Makalah ini terutama memperkenalkan ruang lingkup aplikasi, metode perawatan pelapisan logam, lapisan kromium konvensional, metode pengujian dan sebagainya dari standar ISO 6158-1984 “Pelapisan kromium untuk teknik pelapisan logam”.
Konten subjek dan ruang lingkup aplikasi
Standar ini menetapkan metode representasi pelapisan listrik kromium untuk teknik, informasi yang akan diberikan oleh permintaan kepada pemasok selama pemrosesan dan pemesanan, spesifikasi proses perlakuan panas benda kerja sebelum dan sesudah pelapisan, persyaratan kualitas pelapisan, dan metode pengujian, dll..

ISO 6158-1984 Elektroplating kromium untuk Teknik pelapisan logam

Standar ini berlaku untuk pelapisan listrik aluminium untuk rekayasa pada substrat logam besi atau nonferrous dengan atau tanpa lapisan bawah. Rekayasa pelapisan krom sering disebut dengan “krom tebal” atau “krom keras” lapisan.

Standar ini tidak mencakup permukaan krom tipis untuk tujuan dekoratif pelindung.

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

2 Standar referensi
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 – magnetic method

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 Elektroplating kromium untuk Teknik pelapisan logam

3 Terminologi
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. Method of coating representation
The representation of chrome plating layer and related treatment shall be in accordance with GB1238.

Information TO BE PROVIDED BY THE DEMANDER TO THE SUPPLIER
The standard number of this standard;

B. The composition, content or brand of the matrix metal and its metallographic structure;

Whether stress relief treatment is required before plating;

D. Whether it is necessary to introduce compressive stress, such as shot peening before electroplating;

A detailed description of the main surfaces, all surfaces to which no coating should be applied, and all parts to which the chromium layer is allowed to extend can be made available with drawings or suitably marked samples;

F. any specific requirements or restrictions on pre-plating, such as replacing acid leaching with sandblasting;

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

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;

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

J. The final finishing state of the chrome layer, such as plating, grinding or 1l1 row grinding (lihat Bagian 8.1.2);

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

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

M. Other special requirements.

Catatan :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 Elektroplating kromium untuk Teknik pelapisan logam

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, retak, 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. Different working conditions can also be used, such as appropriately raising the temperature and shortening the time, but it needs to be based on effective implementation experience. Heat treatment should be performed prior to any pre-plating preparation and purification treatment with aqueous solution.

If stress relief is carried out after shot peening or other cold working process, the temperature should not exceed 220 °C. Surface quenched workpiece, stress elimination should be treated at 130~150℃ at least 5h, if the hardness of the matrix surface is allowed to reduce, it can be treated at a higher temperature for a shorter time.

Apakah logam non-ferrous memerlukan perlakuan panas untuk menghilangkan stres harus disepakati oleh pihak pemasok dan permintaan.

Perlakuan panas pada bagian baja sebelum pelapisan kadmium

6.3 Tembakan Peening

Pengenalan tegangan tekan pada permukaan benda kerja yang tidak dilapisi dan akan dilapisi biasanya meningkatkan kinerja beban dan kelelahan benda kerja tersebut dan sebagian mengkompensasi hilangnya kekuatan lelah dengan menghambat penyebaran retakan dari lapisan ke logam dasar..

Stres tekan dapat ditimbulkan melalui shot peening, dan bahan logam yang berbeda dipilih untuk kekuatan peening tembakan yang berbeda.

ISO 6158-1984 Elektroplating kromium untuk Teknik pelapisan logam

6.3.1 Baja

Jika perlu digunakan shot peening untuk meningkatkan kekuatan lelah benda kerja baja, kekuatan tembakan peening (jika tidak ditentukan lain) shall be measured according to the method specified in Appendix c at least the arc height shall be:

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

0.4mm, for steel with tensile strength equal to or greater than 1100Mpa.

On thin workpieces, in order to prevent deformation, a lower spray strength should be selected, so it may not be more satisfactory in avoiding fatigue strength reduction.

If no other provisions are made, the sprayed surface should be completely sprayed, itu adalah, the shot marks should overlap with each other.

6.3.2 Non-ferrous metals

The shot peening strength of non-ferrous metals shall be specified by the user.

Heat treatment of workpiece after electroplating
If required by the Demander, the post-plating heat treatment shall be carried out in accordance with the provisions of Article 7.1 atau 7.2. The heat treatment shall be carried out as soon as possible, generally not exceeding 4h, and shall be scheduled before polishing or other machining operations.

Heat treatment to eliminate hydrogen embrittleness of steel plating parts

7.1.1 Lihat Tabel 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 Elektroplating kromium untuk Teknik pelapisan logam

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 (lihat Bab 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, melepuh, 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, jika proses ini dilakukan oleh petugas pelapisan listrik, pelapisan tersebut harus ditolak sebagai alasannya.

ISO 6158-1984 Elektroplating kromium untuk Teknik pelapisan logam

8.1.2 Kekasaran permukaan

Apakah ada persyaratan kekasaran pada permukaan bagian yang dilapis harus ditentukan oleh permintaan. Ketika ada persyaratan, profiler dapat digunakan untuk mengukur dan menilai. Tingkat penerimaan harus disepakati oleh pihak penawaran dan permintaan.

8.1.3 Ketebalan

Di permukaan utama, ketebalan minimum lapisan krom dan lapisan bawah setelah finishing harus memenuhi persyaratan Permintaan (lihat h di Bab 5):

Ketebalan lapisan ditentukan oleh karakteristik penggunaan benda kerja berlapis krom. Penerapan lapisan pelapisan krom dalam industri sangatlah kompleks, dan sulit untuk mengatur ketebalan lapisan secara ketat. Lampiran A memberikan beberapa contoh aplikasi pelapisan krom dan berbagai pilihan ketebalan lapisan.

8.1.4 Kekerasan

Kecuali ditentukan, nilai kekerasan mikro Hv lapisan tidak boleh lebih rendah dari 750.

8.1.5 Kekuatan ikatan

Lapisan kromium tidak boleh lepas dari substrat bila pengujian dilakukan menurut metode yang ditentukan dalam Pasal 10.2. Jika ada lapisan bawah, tidak boleh ada pemisahan antara lapisan bawah dan matriks, atau antara lapisan bawah dan lapisan kromium.

8.1.6 Jumlah pori per satuan luas (porositas)

Apakah terdapat persyaratan porositas lubang pada lapisan kromium konvensional yang mencapai matriks harus ditentukan oleh pembeli. Lihat Artikel 10.3 untuk metode pengujian. Tingkat penilaian dan penerimaan hasil pengujian harus disepakati oleh pihak pemasok dan permintaan.

8.2 Jenis lapisan kromium lainnya

ISO 6158-1984 Elektroplating kromium untuk Teknik pelapisan logam

8.2.1 Ketentuan Umum

Sesuai dengan kebutuhan kondisi kerja benda kerja yang berbeda, selain lapisan kromium konvensional, jenis lapisan kromium lainnya juga dapat dipilih. Namun, jenis lapisan kromium ini mungkin sangat berbeda tampilannya dari kromium konvensional, kekerasan dan sifat lainnya. Apakah kualitasnya juga disyaratkan oleh ketentuan-ketentuan terkait Pasal 8l harus disepakati oleh pihak pemasok dan permintaan.

Jika peminat membutuhkan jumlah pori per satuan luas atau retakan per satuan panjang lapisan kromium jenis lainnya, lihat Artikel 10.3 untuk metode pengujian. 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, lihat Artikel 10.4 untuk metode pengujian. Tingkat penilaian dan penerimaan hasil pengujian harus disepakati oleh pihak pemasok dan permintaan.

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

8.2.2.1 “Crack free” kromium

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 perawatan panas, may have a negative impact on the corrosion resistance of this kind of coating.

ISO 6158-1984 Elektroplating kromium untuk Teknik pelapisan logam

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. The demander should deal with the type of hole (such as point or groove), the density of the hole and related indicators

And the corresponding test method to make detailed provisions.

8.2.2.3 Cracked chromium

Different from the situation where cracks are formed in the conventional chromium layer, the crack network of cracked chromium is deliberately formed by using a specific process. Diantara mereka, the crack network of microcracked chromium is invisible to the naked eye, and there are more than 250 cracks per 1cm length in any direction of the whole main surface, sedangkan jumlah retakan per 1 cm panjang kromium retak kasar biasanya jauh lebih kecil dibandingkan 250.

Kekerasan kromium retak mendekati kekerasan kromium konvensional. Karena kromium yang retak memiliki struktur yang retak, lebih mudah untuk menyimpan minyak. Jika nikel digunakan sebagai substrat, kromium retak mikro dapat meningkatkan ketahanan terhadap korosi dibandingkan dengan kromium retak kasar.

8.2.2.4 Kromium lapis ganda

Biasanya, lapisan kromium konvensional dilapisi di bagian bawah krom bebas retak, jadi kekerasannya mirip dengan kromium konvensional, dan pada saat yang sama memiliki ketahanan korosi yang tinggi.

ISO 6158-1984 Elektroplating kromium untuk Teknik pelapisan logam

9 Ambil sampel
Inspeksi pengambilan sampel harus dilakukan sesuai dengan persyaratan mutu lapisan yang ditetapkan dalam Bab 8. Metode pengambilan sampel dan tingkat penerimaan harus disepakati oleh pihak pemasok dan permintaan.

10 Metode tes
10.1 Penentuan ketebalan lapisan

Untuk mengukur ketebalan lapisan kromium pada posisi mana pun di permukaan utama, metode pengukuran yang digunakan harus memastikan bahwa kesalahan pengukuran kurang dari 10%.

10.1.1 Metode pengukuran alat teknik

Pembacaan ketebalan secara langsung dapat diperoleh dengan mengukur dimensi benda kerja pada titik referensi yang dipilih sebelum dan sesudah pelapisan. Alat pengukur yang umum digunakan adalah mikrometer, pengukur kedalaman dan sebagainya. Untuk peningkatan (lingkaran luar) atau berkurang (lubang bagian dalam) dari ukuran diameter benda kerja berbentuk silinder, ketebalan lapisan kromium hanya dapat direpresentasikan bila ketebalan lapisan tersebut merata.

The uniformity of the thickness of the chromium layer can be measured in an appropriate manner. Misalnya, 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 Metode magnetik

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 Elektroplating kromium untuk Teknik pelapisan logam

10.1.4 metode Coulomb

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, and other applicable methods in this standard may also be used. For bending tests, the thickness of the chromium layer on the test piece should be 25µm.

It should be noted that various test methods for the bonding strength between the chromium coating and the matrix often have certain limitations, so the test method should be agreed by the supply and demand parties.

10.3 Determination of the number of pores or cracks in the coating

The detection of pores to the substrate in the conventional and “crack-free” chromium layers, as well as pores or cracks in other types of chromium layers, shall be carried out in accordance with the advertised method specified in Appendix D.

10.4 Test method for corrosion resistance of coating

Coating corrosion resistance test method, according to the provisions of GB6458.