Stainless steel

Alloy 309 (UNS S30900) is an austenitic stainless steel developed for high temperature corrosion resistant applications. The alloy resists oxidation up to 1900¡ãF (1038¡ãC) under non-cycling conditions. Frequent thermal cycling reduces oxidation resistance to approximately 1850¡ãF (1010¡ãC).

Stainless steel 304 and stainless steel 304L are also known as 1.4301 and 1.4307 respectively. Type 304 is the most versatile and versatile stainless steel. It is still sometimes referred to by its old name, 18/8, which derives from the nominal composition Type 304 being 18% chromium and 8% nickel.

Type 316/316L is a chromium-nickel austenitic stainless steel containing molybdenum. The addition of molybdenum improves corrosion resistance compared to 304/304L in halide environments and in reducing acids such as sulfuric and phosphoric acid. Type 316L can be dual certified as 316 when the composition meets the carbon lower limit of 316L and the slightly higher strength level of 316.

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.

Annealing is a heat treatment process which alters the microstructure of a material to change its mechanical or electrical properties. Typically, in steels, annealing is used to reduce hardness, increase ductility and help eliminate internal stresses.

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 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.

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

Stainless grade 316Ti contains a small amount of titanium. The titanium content is usually only around 0.5%. Titanium atoms stabilize the structure of 316 at temperatures in excess of 800¡ãC.

While 300 series stainless steels are very popular, they are not universally suitable for all process piping applications. For example, even though they are corrosion resistant, 300 series formulations do not perform well in the presence of chlorides. In these cases, steels with much higher alloy contents such as molybdenum, chromium and nickel are preferred.

Type 316 is much more resistant to sulfuric acid solutions than any other chromium-nickel type. Type 316 is resistant to acid concentrations up to 5% at temperatures up to 120¡ãF (49¡ãC). This type has excellent resistance to higher concentrations at temperatures below 100¡ã F (38¡ã C).

In general, the Type 316 grade can be considered equally good in a given environment. A notable exception is intergranular corrosion in the heat-affected zone on welds and susceptible alloys in sufficiently corrosive environments. In such media, Type 316L is more suitable for welding conditions than Type 316 because the low carbon content increases resistance to intergranular corrosion.

Type 316 alloy is considered suitable for some marine environment applications, such as ship rails and hardware, and the exterior walls of buildings near the ocean that are exposed to salt spray. Type 316 stainless steel shows no evidence of corrosion in the 100-hour, 5% salt spray (ASTM-B-117) test.

Sustained or prolonged exposure of Type 316L to 800-1500¡ãF (427-816¡ãC) may be harmful. In addition, stress relief between 100-1500¡ãF (593-816¡ãC) may cause this Type of slight embrittlement.

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.