Author: new

There are many factors to consider in the selection of coating, including coating type, coating thickness, coating color and coating gloss.

In addition, sometimes even to consider the coating primer and back coating requirements.

At present, the coatings used for color coated steel plate include polyester coating (PE), fluorocarbon coating (PVDF), silicon modified coating (SMP), high weathering coating (HDP), acrylic acid coating, polyurethane coating (PU), plastisol coating (PVC), etc.

Types of common coatings

(1) PE (Polyester)

PE coating for the material has good adhesion, color coated steel plate easy processing and forming, cheap and more products, color and gloss of the choice of large.

Polyester coating is not ideal for uv resistance and coating powder resistance, so the use of PE coating still need to be subject to some restrictions, generally used in areas where air pollution is not serious or need to shape processing products.

▲ suitable industry

General industrial plant and warehouse, not color board corrosion, color board corrosion resistance, anti-aging requirements are not high, more consider the practicality of plant construction and cost performance

(2) SMP(Silicone Mobified Silicone)

As the polyester contains active base -oh / -cooh, it is easy to react with other macromolecules and substances. In order to improve the sunshine resistance and powder resistance of PE, the Silicone resin with excellent color retention and heat resistance is used for denaturation reaction.

And degeneration of PE ratio is between 5% – 50%, SMP provide better the durability of the steel, the corrosion protection duration of up to 10 to 12 years, and, of course, its price is more PE is high, but because of the Silicone resin adhesion and processing of material formability is not ideal, therefore the SMP colorized painting steel does not apply to multiple processing of occasions, most used for building roofs and walls.

(3) HDP(High Polyester)

High weather resistant polyester resin in the synthesis of monomer containing cyclohexane structure, to achieve the flexibility of the resin, weather resistance and cost balance, the use of aromatic polyols and polyacids to reduce the absorption of UV light resin, to achieve the coating of high weather resistance.

Ultraviolet absorbents and steric hindrance amines (HALS) are added to the coating formula to improve the weatherability of the paint film.The high weather resistance polyester coil coating has been recognized by the market in foreign countries.

▲ suitable industry

Metallurgy, power industry non-ferrous metal smelters (copper, zinc, aluminum, lead, etc.) is the most challenging color plate service life, steel mills, power plants will also produce corrosive medium, color plate corrosion requirements are higher.

(4) PVC Plastisol

PVC resin has good water resistance and chemical resistance. Generally, it is coated with high solid parts, and the coating thickness is between 100-300um.

Can provide smooth PVC coating or light embossing treatment for embossing coating;Because PVC coating is a thermal plastic resin, with a high film thickness, can provide good protection of steel plate.But the heat resistance of PVC is weak.

In the early days, it was widely used in Europe, but now it is less and less used due to its poor environmental protection properties.

(5) PVDF

Because of PVDF chemical bonds and bonds, there is a strong bond energy, so the coating has good corrosion resistance and color retention, in building steel plate coating industrial belt, is belongs to the most advanced products, and the molecular weight and structure type of key, so in addition to the chemical resistance, mechanical properties, resistance to ultraviolet radiation and heat resistant performance are also very prominent.

In the general environment, the corrosion – proof life can reach 20-25 years.In recent years, fluorine-containing resin copolymerized with trifluorovinyl chloride and vinyl ester monomer has been widely used in the external walls and metal plates of buildings in China. The content of easily hydrolyzed vinyl ester monomer and fluorine is about 30% lower than that of PVDF, so there is a certain gap between its weatherability and PVDF.For the fluorocarbon coating produced by baosteel, the PVDF content of the coating is not less than 70% (the other is propionic acid resin).

▲ suitable industry

Chemical industry products have volatile characteristics, easy to produce acid or alkali and other corrosive volatile substances, easy to form dewdrop attached to the surface of color plate after water, color plate coating corrosion, and may further corrosion to the zinc layer or even steel plate.

Zn-al-mg alloy coated steel plate is a new type of coating product, and it is also a field that many domestic steel mills have been involved in in recent years.

When we learn about a product, we usually want to know its history. We also need to know the products and development background of domestic and foreign manufacturers.After understanding these two aspects, we can have a more systematic and clear cognition

What is zinc, aluminum and magnesium coated steel plate?

According to the definition of European standard en10346-2015, zinc, aluminum and magnesium coating is a ternary alloy coating whose main component is zinc, in addition, the content of aluminum and magnesium is between 1.5~8% (whose content of magnesium is not less than 0.2%).

Compared with hot-dip galvanizing, aluminum-zinc plating and zinc-ferroalloy, zinc-aluminum-magnesium coating has better corrosion resistance

1, because zinc aluminum magnesium alloy coating is relatively thin, dense, not easy to occur coating peeling;

2. Corrosion products will flow and wrap the incision, so they have better protection for the incision and the incision;

3. Good corrosion resistance in some harsh corrosion environments (such as animal husbandry, coastal areas, etc.);

Development history of zinc, aluminum and magnesium coatings

It is widely believed in the industry that the commercial production and promotion of zinc, aluminum and magnesium coating steel plate is the Japanese steel and Nippon steel two steel mills.

Note: after the merger of Nippon steel and Nippon steel, Nippon steel is now renamed Nippon steel.

In the 1960s and 1970s, steel companies in the United States began to develop zinc, aluminum and magnesium coatings, but they were not commercially produced.

In the ninth century, rixin iron and Nippon steel have done a lot of work in the research and development of zinc, aluminum and magnesium alloy coating, made great progress and started the commercialization of zinc, aluminum and magnesium alloy coating plate.

European steel companies such as ArcelorMittal, Thyssen Krupp, Tara steel European and BlueScope, an established Australian steelmaker, have since succeeded in developing similar products under their own brands.

In recent years, domestic steel mills have also followed up, such as jiusteel, baosteel, steel enterprises such as tang steel have also begun to produce zinc, aluminum and magnesium coating steel plate.

Introduction of zinc, aluminum and magnesium products of major steel mills

ZAM

Steel plant: nissin steel (Japan)

Coating composition: Zn — 6%AI — 3%Mg

Birth time: developed successfully in 1999, and produced commercially around 2001.

Introduction: often regarded as the most authentic primary zinc aluminum magnesium coating products, known as the traditional zinc plating corrosion resistance of 20 times.

Application: widely used in the construction industry, mechanical and electrical industry, highway dark fence, automobile industry, power industry, etc.

DYMAZINC

Steel plant: Nippon steel (Japan)

Coating composition: ZN — 0.2%AI — 0.5%Mg

Date of birth: the same time as the ZAM of Japanese steel.

Introduction: low aluminum and low magnesium composition system, compared with the traditional zinc coating has excellent corrosion resistance, especially suitable for salt hazard areas, corrosion resistance, good processing.

Application: mainly used in construction industry, instead of pure zinc coating.

SUPERDYMA

Steel plant: Nippon steel (Japan)

Coating composition: ZN — 11 %AI — 3%Mg — 0.2%Si

Date of birth: early 21st century (commercially produced after DYMANZIC).

Introduction: high aluminum composition system, super wall corrosion resistance, good formability

Application: mainly used in home appliance industry.

ZM EcoProtect

Steel plant: thyssenkrupp (Germany)

Metal composition: ZN-1%Mg

Date of birth: around 2008.

Description: compared with traditional zinc, aluminum and magnesium coatings, the corrosion resistance is reduced, but it is easy to obtain better surface quality

Application: the alternative product is high surface quality hot dip galvanizing, which is used in electrical cabinets, wheel covers and automotive stamping parts.

Magnelis 

Steel plant: ansegentil (Germany)

Coating composition: ZN – 3.5%AI – 3%Mg

Date of birth: 2010.

Description: the purpose of development is mainly for the environment containing cl ions and ammonia gas, which has good resistance to perforation and corrosion under the film.

Application: suitable for animal husbandry, such as raising pigs, cattle and poultry greenhouses.

ZINCALUME

Steel plant: bosco

Coating composition: add about 2% magnesium to aluminum zinc (55% aluminum)

Date of birth: the traditional ZINCALUME has been upgraded in recent years.

Description: strictly speaking, this coating and the original ZAM zinc-aluminum-magnesium coating are two products, which are modified from the traditional zinc-aluminum-zinc coating (55% aluminum)

And then to.

Application: suitable for replacing traditional aluminum and zinc coating.

PosMAC

Steel plant: posco (Korea)

Metal composition: Zn — 2.5%AI — 3%Mg

Date of birth: No

MACSTAG

Steel plant: posco (Korea)

Obsidian: Zn — 1.4%AI — 1.4%Mg

Date of birth: No

JISCO SCS (registered trademark)

Steel plant: jiusteel (China)

Coating composition: Zn — 11%AI — 3%Mg

Date of birth: No.

Baosteel, BZM is close to thyssen’s ZM EcoProtect, and BAM is close to bosco’s ZINCALUME.

Hot dip galvanized series of metal coating steel plate or steel belt is our trade or processing of the use of the variety, such as galvanized, aluminum zinc, zinc aluminum magnesium coating.According to some foreign promotional materials, about half of the world’s zinc production is used in steel and steel products surface corrosion treatment.

Different hot – coated steel plates have different characteristics and trade, use characteristics.

Typical brand and logo of hot-dip galvanized products

Take hot pure zinc plating products as an example, there are three basic properties: base plate quality, coating type, coating weight, in different standards have different naming and identification methods

JIS G3302 SGCC Z08

Brand interpretation read

S: steel, steel

G: galvanized, galvanized

C: cold rolled, cold rolled

C: general, commercial

The suffix reads Z08

Main attribute: coating weight

Property 1: double thickness coating

Property 2: the minimum mean value of two-sided pure zinc coating weight in three-point test is 80g/m2, and the minimum value of single-point test is 68g/m2

Property 3 corresponds to a coating thickness of 0.017mm

ASTM A653 CS Type B G90

Brand interpretation

A653: ASTM A653/A653M, American standard

CS: general steel, commercial steel

Type B: class B component Type

The suffix reads G90

Main attribute: coating weight

Property 1: double thickness coating

EN 10346 S350GD+Z

Brand interpretation is small

D: flat products for cold forming

X: substrate state is determined

51: serial number, no specific meaning, for general use

D: code for hot dip coating

The suffix reads Z100

Main attribute: coating weight

Property 1: double thickness coating

Attribute 2: the minimum mean value of the total weight of the two-sided pure zinc coating in the three-point test is 100g/m2, while the minimum value of the single point test is 85g/m2

Characteristics and trade points of various hot – plating coatings

Pure zinc coating

Hot dip galvanized zinc pot zinc content is not less than 99%, is the most economic corrosion coating type.

Pure zinc-coated steel plates are divided into two types: zinc-free and zinc-coated, and their corrosion resistance is almost the same.If the subsequent need to spray or paint, no zinc flower products will be more beautiful;While thick zinc layer products are usually flowered (such as zinc layer weight 275g/m2 on both sides)

Aluminum and zinc coating

The plating solution contains about 55% aluminum, about 1.6% silicon, the remaining component is zinc, aluminum zinc coating in most of the environment corrosion resistance is higher than pure zinc coating, aluminum zinc coating steel coils are zinc flowers.Excellent steel mill can produce even beautiful zinc flower, for home appliances products directly bare, but aluminum zinc coating also has some shortcomings.

The welding performance of aluminum and zinc coating steel plate is not as good as that of pure zinc.Because the hardness of the bonded metal after melting is relatively high, the removal efficiency of ordinary grinding tools is very low, which will lead to the scrap of the electrode. Therefore, the welding process should be minimized in use.

In addition, the protection of aluminum and zinc coating on steel plate cutting is far less than that of pure zinc coating (it is far less than that of zinc, aluminum and magnesium coating), the need to do a good job in cutting anti-corrosion work (such as painting closure)

Zinc Aluminum Magnesium coating

This is a coating product with excellent comprehensive performance, developed and mass produced by Japan’s nissin steel company in the early 21st century, and registered the patent and trademark ZAM.The corrosion resistance of zinc-aluminum-magnesium coating is much higher than that of zinc-plating and aluminum-zinc plating, the protection of cutting holes is excellent, and the welding performance is very good.

At the beginning of the construction of photovoltaic farms in China, zinc, aluminum and magnesium steel plates are often used to manufacture photovoltaic supports.An obvious feature of this product is the obvious trace of coating corrosion near the cutting hole.

3 Improvement measures

3.1 improve the accuracy of side guide plate equipment

Rectification of measurement problems found in the system, back side guide of the bell mouth and parallel to the period of transition place there is a big problem of the steps taken two measures, one is parallel to the side guide segment lining board cut thin 15 mm, 2 it is to push the bell mouth whole to run way among the 17 mm, big big reduce the height of the steps, improve the state of strip head into steel, drop we were among the strip local compression of the risk of collapse.

3.2 reduce static friction force of side guide plate

According to side guide friction problem, the factory repair, overhaul guide when ontology to replace copper skateboard, pin shaft, sets, gear, rack, eliminate clearance, more in equipment after the evaluation of static friction force decreased from 12 kn to 7 kn, and daily maintenance, working in the issued standard every day preview of 1 # SG drive side action mechanism, improve the frictional force, in the long run, will serve two hot side guide structure, the sliding friction into rolling friction can significantly reduce the static friction force, thereby greatly reducing the pressure of side guide target and fundamentally solve the problem of surface litter volume.

3.3 sectional pressure control of side guide plate

Under the existing conditions, it is necessary to not only ensure the roll shape, but also reduce the surface and groove rolls, optimize the control strategy of the side guide plate, and develop the pressure control method of the side guide plate sections. The pressure can be reduced to Y% of the target pressure after the drum bites the steel for X seconds. Both X and Y are adjustable parameters, which can be adjusted according to the actual situation.

4 Implementation Effect

After the implementation of the above measures, bread rolls from 500 tons per month to less than 100 tons, a significant effect.5 conclusion

(1) the excessive suwa pressure on the winding side caused the strip edge to collapse and roll up, which was the direct cause of the surface roll;

(2) in terms of equipment accuracy, the step between the side flared mouth and the parallel section transition is too large, resulting in the head hitting when entering the steel, resulting in the skew. In the pressure link, the strip steel is locally compressed, and the edge is strongly compressed. This problem is eliminated by rectifying the equipment;

(3) the sudden static friction force on the winding side causes the target pressure to be large. By making the sudie uniform speed movement, the friction force can be measured indirectly and effectively. The static friction force can be reduced by replacing the gear, rack, copper slider and daily oil drilling.

Under the premise of ensuring the coil shape, the control strategy of pressure section can mitigate the damage of the side suwa to the edge of the strip.

1 Phenomenon Description

In a hot-rolled steel coil warehouse, nearly 400 tons of steel coils are rejected every month due to the abnormal coil shape, which seriously affects the secondary waste drop index of the factory. The abnormal coil shape is mainly the unilateral or bilateral steel coils with lotus leaf edge and edge roll (flanging), which looks like the surface nest, and is called the surface nest coil.Since the edge of the face socket has been rolled up and the plate shape is also arched, if the normal machine resurrection will damage the roll and the plate shape can not be corrected, it can only be revised or scrapped, causing huge quality loss.According to the investigation, this kind of steel coil finish rolling outlet plate shape is normal, laminar flow cooling is normal, so it is inferred that this defect is from the winding, a hot rolling technicians on this defect was analyzed and studied.Will face nest volume information were collected, and one by one at the scene confirmed the material object, from the point of physical roll, steel roll of the central stratification or big overflow edge, have obvious guide section steel roll edge scratch, it is after finishing line open-book falbala, from the point of coiler, 1 reel in the majority, from the thickness specification, mainly concentrated in between 2-4 mm.According to the above phenomenon, it can be determined that the roll of this kind of surface socket is caused by the guide plate of the take-up side. The following focuses on the in-depth analysis of the control link of the take-up side guide plate.

2 Cause Analysis

2.1 winding side guide board control strategy

A hot rolling is a vertical transportation, on the roll quality requirement is very high, if there is a slight overflow, also can appear work side folding defects, so the side guide USES pressure control is good for roll shape, but to avoid head scrap steel, hot-rolled coil, a side guide to use two short stroke and full pressure loop control strategy, the side guide the preset opening and two short trip distribution as shown in table, short stroke on both sides of side guide action schedule same, SG no. 1, for example, a short trip to trigger timing for HMD71 after connecting strip head distance meet 9 meters, namely strip head has just landed on the side guide parallel segments,The trigger timing of the second short stroke is when the integral distance of the strip head reaches 14 meters after HMD71 is connected after the end of a short stroke, and the pressure link begins after the end of the second short stroke. In the pressure link, the drive side of the side guide plate is controlled by the target pressure closed-loop.

2.2 case study of typical face cavity volume

The material of the socket roll is SAE1017, the specification is 2.3*1020*C mm, 1#DC production.In the middle of the steel coil, there is obvious stratification. Within the stratification, there is a typical surface roll. The stratification is relieved by the outside roll, but the roll shape is uneven.

1) the guide USES is full pressure loop control strategy, the head pressure ring when entered into a state of constant, the transmission side guide trip to 78 mm, work side two short stroke to 40 mm, preset opening for B + 80 mm, transmission measurement guide side more than the work left 38 mm, including 20 m m to guide calibration of embedded, equivalent to guide on the strip head pressure ring 18 mm more stable when the trip, the 18 mm consists of two parts, one is the guide of the wear and tear, second, the deformation of the strip (general state of deformation for the transverse bending);

2) from the perspective of the speed of roll, the coil winding to the central roll speed is also slow down, this phenomenon should be a result of rising tension suddenly, and combining with the guide conditions, after the tension should be generated by the guide, the guide of unstable after the tension, leading to the volume fractal layered outside present uneven phenomenon, this is a kind of tension instability phenomenon;

3) at the end of the coil production, the manual operation of the guide plate is required to reduce the opening degree. The reason is that the pressure detection of the side guide plate suddenly becomes smaller, and the drum speed tends to increase and become untensioned. Therefore, the operator reduces the opening degree of the guide plate.

2.3 static friction force of the guide plate on the take-up side

(1) influence of static friction force of side guide plate

The setting of the target pressure of the side guide plate is related to the friction force suffered by the side guide plate. When the static friction force is large, the target pressure of the side guide plate must be large to push the side guide plate, otherwise the steel coil is badly wrong, but the excessive pressure of the guide plate causes great damage to the strip edge.Static friction force has the characteristics of reverse and change, and affected by width or strip shape change, strip of side guide reaction will be instantaneous jump, if you would have a side guide to squeeze to open at this moment, must overcome the pressure of side guide and change to the sum of the static friction force, or it will collapse to form surface litter volume, so need to accurately measure the side guide of friction.

(2) static friction force source of guide plate

The guide plate static friction force mainly comes from the gear rack and rack to meet the copper slider, a hot rolling and two hot rolling contrast, a hot rolling guide rail copper slider is three sliding friction, and the second hot rolling because of the guide wheel, sliding friction into rolling friction, greatly reduce the friction.

Brand Q195

Low carbon content, low strength, good plasticity, toughness, processing and welding performance.Used for rolling sheet metal and wire rod.Cold and hot rolled sheet steel and galvanized, tinned and plastic composite sheet steel made of the original plate are widely used in roof board, decoration board, general dust removal pipe, packaging container, iron drum, instrument shell, switch box, protective cover, railway cars, etc.The coil is cold drawn into low carbon steel wire or galvanized low carbon steel wire, used for binding, tensioning, fixing or as wire mesh, bracelet, etc.

Brand Q215

Slightly stronger than Q195 steel, similar in use to Q195.In addition, it is also widely used for welding steel pipes, galvanized welded pipes, furnace supports, screws, bolts, round nails, wood screws, and metal parts such as punching iron chains.

Brand Q235

Moderate carbon content, good comprehensive performance, strength, plasticity and welding performance, the most widely used.Often rolled into coil or round steel, square steel, flat steel, Angle steel, I steel, channel steel, window frame steel and other steel, thick steel plate.Construction and engineering structures are used extensively.It is used for making steel bars or building factory buildings, high-voltage transmission towers, Bridges, vehicles, boilers, containers, ships, etc. It is also widely used for mechanical parts with low performance requirements.Grade C, D steel can also be used for some professional steel.

Brand Q255

The performance is similar to Q235, with a slight increase in strength and a decrease in plasticity.It is not as widely used as Q235. It is mainly used for bushing and checking

Brand Q275

Strength, hardness is higher, wear resistance is better.Used for manufacturing shaft, agricultural machinery, wear-resistant parts, rail joint splint, pad, wheel, roll, etc.

Brand Q295

Steel contains only a small amount of alloying elements, not high strength, but good plasticity, cold bending, welding and corrosion resistance.Mainly used for building structures, industrial plants, low pressure boilers, low and medium pressure chemical containers, oil tanks, pipelines, cranes, tractors, vehicles and general engineering structures with low strength requirements.

Brand Q345, Q390

Good comprehensive mechanical properties, good welding performance, cold and hot processing performance and corrosion resistance, grade C, D, E steel has good low temperature toughness.Mainly used in ships, boilers, pressure vessels, oil storage tanks, Bridges, power plant equipment, lifting and transportation machinery and other high load welding hooks.

Brand Q420

High strength, especially in normalizing or normalizing and tempering state has higher comprehensive mechanical properties.Mainly used for large ships, Bridges, power plant equipment, medium and high pressure boilers, high pressure vessels, rolling stock, hoisting machinery, mining machinery and other large welding structures.

Brand Q460

The highest strength, in the normalizing, normalizing and tempering or quenching and tempering state has a very high comprehensive mechanical properties, all with aluminum supplementary deoxidization, quality grade C, D, E, can ensure the good toughness of steel spare steel.Suitable for all kinds of large engineering structures and light structures with high strength and heavy load.

The thickness tolerance dispute of hot rolled plate / coil is one of the main disputes that perplex the steel trade industry. It has to be said that there are errors in the analysis of the inquiry and in the purchase of materials.

In order to avoid trade disputes and reduce trade losses, it is necessary to lay a solid foundation for steel trade, and understand and master the provisions of thickness tolerance in the national standard.

One

There are three common requirements for thickness tolerance of hot rolled plate / coil

1. Implementation of international requirements

(for example, GB / T 19189 2011 “quenched and tempered high strength steel plate for pressure vessel”, the thickness requirement refers to GB / T 709 “dimension, shape and allowable deviation of hot rolled steel plate and strip”)

2. Implement the specific requirements of this standard

(for example, Q / BQB 381 2018 “hot rolled steel plates and strips for hydro generators”, with the provisions of the same plate difference and thickness tolerance in the standard)

3. Special requirements for signing the agreement

(for example, the order agreement of some automobile seats’ fine and medium steel plates is made according to the salt requirements of users, usually the confidentiality agreement)

TWO

GB / T709 “dimension, shape, weight and allowable deviation of hot rolled steel plate and strip” is one of the most cited thickness tolerance standards. To understand this standard means to penetrate the basic set of thickness tolerance requirements.

In GB / T709, the type of thickness tolerance of single rolled steel plate (commonly known as medium and thick plate) is divided into four categories: n, A. B, C.

According to the type of thickness deviation

Class n deviation: positive deviation and negative deviation are equal;

Class a deviation: negative deviation according to the nominal thickness;

Class B deviation: fixed negative deviation is 0.3 mm;

Class C deviation: the fixed negative deviation is zero, and the positive deviation is specified according to the nominal thickness.

Three

If a 45mm thick x 3500mm wide x 10m long 07mnnimodr container plate supplied in accordance with GB 19189-2011 is purchased, what is its tolerance range?

As shown in the example above, in the absence of special agreement, the tolerance requirements of this vessel plate shall conform to the class B deviation requirements in GB / T 709, and the class B deviation requirements are as follows:

According to the thickness of 45mm, the horizontal coordinate is > 40.0 ~ 60. This gear is selected; according to the width of 3500mm, the vertical coordinate is > 2500 ~ 4000. The length is not specified

Therefore, it can be compared that the thickness tolerance of this container plate is 45mm (- 0.3 ~ + 1.9mm), that is, the thickness of the actual steel plate should be between 44.7-46.9mm.

Detection of weight of organic or inorganic coating after treatment

Weight method: reference standard has GB/T 9792-2003.Peel off the coating with different solutions, then weigh the weight difference before and after peeling off the coating, and calculate the coating weight.

X-ray fluorescence spectrometry: since most of the post-treatment agents are organic solutions, the weight of the coating can be converted into the coating weight by measuring the weight of the characteristic elements in the coating.

Coating types	Eigenelement
Phosphating film	Phosphorus(P)
Passivation coating	Chromium（Cr）
Chrome-free passivation film	Silicon（Si）or  Titanium（Ti）or（Zr）
Chrome-free fingerprint film	Silicon（Si）or  Titanium（Ti）or（Zr）

Due to different suppliers provide different post-treatment agent formula, such as Japan paka, Germany henkel and so on.Therefore, it is best to establish standard curves with standard samples from the same supplier as the sample.

Determination of iron content in hot-dip galvanized ferroalloy coating

According to the literature, there is a direct relationship between the iron content and the pulverization of the product.

ISO 17925-2004 determination of chemical constituents in zinc or aluminium layers by gravimetric, ICP and atomic absorption spectrometry.

Neutral salt spray test to evaluate corrosion resistance of galvanized sheet

Professional equipment

Atmosphere of water mist with certain concentration of sodium chloride (50g/L)

A certain temperature and humidity (35±2°C)

A certain pH (6.5 ~ 7.2)

The test time can be according to the user’s requirements, such as 48h, 72h, etc

To evaluate the foaming, rusting, adhesion reduction, corrosion spread from scratch, etc

The uniformity and porosity of coating thickness and corrosion spreading degree under salt spray were evaluated.Most conventional, most useful, most extensive accelerated corrosion

Executive standard:

ASTM B117

Gb: GBT1771 GBT10125

One  Galvanized sheet product coating weight index requirements

Continuous hot-dip galvanized/zn-fe-alloy coated steel plates and steel strips:

Hot-dip galvanized coating weight index is generally 40 ~225g/m2

Hot-dip galvanized ferroalloy coating weight index is generally 30 ~ 60g/m2

Continuous hot aluminum zinc alloy coated steel plate and steel strip:

The weight of hot aluminum zinc alloy coating is generally 30 ~ 90g/m2

Continuous electric galvanized/zinc shackle alloy steel plate and steel strip:

The index of electrogalvanizing layer weight is 10 ~ 90g/m2 commonly

Second  for the galvanized layer weight detection

1. Punching sample

The specific sampling method and sampling method are shown in the figure.The standard stipulates that the area of a single sample shall not be less than 5000mm2.

Punch 6 pieces of sample, respectively representing the upper and lower surfaces.

2. Detection method

(1) the weight method

Process: sample weighing – dissolution – weighing again.

The difference between the weighing and the sample area is used to calculate the coating or coating weight per unit area.

The advantage is the absolute measurement, the disadvantage is the sample destruction.

The unit of measurement is g/m2 or mg/m2.

Executive standard:

National standard: GB/T1839

American standard: ASTM A 90/A 90m-07

International standard: IS017925 ISO 1460

(2) X-ray fluorescence spectrometry

A set of standard plates from low to high zinc plating was made to establish the relationship between the X-ray intensity of zinc and the coating weight.Then the ray intensity of zinc in the zinc coating of the sample was converted from the regression equation to the coating weight.The key point of the method is the preparation of standard samples.The unit of measurement is g/m2 or mg/m2

Standard: American standard: ASTM A 754/A 754M

Date: JIS G 3321

Summary:

The gravimetric method must be manually operated while the advantage of X-ray fluorescence spectrometry is that it is fast and can be automatically analyzed in batch.

There are also other instrument methods such as coulomb method, glow spectrometry, or direct thickness gauge to determine the thickness of the coating.The results of different methods will be different.But the products recommended in domestic and foreign standards are gravimetric or X-ray fluorescence spectrometry.In case of any discrepancy in the measurement results, the weight method shall be used as the arbitration method.

Because the coating weight of galvanized sheet is uneven in the direction of the width of the sheet, especially hot galvanized sheet, the coating weight of different positions is different.

Cold rolled low carbon steel plate and steel strip

Cold rolled structural steel plate and steel strip

High strength cold rolled steel plate and steel strip for cold forming

Cold forming with multi – direction high – strength cold – rolled steel plate and steel strip

Cold rolled steel sheet and steel strip for enamel