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Views: 0 Author: Site Editor Publish Time: 2025-06-11 Origin: Site
Carbon steel has the features of high strength, low cost, good processing performance and wide applications. It is widely used in construction, machinery manufacturing, automotive industry, tool production and pipeline systems. This article will help you understand the different types of hydraulic carbon steel fittings and help you choose the best hydraulic carbon steel fittings for you.
Hydraulic carbon steel fittings have become the mainstream choice in the industry with their three core advantages. Firstly, the cost of the same specification is only 40% of that of stainless steel fittings, which can significantly reduce the system cost in engineering machinery and metallurgical equipment used in large quantities. Secondly, the balance between strength and toughness is reflected in the perfect combination of 485-650MPa tensile strength and 18%-25% elongation, which enables the fitting to withstand 700Bar high-pressure shocks and absorb energy through plastic deformation under vibration conditions. Thirdly is its excellent performance for processing. The surface of carbon steel can be hot-dip galvanized, phosphating or Dacromet treated, providing more than 15 years of anti-corrosion protection in conventional industrial environments and can achieve complex structure forming through conventional processing such as turning and milling.
Carbon steel is an alloy with iron and carbon as the main components, and its carbon content ranges from 0.02% to 2.11%. Depending on the carbon content, the hardness, strength and plasticity of carbon steel will show significant differences: the higher the carbon content, the greater the hardness and strength but the plasticity decreases.
Compression fitting is an efficient connection device that achieves sealing through mechanical deformation. Its core consists of three precision components:
Body: A pressure-bearing body forged from carbon steel, with a 24° conical sealing surface processed at the front end, and the surface is galvanized or phosphated for rust prevention.
Cutting ferrule: When the nut is tightened, the ferrule is pushed toward the conical surface of the connector body, and the cutting edge will cut into the outer wall of the steel pipe to a depth of about 0.2-0.3mm.
Compression nut: A hexagonal nut with fine pitch threads that generates axial thrust during tightening. The standard torque range is 22-250N•m (depending on the diameter), and some models have built-in nylon locking rings to prevent vibration loosening.
Working mechanism: When the nut is tightened with a wrench, the ferrule is pushed forward along the 24° cone surface. Then the ferrule radially contracts and the double cutting edges cut into the steel pipe to form two annular sealing belts. At the same time, the rear end of the ferrule expands outward to form an auxiliary seal with the inner wall of the connector body. This metal-to-metal interference fit can achieve zero leakage at a pressure of 700Bar.
Flange fitting is designed for high-pressure and high-flow conditions, and consists of three core components working together:
Body: Forged steel with a thickness of 12-45mm, and the sealing surface is mirror-polished. According to the SAE J518 standard, it is divided into two structures: Code 61 (four bolts) and Code 62 (two bolts), with a pressure bearing capacity of 6000PSI.
O-ring: installed in the rectangular groove on the end face of the flange. Optional according to the features of the medium:
Nitrile rubber (NBR) is used for mineral oil (temperature resistance -30~100℃)
Fluoroelastomer rubber (FKM) withstands high-temperature hydraulic oil (-20~200℃)
High-strength bolt group: with bolts matched with hardened gaskets and precise preload is applied through hydraulic tensioners or torque wrenches.
Sealing process: When the bolts are tightened evenly, the two flanges move toward each other, then the O-ring is compressed axially in the sealing groove to produce radial expansion and forming a continuous annular sealing belt. The key is to control the compression rate of 15%-25%. Excessive compression will cause rubber extrusion failure.
The face sealing fitting solves the leakage problem of vibration conditions through the combination of face and elastomer:
Precision plane end: The end face of the fitting is ground with flatness error. The surface is electrolytically polished and the edge is processed with anti-scratch chamfer.
Special O-ring: FKM rubber ring is used. Some models use PTFE coated rubber technology to reduce the friction coefficient.
Anti-rotation flange nut: SAE J1926 standard twelve-point flange nut, with serrated pattern on the contact surface, built-in anti-rotation pin to prevent installation dislocation.
Sealing principle: The locking force of the nut makes the joint end face fit then the O-ring produces three-way deformation in the confined space:
<400Bar: select ferrule type compression fittings
400-700Bar vibration environment: choose face sealing fittings
>700Bar static pipeline: flange fittings
Mineral oil pipeline: strong oil resistance NBR rubber
Water ethylene glycol system: anti-hydrolysis EPDM rubber
High temperature system: FKM rubber that resistant to 200℃
Compression fittings: use torque wrench to control tightening angle
Flange fittings: tighten bolts in three steps in cross order
Face sealing fittings: apply silicone grease to protect O-ring before installation
Hydraulic carbon steel fittings are an indispensable type in the fitting industry with high strength, low cost, good processing performance and wide application. This article introduces different types of carbon steel fittings and how to choose them. If you want to know different types of carbon steel fittings and their specific uses, please consult the professional technician team of Haodema. We will select products that best meet your needs according to your requirements.
