Carbon cold rolled and hot rolled wire rod

Low-carbon SWRCH6–16A series steels are non-heat-treated materials suitable for cold heading and cold extrusion. These steels are primarily used to produce fasteners with lower strength requirements. Due to the high deformation involved in cold heading and the complexity of the shapes, these materials demand excellent pickling and phosphating quality. When the deformation during cold heading exceeds 1/3, annealing is necessary for certain steel grades. It is recommended that customers prioritize low-carbon grades like SWRCH6A, especially when manufacturing fasteners with significant cold heading deformation. Additionally, selecting wire material specifications that closely match the required product dimensions helps reduce drawing deformation and minimize work hardening effects.

Free return cold rolled steel and hot rolled wire rod

In 2004, Maanshan Iron & Steel Co., Ltd. initiated the National 863 Program "Research on High Performance and Low Cost Cold Rolled Steel" (2003AA331030), aiming to develop an independent production technology for online softening and low-cost cold heading steel wire in China. This initiative marked a major step toward more efficient and cost-effective steel production in the fastener industry.

High-strength fasteners of class 8.8 and above are typically made from medium carbon steel or medium carbon alloy steel. The standard production process includes hot rolling, spheroidizing annealing, cold drawing, cold forming, and quenching and tempering. Spheroidizing annealing is crucial to ensure sufficient plasticity for cold heading. During this process, materials can undergo up to 70–80% total deformation, requiring raw materials with a hardness not exceeding HRB82. However, spheroidizing annealing remains one of the most time-consuming and energy-intensive steps in fastener manufacturing. Traditionally, it takes 12–24 hours in batch or continuous annealing furnaces. As a result, the industry seeks to simplify or even eliminate this process to improve efficiency.

Ma Steel’s high-line technology incorporates the latest advancements in wire rod rolling, creating a unique hot-rolling production line with independent intellectual property rights. The company has developed annealed SWRCH35K-M and CH35A-M hot-rolled wire rods, as well as SWRCH35K-MT and CH35A-MT for fasteners exported to the US market. These products are available in various diameters and are ideal for manufacturing hexagonal bolts and similar fasteners. For products with large deformation, spheroidizing annealing is still necessary. Meanwhile, MFM-1 and MFM-3 hot-rolled wire rods have been successfully developed for ordinary high-strength nuts, while MFM-2 eliminates both annealing and quenching + tempering, directly producing 8.8-grade nuts.

Non-regulated cold rolled steel and hot rolled wire rod

Non-tempered cold heading steel is mainly used for high-strength fasteners such as 8.8, 9.8, and 10.9 grade bolts. Using this type of steel allows manufacturers to skip the pre-drawing annealing and post-bolting quenching and tempering steps, significantly simplifying the production process. This leads to shorter production cycles, reduced energy consumption, and fewer issues like surface oxidation, decarburization, and deformation caused by heat treatment. Japan has already implemented industrial-scale production of such materials.

In 2005, Maanshan Iron & Steel Co., Ltd. participated in the National 863 Program Guided Project “Research and Development of Non-tempered Steel Wire for Low Temperature Controlled Rolling and Controlled Cooling Fasteners” (2005AA001110). In 2008, the company further undertook the National Support Program Project “Development of Low-Cost, High-Strength Non-Quenched and Tempered Cold-Rolled Steel Products for Steel Structure Joints” (2007BAE30B04). The non-tempered steel series developed by Maanshan employs micro-alloying, controlled rolling, and controlled cooling techniques to achieve ultra-fine grain structures. These steels eliminate the need for annealing and finishing processes, meeting current mechanical performance standards (GB/T 3098.22-2009). This new process reduces energy use, manufacturing costs, and environmental impact, making it a green solution that also minimizes defects like quenching cracks and surface decarburization.

Alloy cold heading steel

Steels such as 10B21, ML40Cr, and SCM435 are designed for high-grade fastener applications, including 8.8–12.9 grade products. Through strict process control, these materials deliver superior performance and cost-effectiveness, making them ideal for demanding industrial uses.

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