Mild Steel ERW Pipe, MS ERW Pipe

What is MS ERW Pipe?

The full name of MS ERW Pipe is Mild Steel Electric Resistance Welded Pipe. It refers to a steel pipe produced by a resistance welding process from a low carbon steel coil or strip. We can break this phrase down into two phrases: "MS" and "ERW Pipe" to explain.

What is Mild Steel?

Steel pipes can be divided into carbon steel pipes, stainless steel pipes, and alloy steel pipes according to common materials. Carbon steel pipes can be divided into ordinary carbon steel pipes and high-quality carbon structural pipes.

Carbon steel pipes (CS pipe), as a kind of iron-carbon alloy, have a carbon content that is a key factor affecting their performance. Generally speaking, the carbon content of carbon steel pipes is between 0.08% and 2.11%. This range is determined based on years of production practice, scientific research, and industry standards, and it covers three main types of low carbon steel, medium carbon steel, and high carbon steel.

Mild steel is a carbon steel with a carbon content of less than 0.25%. It is also called mild steel because of its low strength, low hardness, and softness. It includes most of the ordinary carbon structural steel and some high-quality carbon structural steel. Most of them are used for engineering structural parts without heat treatment, and some are used for mechanical parts requiring wear resistance after carburizing and other heat treatments. According to different production methods, low carbon steel pipes can be divided into seamless pipes and welded pipes. ERW pipes are a type of welded pipes.

The influence of different carbon contents on the performance of carbon steel pipes:

1. Low carbon steel: Low carbon steel with a carbon content between 0.08% and 0.25% has good machinability, weldability and toughness. Due to its relatively low hardness, it is easier to perform various processing operations. However, the strength of low carbon steel is also relatively low, and it is usually suitable for some occasions with low strength requirements, such as building materials, manufacturing screws and nuts, etc.

2. Medium carbon steel: Medium carbon steel with a carbon content between 0.25% and 0.60% has relatively good strength, hardness and wear resistance. This makes medium carbon steel widely used in some fields that require higher strength and hardness, such as bearings, transmission shafts, mechanical parts, etc. However, the weldability and toughness of medium carbon steel are relatively poor, and proper heat treatment is required to improve its performance.

3. High carbon steel: High carbon steel with a carbon content between 0.60% and 2.11% has extremely high hardness and strength. This makes high carbon steel very suitable for manufacturing various steel products that need to withstand high loads and high-speed operation, such as springs, saw blades, drill bits, blades, etc. However, the weldability and toughness of high carbon steel are relatively poor, so special attention should be paid to avoid overload and impact during use.

What is ERW in pipe?

ERW refers to electric resistance welding. Electric resistance welding (ERW) is a method of joining metal parts together using resistance and heat. In this process, the metal parts to be welded are connected end to end and clamped together. Depending on the material, ERW pipes can be divided into stainless steel, carbon steel or alloy steel pipes and fittings.

The vast majority of long-distance natural gas pipelines are in three forms: straight seam high frequency welded pipe (ERW), spiral submerged arc welded pipe (SSAW pipe) and straight seam submerged arc welded pipe (LSAW pipe). According to different welding methods, straight seam high frequency welded pipe (ERW) is divided into two forms: induction welding and contact welding. It uses hot-rolled wide steel coil as raw material, and undergoes pre-bending, continuous forming, welding, heat treatment, sizing, straightening, cutting and other processes. Compared with spiral welded pipe, it has the advantages of short weld, high dimensional accuracy, uniform wall thickness, good surface quality, and high compressive strength. However, its disadvantage is that it can only produce small-diameter and medium-diameter thin-walled pipes, and gray spots, unfused, and groove corrosion defects are easily generated at the weld. At present, the most widely used fields are urban gas, crude oil and refined oil transportation.

Advantages of mild steel welding:

1. Material properties
One of the biggest features of low carbon steel welding is the flexibility of the welding material, which is easy to form a variety of shapes during the welding process, which makes welding very easy. In addition, the toughness and defect tolerance of low carbon steel itself also make it a very suitable material for welding.

2. Alloy composition
The alloy content in low carbon steel is very low, usually not exceeding 2%. Therefore, the heat and stress generated when welding low carbon steel are relatively small, and the deformation of the material during welding is also relatively small, which makes low carbon steel welding very suitable for mass production.

3. Strength
The strength of low carbon steel is very high. Because its composition is very soft, it can be easily formed and processed. In low carbon steel welding, the strength of the welded joint can be comparable to that of the parent material, which also makes low carbon steel one of the most commonly used welding materials.

4. Welding method
Low carbon steel can be welded by a variety of welding methods, such as arc welding, gas shielded welding, etc. Among these welding methods, arc welding is the most commonly used method, but gas shielded welding can make the welding results more uniform and of higher quality.

Advantages and disadvantages of MS ERW pipe:

Advantages:

(1) Higher hardness
After heat treatment, MS ERW pipe can obtain higher hardness and better wear resistance. Its hardness in the annealed state is very moderate and has good machinability.

(2) Low production cost
The raw materials of carbon steel are common and easy to obtain, and the production cost is relatively low.

(3) High dimensional accuracy
The dimensional accuracy of ERW steel pipes is higher than that of seamless pipes. This is because seamless pipes (SMLS pipes) are made by continuous perforation of round steel by hot rolling mills, while ERW steel pipes are made of steel strips in a cold rolled state. In comparison, ERW is easier to control in terms of appearance dimensions than SMLS.

Disadvantages:

(1) Corrosion-prone
Compared with stainless steel pipes, low carbon steel pipes are more susceptible to corrosion, and carbon steel parts are generally treated with spray paint. Compared with seamless pipes, ERW pipes have welds and are more prone to leakage of the transported material.

(2) Unstable quality

ERW steel pipes are prone to problems such as carbon segregation in welds and slag inclusions, and the quality of pipe making is unstable.

Read more: Mild Steel Seamless Pipe or Seamless vs Welded pipe