The thickness of the iron is 3mm, with a nickel plating base layer, using the Japanese Yonghui additive KY-Z series, under the conditions of a current density of 20A/dm2 and a rotation speed of 65r/min, hard copper is electroplated in a homemade experimental small tank (solution volume 100L).
　　Eight plated rollers were used, among which five rollers had an additive supplement of 150ml/KAH, electroplating different thicknesses (after grinding and polishing), specifically: roller 1# 6 wires (60um), roller 2# 8 wires, roller 3# 10 wires, roller 4# 12 wires, roller 5# 14 wires; the other three rollers all had a thickness of 10 wires (after grinding and polishing), with additive supplement amounts of roller 6# 90ml/KAH, roller 7# 120ml/KAH, roller 8# 180ml/KAH. The test rollers with different additive supplement amounts needed to undergo a balance test for more than 10 hours before plating to ensure the additive content in the plating solution met the testing requirements.
    Data is tested every 4 days, with 5 data points tested each time. Three of these data points are selected to calculate the average value for a curve graph, and the analyzed data leads to the following conclusions:
　　The relationship between the hardness of the copper plating layer and the shelf life of the hardness with the plating layer.

Chart 1: The relationship between the hardness of the copper plating layer and the thickness of the plating layer.
   

　　From the above curve, it can be concluded that: (1) The hardness of the copper plating layer decreases over time; (2) The greater the thickness of the copper plating layer, the higher its hardness value, the more gradual the hardness change, and the longer the shelf life.
　　2. The relationship between the hardness of the copper plating layer and the consumption of additives (plating thickness 10S).

Chart 2: The relationship between the hardness of the copper plating layer and the consumption of additives.

    From Chart 2, it can be concluded that: (1) Under constant thickness, the greater the additive supplement, the higher the hardness of the copper plating layer; (2) The greater the additive supplement, the more gradual the hardness change, and the longer the shelf life.
　　3. The relationship between the hardness of the chrome plating layer and time (roller 8#, copper layer 10S, chrome layer 1.1S; additive consumption 180ml/KAH).
 

Chart 3: The relationship between the hardness of the chrome plating layer and time.
 

　　From Chart 3, it can be concluded that the hardness of the chrome plating layer decreases relatively quickly within the first month, and then tends to stabilize.
    4. The relationship between the hardness of the chrome plating layer and the thickness of the copper plating layer (additive consumption 150ml/KAH).

Chart 4: The relationship between the hardness of the chrome plating layer and the thickness of the copper plating layer.
 

　　From Chart 4, it can be concluded that: (1) The hardness of the chrome layer is directly related to the hardness of the copper layer; the higher the hardness of the copper layer, the higher the hardness of the chrome layer; (2) The hardness of the chrome layer has an indirect relationship with the thickness of the copper layer; the thicker the copper layer, the higher the hardness, which will also enhance the hardness of the chrome layer.
　　5. The relationship between the hardness of the chrome layer and the additive supplement amount of copper plating (plating thickness 10S, chrome layer 1.1S).

Chart 5: The relationship between the hardness of the chrome layer and the additive supplement amount of copper plating.
 

　　From Chart 5, it can be concluded that the hardness of the chrome layer is closely related to the additive supplement amount of copper plating; the higher the hardness of the copper layer, the higher the hardness of the chrome layer.
　　Summary:
1. The hardness of the copper plating layer gradually decreases over time.
2. The greater the thickness of the copper plating layer, the higher its hardness value and the longer the shelf life.
3. Under constant thickness of the copper plating layer, the greater the additive supplement, the higher the hardness of the copper plating layer, the more stable the hardness change, and the longer the shelf life.
4. The hardness of the chrome layer decreases relatively quickly within the first month, and then tends to stabilize.
5. The hardness of the chrome layer is directly related to the hardness of the copper layer; the higher the hardness of the copper layer, the higher the hardness of the chrome layer.
6. The hardness of the chrome layer has an indirect relationship with the thickness of the copper layer; the thicker the copper layer, the higher the hardness, the longer the shelf life, and the more stable the hardness change of the chrome layer.
7. The hardness of the chrome layer is closely related to the additive supplement amount of copper plating; the greater the additive supplement, the higher the hardness of the copper layer, the more stable the hardness change, and the higher the hardness of the chrome layer, with a more gradual decline in hardness.