WUXI PAZON TECHNOLOGY CO., LTD
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The Nitrocarburized ST52 Rod features a QPQ-treated surface (diffusion zone 0.30–0.40 mm, white layer ≥25 µm) delivering ≥600 HV hardness without chrome plating. Available in φ6–300 mm, up to 8000 mm long, it meets ISO f7 tolerance and 200-hour salt spray rating 9. Built on ST52 steel with excellent weldability, this chrome-free, dimensionally stable rod provides superior wear and corrosion resistance for welded hydraulic cylinders and outdoor equipment, with full customization supported.
PZPR0009
PAZON
The Nitrocarburized ST52 Rod (ST52 QPQ Rod) is precision-machined from premium ST52 (DIN 1.0580 / S355) carbon-manganese steel in a non-heat-treated condition (core hardness ≤210 HB) and treated with an advanced QPQ (Quench-Polish-Quench) nitrocarburizing process—consisting of nitriding, oxidation, polishing, and re-oxidation. This produces a dense white layer and a supportive diffusion zone without relying on chrome plating. ST52 is inherently known for its superior weldability compared to CK45, and combined with the chrome-free, environmentally friendly QPQ finish, this rod is ideally suited for hydraulic cylinders requiring welded connections with high corrosion resistance and low friction, agricultural machinery, marine equipment and outdoor engineering applications.
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
Core Condition & Hardness: Non-heat-treated (as-rolled/cold-drawn), core hardness ≤210 HB
Surface Modification Treatment: QPQ nitrocarburizing (Nitriding + Oxidation + Polishing + Re-oxidation)
Diffusion Layer Depth: 0.30–0.40 mm
White Layer (Compound Layer) Thickness: ≥25 μm
Surface Hardness: ≥600 HV (typical on white layer)
Surface Roughness: Ra≤0.2 μm, Rt≤2 μm (after polishing)
Corrosion Resistance: Tested in neutral salt spray per ISO 9227/ASTM B117 – 200 hours, rating 9 per ISO 10289
Weldability: Excellent (ST52 has a low carbon equivalent and outstanding weldability; the QPQ layer should be mechanically removed from the weld zone prior to welding, and proper preheating and post-weld stress relief are recommended)
Packing: Anti-rust oil + cardboard tube/plastic sleeve + wooden case
Eco-friendly & chrome-free: QPQ process contains no hexavalent chromium, meeting RoHS and environmental directives
High surface hardness: white layer exceeding 600 HV offers excellent scratch and wear resistance
Superior corrosion resistance: 200-hour salt spray rating 9, matching or exceeding hard chrome performance
Excellent weldability: ST52 base material with low carbon equivalent, ideal for welded structural components, combined with QPQ surface protection
Excellent dimensional stability: low processing temperature ensures minimal distortion for precision rods
No delamination risk: the compound and diffusion layers are metallurgically bonded, eliminating peeling concerns
Low friction coefficient: QPQ surface has self-lubricating properties, reducing seal wear and improving cylinder efficiency
Fully customizable: wide choice of dimensions, tolerances, core conditions and alternative surface treatments
In addition to the standard QPQ finish, we offer:
Custom diameters and lengths, including extra-long or oversized rods
Tolerance grades and non-standard OD tolerances
Higher straightness upon request
Quenched & Tempered core for increased mechanical strength
Alternative surface treatments: hard chrome plating, electroless nickel, zinc plating, laser cladding, thermal spray, ceramic coating
Special case depth requirements or selective nitriding protection
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.
Limits and Fits Table | ||||||||||||
Diameter | f7 | f8 | g6 | h7 | h8 | h9 | ||||||
es | ei | es | ei | es | ei | es | ei | es | ei | es | ei | |
>6-10 | -0.013 | -0.028 | -0.013 | -0.035 | -0.005 | -0.014 | 0 | -0.015 | 0 | -0.022 | 0 | -0.036 |
>10-18 | -0.016 | -0.034 | -0.016 | -0.043 | -0.006 | -0.017 | 0 | -0.018 | 0 | -0.027 | 0 | -0.043 |
>18-30 | -0.020 | -0.041 | -0.020 | -0.053 | -0.007 | -0.020 | 0 | -0.021 | 0 | -0.033 | 0 | -0.052 |
>30-50 | -0.025 | -0.050 | -0.025 | -0.064 | -0.009 | -0.025 | 0 | -0.025 | 0 | -0.039 | 0 | -0.062 |
>50-80 | -0.030 | -0.060 | -0.030 | -0.076 | -0.010 | -0.029 | 0 | -0.030 | 0 | -0.046 | 0 | -0.074 |
>80-120 | -0.036 | -0.071 | -0.036 | -0.090 | -0.012 | -0.034 | 0 | -0.035 | 0 | -0.054 | 0 | -0.087 |
>120-180 | -0.043 | -0.083 | -0.043 | -0.106 | -0.014 | -0.039 | 0 | -0.040 | 0 | -0.063 | 0 | -0.100 |
>180-250 | -0.050 | -0.096 | -0.050 | -0.122 | -0.015 | -0.044 | 0 | -0.046 | 0 | -0.072 | 0 | -0.115 |
>250-315 | -0.056 | -0.108 | -0.056 | -0.137 | -0.017 | -0.049 | 0 | -0.052 | 0 | -0.081 | 0 | -0.130 |
>315-400 | -0.062 | -0.119 | -0.062 | -0.151 | -0.018 | -0.054 | 0 | -0.057 | 0 | -0.089 | 0 | -0.140 |
>400-500 | -0.068 | -0.131 | -0.068 | -0.165 | -0.020 | -0.060 | 0 | -0.063 | 0 | -0.097 | 0 | -0.155 |
>500-630 | -0.076 | -0.146 | -0.076 | -0.186 | -0.022 | -0.066 | 0 | -0.070 | 0 | -0.110 | 0 | -0.175 |
>630-800 | -0.080 | -0.160 | -0.080 | -0.205 | -0.024 | -0.074 | 0 | -0.080 | 0 | -0.125 | 0 | -0.200 |
>800-1000 | -0.086 | -0.176 | -0.086 | -0.226 | -0.026 | -0.082 | 0 | -0.090 | 0 | -0.140 | 0 | -0.230 |
>1000-1250 | -0.098 | -0.203 | -0.098 | -0.263 | -0.028 | -0.094 | 0 | -0.105 | 0 | -0.165 | 0 | -0.260 |
>1250-1600 | -0.110 | -0.235 | -0.110 | -0.305 | -0.030 | -0.108 | 0 | -0.125 | 0 | -0.185 | 0 | -0.290 |
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.
Chemical Composition | ||||||||||
Material | C(%) | Si(%) | Mn(%) | P(%) | S(%) | V(%) | Ni(%) | Cr(%) | Mo(%) | Cu(%) |
CK45 | 0.42-0.50 | 0.17-0.37 | 0.50-0.80 | ≤0.035 | ≤0.035 | ≤0.30 | ≤0.25 | ≤0.25 | ||
25Mn | 0.22-0.30 | 0.17-0.37 | 0.70-1.00 | ≤0.035 | ≤0.035 | ≤0.30 | ≤0.25 | ≤0.25 | ||
20# | 0.17-0.24 | 0.17-0.37 | 0.35-0.65 | ≤0.035 | ≤0.035 | ≤0.30 | ≤0.25 | ≤0.25 | ||
ST52 | ≤0.24 | ≤0.55 | ≤1.6 | ≤0.045 | ≤0.045 | 0.01-0.12 | ≤0.50 | ≤0.30 | ≤0.10 | ≤0.55 |
40Cr | 0.37-0.44 | 0.17-0.37 | 0.50-0.80 | ≤0.035 | ≤0.035 | ≤0.30 | 0.80-1.10 | ≤0.30 | ||
42CrMo4 | 0.38-0.45 | 0.17-0.37 | 0.50-0.80 | ≤0.035 | ≤0.035 | 0.07-0.12 | ≤0.03 | 0.90-1.20 | 0.15-0.25 | ≤0.030 |
20MnV6 | 0.17-0.24 | 0.17-0.37 | 1.30-1.60 | ≤0.035 | ≤0.035 | 0.10-0.20 | ≤0.30 | ≤0.30 | ≤0.30 | |
38MnVS6 | 0.34-0.41 | ≤0.80 | 1.20-1.60 | ≤0.025 | 0.02-0.06 | 0.08-0.20 | ≤0.30 | ≤0.08 | ≤0.30 | |
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.
Mechanical Properties | |||||
Material | T.S | Y.S | E% | CHARPY | CONDITION |
CK45 | 610 | 355 | 15 | ＞41J | Normalised |
CK45 | 630 | 540 | 15 | ＞41J | Cold Drawn |
CK45 | 800 | 630 | 20 | ＞41J | Q+T |
25Mn | 620 | 520 | 15 | Cold Drawn | |
20# | 520 | 400 | 15 | Cold Drawn | |
ST52 | 500 | 355 | 22 | Normalised | |
Q345D | 620 | 520 | 15 | ＞27(-20°C) | Cold Drawn |
40Cr | 1000 | 800 | 10 | Q+T | |
42CrMo4 | 980 | 850 | 14 | ＞47J | Q+T |
20MnV6 | 750 | 590 | 12 | ＞40J | Normalised |
38MnVS6 | 850 | 580 | 15 | Normalised | |
