WUXI PAZON TECHNOLOGY CO., LTD
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The Nitrocarburized 42CrMo Rod features a QPQ-treated surface (diffusion zone 0.30–0.40 mm, white layer ≥25 µm) achieving ≥700 HV hardness without chrome plating. Available in φ6–300 mm, up to 8000 mm long, it meets ISO f7 tolerance and 300-hour salt spray rating 9. Built on 42CrMo chromium-molybdenum steel with superior nitriding response, this chrome-free rod provides exceptional wear and corrosion resistance for the most demanding hydraulic cylinders. Full customization supported.
PZPR0034
PAZON
The Nitrocarburized 42CrMo Rod (42CrMo QPQ Rod) is precision-machined from premium 42CrMo chromium-molybdenum alloy steel (AISI 4140 / 42CrMo4) in a non-heat-treated condition (core hardness ≤260 HB) and treated with an advanced QPQ (Quench-Polish-Quench) nitrocarburizing process—consisting of nitriding, oxidation, polishing, and re-oxidation. This process forms an exceptionally dense white layer and a robust diffusion zone without the need for chrome plating. Thanks to the combined effect of chromium and molybdenum, 42CrMo exhibits outstanding nitriding response, achieving much higher surface hardness than standard alloy steels after QPQ. This chrome-free, environmentally superior rod is engineered for heavy-duty hydraulic cylinders, marine equipment, mining machinery, and offshore applications demanding extremely high corrosion and wear resistance.
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 ≤260 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: ≥700 HV (typical on white layer; Cr-Mo alloying significantly enhances hardness)
Surface Roughness: Ra≤0.2 μm, Rt≤2 μm (after polishing)
Corrosion Resistance: Tested in neutral salt spray per ISO 9227/ASTM B117 – 300 hours, rating 9 per ISO 10289
Weldability: Very poor (high carbon equivalent severely impairs weldability; the QPQ layer must be mechanically removed from the weld zone before welding, followed by strict high-temperature preheating and immediate post-weld stress-relief tempering; welding in load-bearing areas is absolutely prohibited)
Packing: Anti-rust oil + cardboard tube/plastic sleeve + wooden case
Eco-friendly & chrome-free: QPQ technology contains no hexavalent chromium, fully compliant with RoHS and green manufacturing directives
Extremely high surface hardness: thanks to chromium and molybdenum, the white layer hardness reaches ≥700 HV, delivering ultimate scratch and wear resistance
Superior corrosion resistance: 300-hour salt spray rating 9, providing protection equal to or better than hard chrome in salty, humid, and chemically aggressive environments
Excellent base strength: even in non-heat-treated condition, 42CrMo alloy steel offers a higher strength foundation than plain carbon and common alloy steels
Outstanding dimensional stability: low process temperature ensures minimal distortion, ideal for high-precision rods without extra straightening
No delamination risk: the diffusion and compound layers are metallurgically bonded, completely eliminating the peeling and spalling failures associated with traditional chrome plating
Low friction coefficient: the self-lubricating QPQ surface significantly reduces seal friction, cutting energy consumption and extending maintenance intervals
Fully customizable: extensive choice of dimensions, tolerances, core conditions, and alternative surface treatments to flexibly meet premium OEM requirements
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 further improved overall strength and fatigue life
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 | |
