Este artigo apresenta principalmente o escopo de aplicação, método de tratamento de chapeamento de metal, camada de cromo convencional, test method and so on of the standard ISO 6158-1984 “Chromium plating for metal coating engineering”.
Subject content and scope of application
This standard specifies the representation method of chromium electroplating for engineering, the information to be provided by the demander to the supplier during processing and ordering, the heat treatment process specification of the workpiece before and after plating, the quality requirements of the plating, and the test method, etc..

ISO 6158-1984 Galvanoplastia de cromo para engenharia de revestimento de metal

This standard applies to aluminum electroplating for engineering on ferrous or nonferrous metal substrates with or without bottom coating. Engineering chromium plating is often referred to as “thick chromium” ou “hard chromium” camada.

This standard does not include thin chrome surfaces for protective decorative purposes.

See Appendix A for examples and descriptions of applications of chromium for engineering.

2 Padrões de referência
GB1238 Metal coating and chemical treatment representation method

GB4955 Metal cover thickness measurement anode dissolved Coulomb method

Thickness of non-magnetic overlay on magnetic metal substrate – método magnético

GB5270 Metal Coatings (electrodeposited and chemically deposited) on Metal substrates – Test method for Adhesion strength GB6458 Metal Coatings – Neutral Salt spray Test (Nss test)

GB6462 Method for microscopic measurement of cross-sectional thickness of metal and oxide coatings

Review of GB6463 metal and other inorganic coating thickness measurement methods

ISO 6158-1984 Galvanoplastia de cromo para engenharia de revestimento de metal

3 Terminologia
Main surface: refers to some surfaces before and after plating on the workpiece, the coating on the surface of the workpiece for the appearance and/or performance is the main role.

4. Método de representação de revestimento
A representação da camada de cromagem e tratamento relacionado deve estar de acordo com GB1238.

Informações A SEREM FORNECIDAS PELO DEMANDANTE AO FORNECEDOR
O número padrão deste padrão;

b. A composição, conteúdo ou marca do metal da matriz e sua estrutura metalográfica;

Se o tratamento de alívio de estresse é necessário antes do revestimento;

d. Se é necessário introduzir tensões compressivas, como shot peening antes da galvanoplastia;

Uma descrição detalhada das principais superfícies, todas as superfícies nas quais nenhum revestimento deve ser aplicado, e todas as partes às quais a camada de cromo pode se estender podem ser disponibilizadas com desenhos ou amostras devidamente marcadas;

f. quaisquer requisitos ou restrições específicas ao pré-revestimento, como substituir a lixiviação ácida por jateamento de areia;

g. If substratum is required, specify the type of substratum, such as nickel or crack-free chromium, etc.;

h. The minimum thickness of the chromium layer to be deposited, if required, the total thickness of the electroplating layer should be stated, if deemed necessary, the maximum thickness of the plating should be stated, especially the repair chromium plating of worn or out-of-tolerance parts. The thickness of the above coating refers to the thickness of the coating on the surface after polishing;

eu. type of chromium layer such as porous, crack-free, microcracked, double-layered or conventional (see Sections 8.1 e 8.2);

j. The final finishing state of the chrome layer, such as plating, grinding or 1l1 row grinding (veja a seção 8.1.2);

k. Permitted surface defects, including type, tamanho, location of defects;

eu. any heat treatment requirements of the workpiece after electroplating;

eu. Other special requirements.

Observação :1) It is difficult to provide such data for the repair of old parts with chromium, and sometimes it is difficult to ensure the quality of the chromium layer.

ISO 6158-1984 Galvanoplastia de cromo para engenharia de revestimento de metal

Treatment of substrate metal before electroplating
6.1 Inspection before disposal

Prior to treatment, the supplier shall inspect the main surface to confirm whether there are obvious surface defects such as pores, rachaduras, and disallowed overburden, or any other defects that would be detrimental to the final finishing. All defects shall be brought to the attention of the purchaser prior to any treatment.

6.2 Stress Relief

If the Demander stipulates that the parts should be subjected to heat treatment to relieve stress before electroplating, it shall be carried out according to the working conditions in Table 1. Diferentes condições de trabalho também podem ser usadas, como aumentar adequadamente a temperatura e encurtar o tempo, mas precisa de se basear numa experiência de implementação eficaz. O tratamento térmico deve ser realizado antes de qualquer preparação pré-revestimento e tratamento de purificação com solução aquosa.

Se o alívio de tensão for realizado após shot peening ou outro processo de trabalho a frio, a temperatura não deve exceder 220 ° C. Peça de trabalho com superfície temperada, a eliminação do estresse deve ser tratada a 130 ~ 150 ℃ pelo menos 5h, se a dureza da superfície da matriz puder reduzir, pode ser tratado a uma temperatura mais alta por um tempo mais curto.

Se os metais não ferrosos requerem tratamento térmico para aliviar o estresse, será acordado entre as partes da oferta e da demanda.

Tratamento térmico de peças de aço antes do revestimento de cádmio

6.3 Shot Peening

The introduction of compressive stress on the surface of unplated and to be plated workpieces usually improves the load and fatigue performance of these workpieces and partially compensates for the loss of fatigue strength by inhibiting the propagation of cracks from the coating into the base metal.

Compressive stress can be introduced by means of shot peening, and different metal materials are selected for different shot peening strength.

ISO 6158-1984 Galvanoplastia de cromo para engenharia de revestimento de metal

6.3.1 Aço

If it is necessary to use shot peening to improve the fatigue strength of steel workpieces, the shot peening strength (if not otherwise specified) shall be measured according to the method specified in Appendix c at least the arc height shall be:

0.3milímetros, for steel with tensile strength less than 1100MPa;

0.4milímetros, para aço com resistência à tração igual ou superior a 1100Mpa.

Em peças finas, para evitar deformações, uma força de pulverização mais baixa deve ser selecionada, portanto, pode não ser mais satisfatório para evitar a redução da resistência à fadiga.

Se nenhuma outra disposição for feita, a superfície pulverizada deve ser completamente pulverizada, aquilo é, as marcas de tiro devem se sobrepor.

6.3.2 Metais não ferrosos

A resistência ao shot peening de metais não ferrosos deve ser especificada pelo usuário.

Tratamento térmico da peça após galvanoplastia
Se exigido pelo Demandante, o tratamento térmico pós-galvanização será realizado de acordo com o disposto no Artigo 7.1 ou 7.2. O tratamento térmico deve ser realizado o mais rápido possível, geralmente não excedendo 4h, e deve ser programado antes do polimento ou outras operações de usinagem.

Heat treatment to eliminate hydrogen embrittleness of steel plating parts

7.1.1 See Table 2 for the heat treatment of steel parts after electroplating. Attention should be paid to:

The heat treatment of 400~480℃ is only suitable for those workpieces with fatigue failure tendency during use.

ISO 6158-1984 Galvanoplastia de cromo para engenharia de revestimento de metal

7.12 The heat treatment of workpieces shall not exceed their tempering temperature.

7.1.3 Surface quenched workpieces should be heated at 130~150℃ for no less than 5h. If the hardness of the matrix is allowed to decrease, it can also be treated at a higher temperature.

7.14 For workpieces without shot peening, the treatment temperature can be appropriately increased and the treatment time can be shortened, but it needs to be based on effective practical experience (see Chapter 6 and note to Table 2).

Heat treatment of steel plating

8 Requirements for coating
8.1 Conventional chrome layer

8.1.1 Appearance

When VIEWED by the NAKED eye, the main surface should be bright or shiny without pitting, bolhas, peeling or any other defect that would adversely affect the final finishing condition. Chroma is not allowed on the surface of the workpiece that is used directly after plating or polished after plating, except for the edges.

The plated parts shall have no visible cracks, and the coating thickness greater than 50µm shall not have cracks reaching the substrate.

When visible blistering or cracking occurs during heat treatment or polishing, if this process is carried out by electroplating personnel, the coating shall be rejected as a reason.

ISO 6158-1984 Galvanoplastia de cromo para engenharia de revestimento de metal

8.1.2 Surface roughness

Whether there is a roughness requirement on the surface of the plated parts shall be specified by the demander. When there is a requirement, the profiler can be used to measure and rate. The acceptance level shall be agreed upon by the supply and demand parties.

8.1.3 Grossura

On the main surface, the minimum thickness of the chrome layer and bottom layer after finishing shall meet the requirements of the Demander (see h in Chapter 5):

The thickness of the coating is determined by the use characteristics of the chrome-plated workpiece. The application of chrome plating layer in industry is very complex, and it is difficult to strictly regulate the thickness of the coating. Appendix A provides some examples of chrome coating applications and a range of coating thickness options.

8.1.4 Dureza

A menos que especificado de outra forma, the microhardness value Hv of the coating should not be lower than 750.

8.1.5 Força de ligação

The chromium layer shall not be separated from the substrate when the test is carried out according to the method specified in Article 10.2. If there is a bottom layer, there should be no separation between the bottom layer and the matrix, or between the bottom layer and the chromium layer.

8.1.6 Number of pores per unit area (porosity)

Whether there is a requirement for porosity of the holes on the conventional chromium layer reaching the matrix shall be specified by the purchaser. See Article 10.3 for the test method. The level of assessment and acceptance of test results shall be agreed upon by the supply and demand parties.

8.2 Other types of chromium layers

ISO 6158-1984 Galvanoplastia de cromo para engenharia de revestimento de metal

8.2.1 General Provisions

According to the needs of different working conditions of the workpiece, in addition to the conventional chromium layer, other types of chromium coating can also be selected. No entanto, these types of chromium layers may differ greatly from conventional chromium in appearance, hardness and other properties. Whether their quality is also required by the relevant provisions of Article 8l shall be agreed upon by the supply and demand parties.

If the demander requires the number of pores per unit area or cracks per unit length of other types of chromium layer, veja o artigo 10.3 for the test method. The level of assessment and acceptance of test results shall be agreed upon by the supply and demand parties except for the relevant provisions of Article 8.2.2.

If the Demander needs to test the corrosion resistance of chromium without crack, double layer chromium or micro-crack chromium with nickel as the bottom layer, veja o artigo 10.4 for the test method. The level of assessment and acceptance of test results shall be agreed upon by the supply and demand parties.

82.2 Characteristics and corresponding quality requirements of other types of chromium layers

8.2.2.1 “Crack free” cromo

Compared with conventional chromium, its hardness is low, brittleness is small, basically crack free, corrosion resistance is high, such as milk white chromium, the thickness of the chromium layer is generally not more than 25µm, and does not carry out finishing, also do not need to be on the high load surface, according to the provisions of Chapter 7 heat treatment, may have a negative impact on the corrosion resistance of this kind of coating.

ISO 6158-1984 Galvanoplastia de cromo para engenharia de revestimento de metal

8.2.2.2 Porous chromium

A mechanical, chemical or electrochemical treatment method can be used to obtain a porous chromium surface for oil storage, such as loose hole chromium. O demandante deve lidar com o tipo de furo (como ponto ou ranhura), a densidade do furo e indicadores relacionados

E o método de teste correspondente para fazer disposições detalhadas.

8.2.2.3 Cromo rachado

Diferente da situação em que se formam fissuras na camada de cromo convencional, a rede de fissuras do cromo rachado é formada deliberadamente usando um processo específico. Entre eles, a rede de fissuras do cromo microfissurado é invisível a olho nu, e há mais de 250 rachaduras por 1 cm de comprimento em qualquer direção de toda a superfície principal, enquanto o número de rachaduras por 1 cm de comprimento de cromo rachado grosso é geralmente muito menor do que 250.

A dureza do cromo rachado é próxima da do cromo convencional. Porque o cromo rachado tem uma estrutura rachada, é mais fácil armazenar óleo. Se o níquel for usado como substrato, o cromo com microfissuras pode melhorar a resistência à corrosão em comparação com o cromo com rachaduras grossas.

8.2.2.4 Cromo de dupla camada

Geralmente, uma camada de cromo convencional é revestida com cromo sem rachaduras na parte inferior, então sua dureza é semelhante à do cromo convencional, e ao mesmo tempo tem alta resistência à corrosão.

ISO 6158-1984 Galvanoplastia de cromo para engenharia de revestimento de metal

9 Pegue amostras
A inspeção por amostragem deverá ser realizada de acordo com os requisitos de qualidade do revestimento estipulados no Capítulo 8. O método de amostragem e o nível de aceitação serão acordados entre as partes fornecedoras e demandantes.

10 Métodos de teste
10.1 Determinação da espessura do revestimento

Para medir a espessura do revestimento de cromo em qualquer posição da superfície principal, o método de medição utilizado deve garantir que o erro de medição seja menor que 10%.

10.1.1 Método de medição de ferramentas de engenharia

A direct reading of the thickness can be obtained by measuring the dimensions of the workpiece at a selected reference point before and after plating. Commonly used gauges are micrometer, depth gauge and so on. For the increase (outer circle) or decrease (furo interno) of the diameter size of the cylindrical workpiece, the thickness of the chromium layer can be represented only when the thickness of the coating is evenly distributed.

The uniformity of the thickness of the chromium layer can be measured in an appropriate manner. Por exemplo, the electroplating surface can be rotated around the axis of the workpiece to measure by a dial meter or by other indirect methods.

10.1.2 Magnetic method

When no nickel coating is used as the bottom layer, the thickness of chromium coating shall be measured according to GB4956.

10.13 Microscopical measurement of cross-sectional thickness

This method belongs to destructive thickness measurement method. Measure the thickness of chrome coating and other bottom coating according to GB6262.

ISO 6158-1984 Galvanoplastia de cromo para engenharia de revestimento de metal

10.1.4 Coulomb method

This method belongs to destructive thickness measurement method. Measure the thickness of chromium coating and nickel substrate according to GB4955. When the thickness of the coating exceeds 50µm, its reliability will be reduced.

In addition to the above thickness measurement methods, can also be used to measure the thickness of the profile size measurement method and other methods specified in GB6463 applicable to chromium coating.

10.2 Determination of bonding strength of coating

The bonding strength of the coating shall be checked according to the bending, grinding saw, thermal shock and other test methods specified in GB5270, e outros métodos aplicáveis ​​nesta norma também podem ser usados. Para testes de flexão, a espessura da camada de cromo na peça de teste deve ser de 25 µm.

Deve-se notar que vários métodos de teste para a resistência de ligação entre o revestimento de cromo e a matriz geralmente apresentam certas limitações, portanto, o método de teste deve ser acordado entre as partes da oferta e da demanda.

10.3 Determinação do número de poros ou fissuras no revestimento

A detecção de poros no substrato nos métodos convencional e “crack-free” camadas de cromo, bem como poros ou rachaduras em outros tipos de camadas de cromo, deve ser realizado de acordo com o método anunciado especificado no Apêndice D.

10.4 Método de teste para resistência à corrosão do revestimento

Método de teste de resistência à corrosão de revestimento, de acordo com as disposições de GB6458.