Chrome Plated 40Cr Rod (Q & T + I.H.)

The Chrome Plated 40Cr Rod (Q & T + I.H.) is manufactured from premium 40Cr alloy structural steel (AISI 5140) using a dual heat treatment—Quenched & Tempered plus Induction Hardened—followed by precision grinding and hard chrome plating. Q&T develops a tough, high-strength core at 220–320 HB, while induction hardening creates a uniform, ultra-hard surface of 52–62 HRC with a depth of 0.5–3.5 mm, further enhanced by an 850–1150 HV hard chrome deposit. The chromium addition significantly improves hardenability, providing a more uniform case and superior core properties compared to plain carbon steels. This extreme “super-strong core + ultra-hard surface” gradient is engineered for the most demanding heavy-duty, high-wear, high-impact hydraulic cylinders—such as large mining equipment, deep-sea machinery, and heavy construction plant—offering a flagship piston rod solution.

• Diameter: Mainly φ6–300 mm, larger custom sizes accepted

• Length: ≤8000 mm, custom lengths available

• Straightness: ≤0.2 mm/M

• Tolerance Grades: IT6–IT9

• OD Tolerance: According to ISO f7/f8/g6/h7/h8/h9; customized tolerances available upon request

• Ovality: Half of the tolerance value ISO f7

• Heat Treatment: Quenched & Tempered + Induction Hardened; customization options: Q&T only, I.H. only, QPQ, etc.

• Core Hardness (Q&T): 220–320 HB

• Surface Hardness (I.H.): 52–62 HRC

• Hardening Depth: 0.5–3.5 mm (adjustable)

• Surface Treatment: Hard Chrome Plated; customization options: EN Plating / Zinc Plating / Laser Cladding / Nitriding / QPQ / Thermal Spraying / Ceramic Coating

• Chrome Thickness: ≥10 μm, mainly 20–40 μm; can be over 100 μm for high-standard requirements

• Chrome Layer Hardness: 850–1150 HV (Vickers 100 gf)

• Surface Roughness: Ra≤0.2 μm, Rt≤2 μm

• Cohesion: No cracks, breaking or detaching after thermal shock (warming up at 300 ℃ and cooling in water)

• Porosity: Tested according to ISO 1456/1458, evaluation according to ISO 10289 rating 8–10. Under 10× magnification, no more than 30 micro white pin-holes per 1000 mm², with diameter not greater than approx. 0.1 mm

• Corrosion Resistance: Tested in neutral salt spray according to ISO 9227/ASTM B117 – 96 hours, rating 9 per ISO 10289

• Weldability: Poor (chromium alloying reduces weldability; welding directly on the induction-hardened layer is prohibited; if necessary, the hardened layer must be mechanically removed beforehand, and strict preheating and post-weld stress relief are mandatory; avoid welding in load-bearing areas)

• Packing: Anti-rust oil + cardboard tube/plastic sleeve + wooden case

• 40Cr alloy steel with dual heat treatment creates a top-tier gradient of “ultra-strong, tough core + ultra-hard, uniform surface”

• Q&T core at 220–320 HB delivers excellent bending, impact, and fatigue resistance with outstanding load-bearing capacity

• Induction-hardened surface at 52–62 HRC, with alloy-enhanced uniformity, provides exceptional wear, indentation, and scratch resistance

• Hard chrome overlay at 850–1150 HV acts as a third protective shield, offering ultimate wear and corrosion protection for extreme conditions

• Tight f7 tolerance and low ovality ensure smooth operation and reliable sealing under heavy loads and high pressure

• 96-hour salt spray rating 9, with a combined anti-corrosion system for harsh environments and extended service life

• Fully customizable to provide an exclusive alloy steel flagship piston rod solution for top-tier heavy-duty OEM equipment

In addition to standard specifications, we offer:

• Custom diameters and lengths, including extra-large sizes

• Tolerance grades and non-standard OD tolerances

• Higher straightness upon request

• Tailored combination of core and induction-hardened case hardness

• Precise control of hardening depth

• Surface treatment alternatives: zinc plating, electroless nickel, laser cladding, nitriding, thermal spray, ceramic coating

• Extra-thick chrome layers beyond 100 μm

• Enhanced corrosion resistance and dedicated packing solutions

Limits and Fits Table

The table below provides shaft deviation values for commonly used tolerance grades f7, f8, g6, h7, h8, and h9 to assist your selection according to seal fits.

Chemical Composition

The table presents the standard chemical composition of frequently used materials such as CK45, 25Mn, 20#, ST52, 40Cr, 42CrMo4, 20MnV6 and 38MnVS6 for your reference.

Mechanical Properties

The following table lists reference tensile strength, yield strength, elongation and impact energy values for CK45 (hot-rolled, cold-drawn, Q&T), 25Mn, 20#, ST52, Q345D, 40Cr, 42CrMo4, 20MnV6 and 38MnVS6 under various conditions.