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Galvanized steel sheet classification and standard specification

Galvanized steel sheet classification and standard specification

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The galvanized sheet is used to prevent corrosion of the surface of the steel sheet and prolong its service life. The surface of the steel sheet is coated with a layer of metallic zinc. This zinc-coat

The galvanized sheet is used to prevent corrosion of the surface of the steel sheet and prolong its service life. The surface of the steel sheet is coated with a layer of metallic zinc. This zinc-coated steel sheet is called galvanized sheet or galvanized steel sheet.

Galvanized sheets are widely used in construction, light industry, automobiles, home appliances, electronics, agriculture, animal husbandry, and fishery, and commodity packaging. In recent years, the demand for galvanized sheet in China's construction, home appliances and other industries has grown rapidly, and the market potential is large. Especially in recent years, with the rapid development of lightweight structures, the production of cars has increased year by year, and the popularity of household appliances has increased. The large-scale export of electronic products by wholly-owned enterprises has enabled the consumption of galvanized sheets to grow rapidly. According to the production method, the galvanized sheet is divided into a hot-dip galvanized sheet and an electrogalvanized sheet. At present, the production of domestic galvanized sheet can not meet the market demand, no matter the quantity or variety. It needs a large amount of imports every year. The domestic galvanized sheet production market share is low, the domestic market is in short supply, and the market potential is huge.

Electrolytic plates are also called galvanized sheets, which are processes that use electrolysis to form a uniform, tight, well-bonded metal or alloy deposit on the part dial. Compared with other hardware, zinc is a relatively expensive and easy-to-plated hardware, which is a low-value anti-corrosion coating. It is widely used to protect steel parts, especially to prevent atmospheric corrosion and to be used for accessories. Plating technology accommodates bath plating (or hang plating), barrel plating (for small parts), artificial plating and continuous plating (for wire and strip).

The electrolysis plate is rolled by the cold connected pressure circuit unit and then annealed by the CAPL unit, and then enters the electro-galvanizing unit. After electroplating is cleaned and plated over the dial, phosphating, passivation, oiling, fingerprint resistance, alloying, etc. may be performed according to different uses. The goods obtained after the treatment are referred to the corresponding substrates regarding the machine performance.

Domestic electroplating filtrate can be divided into four categories

1. Cyanide galvanizing:

Since (CN) is highly toxic, because of the strict restrictions on the use of cyanide in electroplating, it is required to promote the development of cyanide and substituted cyanide electroplating zinc plating systems, requiring the use of low cyanide (microcyanide) plating solution. After electroplating with this process, the quality of the goods is good, especially for color plating, and the pigment remains good after passivation.

2. Zinc galvanizing:

This process evolved from cyanide galvanizing. At present, there are two major factions in China: A) "DPE" series of Wuhan Material Protection Institute; and B) "DE" series of radio and television. Zinc galvanizing due to acidic additives; pH is 12.5-13. By adopting this process, the plating lattice structure is columnar, and the corrosion resistance is good, and it is suitable for positive color galvanizing. Note: After the goods are out of the tank → water washing → light (nitrate + phosphoric acid) → water washing → passivation → water washing → water washing → hot drying → drying → aging treatment (oven body 80 ~ 90 ° C).

3. Sulfide galvanizing:

This process is widely used in the electroplating business, accounting for up to 40%. After passivation (blue and white) decent zinc chrome (comparable to chrome), especially after the addition of water-soluble enamel, it is difficult for electroplating laymen to identify whether it is galvanized or chrome-plated. This process is suitable for white passivation (blue, white, silver).

4. Sulfate galvanizing:

This process is suitable for continuous plating (wire, strip, simple, large and large zero, parts), and the cost is low.

Standard specification for galvanized sheets

1, galvanized sheet size

The relevant product standards specify the standard thickness, length and width recommended for galvanized sheets and their tolerances. The thickness deviation is generally 0.05mm, the length and width deviation is generally 5mm, and the thickness of the board is generally between 0.4-3.2. Please refer to the relevant product standards in this paper.

2. Appearance of galvanized sheet

(1) Surface state: The galvanized sheet has different surface treatment conditions due to different treatment methods in the coating process, such as ordinary zinc flower, fine zinc flower, flat zinc flower, zinc-free flower and phosphating surface. German standards also specify surface levels.

(2) The galvanized sheet shall have a good appearance and shall not have any harmful defects such as no plating, holes, cracks and scum, excessive plating thickness, scratches, chromic acid stains, white rust, etc. Foreign standards are not very clear about the specific appearance defects. Some specific defects should be listed on the contract when ordering.

3. Mechanical properties of galvanized sheet

(1) Tensile test:

Galvanized steel sheet index (unit: g/M2)

JISG3302 Code Z12 Z18 Z22 Z25 Z27 Z35 Z43 Z50 Z60

Galvanizing capacity 120 180 220 250 270 350 430 500 600

ASTMA525 Code A40 A60 G60 G90 G115 G140 G165 G185 G210

Galvanizing capacity 122 183 183 275 351 427 503 564 640

DIN1716 code 100 200 275 350 450 600

Zinc plating amount 100 200 275 350 450 600

1 Performance indicators: Generally speaking, only galvanized sheets for structural, tensile and deep drawing have tensile properties. Among them, the galvanized sheet for the structure is required to have a yield point, tensile strength and elongation, and the elongation is required only for elongation.

2 Test method: Same as the general thin steel plate test method, see the relevant standards provided in this paper.

(2) Bending test:

The bending test is the main item to measure the performance of the sheet. However, the requirements of various standards for various galvanized sheets are not consistent. The US standard does not require bending and tensile tests except for the structural level. In Japan, except for structural grades, building corrugated sheets and general corrugated sheets, bending tests are required.

1 Requirements: Generally, after the galvanized sheet is bent 180, the outer surface shall not have a zinc layer to be detached, and the plate base shall not be cracked or broken;

2 Test method: The sampling part and quantity are shown in the relevant product standard in this paper. The bending angle is 180, the ratio of the inner spacing to the thickness of the test sample, see the relevant product standards listed in this paper.

High-quality, high-grade hot-dip galvanized sheets, especially for galvanized sheets for automobiles and home appliances, are required to have very high surface quality, excellent plate shape, different alloying coatings, good deep-drawing performance and high strength. Therefore, the production of high-quality hot-dip galvanized sheet is a systematic project. The production quality has been demanded for a series of production processes such as smelting, continuous casting, hot rolling, cold rolling and galvanizing, and the production is difficult.


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