The chrome plated piston rod is processed by hot rolling or cold rolling, grinding, polishing and chrome plating. Because the surface layer has residual compressive stress on the surface, which helps to seal the tiny cracks on the surface and hinders the expansion of erosion. Therefore, the corrosion resistance of the surface can be improved, and the generation or expansion of fatigue cracks can be delayed, thereby improving the fatigue strength of the cylinder rod.
Through roll forming, a cold work hardening layer is formed on the surface of the chromed piston rod, which reduces the elastic and plastic deformation of the contact surface of the grinding pair, thereby improving the wear resistance of the surface of the cylinder rod and avoiding burns caused by grinding. After rolling, the surface roughness value of the chrome piston rod is reduced, which can improve the fitting properties. At the same time, the friction damage to the seal ring or the seal when the cylinder rod and piston moves is reduced, and the overall service life of the oil cylinder is improved.
The rolling process is a high-efficiency and high-quality process measure. Now, the rolling effect is proved by taking the 160mn diameter mirror doctor brand cutting rolling head (CK45 chrome plated hollow bar) as an example. After rolling, the surface roughness of the cylinder rod is reduced from Ra3.2-6.3um before rolling to Ra0.4-0.8um, the surface hardness of the cylinder rod is increased by about 30%, and the surface fatigue strength of the cylinder rod is increased by 25%. It is increased by 2-3 times, and the rolling process is about 15 times more efficient than the grinding process. The above data shows that the rolling process is efficient and can greatly improve the surface quality of the cylinder rod.
CHEMICAL COMPOSITION(%) | ||||||||||
| ||||||||||
Steel Grade | C% | Mn% | Si% | S% | P% | V% | Ni% | Cr% | Mo% | Cu% |
CK45 | 0.42-0.50 | 0.50-0.80 | 0.17-0.37 | ≤0.035 | ≤0.035 | / | ≤0.25 | ≤0.25 | / | ≤0.25 |
ST52 | ≤0.22 | ≤1.6 | ≤0.55 | ≤0.04 | ≤0.04 | 0.02-0.15 | / | / | / | / |
20MnV6 | 0.17-0.24 | 1.30-1.70 | 0.10-0.50 | ≤0.035 | ≤0.035 | 0.10-0.20 | ≤0.30 | ≤0.30 | / | ≤0.30 |
42CrMo4 | 0.38-0.45 | 0.5-0.8 | 0.17-0.37 | ≤0.035 | ≤0.035 | 0.07-0.12 | ≤0.03 | 0.90-1.20 | 0.15-0.25 | ≤0.03 |
40Cr | 0.37-0.45 | 0.50-0.80 | 0.17-0.37 | ≤0.035 | ≤0.035 | / | ≤0.30 | 0.80-1.1 | / | ≤0.03 |
MECHANICAL PROPERTIES | |||||
| |||||
Material | Tensile Strength | Yield Strength | Elogation | CHARPY | CONDITION |
CK45 | 610 | 355 | 15 | >41J | Normalized |
CK45 | 800 | 540 | 20 | >41J | Q+T |
ST52 | 500 | 355 | 22 |
| Normalized |
20MnV6 | 750 | 590 | 12 | >41J | Normalized |
42CrMo4 | 980 | 850 | 14 | >47J | Q+T |
40Cr | 1000 | 800 | 10 |
| Q+T |
SUPPLY CONDITION | Ground and chrome plated |
CHROME THICKNESS | 20 to 30 micron |
SURFACE ROUGHNESS | Ra≤0.2 micron and Rt≤2 micro |
TOLERANCE ON DIA | ISO f7 on the diameter |
OVALITY | Half of the tolerance ISO f7 |
STRAGHNESS | ≤0.2MM/M |
SURFACE HARDNEDD | 850-1150 HV(vickers 100g) |
COHESION | No craks,breaking or detaching after thermic shock(warming up at 3200 celsius degrees and cooling in water) |
POROSITY | Test according to ISO 1456/1458 and result yaluation according to ISO 4540 rating 8-10 |
CORROSION RESISTANCE | Test in natural salt spray according to ASTM B117-120hours |
Results evaluation | accordin to ISO4540 RATING7-10 |
WELDABILITY | Good |
PACKING | Anti rust oil to be applied on material and each rod to be packed in paper sleeve |
CERTIFICATE | All certificate related with material heat treatment and plating is required |
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