Stainless steel

Annealing is a heat treatment process mainly used to increase the ductility and reduce the hardness of the material. This change in hardness and ductility is the result of the reduction of dislocations in the crystal structure of the annealed material. Annealing is usually done after the material has undergone a hardening or cold working process to prevent its brittle failure or to make it easier to handle later.

Annealing is a specific process of heat treatment that alters the properties of metal. While there are many different types of heat treatment, annealing is popular because it increases ductability and reduces hardness.

Heat treatment services for stainless steel and metal alloys
Solution annealing (also referred to as solution treating) is a common heat-treatment process for many different families of metals. Stainless steels, aluminum alloys, nickel-based superalloys, titanium alloys, and some copper-based alloys all may require solution annealing.

Solution heat treatment and annealing are common methods for heat treatment of non-ferrous metals. In my last article, I looked at the heat treatment process for ferrous metals like steel. Today you will learn about the following heat treatment processes, including solution heat treatment and annealing. You will also learn about precipitation hardening, nitriding, cold working, decarburization.

Solution treatment is the most common heat treatment method after stainless steel casting process. The carbide phase is completely or substantially dissolved after the austenitic stainless steel is heated to about 1100 ¡ãC .

To make the structure and composition of stainless steel castings uniform, which is especially important for raw materials, because the casting temperature and cooling rate are not the same, resulting in inconsistent microstructure. With high temperatures, the atomic activity intensifies and the ¦Ò phase dissolves, and its chemical composition tends to be uniform. A uniform single-phase structure is obtained after cooling quickly .

To recover the inherent corrosion resistance of stainless steel castings. The corrosion resistance of stainless steel decreases after investment casting. The corrosion resistance of stainless steel castings recovered to the optimum state after solution treatment.

The solution annealing treatment is required prior age hardening / precipitation hardening. The single phase microstructure created during solution annealing is required prior to age hardening, such that only the precipitates formed during age hardening will be present in the final product. The composition, size, and quantities of those precipitates formed during aging will determine the final product’s hardness, strength, and mechanical properties after aging. It is critical that the structure be properly solution treated prior to aging in order to meet all of these requirements.

The austenitic stainless steel 6Mo was developed on the basis of alloy 904l/1.4539. However, the molybdenum content at 6Mo is increased to 6.5%. 6Mo has excellent general corrosion resistance and improved pitting and crevice corrosion resistance. Resistance to stress corrosion cracking is also improved. It is often referred to as super austenitic stainless steel.

Stainless steel 1.4529 HCR is characterized by a high resistance to localized corrosion phenomena such as crevice corrosion, pitting corrosion or chlorine-induced stress corrosion cracking. It also exhibits excellent mechanical properties and can be used over a wide temperature range. It has excellent elasticity and abrasion resistance in contact with sulfuric or phosphoric acid, or chlorides and salts.

Grade 316 is the standard molybdenum-containing grade, second only to 304 in importance in austenitic stainless steels. Compared to 304, molybdenum imparts better overall corrosion resistance to 316, especially higher resistance to pitting and crevice corrosion in chloride environments.

Stainless Steel 316 is a molybdenum austenitic alloy that is highly resistant to corrosive and chloride environments. Typically, this grade of stainless steel is used in exhaust manifolds, heat exchangers, jet engines and many other applications.

SS 316H Forged Tee is a short pipe with a transverse connection at right angles to the pipe. Mostly used to connect multiple pipes to one pipe with two outlets. Usually, they contain an entry. The SS 316 Forged Cross is used to combine or distribute flow by connecting pipes at cross joints and splitting the flow from each pipe.

SS 316 forged pipe fittings are used to bend flow and connect two pipes to each other at different angles. They must be designed in such a way that they do not cause cavitation and excessive pressure loss.

The steel of UNS S31254 is a super austenitic stainless steel. They are high-end stainless steels designed for impact toughness against chloride crevice corrosion, stress corrosion cracking and pitting corrosion. These are austenites with high nickel and chromium content.

304 is chromium-nickel austenitic stainless steel. Better corrosion resistance than Type 302. High ductility, excellent drawing, forming and spinning properties. Inherently non-magnetic, it becomes slightly magnetic when cold worked. Low carbon content means less precipitation of carbides in the heat affected zone during welding and less susceptibility to intergranular corrosion.

Austenitic stainless steels are susceptible to stress corrosion cracking (SCC) in halide environments. Although type 316 alloys are more resistant to SCC than 18Cr-8 Ni alloys due to their molybdenum content, they are still susceptible. Conditions that produce SCC are: (1) the presence of halide ions (usually chloride ions), (2) residual tensile stress, and (3) temperatures in excess of about 120¡ãF (49¡ãC).

Fully austenitic welds are more prone to cracking during welding. For this reason, Type 316 and Type 316L “matching” filler metals are formulated to cure with a small amount of ferrite in the microstructure to minimize cracking susceptibility.

Unlike other types of steel such as 304 and 306, the 316l stainless steel alloy can be used in a variety of applications where high corrosion resistance is required. For example, specialists in the chemical and pharmaceutical industries use it to make surgical tools and medical implants.

normalize
Normalizing is designed to give steel a uniform and fine-grained structure. This process is used to obtain a predictable microstructure and guarantee of mechanical properties of the steel.

316L stainless steel is an austenitic alloy often referred to as “marine grade stainless steel” because it is used in nearly 90% of marine applications – including filtration. In addition to metals such as iron and nickel, 316L contains 16-18% chromium and 2-3% molybdenum. These elements are important because they improve the alloy’s corrosion resistance; chromium interacts with oxygen in seawater to form a protective layer of chromium oxide, while molybdenum improves the metal’s resistance to pitting corrosion. Additionally, 316L has a lower carbon content (hence the use of “L” in its name), which gives it better protection against corrosion.

Applications and Materials
Normalizing is mainly used for normalizing the structure of carbon steel and low alloy steel after forging, hot rolling or casting. The hardness obtained after normalizing depends on the steel dimensional analysis and the cooling rate used (approximately 100-250 HB).

Grade 1.4404 or 316L is an austenitic stainless steel AISI 316 with very good corrosion resistance due to its high chromium and molybdenum content and low carbon content. Its strength in the hardened state is about 600 MPa for large diameters, but for small sections, the strength can be increased by cold working.

normalized basis
Normalizing removes impurities from steel and increases its strength and hardness. This is achieved by changing the size of the grains to make them more uniform throughout the steel sheet. The steel is first heated to a specific temperature and then cooled by air.

Among many applications, products include instrumentation components for the mechanical, chemical, petroleum, watchmaking, food and beverage, and medical industries.

316L can be used in large diameter annealed condition or small cross section cold worked condition.

Normalizing is a heat treatment process used to make metals more ductile and ductile after a thermal or mechanical hardening process. Normalizing involves heating the material to a high temperature and then exposing it to room temperature air after heating, allowing it to cool to room temperature. This heating and slow cooling alters the metal’s microstructure, reducing its hardness and increasing its ductility.

Annealing between 1050 and 1080¡ãC can be done after forging, followed by rapid quenching, especially to restore corrosion resistance, but there is no heat treatment to harden 316L.

It is important that the material used for any project has the correct mechanical properties for the specific application. Heat treatment processes are often used to alter the mechanical properties of metals, and one of the more common heat treatment processes is normalizing.

For high temperature applications, the high carbon variant 316H stainless steel and the stabilized grade 316Ti stainless steel should be used.

The austenitic structure of 316 stainless steel provides excellent toughness even at low temperatures.