nb
AWS A 5.11 EniCrFe-3
NS112 welding parameters and effects (heat input):
The welding operation should be in the heat It is carried out under the low heat input specified in the input table, using stacked bead welding technology, the interlayer temperature does not exceed 120°C, and the welding specifications must be followed.
The heat input Q is calculated according to the following formula:
U=arc voltage, volts
I=welding current, amperes
V=Welding speed, cm/min.
NS112 post-weld treatment (pickling, brushing to remove oxides and heat treatment): Stainless steel wire brushing should be used to remove oxides immediately after welding, that is to say, before the metal has developed a welding color. Brush, so you can get the desired surface quality without the need for pickling. If there are no special requirements or regulations, pickling is usually the last process in welding. Please refer to the section on descaling and pickling. No heat treatment is required before or after welding.