The knowledges about E355 Hydraulic Steel Tube

 E355 Hydraulic steel tube, as the core transmission components of hydraulic systems in construction machinery, mining equipment, and aerospace, directly determine the safety and service life of the equipment.

I. Raw Materials selections:
I. Materials Science: The Foundation of High-Precision Hydraulic Tubes
High-precision hydraulic tubes are made from cold-drawn seamless steel tubes (material grades: ST52.4/30CrMo/SAE 4130), with a yield strength of ≥500MPa and an elongation of ≥15%, ensuring resistance to deformation under high-pressure conditions.

2. Material Pre-treatment Process
Phosphating and Saponification Treatment: Before cold drawing, the tube blanks undergo surface phosphating (ZnCaPO₄ coating) to reduce the friction coefficient. A saponification layer (sodium stearate) further lubricates, ensuring uniform wall thickness after cold drawing (tolerance ±0.1mm).

II. Precision Processing Flow: Five Core Procedures
1. Cold Drawing Forming Process
Die Design: Multi-stage hard alloy dies (HRC≥88) are used, with staged diameter reduction (reduction rate 15%-25%) to avoid stress concentration.

Process parameters: Drawing speed ≤ 3 m/min, coolant temperature 20 - 40℃ (emulsion concentration 8% - 12%), to prevent material overheating and resulting in micro-cracks.

2. Heat treatment strengthening
Quenching + tempering (normalizing treatment):

Quenching: Heat in a salt bath furnace at 920 ± 10℃. The holding time is calculated at 1.5 minutes per millimeter of wall thickness. Cool in oil (40℃ mineral oil) until the martensitic transformation is complete.

Tempering: Heat to 550-600℃ and hold for 2 hours, then air cool to obtain tempered sorbite structure. The hardness should be controlled at 28-32 HRC, achieving a balance between strength and toughness.

3. Inner Hole Finishing
Honing process: Use diamond honing heads (grit W20-W40). After processing, the inner wall roughness Ra is ≤ 0.4 μm, and the roundness error is ≤ 0.01 mm, meeting the requirements for low-resistance flow of high-pressure oil.

4. Surface strengthening treatment
Zinc-nickel alloy (Zn-Ni 12-15%): Double-layer electroplating (pre-plating copper + main plating Zn-Ni), salt spray test ≥ 720 hours without red rust, suitable for corrosive environments such as mines and oceans.

III. Quality Inspection: Stringent Industry Standard Execution System
Mechanical property testing, non-destructive testing, pressure and burst testing, dimensional accuracy inspection

The processing of hydraulic oil tubes is a comprehensive manifestation of materials science, thermodynamics and precision manufacturing technology. ANBAO GROUP, with its meticulous control over process parameters and a full-process quality traceability system, continuously provides global customers with highly reliable hydraulic pipeline solutions.Contact us for more custom engineering.