Materials

Carbon Steel (Mild steel)

Standard steel in use, it is the most common of construction material. When properly maintained it will give decades of service, it is easily worked, has good weld-ability and though corrosion is its main problem can be protected with coatings of different types.

Creep Resistant Steels

Commonly known as Chrome-Molly steels, and Sometimes know as high strength low alloy steels (HSLA) the small qualities of Chrome (Typically 1¼ to 2½%) and Molybdenum (Typically ½ to 1%) make this a good steel to use when required to operate in the higher temperature range. But the higher Carbon equivalent means cooling must severely retarded, this calls for pre-heat of 100 C plus. Also only low Hydrogen electrodes or process's can be used.

Corrosion Resistant Steels

There are a large variety of Stainless steels, any steel with more than 11.4 % Chromium will have the title stainless steel, and it depends on the continuous film of Chromium Oxide for its resistance to corrosion. These steels generally have a higher tensile strength than Carbon steel. Stainless steels fall under 1 of 3 groups, Austenitic, Ferritic and Martensitic.

Duplex Steels

Sometimes known as SAF or Austenitic Ferritic stainless steel these are comparatively new, over the last 30 years. They offer a greater resistance to chloride and sulphur corrosion. Common use is in desalination plants and Petrochemical Industry . Duplex steels rely on the micro structure for their superior resistance to corrosion ; the welding controls maintain this structure. Therefore it is essential the weld size, energy input and interpass temperature are controlled. Welding without a consumable is not recommended . The welder must understand a satisfactory radiograph is not a guarantee of a weld that has equal corrosion resistance to the parent material.

Low Temperature Steels

These are steels designed operate at low temperature, nickel is a component used when good impact properties are required at low temperatures. As mentioned above, a good radiograph is not evidence of satisfactory impact properties in the weld. To obtain good impact properties the weld and HAZ must have a find grain structure. Radiographs do not see grain structure and a weld MUST equal the parent material.

Quenched & Tempered Steels