A Customer Case on Body Steel, Rod Hardness and Ferritic Nitrocarburising
When selecting a hydraulic cylinder for an industrial application, engineers often focus on bore, stroke, pressure and mounting configuration.
However, the materials used for the cylinder body and rod are equally important.
The choice of steel, heat treatment and surface treatment directly affects the mechanical properties, wear resistance and long-term reliability of the cylinder.
A technical request received by the Vega Team illustrates this point. A Customer requested detailed information about the materials and hardness used for the body and rod of a CM-series hydraulic cylinder.
The Vega Team provided a precise specification:
- Cylinder body: C40 steel, or equivalent steel with the same characteristics, without hardening treatment.
- Rod: 40CrMnMo7 steel, or equivalent, hardened and tempered to 32–36 HRC.
- Rod surface treatment: ferritic nitrocarburising TF1 + AB1 NcE2 according to UNI 10931.
- Surface hardness: HV1 > 630.
- Treatment depth: > 0.2 mm.
These specifications provide an excellent example of how different parts of the same hydraulic cylinder can require completely different material strategies.
1. The Cylinder Body and Rod Have Different Jobs
A hydraulic cylinder is not simply a steel tube with a piston inside.
Each component has a specific mechanical function.
The cylinder body must provide structural resistance and maintain the required internal geometry.
The rod, on the other hand, is subjected to repeated movement and interacts directly with the sealing and guiding system.
This means that the material requirements are not necessarily the same.
The Case 195 documentation clearly reflects this approach: Vega specified one steel for the body and a different, higher-performance alloy steel for the rod.
2. C40 Steel for the Cylinder Body
For the cylinder body, Vega specified:
Steel C40 UNI EN 10083/1
or an equivalent material with the same characteristics.
The specification also states:
without hardening treatment.
The choice illustrates an important engineering principle.
A component does not automatically require the hardest possible material.
The correct material is the one that provides the required combination of:
- mechanical strength;
- machinability;
- dimensional stability;
- structural resistance;
- manufacturing performance.
For a cylinder body, the material must primarily provide a stable and sufficiently strong structure in which the internal components can operate correctly.
3. Why the Rod Requires a Different Material
The piston rod has a more demanding surface function.
It moves repeatedly through the cylinder and interacts with:
- rod seals;
- guide components;
- external environment;
- mechanical loads.
For this reason, the rod specified in the Customer response uses:
40CrMnMo7 alloy steel,
or an equivalent steel with the same characteristics.
Unlike the body, the rod is specified as:
hardened and tempered to 32–36 HRC.
This is a fundamental difference between the two components.
4. What Does 32–36 HRC Mean?
HRC refers to the Rockwell hardness scale C.
A hardness specification of:
32–36 HRC
defines the required hardness range of the hardened and tempered rod material.
Hardness is important because it provides resistance against mechanical deformation and contributes to the rod’s ability to withstand repeated service conditions.
However, bulk hardness is only one part of the rod’s performance.
The surface itself also needs to be engineered appropriately.
This is why Vega specifies an additional surface treatment.
5. Ferritic Nitrocarburising: Why Treat the Rod Surface?
The rod specified in the Customer case receives:
Ferritic Nitrocarburising TF1 + AB1 NcE2 according to UNI 10931.
Ferritic nitrocarburising is a thermochemical surface treatment designed to modify the properties of the surface layer of a steel component.
The important engineering concept is that the rod can have:
a tough mechanical core
combined with:
a harder and more wear-resistant surface layer.
This combination is particularly useful for components that experience repeated sliding and mechanical contact.
6. Bulk Hardness and Surface Hardness Are Not the Same Thing
The Case 195 specification contains two different hardness concepts:
32–36 HRC
for the hardened and tempered rod,
and:
HV1 > 630
for the treated surface.
These values should not be interpreted as two alternative specifications for the same measurement.
They refer to different aspects of the material and treatment.
The first describes the hardness condition of the rod after hardening and tempering.
The second specifies the hardness of the treated surface layer.
This distinction is extremely important when discussing hydraulic-cylinder rods.
7. Surface Hardness Above HV1 630
The Vega specification requires:
HV1 > 630
after the ferritic nitrocarburising treatment.
The HV designation refers to Vickers hardness.
The “1” indicates the test force used for the Vickers measurement.
Therefore, this specification is specifically related to the hardness of the treated surface.
The purpose is not simply to make the entire rod harder.
It is to engineer the surface so that it can withstand the demanding conditions associated with repeated rod movement.
8. Treatment Depth Greater Than 0.2 mm
The specification also states:
Depth > 0.2 mm.
This is another important parameter.
A surface treatment is not defined only by surface hardness.
The depth of the treated layer also matters.
A treatment that affects only an extremely thin surface region would provide different performance from one with a deeper effective layer.
By specifying a depth greater than 0.2 mm, Vega establishes an additional technical requirement for the treated rod.
9. Why the Rod Surface Is Critical for Hydraulic Cylinders
The piston rod is one of the most exposed components of a hydraulic cylinder.
During operation it repeatedly moves relative to the sealing and guiding components.
The rod surface therefore influences:
- friction;
- wear;
- sealing performance;
- service life;
- resistance to surface damage.
Vega’s general technical documentation confirms the importance of rod material and surface properties. Its materials page states that the rod is the most stressed part of the cylinder and that Vega uses hardened alloy steel for this component.
10. The Relationship Between Rod and Seals
A hydraulic seal does not work independently.
It works against the surface of the rod.
This means that the performance of the sealing system depends partly on the condition of the rod surface.
A properly engineered rod should provide a suitable surface for repeated sliding contact.
If the rod surface deteriorates, the consequences can include:
- increased friction;
- accelerated seal wear;
- leakage;
- reduced service life.
For this reason, material selection and surface treatment are an integral part of hydraulic-cylinder design.
11. Why a Harder Surface Does Not Mean a Better Entire Cylinder
It is tempting to think that simply increasing hardness always improves a component.
That is not necessarily true.
A hydraulic-cylinder rod must achieve a balance between:
- strength;
- toughness;
- surface hardness;
- wear resistance;
- dimensional stability;
- compatibility with seals.
The Case 195 specification demonstrates this balance.
The rod is first:
hardened and tempered to 32–36 HRC
and then receives:
ferritic nitrocarburising.
The objective is therefore not simply “maximum hardness.”
It is a carefully defined combination of bulk properties and surface properties.
12. Material Selection Must Follow the Application
The Customer requested the information because the material characteristics of the CM cylinder were relevant to the application.
This is an important engineering practice.
Before selecting a hydraulic cylinder, it can be useful to consider:
- operating pressure;
- operating temperature;
- number of cycles;
- rod loading;
- environment;
- lubrication;
- type of hydraulic fluid;
- expected service life.
These parameters influence the required material and sealing strategy.
13. The V450CM and Heavy-Duty Applications
The current Vega V450CM documentation describes the series as heavy-duty short-stroke compact hydraulic cylinders, designed for applications such as moving carts, pins and plugs in plastic injection molds and for moving ejection plates.
The official Vega documentation also describes the V450CM rod and piston as being manufactured from high-quality chromium-molybdenum steel.
This is consistent with the broader engineering principle illustrated by the Customer case: the rod is a highly stressed component and requires appropriate material properties.
14. Materials Are Part of Cylinder Reliability
Reliability does not begin when the cylinder is installed.
It begins during engineering and material selection.
The chain is:
Material
↓
Heat treatment
↓
Surface treatment
↓
Machining
↓
Sealing
↓
Assembly
↓
Application
A weakness at any stage can influence the final performance of the cylinder.
15. Why Surface Treatment Is Especially Important in High-Cycle Applications
A hydraulic cylinder can perform thousands, hundreds of thousands or millions of movements during its lifetime.
Every movement exposes the rod surface to repeated contact.
The greater the number of cycles, the more important the relationship between:
rod material + surface treatment + seals + guides
becomes.
Vega’s current technical content also discusses fatigue and high-cycle loading as important considerations for hydraulic-cylinder rods.
Although the Case 195 document does not report a failure, the material specification provides an excellent example of how the rod is engineered for demanding service.
16. What the Customer Case Actually Demonstrates
It is important not to turn the technical correspondence into a failure case that it does not document.
The Customer did not report a broken rod or damaged cylinder in the supplied document.
Instead, the Customer asked Vega for technical parameters concerning:
- body material;
- rod material;
- hardness.
The Vega Team responded with the precise material and treatment specifications.
Therefore, the real value of this Customer Case is technical transparency about cylinder construction, rather than troubleshooting a documented failure.
17. Why Technical Material Data Matters to Customers
Customers may need material information for many reasons.
For example:
- internal engineering approval;
- mold qualification;
- material traceability;
- comparison with specifications;
- maintenance planning;
- supplier qualification;
- application engineering.
Providing specific material grades and treatment parameters allows engineers to evaluate whether the cylinder is suitable for their application.
18. The Difference Between “Steel” and a Technical Material Specification
Simply stating:
“The cylinder is made of steel.”
does not provide enough technical information.
A useful material specification identifies, where relevant:
- material grade;
- applicable standard;
- heat-treatment condition;
- hardness;
- surface treatment;
- treatment depth.
The Vega response provides precisely this level of information for the CM cylinder.
19. A Complete Rod Specification
The Customer Case allows the rod specification to be summarized as follows:
Material:
40CrMnMo7 or equivalent.
Heat treatment:
Hardened and tempered.
Hardness:
32–36 HRC.
Surface treatment:
Ferritic nitrocarburising TF1 + AB1 NcE2.
Standard:
UNI 10931.
Surface hardness:
HV1 > 630.
Treatment depth:
0.2 mm.
This is significantly more useful to an engineer than simply specifying “hardened steel rod.”
20. A Complete Body Specification
The body specification is simpler:
Material:
C40 steel according to UNI EN 10083/1, or equivalent material with the same characteristics.
Hardening:
No hardening treatment.
The difference between the body and rod specifications illustrates how each component is engineered according to its function.
21. What Engineers Should Ask When Selecting a Hydraulic Cylinder
When a hydraulic cylinder is being evaluated for a demanding application, useful technical questions include:
About the body
- What material is used?
- What standard applies?
- Is heat treatment used?
About the rod
- What material is used?
- Is it hardened and tempered?
- What is the hardness?
- Is there a surface treatment?
- What is the treatment depth?
About the sealing system
- Which materials are used?
- What temperature range is supported?
- What fluids are compatible?
About the application
- What pressure is required?
- How many cycles are expected?
- What loads act on the rod?
- Is there any lateral load or misalignment?
These questions help engineers evaluate the complete cylinder rather than only its dimensions.
22. The Importance of Equivalent Materials
The Vega response does not limit the specification to one exact commercial steel grade.
It states:
“or similar with the same characteristic”
for both the body and rod materials.
This is an important distinction.
An equivalent material should not be selected simply because it has a similar name.
It must provide the required characteristics for the application and manufacturing process.
23. Material Selection Is an Engineering Decision
The most important lesson from this Customer Case is that material selection should be treated as part of the engineering design.
For a hydraulic cylinder:
Body material provides the structural foundation.
Rod material provides the mechanical performance required by the moving component.
Heat treatment modifies the bulk mechanical properties.
Surface treatment improves the properties of the working surface.
Sealing system completes the functional interface.
Together, these elements determine the cylinder’s performance.
Conclusion
A Customer contacted the Vega Team requesting the material and hardness specifications of the body and rod used in a CM-series hydraulic cylinder.
Vega specified C40 steel or an equivalent material for the cylinder body, without hardening treatment.
For the rod, Vega specified 40CrMnMo7 or an equivalent steel, hardened and tempered to 32–36 HRC, followed by ferritic nitrocarburising TF1 + AB1 NcE2 according to UNI 10931. The specified surface hardness is HV1 > 630, with a treatment depth greater than 0.2 mm.
The case highlights a fundamental principle of hydraulic-cylinder engineering:
The performance of a hydraulic cylinder begins with the correct combination of materials, heat treatment and surface treatment.
The body and rod do not perform the same function, so they do not necessarily require the same material or treatment.
For the rod in particular, the combination of alloy steel, controlled bulk hardness and a dedicated surface treatment is an important part of designing a component capable of operating reliably under repeated mechanical movement.
Useful and Verified URLs
I checked these links against icvega.com and vegacylinders.com. The descriptions are intentionally in English, matching this article.
- Materials and Components for Hydraulic Cylinders — Official Vega Cylinders page explaining the materials used for cylinder bodies and rods, together with the sealing and guide components selected for hydraulic-cylinder applications. Materials and Components for Hydraulic Cylinders
- V450CM Heavy-Duty Short-Stroke Compact Hydraulic Cylinders — Official Vega product page describing the V450CM heavy-duty cylinder family, including its steel body, chromium-molybdenum steel rod and typical applications in plastic injection molds. V450CM Heavy-Duty Short-Stroke Compact Hydraulic Cylinders
- Hydraulic Cylinders for Molds — Official Vega catalog page covering the hydraulic-cylinder families designed for plastic injection and die-casting molds, including the V450CM series. Hydraulic Cylinders for Molds
- Why Hydraulic Cylinder Rods Fail: Understanding Fatigue Failure in High-Cycle Applications — iCVEGA technical article explaining how repeated loading can contribute to hydraulic-cylinder rod fatigue and why rod material and application conditions matter. Why Hydraulic Cylinder Rods Fail: Understanding Fatigue Failure in High-Cycle Applications
