Metallic coating--Hot dipped aluminum coatings on ferrous articles--Specification
Some standard content:
ICS25.220.20
National Standard of the People's Republic of China
GB/T18592—2001
Metallic coating
Hot dipped aluminum for steel products
Technical conditions
Metallic coating--Hot dipped aluminum coatings on ferrous articles Specification 2001-12-17 Issued
People's Republic of China
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
Implementation on 2002-06-01
GB/T18592--2001
Cited Standards
Classification of Hot-Dip Aluminized Coatings
Quality Requirements of Materials
Hot-Dip Aluminized Process
Hot-Dip Aluminized Process
Macroscopic Inspection of Hot-Dip Aluminized Coatings
Determination of Coating Amount of Hot-Dip Aluminized Coatings (Weighing Method) 10
Measurement of Thickness of Hot-Dip Aluminized Coatings
Evaluation of Porosity Level of Diffusion-Type Hot-Dip Aluminized Coatings 11
12 Crack level assessment objectives
13 Assessment of interface type between diffusion-type hot-dip aluminum layer and base metal·Mechanical properties of hot-dip aluminum parts*
15 Determination of sampling and inspection items
16 Product acceptance·
17 Product packaging and labeling
Appendix A (Standard Appendix) Test method for coating amount of hot-dip aluminum layer Dissolution weighing method Appendix B (Standard Appendix) Microscope assessment method for pore level of diffusion-type hot-dip aluminum layer Microscope assessment method for crack level of diffusion-type hot-dip aluminum layer Appendix C (Standard Appendix)
Appendix D (Suggestive Appendix)
Assessment of interface type between diffusion-type hot-dip aluminum layer and base metal GB/T18592—2001
In order to meet the import and export trade and foreign economic and technical exchanges of hot-dip aluminum products, this national standard for hot-dip aluminum is specially formulated. Appendix A, Appendix B and Appendix C of this standard are all standard appendices; Appendix D of this standard is a suggestive appendix.
This standard is proposed by China Machinery Industry Federation and is under the jurisdiction of National Technical Committee for Standardization of Metallic and Non-metallic Coatings. The responsible drafting units of this standard are Wuhan Institute of Material Protection and Hubei Yunmeng Chemical Machinery Factory. The participating drafting units of this standard are Institute of Mechanics, Chinese Academy of Sciences. The main drafters of this standard are Zhao Xiaoyong, Wu Yong and Xia Yuan. 1 Scope
National Standard of the People's Republic of China
Metallic Coating
Hot Dip Aluminum Coating on Ferrous Articles
Technical Conditions
Metallic Coating-Hot Dipped Aluminum Coatingson Ferrous Articles-SpecificationGB/T18592—2001
This standard specifies the process requirements for hot dipped aluminum coating on steel and the quality inspection method for hot dipped aluminum coating. This standard is applicable to steel structural products with heat resistance and corrosion resistance requirements. It is not applicable to hot dipped aluminum sheets, strips and wire products produced in continuous production. 2 Referenced standards
The clauses contained in the following standards constitute the clauses of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T228—1987Methods for tensile testing of metals
GB/T1196—1993Aluminum ingots for remelting
GB/T4956—1985Magnetic method for measuring the thickness of non-magnetic coatings on magnetic metal substrates (eqvISO2178:1982)GB/T6462-1986Microscopic measurement method for cross-sectional thickness of metal and oxide coatings (eqvISO1463:1982)GB/T9790—1988Vickers and Knoop microhardness test for metal coatings and other related coatings (negISO4516:1980)
3 Definitions
This standard adopts the following definitions.
3.1 Hot dip aluminum (hot dip aluminum, hot dip aluminum, liquid aluminum) hotdipped aluminum is a process method of immersing steel workpieces in molten aluminum and keeping them warm for a certain period of time so that aluminum (and other additional elements) cover and penetrate into the surface of the steel to obtain a hot dip aluminum layer.
3.2 Hot dip aluminum layer hotdippedaluminumcoating is an aluminum and aluminum-iron alloy layer formed on the surface of steel parts by hot dip aluminum coating process, which is divided into immersion type hot dip aluminum layer and diffusion type hot dip aluminum layer.
3.3 Immersion type hot dip aluminum layer as-dippedaluminumcoating is a coating obtained by hot dip coating directly in aluminum liquid. The outer layer is an aluminum coating layer, and the inner layer is an aluminum-iron alloy layer. 3.4 Diffusion type hot dip aluminum coating is a hot dip aluminum layer obtained by hot dip coating in aluminum liquid and then diffusion treatment. This layer is entirely composed of aluminum-iron alloy layer. 3.5 Aluminum overlay aluminum overlay
The outer surface layer of the immersion hot-dip aluminum layer, its composition is basically the same as that of the aluminum liquid. 3.6 Alloy layer alloy layer
Mainly composed of aluminum-iron alloy formed by the mutual diffusion of aluminum and iron. Approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on December 17, 2001 and implemented on June 1, 2002
GB/T18592—2001
3.7 Effective area of hot dipped aluminum The loading area in the aluminum liquid where the aluminum liquid composition and heating temperature can meet the requirements of the hot-dip aluminum coating process. 3.8 Uncoating
The phenomenon that the immersion hot-dip aluminum product is not coated with aluminum in the appearance inspection. 3.9 Undiffusing
The phenomenon that the aluminum-iron alloy layer is not formed in the local area of the diffusion hot-dip aluminum product in the appearance inspection. 3.10 Weight of coating The mass of aluminum (and other additional elements) applied to the surface of the workpiece after hot-dip aluminum coating, expressed as the mass added per unit area g/m. 4 Classification of hot-dip aluminum coating
4.1 Classification by treatment method
a) Immersion type hot-dip aluminum coating.
b) Diffusion type hot-dip aluminum coating.
4.2 Classification by coating material type
a) Aluminum layer.
b) Aluminum-silicon alloy layer.
5 Material quality requirements
5.1 Steel and iron
The quality requirements of the base material (steel and iron) of hot-dip aluminum products shall comply with the provisions of the corresponding national standards or industry standards. 5.2 Aluminum ingots
The aluminum content of aluminum ingots for hot-dip aluminum coating shall not be less than 99.5%, and the special first-grade, special second-grade or first-grade aluminum ingots in GB/T1196 are applicable. 6 Hot-dip aluminum plating process
6.1 Immersion hot-dip aluminum plating process
Degreasing→Rust removal→Plating aid→Hot-dip aluminum plating→Calibration→Cleaning→Inspection6.2 Diffusion hot-dip aluminum plating process
Degreasing→Rust removal→Plating aid→Hot-dip aluminum plating→Calibration-Cleaning→Inspection→Diffusion treatment—→Calibration→Cleaning→Inspection7 Hot-dip aluminum plating process
7.1 Degreasing
The oil stains on the surface of the workpiece must be completely removed. Low-temperature heating degreasing, alkaline solution cleaning degreasing, or organic solvent cleaning degreasing can be used. 7.2 Rust removal
The rust products on the surface of the workpiece must be completely removed. Mechanical or chemical rust removal methods can be used. 7.3 Plating aid
The workpiece that has been degreasing, rust removal and cleaned must be plated before entering the aluminum liquid. The plating aid method can be an aqueous solution method, a molten salt method or a gas method.
7.4 Hot-dip aluminum plating
7.4.1 Hot-dip aluminum plating liquid
The chemical composition of aluminum liquid in the effective hot-dip aluminum plating area shall in principle comply with the provisions of Table 1. Hot-dip aluminum plating liquid should generally be sampled, analyzed and adjusted after every 8 hours of use. The scum on the surface of the aluminum liquid should be removed in time, and the slag at the bottom of the liquid should also be removed regularly. 2
Coating material category
Aluminum-silicon
7.4.2 Hot-dip aluminum plating temperature
GB/T18592—2001
Table 1 Chemical composition of hot-dip aluminum plating liquid
Total amount of other impurities
The hot-dip aluminum plating temperature shall in principle comply with the provisions of Table 2. Carbon steel parts generally take the lower limit; alloy steel and cast iron parts generally take the upper limit. The temperature deviation of the effective aluminum plating area of the hot-dip aluminum plating liquid is ±10℃. Table 2
Clad material categories
Aluminum-silicon
7.4.3 Hot-dip aluminum plating time
Hot-dip aluminum plating liquid temperature
Insulation temperature
700~780
670~740
The recommended hot-dip aluminum plating time for carbon steel and low-alloy steel parts is shown in Table 3. The hot-dip aluminum plating time for medium- and high-alloy steel and cast iron parts with the same wall thickness should be increased by 20%~30%.
Table 3 Hot-dip aluminum plating time for carbon steel
Workpiece wall friction
7.4.4 Cooling after furnace
Immersion type hot-dip aluminum plating layer
Hot-dip aluminum plating time
Diffusion type hot-dip aluminum plating layer
After the workpiece is discharged from the aluminum liquid, take timely measures such as vibration or air blowing to remove excess aluminum liquid on the surface, air cool to room temperature, and pay attention to avoid rapid cooling at high temperatures.
7.5 Correction
When the deformation of hot-dip aluminum parts exceeds the tolerance, correction treatment should be carried out. 7.6 Surface cleaning
Remove the residual slag or other dirt on the surface of hot-dip aluminum parts by mechanical or chemical methods. After chemical cleaning, they should be cleaned and dried.
7.7 Diffusion treatment
7.7.1 The general diffusion insulation temperature is 850~930C; the insulation time is 3~5h. If the layer thickness requirement is the main requirement, the upper limit of the diffusion insulation temperature and time can be taken; if the strength requirement of the base metal is the main requirement, the lower limit of the diffusion insulation temperature and time can be taken. 7.7.2 The cooling method after diffusion treatment should be selected according to the required mechanical properties of the base metal. Furnace cooling or air cooling. 8 Macro inspection of hot-dip aluminum layer
8.1 Visual inspection
8.1.1 The hot-dip aluminum layer formed on the surface of the base metal should be continuous and complete. 8.1.2 The surface of the impregnated hot-dip aluminum products shall not have defects such as slag, dull color and leakage that obviously affect the appearance quality. 3
GB/T18592—2001
8.1.3 The surface of the diffusion-type hot-dip aluminum products shall not have defects such as leakage, cracks and peeling. 8.2 Adhesion test
8.2.1 Immersion-type hot-dip aluminum layer
Use a hard knife tip and apply appropriate pressure. Score the flat part until the aluminum coating on the surface is penetrated. The aluminum coating on both sides of the scribed line 2.0mm should not peel or fall off. 8.2.2 Diffusion-type hot-dip aluminum layer
Use a hard knife tip and apply appropriate pressure to score (or manually saw) the flat part until the compound layer is penetrated. The compound layer on both sides of the scribed line (or sawing line) 2.0mm should not peel or fall off. 8.3 Deformation test
Use ruler, vernier caliper, micrometer, etc. to measure the deformation of hot-dip aluminum products such as deflection, elongation, and thickening. 9 Determination of the coating amount of hot-dip aluminum layer (weighing method) 9.1 The coating amount of hot-dip aluminum layer shall comply with the provisions of Table 4. Table 4 Coating amount of hot-dip aluminum layer
Immersion type
Diffusion type
9.2 Coating amount measurement method
Coating material
Aluminum-silicon
Coating amount
≥160
≥240
9.2.1 Furnace attached sample method
Mechanically cut the sample from the workpiece or select the parallel sample from the same batch of materials as the workpiece. After degreasing and rust removal, weigh the sample before hot-dip aluminum plating (Wg, accuracy is 0.01g). The sample is hot-dip aluminum-plated together with the workpiece, and then the mass after hot-dip aluminum-plating is weighed (W2g, accuracy is 0.01g). Use a vernier caliper to measure (accuracy is 0.1mm) the hot-dip aluminum-plated area of the sample (S, mm2). The unit area coating amount of hot-dip aluminum-plated for this batch of workpieces (C, g/m*) can be calculated: C=kW-Wic
9.2.2 Dissolution weighing method
(g/m2)
The dissolution weighing method shall be carried out in accordance with Appendix A of this standard (Appendix to the standard). 10 Measurement of the thickness of the hot-dip aluminum layer
10.1 The thickness of the hot-dip aluminum layer shall comply with the provisions of Table 5. K-1X108
Table 5 Thickness of hot-dip aluminum layer
Immersion type
Diffusion type
10.2 Microscope measurement method
10.2.1 Sample preparation
Coating material
Aluminum-silicon
The preparation of thickness measurement samples shall be carried out in accordance with GB/T6462. Recommended etchants for indicating the thickness of hot-dip aluminum coating are shown in Table 6. 4
GB/T18592—2001
Table 6 Etchant for indicating the thickness of hot-dip aluminum coating Etchant
Nitric acid solution (d=1.42) 4mL
95% ethanol solution 96mL
Nitric acid solution (d=1.42) 5mL
95% ethanol solution 85mL
Hydrofluoric acid solution (d=1.14) 10mL
10.2.2 Determination of the measurement field
Scope of application
Interface line and organization display of the non-destructive hot-dip aluminum coating of various types of steel
Interface line and organization display of the diffusion-type hot-dip aluminum coating of various types of steel
The sample is divided into 6 equal parts according to its cross-sectional length, and the 5 equal points in the middle are used as the measurement field (see Figure 1). 10.2.3 Measurement of thickness value
Measure the maximum and minimum thickness values of the hot-dip aluminum coating in each measuring field of view (see Figures 2 and 3). 10.2:4 Calculation of results
Take the arithmetic mean of 10 measured values (5 maximum values 8m and 5 minimum values mm) measured in 5 measuring fields of view as the thickness of the hot-dip aluminum coating.
10.3 Thickness gauge inspection methodbzxz.net
10.3.1 Use a magnetic thickness gauge to measure the thickness of the hot-dip aluminum coating in accordance with GB/T4956. 10.3.2 When measuring the thickness, take the average value of the 5-point readings at each test position as a measurement value. The three measurement values of each measuring piece meet the requirements of Table 5 and are qualified.
10.4 Arbitration
When there is a dispute over the measurement results of the thickness gauge inspection method, the measurement results of the microscope measurement method (GB/T6462) shall prevail. 11 Assessment of the porosity level of diffusion-type hot-dip aluminum coating 11.1 The assessment method of the porosity level of diffusion-type hot-dip aluminum coating is shown in Appendix B (Appendix to the standard). 11.2 The qualified level of porosity is determined according to the product use conditions. Generally, porosity levels 1 to 3 are qualified, and levels 4 to 6 are unqualified. 11.3 The thickness of the porous layer shall not be greater than three-quarters of the thickness of the hot-dip aluminum coating. 12 Assessment of the crack level of diffusion-type hot-dip aluminum coating 12.1 The assessment method of the crack level of diffusion-type hot-dip aluminum coating is shown in Appendix C (Appendix to the standard). 12.2 The crack level of diffusion-type hot-dip aluminum coating of carbon steel and low alloy steel (Series A) is shown in Appendix C, and is assessed according to Table C1 and Figure C1; the crack level of diffusion-type hot-dip aluminum coating of medium and high alloy steel (Series B) is shown in Appendix C, and is assessed according to Table C2 and Figure C2. The qualified level of crack is determined according to the product use conditions. Generally, it is stipulated that cracks of grade A are qualified for grade 0 to 3, and unqualified for grade 4 to 6; cracks of grade B are qualified for grade 1 to 4, and unqualified for grade 5 to 7.
Base metal
Hot-dip aluminum layer
Figure 1 Method for determining the field of view of hot-dip aluminum sample measurement Aluminum covering layer
GB/T18592—2001
Immersion type hot-dip aluminum layer
Alloy layer
Figure 2 Method for measuring the thickness of immersion type hot-dip aluminum layer Diffusion type hot-dip aluminum layer
Alloy layer
Metal base
Figure 3 Method for measuring the thickness of diffusion type hot-dip aluminum layer 12.3 The depth of the crack shall not exceed three quarters of the thickness of the hot-dip aluminum layer. 13 Evaluation of the interface type between the diffusion type hot-dip aluminum layer and the base metal metal base
13.1 The interface type between the diffusion type hot-dip aluminum layer and the base metal is divided into five types according to the interface shape of the hot-dip aluminum layer. The evaluation method is shown in Appendix D (suggestive Appendix).
GB/T18592--2001
13.2 In principle, it is stipulated that Type A, Type B, and Type C are qualified, Type E is unqualified, and whether Type D is qualified or not can be agreed between the user and the manufacturer according to the product use conditions.
14 Mechanical properties of hot-dip aluminum parts
14.1 Tensile test
14.1.1 Cut the sample from the hot-dip aluminum part by mechanical method (retain the surface hot-dip aluminum layer) or take the sample from the same batch of materials and process it with the workpiece under the same hot-dip aluminum operation conditions. 14.1.2 The preparation of the sample and the tensile test method shall be carried out in accordance with GB/T228 or relevant regulations. 14.1.3 When calculating strength, the surface thickening caused by the hot-dip aluminum coating process should not be included in the cross-sectional dimensions of the test piece. 14.2 Microhardness test
The microhardness test of the hot-dip aluminum coating is carried out in accordance with GB/T9790. 14.3 Matrix performance test
The mechanical performance test items and technical indicators of the hot-dip aluminum substrate shall be agreed upon by the user and the manufacturer in the product ordering technical conditions.
15 Determination of sampling and inspection items
15.1 For a batch of hot-dip aluminum parts with the same specifications and dimensions that have passed the visual inspection, at least three pieces shall be randomly selected.
15.2 Each sample shall be subjected to the measurement of the thickness of the hot-dip aluminum layer, the evaluation of the porosity level, the evaluation of the crack level and the mechanical property test. The number of inserted samples, the extraction location and the inspection items may also be determined in consultation with the user according to the specific situation. The coating amount of the hot-dip aluminum layer may be used instead of the measurement of the thickness of the hot-dip aluminum layer; the interface type evaluation between the hot-dip aluminum layer and the base metal may be used instead of the scratch test. 16 Product Acceptance
At the time of delivery, acceptance shall be carried out in accordance with this standard and an acceptance report and product certificate shall be provided. If any technical requirements in Chapters 8 to 12 and 14 to 15 of this standard are not met, it shall be deemed that the acceptance has not passed. 17 Product Packaging and Marking
17.1 Packaging
Hot-dip aluminum products shall be properly packaged to prevent damage and rust. 17.2 Marking
Hot-dip aluminum products that meet the requirements of this standard shall be marked with the GB/T18592 mark and the corresponding coating material type, manufacturer name, production batch number, and factory date.
GB/T18592—2001
Appendix A
(Appendix to the standard)
Test method for hot-dip aluminum coating plate Dissolution weighing method This appendix specifies the test method for measuring the coating amount of hot-dip aluminum coating by the dissolution weighing method and the calculation method of the coating amount. A1 Basic principle
The hot-dip aluminum coating is dissolved by chemical method, and the mass of the hot-dip aluminum coating before and after dissolution is weighed. The mass difference per unit area before and after dissolution obtained by calculation is the coating amount of the hot-dip aluminum coating. A2 Sampling
A2.1 Randomly select samples from the batch of workpieces according to the quantity specified in Chapter 15 of this standard. When the workpiece is large, a part of the representative part of the workpiece can be cut off as a sample. The specific part shall be negotiated by the supply and demand parties. A2.2 The surface area of the hot-dip aluminum coating of each sample shall not be less than 2000mm. A2.3 Clean the surface of the sample with an organic solvent or other suitable solvent, and weigh the mass before dissolution after drying (W1, g, accuracy is 0.01g). A3 Dissolution method
A3.1 Dissolving solution and preparation
A3.1.1 SbCI.-HCI solution
Dissolve 200g antimony trichloride (SbCls) in 1000mL hydrochloric acid (HCl, specific gravity 1.19). A3.1.2 SbCl2-HCI solution
Dissolve 100g antimony dichloride (SbClz·2HzO) in 1000mL hydrochloric acid (HCl, specific gravity 1.19). A3.1.3 SbCls-SbCl2-HCI solution
Take 100 mL of each solution prepared in A3.1.1 and A3.1.2 and mix them for later use. If the thickness of the hot-dip aluminum coating to be tested is very thick or the surface area of the coating of the sample exceeds 2000mm, the amount of the solution should be increased, but the ratio of the two solutions should still be maintained at 1:1 (volume ratio).
A3.2 Dissolution method
Immerse the sample completely in the SbCls-SbCl,-HCI solution to dissolve and remove the hot-dip aluminum coating until bubbles stop. The solution temperature must not exceed 38°C. Take out the sample, rinse it in tap water and wipe it with a soft fabric to remove the reaction products on the surface of the sample. Dry it with hot air, and after cooling, weigh the mass of the sample after the coating is dissolved (W2.g, accuracy is 0.01g). A4 Measurement of the surface area of the hot-dip aluminum layer of the sample
Use a vernier caliper to measure the surface area of the hot-dip aluminum layer of the sample (S, mm2). A5 Calculation of the hot-dip aluminum layer coating
Based on the above measurement results, the coating amount of the hot-dip aluminum layer of the workpiece (C, B/m\) can be calculated as: Wi-W,
K-1×10%
B1 Instruments
Various types of metallographic microscopes.
B2 Sample preparation
GB/T18592—2001
Appendix B
(Appendix to the standard)
Microscopic evaluation method for the pore level of the diffusion-type hot-dip aluminum layer B2.1 Cut the sample mechanically in a cold state, and its cross section should be perpendicular to the hot-dip aluminum layer. B2.2 The sample should be inlaid or clamped with a fixture to prevent chamfering. B2.3 The sample should be polished after grinding.
B3 Porosity level assessment
B3.1 The pore level assessment is carried out on the polished surface of the sample. B3.2 The pore level is assessed according to Table B1 and rating chart B1, and is divided into 6 levels. B3.3 The assessment result is expressed as the maximum pore level of the sample. B3.4 The magnification is generally 200 times.
Table B1 Porosity level and characteristics
Maximum pore size
>0.015~0.030
>0.030~0.060
>0.060~0.120
Note: The elliptical pore size is determined by the arithmetic mean of its major and minor axes. Supplementary explanation
Not a network
Network formed1 The specimen is cut mechanically in a cold state, and its cross section should be perpendicular to the hot-dip aluminum layer. B2.2 The specimen should be inlaid or clamped with a fixture to prevent chamfering. B2.3 The specimen should be polished after grinding.
B3 Porosity level assessment
B3.1 The pore level assessment is carried out on the polished surface of the specimen. B3.2 The pore level is assessed according to Table B1 and rating chart B1, and is divided into 6 levels. B3.3 The assessment result is expressed as the maximum pore level of the specimen. B3.4 The magnification is generally 200 times.
Table B1 Porosity level and characteristics
Maximum pore size
>0.015~0.030
>0.030~0.060
>0.060~0.120
Note: The elliptical pore size is determined by the arithmetic mean of its major and minor axes. Supplementary explanation
Network not formed
Network formed1 The specimen is cut mechanically in a cold state, and its cross section should be perpendicular to the hot-dip aluminum layer. B2.2 The specimen should be inlaid or clamped with a fixture to prevent chamfering. B2.3 The specimen should be polished after grinding.
B3 Porosity level assessment
B3.1 The pore level assessment is carried out on the polished surface of the specimen. B3.2 The pore level is assessed according to Table B1 and rating chart B1, and is divided into 6 levels. B3.3 The assessment result is expressed as the maximum pore level of the specimen. B3.4 The magnification is generally 200 times.
Table B1 Porosity level and characteristics
Maximum pore size
>0.015~0.030
>0.030~0.060
>0.060~0.120
Note: The elliptical pore size is determined by the arithmetic mean of its major and minor axes. Supplementary explanation
Network not formed
Network formed
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