The core of a steel wire rope is one of its most crucial components, as it directly affects the rope’s performance, strength, flexibility, and durability.Through this article, we will provide readers with a detailed introduction to the types of wire rope cores, their roles, application scenarios and how to choose a core.

Structure of Steel Wire Rope Cores
The structure of a steel wire rope core consists of several key components:
Steel Core (IWRC):

- Core made of a separate steel wire rope.
- Provides a rigid, high-strength structure.
- Resists crushing and deformation.
Fiber Core (FC):

- Core made from natural or synthetic fibers (e.g., polypropylene or sisal).
- Offers flexibility and better shock absorption.
- Softer and lighter than steel cores.
Differences Between IWRC and FC
The main differences between IWRC (Independent Wire Rope Core) and FC (Fiber Core) in steel wire ropes are as follows:
Strength and Durability:
- IWRC: Higher tensile strength, better load-bearing capacity.
- FC: Less strength, suitable for lighter applications.
Flexibility:
- IWRC: Less flexible, better for heavy-duty use.
- FC: More flexible, ideal for applications requiring frequent bending.
Resistance to Crushing:
- IWRC: Excellent resistance to crushing and deformation, suitable for multi-layer winding.
- FC: Susceptible to crushing, better for single-layer applications.
Weight:
- IWRC: Heavier due to the steel core.
- FC: Lighter, easier to handle.
Environmental Resistance:
- IWRC: Performs well in harsh environments, including high temperatures.
- FC: Better for corrosive environments when paired with galvanized or stainless wires.
Common Steel Wire Rope Core (IWRC and FC) Structures
Being a wire rope manufacturer for more than 30 years, in the following table we present the most common wire rope constructions used by our customers in their daily applications:
Common Steel Wire Rope (IWRC and FC) Structures | |||
Core Structure | Wire Rope Structure | Application Scenarios | |
6×19 Class | 6x19S+IWRC | ![]() | 6x19S steel wire ropes with IWRC (Independent Wire Rope Core) or FC (Fiber Core) are versatile and widely used in various applications. Commonly applied in lifting, hoisting, cranes, and marine environments. IWRC provides higher strength and durability for heavy-duty tasks, while FC offers better flexibility and shock absorption, making it suitable for lighter operations. |
6x19S+FC | ![]() | ||
6×25 Class | 6x25F+IWRC | ![]() | Both 6x25F+IWRC and 6x25F+FC construction steel wire ropes are commonly used in various industrial applications due to their high strength and durability. |
6x25F+FC | ![]() | ||
6×36 Class | 6x36WS+IWRC | ![]() | Both 6x36WS+IWRC and 6x36WS+FC steel wire ropes are used in heavy-duty applications requiring high strength and durability. They are ideal for cranes, hoists, and mining equipment, providing excellent resistance to wear and fatigue. The IWRC variant offers added strength, while the FC variant provides flexibility and is lighter. Both are suitable for demanding industrial environments. |
6x36WS+FC | ![]() | ||
6×37 Class | 6x37M+IWRC | ![]() | Both 6x37M+IWRC and 6x37M+FC steel wire ropes are used in heavy-duty applications requiring high strength and durability. They are ideal for cranes, hoists, mining equipment, ship mooring, and offshore cranes, providing excellent resistance to wear and fatigue. |
6x37M+FC | ![]() | ||
35×7 Non-Rotating | 35(W)×7 EP IWRC | ![]() | The 35W×7 EP IWRC steel wire rope is primarily used in high-strength, anti-rotation applications such as rotary drilling rigs, vertical shaft hoisting, port machinery, and other heavy-duty lifting operations. |
These structures are commonly used in various applications, and the choice between FC and IWRC depends on the specific requirements of the application, such as load capacity, flexibility, and environmental conditions.
How to Choose the Core of Steel Wire Rope: IWRC or FC?
The core of a steel wire rope plays an essential role in its performance and longevity. Whether choosing a steel core for heavy-duty operations or a fiber core for flexibility and shock absorption, understanding the application’s specific needs ensures safety, reliability, and cost-effectiveness.
Assess the application’s load requirements:
- Heavy loads: Choose IWRC.
- Light loads: Choose FC.
Consider the working environment:
- Harsh, high-temperature, or high-friction environments: Opt for IWRC.
- Corrosive or marine environments: Opt for FC with galvanized or stainless wires.
Evaluate handling needs:
- If flexibility and ease of use are critical, FC is preferable.
Factor in cost:
- IWRC is generally more expensive than FC due to its higher strength and durability.
Need a Customized Solution for Steel Wire Rope?
When you need a customized solution for steel wire rope, KNKT stands out as a premier supplier in China. Here are the key advantages of choosing KNKT:
- 36 Years of Expertise: With 36 years of experience in the steel wire rope industry, KNKT has honed its expertise and technical capabilities to deliver top-notch products.
- International Certifications: KNKT is proud to hold international certifications such as ISO, GOST, and API. These certifications are a testament to our commitment to quality and adherence to global standards.
- High-Quality Production: We strictly follow international standards in our manufacturing processes to ensure the highest quality of steel wire ropes. Our products are designed to meet the most rigorous requirements, providing reliability and durability.
- Customized Solutions: At KNKT, we understand that each project has unique needs. Our ability to offer customized solutions means we can tailor our steel wire ropes to meet your specific application requirements, ensuring optimal performance and safety.
- Trusted Supplier: As a leading supplier in China, KNKT has built a reputation for reliability and excellence. Our clients trust us to deliver high-quality products that meet their expectations and enhance their operations.
Choose KNKT for your steel wire rope needs and experience the difference that decades of expertise and a commitment to quality can make.