Thermal spray technology to repair printing rollers
2019-01-29 06:02:06
After the printing roller is used for a certain period of time, its surface is corroded and worn, which affects the quality of the printed product. General solutions include grinding, plating, and replacement of new parts. We use thermal spray technology to repair, after more than 4 years of experimental applications, has achieved very good results.
1. Technical requirements (1) The bond strength between the coating and the substrate is greater than 40 MPa, and the surface hardness is about HRC35.
(2) The coated alloy has good resistance to oxidation and corrosion.
(3) No microscopic pits on the surface.
(4) The dimensional accuracy reaches φ300±20.01mm, the radial full runout error must not exceed 0.02mm, and the surface finish Ra=0.8μUm.
2. Pre-preparation work (1) Preparation of alloy powder According to the characteristics and application of the printing cylinder, the composition of the alloy powder was determined as follows:
C ≤ 0.15% Crl0% ~ 15%
B1.5% to 2.5% Si2.5% to 3.5%
Mo2.5% to 4.0% Fe≤5%
Cu3% to 5% Ni Residue After the alloy powder is placed, it is sieved with a 300 mesh sieve and baked at 150°C to 200°C for one or two hours.
(2) Drum pretreatment The cleaned drum is placed in an oven, baked at 300°C for 3 to 4 hours, and then lifted out and clamped on a C6140 lathe. The center hole of the drum shaft end is used as the reference for clamping. The shaft diameter is matched and the rough oxide is removed from the surface oxide layer after clamping, until a completely new surface is exposed.
(3) Prepare auxiliary equipment Prepare oxygen cylinders, acetylene bottles, pressure gauges, modified SPTH-6 ton guns, and pressure pipes. After being connected, adjust it to neutral flame.
3. Repair (1) Spray Place the prepared alloy powder in the powder bucket, adjust the oxygen pressure to 0.81~1.01MPa, adjust the acetylene pressure to 0.05~0.10MPa, adjust the speed of the lathe spindle to 20r/min, ignite the spray gun and open the powder. Valve, first spray a thin layer of nickel coated aluminum powder on the roller, and then spray the alloy powder, until there is more than 0.2mm allowance can stop spraying.
After stopping spraying, the drum continued to rotate at a low speed. After the air was cooled to room temperature, the quality of spraying was checked.
(2) Carry out finishing after confirming that the coating has no quality problems. A 0.1mm grinding allowance is reserved for finishing the car. The finishing car is turned to the grinding machine and finely ground to φ300±0.01mm.
Finally, the radial full runout error and surface hardness are checked, and they can be delivered after they are used.
The Xinhua Printing Factory in Dachuan District of Sichuan Province processed two printing cylinders for testing in 1994. From the use of these years, none of the cylinders was corroded and scratched. The effect was very good. The repaired roller's anti-corrosion performance, anti-hard spot scratching and wear resistance are both higher than those of the original. The service life is 2 to 3 times longer than the original. When the plant used the winter and summer vacations to repair equipment in the past two years, it also removed 6 rollers for thermal spray repair. This alone created a profit of 200,000 to 300,000 yuan for the factory.
1. Technical requirements (1) The bond strength between the coating and the substrate is greater than 40 MPa, and the surface hardness is about HRC35.
(2) The coated alloy has good resistance to oxidation and corrosion.
(3) No microscopic pits on the surface.
(4) The dimensional accuracy reaches φ300±20.01mm, the radial full runout error must not exceed 0.02mm, and the surface finish Ra=0.8μUm.
2. Pre-preparation work (1) Preparation of alloy powder According to the characteristics and application of the printing cylinder, the composition of the alloy powder was determined as follows:
C ≤ 0.15% Crl0% ~ 15%
B1.5% to 2.5% Si2.5% to 3.5%
Mo2.5% to 4.0% Fe≤5%
Cu3% to 5% Ni Residue After the alloy powder is placed, it is sieved with a 300 mesh sieve and baked at 150°C to 200°C for one or two hours.
(2) Drum pretreatment The cleaned drum is placed in an oven, baked at 300°C for 3 to 4 hours, and then lifted out and clamped on a C6140 lathe. The center hole of the drum shaft end is used as the reference for clamping. The shaft diameter is matched and the rough oxide is removed from the surface oxide layer after clamping, until a completely new surface is exposed.
(3) Prepare auxiliary equipment Prepare oxygen cylinders, acetylene bottles, pressure gauges, modified SPTH-6 ton guns, and pressure pipes. After being connected, adjust it to neutral flame.
3. Repair (1) Spray Place the prepared alloy powder in the powder bucket, adjust the oxygen pressure to 0.81~1.01MPa, adjust the acetylene pressure to 0.05~0.10MPa, adjust the speed of the lathe spindle to 20r/min, ignite the spray gun and open the powder. Valve, first spray a thin layer of nickel coated aluminum powder on the roller, and then spray the alloy powder, until there is more than 0.2mm allowance can stop spraying.
After stopping spraying, the drum continued to rotate at a low speed. After the air was cooled to room temperature, the quality of spraying was checked.
(2) Carry out finishing after confirming that the coating has no quality problems. A 0.1mm grinding allowance is reserved for finishing the car. The finishing car is turned to the grinding machine and finely ground to φ300±0.01mm.
Finally, the radial full runout error and surface hardness are checked, and they can be delivered after they are used.
The Xinhua Printing Factory in Dachuan District of Sichuan Province processed two printing cylinders for testing in 1994. From the use of these years, none of the cylinders was corroded and scratched. The effect was very good. The repaired roller's anti-corrosion performance, anti-hard spot scratching and wear resistance are both higher than those of the original. The service life is 2 to 3 times longer than the original. When the plant used the winter and summer vacations to repair equipment in the past two years, it also removed 6 rollers for thermal spray repair. This alone created a profit of 200,000 to 300,000 yuan for the factory.
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