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.

University Testing
Metallographic Polishing
Rockwell Hardness Tester
Impact Testing
Spectral Analysis Machine
Hardness Tester
Surface Roughness

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.

Salt Spray Testing  ASTM B117



Chrome Thickness


Surface Hardness of Chrome Layer


< Ra 0.2

> 25 μm

> 96 Hours R9

> 750HV


< Ra 0.2

> 50 μm

> 120 Hours R9

> 750HV


< 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


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


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

Material : ST52,CK20,CK45,27SiMn,E355,1026

Supply Condition



Straightness (mm/M)

ID Tolerance

WT Tolerance

Roughness (μm)

Cold Drawn





± 5%


Cold Roll





± 5%







± 5%

≤ 0.4






± 5%

≤ 0.3

Technical Characteristics of Hard Chrome Plated Rod/Hollow Bar

Material : CK45,ST52,40Cr,42CrMo

Specification (ID mm )

Ø6 - Ø12

Ø16 - Ø25

Ø30 - Ø50

Ø55 – Ø100

Ø105 – Ø180

Length (mm)






Surface Roughness

Max. Ra 0.2 μm

Surface Hardness

Min. 55HRC


Max. 0.2/1000 mm

Roundness Tolerance

GB1184 L9

Chrome Layer

0.02-0.03 mm

Full Length Tolerance

GB1800 IT L7

OD Tolerance


Quenching and Tempering Hardness


What is the process of tube ?