Showing posts with label stainless steels. Show all posts

Thursday, October 22, 2015

Selection of Stainless Steel for Building External Application By yaang.com

Stainless steel is selected for architectural applications, as with most other applications, for their corrosion resistance. This is usually the prime consideration.

Environmental factors such as temperature and humidity need to be taken into account, but the location of the proposed site is the initial consideration. The Nickel Institute's 'Stainless Steel in Architecture, Building and Construction Guidelines for Corrosion Prevention' publication categorizes sites as either: Rural,Urban,Industrial,Marine

Selecting Steel Tubing Materials for Power Generation Heat Exchangers By yaang.com

A power plant engineer has many choices when selecting steel tubing materials for his condenser, feedwater
heater or balance-of-plant application. The wide variety of stainless steel choices available (ASTM lists
over 75 alloys) gives the engineer greater flexibility to choose the best candidate to meet budgetary
constraints and still provide the performance needed for the lifetime of the plant. Unfortunately, upset
conditions can be common in power generation, and these can result in premature unexpected failure of
steel tubing and piping materials.

Cleaning Care And Maintenance of Stainless Steel By yaang.com

Stainless steels are selected for applications where their inherent corrosion resistance, strength and aesthetic appeal are required. However, dependent on the service conditions, stainless steels will stain and discolour due to surface deposits and so cannot be assumed to be completely maintenance-free. In order to achieve maximum corrosion resistance and aesthetic appeal, the surface of the stainless steel must be kept clean. Provided the grade of stainless steel and the surface finish are correctly selected, and cleaning schedules carried out on a regular basis, good performance and long service life will result.

Avoiding Iron and Stainless Steel Contamination By yaang.com

To have their optimum corrosion resistance, stainless steel surfaces must be clean and have an adequate supply of oxygen to maintain their passive surface layer.
Rust staining can occur and has been reported as anything from a slight brown 'bloom' on the surface to severe surface pitting or rusty scour marks on items such as handrails. These effects are usually due to surface contamination from contact with non-stainless steel items.

Post weld cleaning and finishing of stainless steels By yaang.com

Methods for post fabrication and welding clean-up of stainless steels are well documented. One issue is whether the heat tint discolouration in the heat-affected zone of stainless steel welds should be removed.

Duplex Stainless Steel UNS 31803 (F51), UNS 32205 (F60) By yaang

Deriving the Duplex name from the presence of both Austenite and Ferrite in similar proportions, Duplex Stainless Steels combine excellent corrosion resistance with high strength. The typical mechanical properties would be double that of a single phase austenitic grade such as 316, while, for example, offering superior stress corrosion cracking resistance in chloride solutions.

Standard Duplex Stainless Steels typically have a 22% Chromium and 5% Nickel and in the 1960's Langley Alloys developed the first 25% Chromium Duplex alloy, Ferralium 255, and coined the phrase Super Duplex.

Selection of stainless steel for handling nitric acid (HNO3) By yaang.com

Nitric acid is strongly oxidising and promotes the resistance of stainless steel to corrosion.
Generally stainless steel are resistant to corrosion in nitric acid. Nitric acid is used in the chemical passivation of stainless steel.

Commercially concentrated acid is around 65 wt % (sg = 1.40). Higher concentrations obtained by removing water, which can involve the use of sulphuric acid, which has a high affinity for water.

Corrosion resistance of stainless steel

Common Name for Chemical and Selection of Stainless Steel By yaang.com

The 'appropriate grades' notes are taken from the Avesta Sheffield Corrosion Handbook and are shown for general guidance only. Specific grade selection should be rechecked with corrosion tables. A link to the SST ORG web site article that describes where to find the corrosion tables on the Stainless steel tube corrosion can be found in the Related Links section of this article.

The table is referenced by the common name.
Common Chemical Names

Corrosion Resistant Stainless Steel Tube By yaang.com

In our product programme we offer our customers two classes of Stainless Steel grades that have an excellent resistance to corrosion stainless steel. Austenitic-ferritic Duplex stainless steels are characterised by their excellent mechanical qualities, particularly their high stress corrosion cracking resistance. They are especially well-suited for maritime applications and in the chemical industry. Their excellent resistance to corrosion enables them to withstand a chloride medium, particularly under mechanical stress. This makes them superior to austenitic steel in many cases.

Stainless Steels: High Temperature Resistance By yaang.com

Stainless steels are most commonly used for their corrosion resistance. The second most common reason stainless steels are used is for their high temperature properties; stainless steels can be found in applications where high temperature oxidation resistance is necessary, and in other applications where high temperature strength is required. The high chromium content which is so beneficial to the wet corrosion resistance of stainless steels are also highly beneficial to their high temperature strength and resistance to scaling at elevated temperatures.

Stainless Steels Sorting and Identification Tests By yaang.com

Stainless Steels Sorting and identification tests are non-destructive, inexpensive and rapid procedures, usually carried out on different grades of stainless steels. Sorting of product procedures is particularly useful when Stainless Steel bars of Stainless Steel grade 303 and 304 have been accidentally stored together, or when Stainless Steel grade 304 and Stainless Steel 316 sheet offcuts are mixed.

Although these tests are extremely useful, they have certain limitations too. It is difficult to sort one heat from another of the same grade using these tests. For instance, type stainless steel 304 cannot be readily sort from stainless steel 321, stainless steel 316 from stainless steel 316L or stainless steel 304 from stainless steel 304L.

The effects of alloying elements by yaang.com

The different alloying elements have specific effects on the properties of a stainless steel. It is the combined effect of all the alloying elements, heat treatment, and, to some extent, impurities that determine the property profile of a certain steel grade. It should be noted that the effect of the alloying elements differs to some extent between the different types of stainless steel.

Martensitic and precipitation hardening stainless steel grades by yaang.com

Martensitic and precipitation hardening stainless steels are heat treatable and can therefore provide hardness and strength in a wide range. Allowing to workability they are supplied in solution annealed condition. The downstream manufacturer performs final heat treatment to meet the mechanical properties required.

Martensitic grades are basically Fe-Cr alloys with a higher carbon content than ferritics which enables them to harden on cooling in air, oil or water. Depending on grade and intended use, ductility is improved by tempering.

Introduction To Stainless Steels Grades And Families By yaang.com

Stainless steels are iron-based alloys containing a minimum of about 10.5% chromium; this forms a protective self-healing oxide film, which is the reason why this group of steels has their characteristic "stainlessness" or corrosion resistance. The ability of the oxide layer to heal itself means that the steel is corrosion resistant, no matter how much of the surface is removed. This is not the case when carbon or low alloy steels are protected from corrosion by metallic coatings such as zinc or cadmium or by organic coatings such as paint.

Can I use stainless steel at low temperatures or high temperatures?

Can I use stainless steel at low temperatures?

Austenitic stainless steels are extensively used for service down to as low as liquid helium temperature (-269 deg C). This is largely due to the lack of a clearly defined transition from ductile to brittle fracture in impact toughness testing.

How many types of stainless steel are there? by yaang.com

Stainless steel is usually divided into 5 types:

Precipitation hardening (PH) Stainless Steels - These stainless steels can develop very high strength by adding elements such as Copper, Niobium and Aluminium to the stainless steel. With a suitable “aging” heat treatment, very fine particles form in the matrix of the stainless steel which imparts strength.