- Ningbo Zhongli bolts manufacturing Co., Ltd. +86-574-86587617
- tan@nbzyl.com
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High-precision flat washers and structure-grade bolts designed for critical mechanical applications.
In modern industrial construction and mechanical design, a flat washer for engineering is not merely a spacer but a critical component that ensures structural integrity and uniform force distribution. When heavy steel structures are assembled using high-tensile fasteners, the load exerted by a tightened bolt must be evenly dispersed across the joint surface. Without a high-quality flat washer, the localized pressure can cause material indentation, thread deformation, and eventual joint loosening under dynamic stress.
From structural engineering projects like bridges and steel-framed skyscrapers to complex automotive assemblies, flat washers play a pivotal role. They prevent surface wear, cover oversized or irregular clearance holes, and act as a reliable barrier against galvanic corrosion when different metals are clamped together. By choosing the correct grade and dimension of structural washers—such as ASTM F436, DIN 125, or DIN 7989—engineers can guarantee that joint preloads are sustained throughout the operational lifespan of the machinery or infrastructure.
Ningbo Zhongli Bolts Manufacturing Co., Ltd. founded in 2003, is a professional manufacturer of high-strength fasteners in different specifications for various models, which is covering an area of about 10,000 square meters, registered capital of 1500,000 RMB, with the total annual productivity of 8,000 tons per year. The company has set up several sales branches in different provinces in China. Meanwhile, the company's products are exported to Europe, USA, Middle East, Africa, Southeast Asia and other regions. The company has strong technical ability, complete testing equipments and a variety of fully automatic multi-station cold and hot heading machines, so as to provide you with reliable and high quality products.
Our main products ZYL brand fasteners include structural hex bolts ASTM A325 type 1, A490, hex head bolts DIN931, DIN933, EN14399, DIN6914, ISO4014, ISO4017 Gr8.8 Gr10.9 Gr12.9, ANSI B18.2.1 UNC and UNF Gr5, Gr8, fine pitch hex bolts DIN960, DIN961 Gr8.8 Gr10.9 Gr12.9, hex socket cap screws DIN912, ISO4762 Gr8.8 Gr10.9 Gr12.9 with surface Black, Zinc plated, Hot dip galvanized. Diameters from M10 to M48, length no limited. Hex Flange bolts DIN6921 Gr8.8 Gr10.9 with serration, thread rod A193 B7 long sizes and short sizes with 2H nuts, stud bolts. We also can supply hex nuts DIN934, DIN6915, plain washers DIN125, DIN126, DIN6916, spring washers DIN127 with Black, Zinc plated and Hot dip galvanized surface.
Our physical and mechanical test results can reach to ISO898-1 for bolts and ISO898-2 for nuts. Through scientific management, Ningbo Zhongli Bolts Manufacturing Co., Ltd. obtained ISO9001 certificate of Quality Management System. Quality is the most important for us. We have strict production and inspection equipments to support this point. We hope to establish business relationship with all over the world, and our business can bring in mutual benefits for both parties.
How the global fastener industry is adopting high-precision flat washers to tackle modern engineering challenges.
Integration of IoT-enabled cold forging machines and automated sorting systems ensures zero-defect production of flat washers, complying with strict aerospace and structural standards.
Hot-Dip Galvanizing (HDG), Dacromet, and Geomet coatings are replacing traditional zinc plating in offshore wind energy and marine engineering to achieve over 1000 hours of salt spray resistance.
Modern engineering demands washers that match the mechanical properties of Grade 8.8, 10.9, and 12.9 bolts. ASTM F436 and DIN 6916 hardened washers are now mandatory in heavy steel structures.
The application of flat washers spans across several sophisticated engineering sectors:
Our state-of-the-art manufacturing flow ensures every flat washer and bolt meets global engineering standards.
Inside ZYL's advanced manufacturing plant, utilizing high-precision machinery to produce industrial-grade fasteners.
Detailed comparison of international washer standards to guide structural design engineers.
Selecting the right flat washer for engineering requires a thorough understanding of dimensions, material properties, and standards. The most common standards used in modern industrial applications include:
| Standard | Type / Description | Typical Application | Key Mechanical Property |
|---|---|---|---|
| ASTM F436 | Hardened Circular Washers | Structural steel joints, paired with A325/A490 bolts | 38 to 45 HRC hardness range |
| DIN 125 / ISO 7089 | Plain Washers (Medium series) | General mechanical engineering assemblies | Available in 140 HV, 200 HV, and 300 HV |
| DIN 7989 | Thick Washers for Steel Structures | Heavy timber and structural steel frames | Increased thickness (up to 8mm) for load distribution |
| DIN 6916 / EN 14399-6 | High-strength structural bolting washers | Preloaded structural bolting assemblies | Quenched and tempered steel, high precision |
The choice of material coating directly affects the durability of flat washers. While plain black steel washers are suitable for internal assemblies protected from moisture, external steel frameworks require Hot-Dip Galvanizing (HDG) or Zinc Plating. The HDG process forms a thick, metallurgical bond of zinc-iron alloys that shields the carbon steel from moisture, acidic rain, and industrial pollutants. In high-tensile structural connections, hydrogen embrittlement must be prevented during the pickling and plating stages, making strict quality inspections mandatory.
Why global buyers choose Ningbo Zhongli Bolts Manufacturing Co., Ltd. as their long-term partner.
A Professional Sales and Technical Team with More Than 20 Years History.
We Have Our Own Testing Equipment and Laboratory, Our Products Have Initial Inspection, Patrol Inspection, And Final Inspection.
Our Factory Has Its Own Cold Forged, Hot Forged, And Heat Treatment Equipment.
Standard Fasteners in Stock, Non-standard Fasteners Can Be Customized.
We Have Passed ISO 9001, EN 15048, EN 14399, AD2000 and CE Certificates.
We hope to establish business relationship with all over the world, and our business can bring in mutual benefits for both parties.
Quality assurance is the foundation of Ningbo Zhongli Bolts Manufacturing Co., Ltd. Our in-house testing laboratory is equipped with high-precision testing instruments to conduct physical, dimensional, and mechanical property checks on every batch of structural washers and hex bolts.
Our comprehensive inspection procedures include:
EN 15048 CE Certification, EN14399 CE Certification, ISO9001 Certificate
Trusted by engineers and heavy industries globally. Grasp first-hand feedback from our structural construction projects.
Explore our full line of ASTM, DIN, and ISO compliant heavy-duty steel structure gaskets, carbon steel bolts, and spring washers.
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