Must Know: Carbon Steel & Welded Carbon Steel 5 Points

Contents
erw carbon steel pipe

About Welded Carbon Steel

Carbon Content:

Carbon steel is defined as steel with a carbon content of less than 2.11%, containing small amounts of Mn, Si, S, P, O, and other impurities. Iron-carbon alloys with various impurities are categorized as carbon steels. Based on carbon content:

 

Industrial pure iron – carbon content Wc < 0.04% iron-carbon alloy;

Low carbon steel – carbon content Wc < 0.25% carbon steel;

Medium carbon steel – carbon content 0.25% < Wc < 0.60% carbon steel;

High carbon steel – carbon content Wc > 0.60% carbon steel.

The Importance of Welding Carbon Steel:

Carbon steel is a versatile and robust material used in construction, energy, and automotive industries. In construction, it ensures the robustness of buildings. In energy, it facilitates efficient transportation through oil and gas pipelines. Welded carbon steel plays a vital role in providing structural strength, corrosion resistance, and reliability across various industries.

welded steel pipe

Welding Processes

Welding Influencing Factors:

The higher carbon content results in increased hardness and decreased weldability. Different carbon contents require adjusted welding methods.

Alloying Elements:

The presence of alloying elements, like manganese or silicon, influences the welding process. Identifying impurity levels helps determine the appropriate welding method.

Other Alloying Elements:

Elements such as phosphorus, sulfur, oxygen, and nitrogen impact weldability. Sulfur, for instance, can lead to “thermal embrittlement” and weld porosity, emphasizing the need for strict testing.

Carbon Steel Welding Points

Before welding, measures to reduce defects and improve pipe quality include:

  • Preheating and maintaining inter-channel temperature during welding.
  • Use of low hydrogen or ultra-low hydrogen welding materials.
  • Continuous welding to avoid interruptions.
  • Starting the arc in the groove to prevent base material bruising.
  • Avoiding forming, correcting, and assembling at low temperatures.
  • Enhancing cold working conditions where possible.

Welding Influencing Factors:

The higher carbon content results in increased hardness and decreased weldability. Different carbon contents require adjusted welding methods.

Gas Shielded Welding:

Includes argon arc welding, argon arc argon welding, and argon arc mixed gas welding. Inert gas protection prevents pollution, enhancing welded joint quality.

High-Frequency Induction Welding:

Suitable for small-diameter carbon steel pipe production, using high-frequency current for rapid heating and efficient welding in mass production.

Important Note:

The weldability of carbon steel decreases with higher carbon content due to increased hardness. Slow cooling is crucial to prevent cracking. 

Tailor welding measures based on carbon content, considering issues like structural constraints and unbalanced thermal stress. High carbon steel requires special attention to prevent quenching-induced cracks.

Our Advantages

  1. Over 25 years of experience in pipeline production and installation.
  2. Comprehensive inspection equipment.
  3. Independent product serial numbers for traceability.
  4. Advanced production equipment – Seamer high-frequency welding machine from the United States.
  5. Complete qualifications – API 5L/API 5CT/FM/UL fire pipe certification, etc.
  6. Wide range of products – independently developed solar torque tubes, highly favored in the European market.
  7. Customers spread across the globe.
  8. Excellent after-sales service and sense of responsibility.

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