Main products introduction of Ningbo Zhongli Bolts Manufacturing Co., Ltd.

Ningbo Zhongli Bolts Manufacturing Co., Ltd., established in 2003, is a prominent manufacturer of high-strength fasteners headquartered in Zhejiang Province, China. With a factory area spanning 10,000 square meters and an annual production capacity exceeding 8,000 metric tons, the company specializes in producing a wide range of standardized and customized fasteners, including hex bolts, structural bolts, and non-standard specialty fasteners. Their products adhere to international standards such as GB (Chinese National Standards), DIN (German Industrial Standards), ISO (International Organization for Standardization), and ANSI/ASME (American Standards), catering to industries like construction, automotive, machinery, and energy. 

The company’s product portfolio is centered on high-performance fasteners, particularly DIN933 and DIN931 hex head bolts, which are widely recognized for their mechanical reliability and adaptability to demanding environments. Below is a detailed overview of these products, with a focus on their 10.9-grade variants.  

1. DIN933 and DIN931 Hex Bolts: 

 DIN933 and DIN931 are German-standard hex bolts distinguished by their thread configurations: 

-  DIN933 : Features a  full-threaded  design, ensuring uniform stress distribution across the entire bolt length. This makes it ideal for applications requiring high clamping force, such as heavy machinery and structural assemblies. 

-  DIN931 : Designed with a  partial thread  (half-threaded), offering a combination of threaded and unthreaded shank sections. This configuration is optimal for joint connections where shear resistance and alignment precision are critical, such as in automotive chassis or hydraulic systems. 

 Grade 10.9 : 

The 10.9-grade designation signifies a  high tensile strength  of 1,040 MPa and a yield strength of 940 MPa, achieved through advanced heat treatment and alloy steel materials (e.g., SCM435 or equivalent). These bolts undergo strict quality control processes, including hardness testing (39–44 HRC) and surface treatments such as  black oxide coating  or  zinc plating  to enhance corrosion resistance. 

2.   Manufacturing Process and Quality Assurance

Ningbo Zhongli employs state-of-the-art production technologies to ensure the precision and durability of its bolts: 

-  Cold Forging : Multi-station cold heading machines shape raw alloy steel into bolts with minimal material waste, ensuring consistent dimensional accuracy. 

-  Heat Treatment : Controlled quenching and tempering processes optimize the microstructure of the steel, achieving the required 10.9-grade mechanical properties. 

-  Surface Treatment : Options include galvanization, hot-dip galvanizing, and black oxide coatings, tailored to resist environmental factors like moisture and chemical exposure. 

The company holds ISO 9001:2015 certification  and utilizes advanced testing equipment, such as tensile testers and metallurgical analyzers, to verify compliance with international standards. 

3.   Applications and Industry Relevance

10.9-grade DIN933 and DIN931 bolts are pivotal in high-stress applications: 

-  Construction and Infrastructure : Used in steel frameworks, bridges, and wind turbine assemblies due to their load-bearing capacity. 

-  Automotive and Machinery : Critical for engine components, hydraulic systems, and heavy equipment where vibration resistance is essential. 

-  Energy and Petrochemicals : Deployed in oil pipelines and offshore platforms, leveraging their corrosion-resistant coatings. 

4.   Customization and Global Reach

Ningbo Zhongli offers extensive customization services for non-standard bolts, including tailored dimensions (diameters from M8 to M100, lengths up to 6,000 mm), thread types (fine or coarse), and material grades (e.g., B7 stud bolt, A325). Their products are exported to Europe, North America, Southeast Asia, and the Middle East, supported by partnerships with global distributors and a robust logistics network. 

Conclusion:

Ningbo Zhongli Bolt Manufacturing Co., Ltd. stands out as a leader in high-strength fastener production, combining rigorous quality control, advanced manufacturing techniques, and a customer-centric approach. Their DIN933 and DIN931 grade 10.9 hex bolts exemplify engineering excellence, meeting the stringent demands of diverse industries worldwide. For further details, refer to the company’s official resources or industry exhibitions such as the Shanghai Fastener Professional Exhibition.