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FOSHAN FEROSTEEL CO., LTD

FOSHAN FEROSTEEL CO., LTD
FOSHAN FEROSTEEL CO., LTD

FOSHAN FEROSTEEL CO., LTD

FOSHAN FEROSTEEL CO., LTD
FOSHAN FEROSTEEL CO., LTD

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Process technology 丨 Stainless steel alloy plating hard chrome process
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Process technology 丨 Stainless steel alloy plating hard chrome process

  • Categories:FAQS
  • Author:Ferosteel
  • Origin:Ferosteel
  • Time of issue:2020-05-19 10:34
  • Views:

(Summary description)High-tungsten stainless steel can be widely used in precision instruments, especially in aviation products. High tungsten stainless steel parts electroplated with hard chromium can improve its hardness, wear resistance, corrosion resistance, etc., but are prone to defects such as missing plating and partial thinning. This work uses some special process measures to ensure the quality of electroplated hard chromium in high tungsten stainless steel parts in aviation products.     1. Craftsmanship     1.1 Chrome plating process     Parts → blown wet sand → alkaline degreasing → hot water washing → cold water washing → activation → cold water washing → chrome plating → dehydrogenation.     1.2 Pre-treatment of chrome plating     (1) The chemical properties of the high-tungsten stainless steel are very stable and difficult to be activated. In the pre-treatment, wet-blown sand treatment is adopted to activate its surface. Compared with blown dry sand, blown wet sand can make the surface of high-tungsten stainless steel finer, more suitable for precision parts, and also has the advantage of less pollution. Wet sand blown parts can be chrome plated immediately after cleaning. The following degreasing and activation steps can be omitted. If other steps are required, perform other steps after blow drying.     (2) The degreasing process of the high-tungsten stainless steel before chromium plating is roughly the same as the conventional chrome plating. The organic solvent degreasing, electrochemical degreasing, and chemical degreasing methods can be used. The surface of the parts must be cleaned to a water film Not broken. If electrochemical degreasing is used, cathode degreasing should be avoided to prevent hydrogen embrittlement.     The degreasing method adopted in this test is: Oakite 45 ~ 60g / L, 50 ~ 60 ℃, 10 ~ 12min.     (3) Activation is necessary after degreasing to ensure good adhesion when electrodepositing hard chromium. The activation of high-tungsten stainless steel is carried out in 2530mL / LH2SO4 (p = 1.84g / cm3) solution, and it can be immersed at room temperature for 2 to 5 minutes.     1.3 Hard chrome plating     Similar to the general stainless steel material hard chrome plating, the non-plated part should be insulated before plating. The parts are pre-treated by immersing in hot water of 50 to 60 degrees Celsius to make the temperature of the parts and the temperature of the hard chrome plating solution Be consistent. The parts should be charged with a man-powered trough, using a stepped small current. The size of the small step current should be adjusted according to the area. When the area is small, the small step current should be reduced, and when the area is large, the small step current should be increased. For the parts with complex shapes, the stepped small current has a longer residence time, and the residence time decreases with the increase of the current, and the effect is very good.     Regulator cover parts (material is AMS5616, mass fraction is 0.17% C, 13% Cr, 2% Ni, 3% W) when the bottom plane is electroplated with hard chrome, the shape of the bottom plane (see Figure 1) is more complicated Wet sand activates the surface, but because of insufficient solution flow in the cavity of the part during the electroplating process, the activation of the bottom plane is not sufficient, and a small area of ​​missed plating will occur. The traditional stepped small current cannot completely solve the problem of leak plating. For example, a step-and-step small current method with a longer stay (15A stay for 15min, 10A stay for 10min, 15A stay for 5min). Stainless steel is easy to passivate, the overpotential is small during the deposition of chromium, and it is not easy to be activated compared to ordinary stainless steel. The stepped low-current power supply that stays for a long time causes the cathode (ie, parts and accessories) to generate a large number of new ecological hydrogen atoms for a long period of time, and as the current increases, the new ecological hydrogen atoms will increase accordingly. These new ecological hydrogen atoms have a very high reducing ability, so that the passive film on the stainless steel surface is continuously reduced, thereby activating the surface of the part, especially the large current in the small step current can fully activate the complex parts of the part.     The pre-treatment of the ladder small current transmission for a long time and the wet sand blowing not only help to improve the bonding force between the coating and the substrate, but also help to ensure the integrity of the coating and ensure the quality of the plating. The treatment process has little damage to the stainless steel substrate. Afterwards, impact plating with 1.5 to 2.0 times the normal current density for 30 to 60 seconds can produce a dense and well-bonded thin chromium layer in a relatively short time. This kind of impact plating is indispensable for parts w

Process technology 丨 Stainless steel alloy plating hard chrome process

(Summary description)High-tungsten stainless steel can be widely used in precision instruments, especially in aviation products. High tungsten stainless steel parts electroplated with hard chromium can improve its hardness, wear resistance, corrosion resistance, etc., but are prone to defects such as missing plating and partial thinning. This work uses some special process measures to ensure the quality of electroplated hard chromium in high tungsten stainless steel parts in aviation products.

    1. Craftsmanship

    1.1 Chrome plating process

    Parts → blown wet sand → alkaline degreasing → hot water washing → cold water washing → activation → cold water washing → chrome plating → dehydrogenation.

    1.2 Pre-treatment of chrome plating

    (1) The chemical properties of the high-tungsten stainless steel are very stable and difficult to be activated. In the pre-treatment, wet-blown sand treatment is adopted to activate its surface. Compared with blown dry sand, blown wet sand can make the surface of high-tungsten stainless steel finer, more suitable for precision parts, and also has the advantage of less pollution. Wet sand blown parts can be chrome plated immediately after cleaning. The following degreasing and activation steps can be omitted. If other steps are required, perform other steps after blow drying.

    (2) The degreasing process of the high-tungsten stainless steel before chromium plating is roughly the same as the conventional chrome plating. The organic solvent degreasing, electrochemical degreasing, and chemical degreasing methods can be used. The surface of the parts must be cleaned to a water film Not broken. If electrochemical degreasing is used, cathode degreasing should be avoided to prevent hydrogen embrittlement.

    The degreasing method adopted in this test is: Oakite 45 ~ 60g / L, 50 ~ 60 ℃, 10 ~ 12min.

    (3) Activation is necessary after degreasing to ensure good adhesion when electrodepositing hard chromium. The activation of high-tungsten stainless steel is carried out in 2530mL / LH2SO4 (p = 1.84g / cm3) solution, and it can be immersed at room temperature for 2 to 5 minutes.

    1.3 Hard chrome plating

    Similar to the general stainless steel material hard chrome plating, the non-plated part should be insulated before plating. The parts are pre-treated by immersing in hot water of 50 to 60 degrees Celsius to make the temperature of the parts and the temperature of the hard chrome plating solution Be consistent. The parts should be charged with a man-powered trough, using a stepped small current. The size of the small step current should be adjusted according to the area. When the area is small, the small step current should be reduced, and when the area is large, the small step current should be increased. For the parts with complex shapes, the stepped small current has a longer residence time, and the residence time decreases with the increase of the current, and the effect is very good.

    Regulator cover parts (material is AMS5616, mass fraction is 0.17% C, 13% Cr, 2% Ni, 3% W) when the bottom plane is electroplated with hard chrome, the shape of the bottom plane (see Figure 1) is more complicated Wet sand activates the surface, but because of insufficient solution flow in the cavity of the part during the electroplating process, the activation of the bottom plane is not sufficient, and a small area of ​​missed plating will occur. The traditional stepped small current cannot completely solve the problem of leak plating. For example, a step-and-step small current method with a longer stay (15A stay for 15min, 10A stay for 10min, 15A stay for 5min). Stainless steel is easy to passivate, the overpotential is small during the deposition of chromium, and it is not easy to be activated compared to ordinary stainless steel. The stepped low-current power supply that stays for a long time causes the cathode (ie, parts and accessories) to generate a large number of new ecological hydrogen atoms for a long period of time, and as the current increases, the new ecological hydrogen atoms will increase accordingly. These new ecological hydrogen atoms have a very high reducing ability, so that the passive film on the stainless steel surface is continuously reduced, thereby activating the surface of the part, especially the large current in the small step current can fully activate the complex parts of the part.

    The pre-treatment of the ladder small current transmission for a long time and the wet sand blowing not only help to improve the bonding force between the coating and the substrate, but also help to ensure the integrity of the coating and ensure the quality of the plating. The treatment process has little damage to the stainless steel substrate. Afterwards, impact plating with 1.5 to 2.0 times the normal current density for 30 to 60 seconds can produce a dense and well-bonded thin chromium layer in a relatively short time. This kind of impact plating is indispensable for parts w

  • Categories:FAQS
  • Author:Ferosteel
  • Origin:Ferosteel
  • Time of issue:2020-05-19 10:34
  • Views:
Information

High-tungsten stainless steel can be widely used in precision instruments, especially in aviation products. High tungsten stainless steel parts electroplated with hard chromium can improve its hardness, wear resistance, corrosion resistance, etc., but are prone to defects such as missing plating and partial thinning. This work uses some special process measures to ensure the quality of electroplated hard chromium in high tungsten stainless steel parts in aviation products.

    1. Craftsmanship

    1.1 Chrome plating process

    Parts → blown wet sand → alkaline degreasing → hot water washing → cold water washing → activation → cold water washing → chrome plating → dehydrogenation.

    1.2 Pre-treatment of chrome plating

    (1) The chemical properties of the high-tungsten stainless steel are very stable and difficult to be activated. In the pre-treatment, wet-blown sand treatment is adopted to activate its surface. Compared with blown dry sand, blown wet sand can make the surface of high-tungsten stainless steel finer, more suitable for precision parts, and also has the advantage of less pollution. Wet sand blown parts can be chrome plated immediately after cleaning. The following degreasing and activation steps can be omitted. If other steps are required, perform other steps after blow drying.

    (2) The degreasing process of the high-tungsten stainless steel before chromium plating is roughly the same as the conventional chrome plating. The organic solvent degreasing, electrochemical degreasing, and chemical degreasing methods can be used. The surface of the parts must be cleaned to a water film Not broken. If electrochemical degreasing is used, cathode degreasing should be avoided to prevent hydrogen embrittlement.

    The degreasing method adopted in this test is: Oakite 45 ~ 60g / L, 50 ~ 60 ℃, 10 ~ 12min.

    (3) Activation is necessary after degreasing to ensure good adhesion when electrodepositing hard chromium. The activation of high-tungsten stainless steel is carried out in 2530mL / LH2SO4 (p = 1.84g / cm3) solution, and it can be immersed at room temperature for 2 to 5 minutes.

    1.3 Hard chrome plating

    Similar to the general stainless steel material hard chrome plating, the non-plated part should be insulated before plating. The parts are pre-treated by immersing in hot water of 50 to 60 degrees Celsius to make the temperature of the parts and the temperature of the hard chrome plating solution Be consistent. The parts should be charged with a man-powered trough, using a stepped small current. The size of the small step current should be adjusted according to the area. When the area is small, the small step current should be reduced, and when the area is large, the small step current should be increased. For the parts with complex shapes, the stepped small current has a longer residence time, and the residence time decreases with the increase of the current, and the effect is very good.

    Regulator cover parts (material is AMS5616, mass fraction is 0.17% C, 13% Cr, 2% Ni, 3% W) when the bottom plane is electroplated with hard chrome, the shape of the bottom plane (see Figure 1) is more complicated Wet sand activates the surface, but because of insufficient solution flow in the cavity of the part during the electroplating process, the activation of the bottom plane is not sufficient, and a small area of ​​missed plating will occur. The traditional stepped small current cannot completely solve the problem of leak plating. For example, a step-and-step small current method with a longer stay (15A stay for 15min, 10A stay for 10min, 15A stay for 5min). Stainless steel is easy to passivate, the overpotential is small during the deposition of chromium, and it is not easy to be activated compared to ordinary stainless steel. The stepped low-current power supply that stays for a long time causes the cathode (ie, parts and accessories) to generate a large number of new ecological hydrogen atoms for a long period of time, and as the current increases, the new ecological hydrogen atoms will increase accordingly. These new ecological hydrogen atoms have a very high reducing ability, so that the passive film on the stainless steel surface is continuously reduced, thereby activating the surface of the part, especially the large current in the small step current can fully activate the complex parts of the part.

    The pre-treatment of the ladder small current transmission for a long time and the wet sand blowing not only help to improve the bonding force between the coating and the substrate, but also help to ensure the integrity of the coating and ensure the quality of the plating. The treatment process has little damage to the stainless steel substrate. Afterwards, impact plating with 1.5 to 2.0 times the normal current density for 30 to 60 seconds can produce a dense and well-bonded thin chromium layer in a relatively short time. This kind of impact plating is indispensable for parts with more complicated shapes. It can effectively ensure the integrity of the plating layer, after which the normal current density is restored and the hard chrome plating is performed.

    1.4 Post-plating treatment

    After the parts are plated with hard chrome, they must be dehydrogenated within 4h at a temperature of 190qC for 3h to prevent hydrogen embrittlement.

    2. Conclusion

    The high-tungsten stainless steel alloy hard chrome plating process is special because of its high tungsten content. It is treated by two special methods: wet sand blowing and long-term stepped small current power transmission. Plating problem, and good binding force, little damage to the stainless steel substrate. Electroplating hard chrome with this process meets the performance and technical requirements: after the test piece is broken, no chrome plating layer is separated from the substrate; there are no more than 15 independent points or pits on the total area of ​​0.098m2 and the depth is not greater than 8.47 × 10-3m; Hardness ≥850HV.

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