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New plating process for anti-friction layer of sliding bearing (4)
Source: Bearing network time: 2017-10-13
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5.1 Experimental conditions Anode composition: PbSn10,
Temperature: 20~25°C,
Power supply: three-phase full-wave silicon rectifier,
Several scales of the test piece: 100×50×4,
The composition of the test piece fabric (ie the substrate to be plated): CuPb22Sn2,
The appearance roughness of the test piece fabric: Ra0. 4.
Fixed component content.
Sn 2+: 15g / ι, Cu: 5g / ι, stabilizer: 5g / ι, additive: 2g / ι,
Table 1 Column number, factor comparison table ------------------------------------------ --------------
L9(3< 1 2 3 5
Sup>4) column number -------------------------------------------- ------------
Factor ABCD
-------------------------------------------------- ------
Table 2 Factor, Level Table -------------------------------------------- -----------------
Horizontal/number free fluoroboron lead ion free boric acid cathode current/factor acid [HBF [H3 density (DK)
Ub>4] BO
3 sub>]
ABCD
-------------------------------------------------- -----------
1 75g/ι 250g/ι 25g/ι 4A/dm2
2 150g/ι 150g/ι 35g/ι 3A/dm2
3 300g/ι 80g/ι 15g/ι 2A/dm2
-------------------------------------------------- -----------
5.2 factors and their levels of free fluoroboric acid (HBF4) concentration (A): A1 = 70g / ι, A2 = 150g / ι, A3 = 300g / ι.
Concentration of lead ion (Pb2+) (B): B1=250g/ι, B2=150g/ι, B3=80g/ι.
Concentration of free boric acid (H3BO3) (C): C1=25G/ι, C2=35g/ι, C3=15g/ι.
Anode power density (DK) (D): D1 = 4A / dm2, D2 = 3A / dm2, D3 = 2A / dm2.
5.3 The experimental process and its results evaluation after careful and careful preparation; according to the orthogonal experimental plan (see Table 3) carefully organized nine experiments; the experimental results were evaluated.
Table 3 Orthogonal experimental plan and its results analysis table L9 (34)
-------------------------------------------------- -----------
Experiment No./Water 1 2 3 4 Experimental Results Rating Flat/Column----------------------------------- --------------------------
1 1 1 1 1 100
2 1 2 2 2 100
3 1 3 3 3 95
4 2 1 2 3 80
5 2 2 3 1 65
6 2 3 1 2 70
7 3 1 3 2 45
8 3 2 1 3 50
9 3 3 2 1 30
-------------------------------------------------- -----------
K1 295 225 220 195
K2 215 215 210 215
K3 125 195 205 225
R 56.6 10. 0 5. 0 10. 0
-------------------------------------------------- -----------
In Table 3; K1 is the sum of the first level scores in each column, K2 is the sum of the second level scores in each column, and K3 is the sum of the third level scores in each column.
R=(Kmax Kmin)/3.
The order of influence of four factors on the quality of bearing antifriction coating is A>B=D>C. The concentration of free fluoroboric acid has the greatest influence; the concentration of lead ion and the influence of cathode current density are the second; the concentration of free boric acid has the least influence. .
Now analyze the influence of each level of each factor on the quality of the anti-friction coating.
In A: K1>K2>K3; the first level is the best.
In B: K1>K2>K3; the first level is the best.
In C: K1>K2>K3; the first level is the best.
In D: K3>K2>K1; the third level is the best.
After the above analysis; the best combination condition is A1B1C1D3. The best plating condition obtained by orthogonal experiment is HBF4 (free): 70g/ι,
Pb2+: 250g/ι,
H3BO3 (free): 25g/ι,
DK: 2A/dm2.
In the practice of production; think about the conductivity of the bath and the loss of the elements; adjust the concentration of free fluoroboric acid and the concentration of lead ions; the former is properly adjusted; the latter is properly adjusted. From Table 3 can also It can be seen that when the DK is within the scale of 2~3A/dm2; the quality of the coating is not much different; it is considered that the production progresses; therefore, it is determined to be within the appropriate scale. When the temperature is lowered; the free boric acid is easy to separate and crystallize; Therefore, the concentration is considered to be slightly lower.
The various factors have been weighed extensively; the process of electroplating the ternary alloy antifriction layer has been improved as follows.
Pb2+ (participated in the form of Pb(BF4)2): 150~200g/ι,
Sn2+ (in the form of Sn(BF4)2): 10~20g/ι,
Cu2+ (participated in the form of Cu(BF4)2): 3~6g/ι,
HBF4 (free): 70~120g/ι,
H3BO3 (free): 20~25g/ι,
Stabilizer: 3~10g/ι,
Additive: 0. 5~5g/ι,
Temperature (T): 15~35°C,
Cathode current density (DK): 2~2. 8A/dm2,
Time (t): 15~35min,
Coating thickness (δ): 15~30μm,
Anode composition: PbSn9~11,
The ratio of anode area to cathode area: 2.
6 The improved process has experienced many years of production and operation testing. The result is that the coating crystal is fine and lubricated; it eliminates the shortcomings of airflow streaks, pinholes, pits, nodules, roughness, etc. The loss rate of the shunt products is originally The reduction of about 0.5% to less than 0.1% today, the rate of qualified products in one inspection has increased from about 90% to 99% today. It can be seen that the quality of the plating products has improved significantly.
Once; each anode orientation can only be plated with a pair of bearing bushes; DK open middle and lower limits also have rough coatings, streaks and other shortcomings. After the improvement process; each anode orientation can be plated with 2~4 sub-bearings; cathode current density ratio The progress is nearly 50%; and the crystallization of the coating is still very fine. The improved process progress is 2~4 times.
The order quantity of our factory has been increasing year by year; the output value has increased year by year; the current annual output value has reached more than 10 million yuan. The direct economic benefits have reached tens of millions of yuan in the past ten years. Together with the localization of the main engine and the imported main engine A suitable number of high-quality bearing components have been supplied. These years; some of the bearing products of our factory have entered the world market. I am fortunate to have a certain relationship with the improvement of the quality of the plating.
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