CARBON STEEL

Carbon steel is steel in which the main interstitial alloying constituent is carbon in the range of 0.12–2.0%. The American Iron and Steel Institute (AISI) defines carbon steel as the following: "Steel is considered to be carbon steel when no minimum content is specified or required for chromium, cobalt, molybdenum, nickel, niobium, titanium, tungsten, vanadium or zirconium, or any other element to be added to obtain a desired alloying effect; when the specified minimum for copper does not exceed 0.40 percent; or when the maximum content specified for any of the following elements does not exceed the percentages noted: manganese 1.65, silicon 0.60, copper 0.60."^[1]

The term "carbon steel" may also be used in reference to steel which is not stainless steel; in this use carbon steel may include alloy steels.

As the carbon percentage content rises, steel has the ability to become har

der and stronger through heat treating, however it becomes less ductile. Regardless of the heat treatment, a higher carbon content reduces weldability. In carbon steels, the higher carbon content lowers the melting point.^[2]

Carbon steel is broken down into four classes based on carbon content:

Mild and low-carbon steel

Mild steel, also called plain-carbon steel, is the most common form of steel because its price is relatively low while it provides material properties that are acceptable for many applications, more so than iron. Low-carbon steel contains approximately 0.05–0.3% carbon^[1] and mild steel contains 0.3–0.6%^[1] carbon; making it malleable and ductile. Mild steel has a relatively low tensile strength, but it is cheap and malleable; surface hardness can be increased through carburizing.^[3]

It is often used when large quantities of steel are needed, for example as structural steel. The density of mild steel is approximately 7.85 g/cm³ (7850 kg/m³ or 0.284 lb/in³)^[4] and the Young's modulus is 210 GPa (30,000,000 psi).^[5]

Low-carbon steels suffer from yield-point runout where the material has two yield points. The first yield point (or upper yield point) is higher than the second and the yield drops dramatically after the upper yield point. If a low-carbon steel is only stressed to some point between the upper and lower yield point then the surface may develop Lüder bands.^[6] Low-carbon steels contain less carbon than other steels and are easier to cold-form, making them easier to handle.^[7]

Higher carbon steels

Carbon steels which can successfully undergo heat-treatment have a carbon content in the range of 0.30–1.70% by weight. Trace impurities of various other elements can have a significant effect on the quality of the resulting steel. Trace amounts of sulfur in particular make the steel red-short, that is, brittle and crumbly at working temperatures. Low-alloy carbon steel, such as A36 grade, contains about 0.05% sulfur and melts around 1426–1538 °C (2599–2800 °F).^[8] Manganese is often added to improve the hardenability of low-carbon steels. These additions turn the material into a low-alloy steel by some definitions, but AISI's definition of carbon steel allows up to 1.65% manganese by weight.

Medium carbon steel

Approximately 0.30–0.59% carbon content.^[1] Balances ductility and strength and has good wear resistance; used for large parts, forging and automotive components.^[9][10]

High-carbon steel

Approximately 0.6–0.99% carbon content.^[1] Very strong, used for springs and high-strength wires.^[11]

Ultra-high-carbon steel

Approximately 1.0–2.0% carbon content.^[1] Steels that can be tempered to great hardness. Used for special purposes like (non-industrial-purpose) knives, axles or punches. Most steels with more than 1.2% carbon content are made using powder metallurgy. Note that steel with a carbon content above 2.0% is considered cast iron.

Q: I have a new fabrication project for furnace racks made with 304H stainless steel and the specifications say to weld it with an E308H electrode.  However, I already have some E308/E308L stick electrodes and want to know if I can use those instead?  What is the difference between 308, 308L and 308H?  I actually have two brands of E308 / E308L electrodes, one type has a “-16” after the 308 numbers and the other has a “-17”.  What do those mean?

A:  First, note that an American Welding Society (AWS) E308 classification electrode is meant for welding Austenitic types of stainless steel.  Therefore, this article will only address this type.  While Austenitic stainless steels are very common, there are also Ferritic, Martensitic, Duplex and Precipitation Hardening types of stainless steels.

The answer to your first question is no, an E308 / E308L stainless steel electrode is not meant for use on an AISI type 304H base metal.  You do need to use an E308H electrode.  The reason why will be explained shortly.  Regarding your second question, “308” is a particular type of stainless steel.  It is typically used to make welding electrodes and used to join common types of austenitic stainless steels, such as 301, 302, 304 and 305.  The “H” and “L” designators indicate a specific composition of the electrode.  More specifically, they refer to the carbon percentage in the electrode, with “H” electrodes in the high end and “L” electrodes in the low end of the electrode’s carbon range.  An E308 type stainless steel electrode must have a maximum of 0.08% by weight of carbon (C).  An E308H electrode however, must have at least 0.04%C, up to a maximum of 0.08% C.  Carbon content in the range of 0.04 – 0.08% provides higher tensile and creep strengths at elevated temperatures.  They are primarily used in industrial equipment at high service temperatures (sometimes over 2,000°F (1,093°C).  Therefore, an E308H electrode would be the appropriate choice for your furnace rack project.  Conversely, an E308L electrode can have no more than 0.04% C.  The “L” type electrodes are sometimes referred to as “ELC” (extra low carbon) types.  The lower carbon content helps minimize the damaging effects to the corrosion resistance of the heat affected zone (i.e. sensitization) caused by intergranular carbide precipitation.  They are most often used for weldments that operate in severe corrosive conditions at temperatures under 800°F (427°C) 

Note that a particular electrode could, and often is, dual classified.  It could be classified as E308 / E308L or as E308 / E308H.  The 308 grade has a broader carbon range, so if a particular electrode’s carbon content falls within the tighter L or H carbon level requirements, it also meets the more general 308 requirement.  However, you could never have an E308L / E308H classified electrode, as one electrode could never have a carbon content that fits within both the low and high end of the carbon range.  Note also that the “H” and “L” carbon designators can apply to other types of austenitic stainless steels besides E308.  Some examples include E309H, E309L, E310H, E316H, E316L, etc.

Your third question refers to the type of coatings that are available for stainless steel shielded metal arc (stick) electrodes.  There are three types of coating, a “15”, “16” and “17”.  A “15” electrode has a lime based coating and is intended for DC+ polarity only.  They have a lighter slag than the other two types and used for all position welding, with some electrodes of this type used primarily for vertical down welding.  A “16” electrode has a titania or rutile based coating and can be used with both DC and AC polarity.  Electrode sizes of 5/32 in. (4.0 mm) and smaller are often used for all welding positions.  Note, there is also a “26” classification, which is the same as a “16” type coating, but for higher deposition applications and limited to the flat and horizontal position only.  A “17” electrode has a silica-titania type coating and is a modification of a 16 coating, in that some of the titania is replaced with silica.  They also can be used with both DC and AC polarity.  Additional silicon in the coating acts as a wetting agent, having the effect of increasing puddle fluidity.  This is particularly helpful with stainless steel, as it tends to have more of a sluggish weld bead than carbon steel.  Seventeen type electrodes produce a flatter bead profile than the other two types and are often used for flat and horizontal position welding.  However, electrode sizes of 5/32 in. (4.0 mm) and smaller can be used for all position welding.   Note that with a vertical up progression, the slower freezing slag will require more of a weave technique than with a 16 type electrode.

Figure 1: Examples of “H” and “L” Type Stainless Steel Electrodes

GENERATORS MARKET IN PAKISTAN

 Yamaha generator are loaded with cutting edge engineering that not only ensures great performance in all operations you expect from a generator but also makes them superb in user friendliness, economy, sound levels and reliability.

Get your Yamaha generator today and experience a higher level of ease and effortless usage that only the most superior technology in the power equipment industry can offer. Yamaha generators will make your work easier, more proficient and more resourceful.

http://www.ypel.com.pk/

In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric current to flow through an external circuit. The source of mechanical energy may be a reciprocating or turbine steam engine, water falling through a turbine or waterwheel, an internal combustion engine, a wind turbine, a hand crank, compressed air, or any other source of mechanical energy. Generators provide nearly all of the power for electric power grids.
The reverse conversion of electrical energy into mechanical energy is done by an electric motor, and motors and generators have many similarities. Many motors can be mechanically driven to generate electricity and frequently make acceptable generators.
http://www.shophive.com/shophive/Generator-c-426.pakistan.html

http://www.pel.com.pk/genset.html