Repair of hydraulic cylinder bar

- Jul 18, 2019-

After the hydraulic cylinder bar of the hydraulic cylinder is pulled, if it is not treated in time, it will affect the normal use, but the hydraulic cylinder will not work. Our repair method is to repair the lighter stretch marks by local grinding and polishing; for the heavy pull marks, it is repaired by welding and manual grinding.


The formation of the pull marks: After the crane was disintegrated, it was found that a piston rod of the variable amplitude cylinder was severely pulled, and the pull marks were side by side. The main cause of the piston rod strain is: after the dust-proof ring is embrittled and lost in a block form, not only the dust-proof effect is lost, but also a lot of dust and magazines are accumulated there, so that the piston rod is directly ground with impurities, resulting in a piston. The rod was pulled and the scratches scraped the rubber seal assembly of the cylinder port, causing serious leakage of the hydraulic cylinder.


Repair requirements: the filler and the base metal must be combined firmly and smoothly; the seasoning must be durable and easy to process by hand; manual machining must ensure that the piston rod diameter error is less than 0.06mm. After analysis, it was decided that the filler used was J422 electrode. Because the acid electrode is not sensitive to rust, oil and moisture, it is not easy to produce hydrogenation holes; the process is good and easy to operate; the weld is beautifully formed; the material hardness is moderate, easy to process by hand; the arc is stable, the penetration is large, and the base metal The combination is firm.


Repair process:


(1) Clean the parts to be welded first, then use the wet mud to keep the traces around.


(2) Select a welding rod with a diameter of 2.5mm, adjust the current of the welding machine to 120A, and adopt a straight line method to smoothly apply welding.


(3) After all the welding is completed, the mud and slag are removed, and the rough boring is performed along the circumference of the piston rod to maintain a machining allowance of 0.1-0.2 mm.


(4) A cylinder with an outer diameter of 185 mm, an inner diameter of 125 mm and a length of 150 mm is sawed along the axis (one outer diameter of the piston rod is 125 mm), one is a rough mold, and the other is a fine mold.


(5) Apply a thin layer of red ink on the inner wall of the rough mold, then press the rough mold against the part to be repaired of the piston rod to reciprocate several times along the axis, and then use the fine boring to make the heavy red mark on the piston rod. Get rid of it. This is repeated repairs, leaving a machining allowance of 0.04-0.07mm.


(6) The piston rod is then ground to a specified size by using a 320-mesh sand slag kerosene in combination with a precision mold.


(7) Finally, hand-polished with kerosene on the back of the abrasive cloth. After measurement, the maximum error is only 0.03mm.


After the crane was repaired, after a year and a half of use, the variable-width hydraulic cylinder never showed any leakage, and the piston rod was smooth and rust-free.