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Quality Control on Material
Material Chemical and Mechanical Analysis
Ningbo LD has its own lab on material testing, we do chemical and mechanical testing on every batch of material we received, once the material are qualified, all detail information will be recording in ERP system. Customer will receive material certification for quality chaining.
Salt Spray Testing on Rod
Chrome Plated Rods
Chrome Plated Rods are produced from medium carbon cold-finished or hot rolled steel bars usually in Steel 1045/1050 or 10v45 grades. The bars need to be polished, and chrome plated to a minimum thickness of 0.0005”, and 0.001” per side. Chrome Plated Rods are specifically designed to be used for most piston rod applications in hydraulic cylinders.
Nikrom Rod
As some of customers’ machines working environment is highly corrosive conditions, which required very high corrosion resistance. Ningbo LD provides an option of Nikrom rod.
Due to the presence of natural micro cracks in the chromium layer, erosion may penetrate the coating. In corrosive environments or strictly safe applications, exposure to the risk of mechanical damage, oil film alone is not enough to protect in the field.
This is especially true if the piston rod remains elongated for a long time as the oil film dries out. By combining the chromium plating with the lower nickel layer. Nikrom can greatly improve the corrosion resistance regardless of the overall oil film protection state of the piston rod.
What is difference between Chrome Rod and Nikrom Rod?
Nitrided-Treating Rods
Compared with chrome plated rods, Nitrided rods’ black colored surface finish is very hard, and the hardness can be above 55 HRC. The process of liquid nitriding begins with the cleaning and super-polishing of the material to a surface roughness of 6 to 10 Ra.
The improved corrosion resistance can reach the requirements of 500-1000 Hours by Salt Spray Testing (ASTM B117), the nitrided rods are normally sufficient to protect the shaft during its entire life. Nitrided rods are cost effective alternative way for longer time salt spray testing requirements.
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Salt Spray Testing ASTM B117 |
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Surface |
Roughness |
Chrome Thickness |
NSS |
Surface Hardness of Chrome Layer |
Chrome |
< Ra 0.2 |
> 25 μm |
> 96 Hours R9 |
> 750HV |
Chrome |
< Ra 0.2 |
> 50 μm |
> 120 Hours R9 |
> 750HV |
Nitride |
< Ra 0.2 |
... |
> 150 Hours R9 |
Rod Surface Hardness 55-60HRC |
Chrome(CROMAX C) |
< RA 0.2 |
> 20um |
> 350 Hours R9 |
> 850HV |
Ni-Cr Plating(NIKROM 150) |
< RA 0.2 |
> 20um |
> 500 Hours R9 |
> 850HV |
Ni-Cr Plating(NIKROM 150) |
< RA 0.2 |
> 20um |
> 1500 Hours R9 |
> 850HV |
Casting Fabrication For Hydraulic Cylinder Components
Ningbo LD has over 30 years experiences in casting fabrication. We have great flexibility in offering cast components in our hydraulic cylinder designs. Cast components are made from pouring molten metal into a pre-engineered molds that produces a specific shape or form. The most common cast items in our hydraulic cylinders are rod clevis or base end clevis as well as customized end caps.
The benefits of Casting components :
Cost Saving
Reducing welding processing steps for complex shapes
Better finish looking
Excellent machinability with increased strength
Repetitive and precise process
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Forging Fabrication For Hydraulic Cylinder Components
What is the process of Forging ?
Forging is the process of working or forming metal to the desired shape by impact or pressure from hammers, presses or forging machines. The metal object produced through this process is termed a forging.
Forging Advantages ?
Forgings are superior over castings and fabrications as the structural integrity can withstand the higher forces that exist in a rigorous or high duty cycle application.
Why Choose Forging ?
Forgings are best used in high duty cycle or more rigorous applications where a more durable, high quality hydraulic cylinder is required. This could be within markets such as construction, mining, refuse etc. Forged hydraulic cylinder components provide the best impact resistance due to the improved directional strength of the grain structure created through the forging process. Forgings can also reduce cost in material, machining and even warranty due to it's superior quality.
Grain Flow Comparison
Forged Bar
A forged bar contains a directional alignment that is oriented in the direction to achieve maximum strength. This grain flow will yield ductility and resistance to impact and fatigue.
Machined Bar
A machined bar contains a unidirectional grain flow due to the changes in contour and exposed grain on the ends. This is more prone to fatigue and more sensitive to stress corrosion cracking
Cast Bar
A cast bar contains no grain flow or directional strength.
The benefits of Forging components :
Superior strength with directional grain flow
Excellent metallurgical properties with very consistent results
Improved structural integrity and products’ reliability
The elimination of welding results in a much stronger cylinder rod or component
Simplifying the manufacturing requirements
Reject, rework and replacement costs are greatly reduced compared with casting
Reduced warranty cost, improved quality warranty
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Multi-selective Hydraulic Cylinder Tube
CDS Tube (Cold Drawn Seamless Tube)
Honed Tube
SRB Tube (Skived and Roller Burnished Tube)
Hollow Bar
Hard Chrome Plated Rod
Technical Characteristics of Hydraulic Cylinder Tube |
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Material : ST52,CK20,CK45,27SiMn,E355,1026 |
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Supply Condition |
ID(mm) |
Length |
Straightness (mm/M) |
ID Tolerance |
WT Tolerance |
Roughness (μm) |
Cold Drawn |
32-250 |
≤12M |
0.2-0.5 |
/ |
± 5% |
0.8-1.6 |
Cold Roll |
25-100 |
≤12M |
0.2-0.5 |
/ |
± 5% |
0.8-1.2 |
Honing |
32-500 |
≤11M |
0.2-0.3 |
H8-H9 |
± 5% |
≤ 0.4 |
SRB |
42-200 |
≤6M |
0.2-0.3 |
H8-H9 |
± 5% |
≤ 0.3 |
Technical Characteristics of Hard Chrome Plated Rod/Hollow Bar |
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Material : CK45,ST52,40Cr,42CrMo |
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Specification (ID mm ) |
Ø6 - Ø12 |
Ø16 - Ø25 |
Ø30 - Ø50 |
Ø55 – Ø100 |
Ø105 – Ø180 |
Length (mm) |
800-2000 |
800-3000 |
800-5000 |
1000-7000 |
1000-9000 |
Surface Roughness |
Max. Ra 0.2 μm |
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Surface Hardness |
Min. 55HRC |
Straightness |
Max. 0.2/1000 mm |
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Roundness Tolerance |
GB1184 L9 |
Chrome Layer |
0.02-0.03 mm |
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Full Length Tolerance |
GB1800 IT L7 |
OD Tolerance |
ISO F7-F8 |
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Quenching and Tempering Hardness |
HB220-267 |
What is the process of tube ?