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Price v/s Quality: Explore Quality Puzzle of Rebar Coupler Material

In construction industry now a days rebar coupler capturing huge market that is recommended by IS 16172:2014. It increases strength of structure and enhance the safety of structure. Here we will discuss about properties of different rebar coupler material like Mild Steel (MS), EN8 & EN8D and we also discuss about seamless process of rebar couplers so that how customers confused with quality of rebar coupler available in the markets.

Why price is different of same diameter of coupler?

In the manufacturing of rebar coupler, different steel material grades are used. The rate of rebar coupler depends upon quality of material used for making of rebar coupler and what are mechanical properties of coupler material like yield strengthultimate tensile strengthcarbon content and percentage elongation etc.

Here some grades of rebar coupler material and process that is used for coupler manufacturing and we talk about how they are different from each other.

·      Mild Steel (MS)

·      EN8

·      EN8 D

What is Mild Steel (MS) material?

Low-carbon steel, also known as mild steel is now the most common form of steel because its price is relatively low while it provides material properties that are acceptable for many applications. Low-carbon steel contains approximately 0.05–0.25% carbon making it malleable and ductile. Mild steel has a relatively low tensile strength, but it is cheap and easy to form and it also used for manufacturing of rebar coupler. Rate of Mild steel rebar coupler are less then EN8D but it has low tensile strength.

Grade Tensile strength
Yield strength
Percentage elongation(%)
Mild steel (MS) 400-500 250 20-30

What is EN8?

EN8 is a steel material used for manufacturing of rebar coupler that contains 0.35-0.45 carbon percentage and we discuss the various property of EN8 grade.

· Tensile strength: EN8 material grade exhibits tensile strength of 550 MPa that is used for manufacturing of rebar coupler.

· Yield strength: yield strength of EN8 is 280 MPa and it indicates beginning of permanent deformation of steel materials.

· Hardness: hardness of EN8 material is 152HB, indicate durability of product against wear and abrasion. HB represent Brinell hardness of material that is unit of hardness.

· Elongation: percentage elongation of EN8 has moderate level of elongation. Which is ranges of 15-16%, elongation indicates increase in length of material before failure.

What is EN8D?

EN8D also rebar coupler material having better mechanical property then mild steel (MS) and EN8, in EN8D “D” indicate ductility of material. It has more ductile strength then EN8 and having more yield strength and tensile strength with elongation. EN8D rebar coupler little costlier then EN8 because it has better material quality.

Grade Tensile strength
Yield strength
Percentage elongation(%) Hardness
EN8D 620 320 17 183

Grade Tensile strength (MPa) Yield strength (MPa) Percentage elongation (%)
Mild steel (MS) 400 250 25
EN8 550 280 16
EN8D 620 320 17

Seamless process of rebar coupler:

Cold drawn process:

In cold drawn process of rebar coupler raw steel bars converted into couplers and enhance their mechanical properties.  after cold drawn process the tensile and yield strength of material has been increase and more then MSEN8 and EN8D rebar coupler materials. Cold drawn process is quite expansive that’s why cold drawn rebar coupler is costlier then EN8D rebar coupler.

Cold Drawing:

The process of cold drawing is used to heated steel bars. They go through several dies with progressively smaller apertures. The bars’ length is increased while their diameter is decreased by this technique. Cold drawing improves mechanical qualities like strength and hardness by fine-tuning the grain structure.

Cutting and Threading:

The steel bars are cut into standard rebar coupler lengths after being cold drawn. Next, both ends of each length are threaded to make it simple to join reinforcing bars.

Hot roll process:

1. Material selection: Steel is frequently used because it has the necessary qualities of strength, corrosion resistance, and durability.

2. Heating: To make the chosen material more flexible and appropriate for shaping, it is heated to a certain temperature.

3. Forming: Using specialized equipment, the heated material is then molded into the required shape, such as a cylindrical or tubular shape. Processes including rolling, piercing, and extrusion can accomplish this.

4. Sizing: The manufactured product undergoes further processing to get the required tolerances and dimensions. that improve the mechanical qualities and surface polish, including cold drawing or cold rolling.

Seamless process of rebar coupler Yield strength (MPa) Ultimate tensile strength (MPa)
Cold drawn 530 660
Hot roll 420 650

Conclusion: In this article we discussed about grade of rebar coupler material and seamless process of rebar coupler & their mechanical properties like tensile strength and yield strength includes elongation. In market rebar coupler available grade of mild steel (MS)EN8 and EN8D but customer cannot identify grade of rebar coupler by visual we can verify by only from chemical composition of material. EN8D grade rebar coupler has better tensile strength and ductile strength then EN8 grade coupler. So, buying before any product like rebar coupler firstly check its quality because safety of structure is our first priority.