Category: WELDING METALLURGY

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Blue colour when welding Stainless steel

Amarine Antonio

Oxidation of the root bead and adjacent HAZ during welding of stainless steels is commonly called heat-tint. A chromium-rich scale is formed, which is typically not very protective, and the stainless steel surface becomes chromium-depleted: these effects may impair the corrosion resistance of stainless steel welds. Tests performed in various corrosive environments have shown that susceptibility to pitting and crevice corrosion is greater when the surface is heat-tinted, and the colour of the heat-tint is an indicator of the degree of susceptibility to corrosion. For example, purple-blue oxides are generally the most susceptible to corrosion attack. The critical pitting temperature, … Continue reading Blue colour when welding Stainless steel

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Hardness test for Duplex, Super duplex

Amarine Antonio

It is sometimes necessary to meet hardness limits for duplex and super duplex stainless steels, and it is convenient to be able to convert between the Rockwell C (HRC) and Vickers (HV) hardness scales. A conversion exists for carbon steel in ASTM E140 but there is no standard conversion for duplex and super duplex grades and the carbon steel conversion has been shown to be inappropriate for these high alloy steels. A correlation between the two hardness scales for duplex and super duplex grades has been developed at TWI from a compilation of data supplied by various organizations. There was … Continue reading Hardness test for Duplex, Super duplex

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Heat treatment on TMCP steels

Amarine Antonio

In marine, O&G, MOU construction: A large amount of high strength, heavy wall pipe is manufactured using a thermo-mechanically controlled processed (TMCP) steel plate. It is generally accepted that these steels are not designed for subsequent PWHT and may suffer some degradation in their mechanical properties when re-heated above critical temperatures. A number of standards, specifications and technical publications acknowledge the influence of PWHT on mechanical properties of the TMCP plate, but provide limited guidance (depend on supplier quality) on how it will affect the properties. Others refer directly to a detrimental effect, such as BS 4514-1, which states “when PWHT … Continue reading Heat treatment on TMCP steels

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Rimmed Steel, Semi-killed Steel, Fully killed steel

Amarine Antonio

Some low-carbon steels are available in three grades: “rimmed”, “semi-killed”, and “fully-killed”. The terms themselves are derived from the action of the steel when it is poured into an ingot mold after leaving the furnace. In terms of welding, they indicate whether or not there is oxygen in the steel which may cause weld porosity when certain welding processes are used. All carbon steels contain some oxygen. The very nature of the furnaces in which they are made makes this inevitable. It’s what happens to the oxygen when a weld is made that is significant. When a rimmed steel is welded, some … Continue reading Rimmed Steel, Semi-killed Steel, Fully killed steel

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What is OCV Open Circuit Voltage Maximum value

Amarine Antonio

Open Circuit Voltage Open circuit voltage is the voltage at the electrode before striking an arc (with no current being drawn). The open-circuit voltage is much like the higher surge of pressure you might observe when a water hose nozzle is first opened. It is easy to see that the initial pressure from the garden hose was higher than the pressure of the continuous flow of water. The open-circuit voltage is usually between 50 and 80 V. The higher the open-circuit voltage, the easier it is to strike an arc because of the initial higher voltage pressure. Additional question? What is … Continue reading What is OCV Open Circuit Voltage Maximum value

PIPING, WELDING, WELDING METALLURGYLeave a comment

Weld Carbon steel to Stainless steel

Amarine Antonio

It is not uncommon to find fabricating shops that are welding a variety of metals including carbon steel, stainless steel, aluminum, and nickel alloys.  In many cases, some of these materials need to be welded to other types.  Once a very common situation, especially in shipbuilding, oil & gas projects in welding carbon steel to stainless. One of the most frequent questions we receive about this is what filler metal to use.  Welding dissimilar metals can be tricky, especially when you get into the exotic alloys.  Always consult with the manufacturer of the base material or seek the expert advice … Continue reading Weld Carbon steel to Stainless steel

BASIC THEORIES, Metallurgy, WELDING METALLURGY1 Comment

ALLOY ELEMENT AFFECTION IN STEEL PROPERTIES

Amarine Antonio

If you are in steel industry, have you ever notice what all those chemical composition listed on a steel materials test report really mean? You may only know different steel grade has many different chemical composition and elements in different amount. Here in this post, we sort out and list 21 chemical elements and effects on steel properties. 21 Chemical Elements and Effects on Steel Mechanical Properties Steel in general is an alloy of carbon and iron, it does contain many other elements, some of which are retained from the steel making process, other elements are added to produce specific properties. … Continue reading ALLOY ELEMENT AFFECTION IN STEEL PROPERTIES