Technical requirements for barrels for raw and auxiliary materials
Text / Yang Wenliang
The national standards (GB/T 912, GB/T 2518, GB/T 11253, YB/T 5037) of the four steel sheets listed in GB/T325.1 of the national standard of steel drums are actually the lowest materials for steel drums. According to recent developments, these standard materials have become increasingly inapplicable to the needs of steel drum production. These standard materials not only make the quality of steel drums not meet the requirements of users, but also have low product qualification rate and high scrap rate, resulting in high cost of steel drums. Due to the non-speciality of the standard, the specific requirements for the steel plate production enterprises and the barrel industry to select the steel plate product standards are not clear; at the same time, there is no specific steel plate and steel strip for the purpose of the steel drum, the characteristics of the loaded materials, and the processing characteristics. Standards and specifications. Because there is no special steel plate standard in the barrel industry, the standards for steel plates used by enterprises for barrel making are also different, resulting in uneven quality of steel drums.
To meet the needs of steel drum production, the performance requirements of the materials should meet the minimum requirements set forth in the standard. This is a basic requirement, but not the best condition. In actual production, companies use thin steel plates of SPCC, ST12, Q195 and other materials. These are not special steel plates, but they basically meet the needs of steel drum production.
Since the quality of raw materials has a very large impact on the quality and cost of steel drums, in recent years, major steel companies in China have witnessed the development of special materials for steel drums. The specific requirements for raw and auxiliary materials for steel drum production are now detailed.
First, the main raw material for steel drum production - thin steel plate
1, size requirements
(1) The thickness and allowable deviation of the steel sheet material for steel drums are shown in Table 1 below.
Table 1 Nominal thickness and allowable deviation of steel plate and steel strip (unit: mm)
Nominal deviationThickness tolerance
0.30, 0.40, 0.50
+0.01
-0.01
0.60, 0.70
0
-0.03
0.80, 0.90, 1.00, 1.10, 1.20, 1.50
0
-0.04
Note: The allowable deviation of the thickness within the head and tail of the steel strip is allowed to exceed 50% of the specified value.
(2) The nominal width range and allowable deviation of steel sheets for steel drums are shown in Table 2.
Table 2 The allowable deviation of the nominal width and width of the steel strip (unit: mm)
Nominal widthAllowable deviation
≤1000
+2
0
>1000
+3
0
2, shape requirements
(1) The radius of the steel belt shall not exceed 3 mm in any length of 2000 mm. The steel plate shall be cut at a right angle and the slope shall not be greater than 1% of the width of the steel plate. The height of the single-sided tower of the steel coil shall not exceed 20 mm.
(2) The unevenness requirements of the steel plate are shown in Table 3.
Table 3 Unevenness requirements of cold rolled steel sheets (unit: mm)
Nominal thicknessIrregularity per meter
Width ≥1000
Width >1000
<1.00
≤12
≤10
≥1.00～1.20
≤10
≤8
3. Technical requirements
(1) Chemical composition: The steel grade and chemical composition (melting analysis) requirements are shown in Table 4.
Table 4 Steel grade and chemical composition (unit: %)
useDeoxidation mode
Chemical composition, no more than
C
Si
Mn
S
P
Al
Steel drum
Aluminum calm
0.08
0.03
0.25
0.025
0.025
0.060
The trace elements Ni, Cr and Cu in the steel are not more than 0.10%, respectively; As and Sn are not more than 0.05% respectively.
(2) Mechanical properties: The mechanical properties of steel plates and steel strips are shown in Table 5.
Table 5 Mechanical properties of steel plates and strips
useYield strength, MPa
Tensile strength, MPa
Elongation after break, %
Steel drum
≤220
280-350
≥35.0
(3) Bending test: Steel plates and steel strips shall be subjected to bending tests in accordance with Table 6. No cracks shall appear on the surface of the specimen after bending.
Table 6 Bending test of steel plate and steel strip
Bending angleBending diameter
180°
d=0
(4) Hardness: The Rockwell hardness test value of the steel plate and the steel strip in the delivery state is not more than 60 HRB.
(5) Cupping value: The cupping value requirements of the steel plate and steel strip in the delivery state are shown in Table 7.
Table 7 Cup protrusion value (unit: mm)
Nominal thicknessCup value, not less than
0.60
9.0
0.70
9.2
0.80
9.4
0.90
9.6
1.00
9.8
1.10
9.9
1.20
10.1
1.50
10.5
(6) Surface quality: The surface of the steel plate shall not have defects such as delamination, cracks, crusting, folding, inclusions, holes, scratches, etc. In view of the continuous production characteristics of cold-rolled steel strips, it is possible to allow defective delivery, the general defects are calculated according to the length of 2 meters, and the surface quality is supplied in three grades (as shown in Table 8). Barrel companies can be selected according to actual needs.
Table 8 Surface quality of steel plate
levelSurface Quality
A
The part of the defect shall not exceed 4% to 8% of the total length of the steel strip of this coil.
B
The part of the defect shall not exceed 2% to 4% of the total length of the steel strip of this coil.
C
The part of the defect shall not exceed 2% of the total length of the strip
(7) Surface cleanliness: The surface is divided into 2 levels according to the degree of cleanliness, which is cleaner and cleaner. According to the production process and oiling conditions, the degree of cleanliness is divided into three grades, namely mild, moderate and heavy oil. The surface cleanliness requirements corresponding to the production process state are shown in Table 9. Barrel companies can choose steel plates with different cleanliness as needed.
Table 9 Surface cleanliness of steel plates (unit: mg/m2)
Surface cleanlinessOil quantity
Total surface residue
Residual iron
Production process status
no greater than
Cleaner
500
250
Annealed, flattened, not oiled
clean
300
100
Annealing, leveling, degreasing
Lightly oiled
500
1000
280
Annealing, leveling, oiling
Moderate oiling
1000
1500
280
Annealing, leveling, oiling
Heavy oiling
2500
3000
280
Annealing, leveling, oiling
Lightly oiled
500
1000
150
Annealing, leveling, degreasing, oiling
Moderate oiling
1000
1500
150
Annealing, leveling, degreasing, oiling
Heavy oiling
2500
3000
150
Annealing, leveling, degreasing, oiling
Second, steel barrel production auxiliary materials
1, crimping sealant
The seal packing used in the crimping is commonly called sealant, which is mostly made of natural latex. When the steel drum is produced, it is sprayed on the bottom of the bucket and the top seam, and the bottom, top and barrel are sealed. The sealing filler is filled in the gap of the curling edge and plays a sealing role. The seals of the seals are commonly used in the gaskets of the flanges and the washers in the buckets. They are usually made of rubber. They are made of other materials depending on the contents of the steel drums. Foam rubber or rubber ring seals are often used in open steel drum sealers.
Because steel drums contain a wide variety of cargo types with different chemical and physical properties, it is impossible to have a versatile sealing material to meet the needs of all cargoes. In special needs, the sealing material must be selected according to the different needs of the goods. Otherwise, the sealing material may react with the cargo, resulting in problems such as seal failure and cargo contamination deterioration. For commonly used sealing materials, generally should be selected according to the following requirements.
(1) Selection of crimp sealing packing
Generally speaking, when the steel drum is loaded with goods without special requirements, the conventional sealant can be used; when the goods may dissolve or the conventional sealant fails, the chemical special sealant should be used; if the goods have high hygiene requirements, or seal If the glue will contaminate the goods and the goods are deteriorated, the special sealant for food should be used. For all kinds of sealants, due to the requirements of production process and sealing performance, certain physical and chemical properties must be met. The quality requirements of common sealants are shown in Table 10.
Table 10 Quality requirements for steel drum sealing packing
Quality IndexQuality requirements
Type 8210, Type 8710
BL90 type
Exterior
Milky white or red viscous liquid with no visible impurities or clots
The product is milky white or colored, viscous and delicate liquid with no obvious impurities.
Total solids
≥40%
74±4%
Viscosity
≥100mpa.s
≥300mpa.s
Film density
0.90 to 1.10g/cm3
≥1.7g/cm3
pH value
9.5 to 12.0
10.0±1.0
Dry film chemical stability
K ≥ 0.70, and can produce a certain amount of volume expansion
K ≥ 0.70, and can produce a certain amount of volume expansion
health standard
Should meet the requirements of GB4807 standard
Should meet the requirements of GB4807 standard
Consumption quota
50-60 steel drums for 200L
50-60 steel drums for 200L
Generally, the sealant production enterprises can adjust the total solids and viscosity fineness according to the requirements of the users to meet the special requirements of the barrel manufacturers.
All kinds of sealants have a certain scope of application. The barrel making enterprises can do the immersion test according to the actual situation to prevent the filler from adapting to the accident of the contents to ensure the quality of the steel drum. During the test, a small amount of glue is applied to the glass. After it is completely dried, it is cut into squares and soaked in the solvent to be contained for one week. If it is expanded, it means that it is applicable. If it is completely dissolved, it means not applicable.
(2) Requirements for use:
a) The sealant must be stirred evenly before use to ensure the viscosity of each barrel is consistent. After mixing, it should be added to the container and filtered with a 20 mesh filter to avoid a small amount of clot blocking the gun, which will affect the glue injection effect.
b) When applying, brush the brush with cold water to wash it, damp the water, and apply a proper amount of sealant. Brush the brush when you pause the brush to prevent condensation and make it easier to use it next time.
c) Both manual brushing and mechanical spraying should be pre-coated, let it dry naturally for 1 to 3 hours at room temperature, and spray once again (except BL90 type) to increase the insurance factor.
d) If the glue is too thick, add a small amount of distilled water or cold water (do not add any other solvent). Under normal circumstances, avoid dilution as much as possible to avoid product quality change.
e) The sealant must not be in contact with air for a long time to prevent direct sunlight and away from heating equipment to prevent solidification.
f) The maximum temperature resistance of the sealant can reach 180 °C. If it exceeds 180 °C, it will stick to the coke and affect the sealing effect.
2, closed steel barrel seals
(1) Selection of sealer seals
Selection of steel drum seals: The types and uses of common closed steel drum seals are shown in Table 11. The type and use of the open steel barrel sealing rubber ring are shown in Table 12.
Table 11 Selection of closed steel barrel seals
Seal typePerformance and use
natural rubber
It has the advantages of good elasticity, cold resistance and wear resistance. High mechanical strength, suitable for containing water, alcohol, car brake oil and other goods. Not suitable for petroleum oils, fuel oils, etc.
Nitrile rubber
The petroleum-resistant base oil, hydrocarbon-resistant and water-resistant properties increase with increasing acrylonitrile content, but the low-temperature properties and gas permeability decrease. Not suitable for phosphate acid oils and oils containing polar additives.
EPDM
It is excellent in heat resistance, cold resistance, weather resistance and ozone resistance, and is suitable for phosphate ester oils, water-based substances, chemicals, etc., and is not suitable for mineral oils.
Acrylate
It has higher temperature resistance than nitrile rubber and good oil resistance, especially resistant to oils containing polar additives. However, it is resistant to water, cold, and acid and alkali.
fluororubber
Good heat resistance, oil resistance, chemical resistance and aging resistance. Suitable for almost all oils. However, it is not suitable for ketones and esters, and has poor cold resistance.
Silicone Rubber
It is resistant to oil, solvent, oxygen and aging. It hardly swells in gasoline, but its strength is low, and its tear resistance and wear resistance are poor.
PTFE
It has excellent chemical stability and corrosion resistance. It can resist all other chemicals except molten metal sodium and liquid fluorine. It is widely used in various occasions requiring acid and alkali resistance and organic solvents. It has sealing property, high lubrication, non-stickiness, electrical insulation and good anti-aging ability, and excellent temperature resistance. However, the elasticity is not good, which affects its sealing performance.
Polyethylene
It has excellent low temperature resistance, good chemical stability, resistance to most acid and alkali corrosion, odorless, non-toxic, insoluble in common solvents at normal temperature, low water absorption, and no swelling; but polyethylene is environmental stress Very sensitive, poor heat aging. The small elasticity is also a major drawback of its use as a seal.
nylon
Nylon has high mechanical strength, high softening point, heat resistance, oil resistance, weak acid resistance, alkali resistance and general solvent, self-extinguishing, non-toxic, odorless and weather resistant. The disadvantage is that the water absorption is large and the elasticity is small. It is suitable for use in high temperature environments or in environments prone to fire.
Table 12 Selection of open steel drum seals
Seal typePerformance and use
natural rubber
It has the advantages of good elasticity, cold resistance and wear resistance. High mechanical strength, suitable for containing water, alcohol, car brake oil and other goods. Not suitable for petroleum oils, fuel oils, etc.
Chlorinated butyl rubber
Low gas permeability and moisture permeability, good shock absorption, low glass transition temperature, good aging resistance and weather resistance under atmospheric conditions, vulcanization diversity, fast vulcanization speed, and good rubber and metal adhesion properties.
EPDM
It is excellent in heat resistance, cold resistance, weather resistance and ozone resistance, and is suitable for phosphate ester oils, water-based substances, chemicals, etc., and is not suitable for mineral oils.
High density natural rubber
It has the characteristics of natural rubber, but it has higher density, hardness, elasticity and deformation than ordinary natural rubber.
Natural rubber for food
It is made of natural rubber and is made into natural rubber products. It has reached the food grade through the use of rubber testing standards for national food contact. Other physical and chemical properties are the same as natural rubber.
PVC styrofoam
Has good corrosion resistance and sealing. The styrofoam is made of polyvinyl chloride resin as the main raw material. When used, the styrofoam is injected into the groove of the top of the bucket and placed in a heatable baking equipment. After a certain period of time, the styrofoam is plasticized and plasticized. The micro-bubbles are uniformly generated in the sealing strip to become a sponge-like elastomer. The degree of softness is proportional to the temperature of the heating in time. This sealing material is suitable for almost all sealing requirements of open steel drums.
(2) Quality requirements for common rubber seals
(a) Appearance quality requirements of the sealing ring: the impurity area of ​​the sealing ring is not more than 1mm2, and shall not exceed 5; the height of the concave and convex shall be less than 0.8mm and not more than 5; the height and width of the burr shall not exceed 0.8mm; No more than 8.
(b) The physical performance requirements of the rubber seal are shown in Table 13.
Table 13 Physical performance requirements of common rubber seals
Physical propertiesPerformance
natural rubber
Nitrile rubber
EPDM
Acrylate
fluororubber
Silicone Rubber
Hardness (Shore A), degree
35±10
65±10
70±10
65±10
70±10
65±10
Tensile strength, MPa
≥4
≥3
≥5
≥4
≥5
≥7
Elongation at break, %
≥200
Permanent deformation at break (70 ° C, 22 h), %
≤50
Hot air aging
Hardness change (Shore A), degree
0 to +15
Tensile strength change rate, %
≤-30
Elongation at break, %
≤-50
Liquid resistant (1# standard oil) volume change rate, %
-15~+45
3, steel drum inside and outside coating
Through the years of experiments in the barrel industry, most of the exterior surface coatings currently use amino drying enamel. This kind of paint can basically meet the requirements of the standard "material with strong adhesion, weather resistance and durability". For small batch production or no coating equipment and drying equipment, other paints, such as alkyd paint and epoxy paint, are used, but the effect is far less than that of amino baking paint.
The inner surface coating is generally required to be compatible with the contents, not to react with the goods, to deteriorate the goods or to invalidate the inner coating. There are two types of commonly used food inner coatings and chemical special inner coatings, all of which have strict requirements.
(1) Commonly used amino baking enamel
(a) Technical requirements: The paint is usually prepared by grinding a special structure alkyd resin, amino resin and various weather resistant pigments, adding additives, solvents and the like. The paint film after drying of the amino paint is bright, bright, hard film, excellent adhesion, good weather resistance and chemical resistance. It can be added with a catalyst to lower the baking temperature to achieve low temperature and fast drying, and effectively save energy consumption. The general technical requirements for the amino baking enamel used for the outer coating of steel drums are shown in Table 14.
Table 14 Technical requirements for amino drying enamel
projectindex
Paint film color and appearance
Meet the standard sample requirements, the film is flat
Fineness, μm
≤20
Viscosity (coating - 4 cups), S
≥80
Drying time (130 ° C), min
≤30
Gloss, 60 ° C meter
≥80
Hardness (pencil method)
≥H
Impact strength
≥40
Adhesion, level
≤2
Flexibility, mm
≤2
Water resistance (40 ° C, 24 h)
No foaming allows slight change 2h recovery
(b) Painting process requirements:
- Before the coating, the surface of the steel drum should be degreased, rusted, pickled, phosphatized, etc.;
- The paint should be thoroughly stirred before use and filtered with a 120 mesh copper wire cloth or a silk filter cloth to remove mechanical impurities;
- It is generally required to use spray coating or electrostatic spraying.
- Matching thinner: special amino paint thinner.
- Spray viscosity: 18 ~ 24s (coating-4 viscosity meter);
- Drying conditions: After spraying, place in a clean, dust-free environment for about 5 minutes to level and then bake.
- Baking temperature: 130 ° C / 30 min. When 0.2% catalyst is added to the paint, the tunnel temperature can also be raised to 115 ° C / 30 min, or 130 ° C / 15 min.
(c) Note on painting production:
-The spraying environment requires ventilation and dust-free, and should be equipped with a special spray booth to ensure the quality of the spray.
- The air compressor should be equipped with a water separator to make the compressed air oil-free.
- Paint should be stored in a dry, cool place away from fire.
-Enhance ventilation during work, the operator should pass professional training and strictly abide by the operating procedures.
(2) Common interior surface coatings
(a) Types and uses of coatings in common steel drums:
The types and uses of steel drums commonly used in China are shown in Table 15.
Table 15 Types and uses of paints in common steel drums
Paint typecolour
use
360 (PVB coating)
Various colors
The original paint is colorless and transparent, suitable for food, chemicals, grease resistance, cold resistance
361 (PPH coating)
Light yellow transparent
Chemical resistance, grease resistance, solvent resistance, weak acid and alkali resistance
362 (PHP coating)
Brown transparent
Chemical resistant, resistant to hydrochloric acid and organic acids, solvent resistant
400 (PAA coating)
Colorless and transparent
This is a water-soluble coating suitable for food and anti-corrosion, anti-rust, anti-oxidation
620 (EPA coating)
Colorless and transparent
Suitable for food, medicine, chemical resistance, grease resistance, solvent resistance, salt spray resistance, acid and alkali resistance
622 (EPR coating)
cream color
Suitable for food, medicine, chemical resistance, grease resistance, solvent resistance, salt spray resistance, acid and alkali resistance
891 (PU coating)
Colorless and transparent
This is a room temperature curing coating for rust, water, oxidation, chemical, grease and solvent resistance.
ZFT-1 (PVF coating)
gray
Suitable for oils, esters, etc.
ZFT-2 (PVF coating)
green
Suitable for chemical, pesticide products, etc.
ZFT-8 (PVF coating)
Milk yellow
Suitable for food, etc.
SP-1
Rice yellow
Suitable for food, etc.
PPG 2088
Milk yellow
Suitable for many purposes
(b) Performance requirements for common food coatings
Taking SP-1 food-specific internal coating as an example, it is made by grinding and blending special structural resin, strong acid-resistant pigment and auxiliary agent. The product should meet the national food hygiene standards and should be used when exporting steel drum packaging. US FDA certification. The bright and hard color of the paint film conforms to people's habits of food color, has good adhesion on the inner wall of the steel drum, has good chemical resistance, can continue to resist common food acids such as citric acid, and can directly contact food for a long time. The health indicators are shown in Table 16.
Table 16 Hygienic indicators of food interior coatings
ClaimIndicator requirements
index
24h extract in distilled water at 120 degrees Fahrenheit
18mg/in2
Max<0.1mg/in2
2h extract 0.1mg/in2 in 8% alcohol at 150 degrees Fahrenheit
18mg/in2
Max<0.1mg/in2
30mg extract 0.1mg/in2 in Zhenggeng solution at 70 degrees Fahrenheit
18mg/in2
Max<0.1mg/in2
When the food is coated with internal paint, the following should be noted:
- Before the coating, the surface of the inner wall of the steel drum should be degreased, derusted, pickled, phosphatized, etc.;
- The paint should be thoroughly stirred evenly before use and filtered with a 120 mesh copper wire cloth filter cloth to remove mechanical impurities;
-The coating is mainly sprayed, and electrostatic spraying can also be used;
- matching thinner: special thinner for food coating;
- Spray viscosity: 15 ~ 25s (coating-4 viscosity meter);
- Drying conditions: After spraying, place in a clean, dust-free environment for about 10 minutes, then bake.
- Baking temperature: 150 ° C or more, 30 min.
(3) New environmentally friendly waterborne coatings
Because of the growing demand for environmental protection in recent years, companies that use solvent-based coatings have begun to shift to environmentally friendly coatings, the most notable of which are water-based coatings. Most barrel companies believe that waterborne coatings will be the direction of coating development in the barrel industry.
(a) Characteristics of steel drum waterborne coatings
Since the water-based paint product uses water-based resin and water-based auxiliary solvent, it has the characteristics of non-combustible, non-explosive, environmentally safe; its film-forming material is also a conventional epoxy, acrylic, polyester film-forming material, so the anti-corrosion of the film The rust resistance is no different from the familiar paints in the industry.
In terms of safety and environmental protection of product applications, the superior advantages of water-based paints are also obvious:
- Low dilution cost: In the application process, the water is diluted to adjust the viscosity, completely eliminating the toxic and flammable potential of the organic solvent, and saving a lot of dilution costs.
- There is no potential risk in product application: In the two aspects of coating coating and drying, there are high levels of harmful substances. There are two hidden dangers in the paint: the paint construction workers can't avoid the high volatile environment of toxic solvents and easily lead to poisoning; The mixture of combustible volatiles and air reaches a certain concentration, and it is easy to detonate when exposed to open flames or sparks. The occurrence of these two conditions will bring great risks to the application enterprises, while the evaporation of water-based paints is mainly moisture, the above two Hidden dangers naturally do not exist.
- Energy-saving and emission-reducing benefits: Due to the use of water-based materials, the discharged substances are harmless substances, and the water-based paints have no irritating odor as paint, thus effectively improving the application environment. From the stable employment of enterprises to emission reduction indicators and other aspects, it provides very valuable conditions for application companies.
- Fully recycling and reuse of water-based paint: The coating method of steel drum is mainly sprayed, and its utilization rate is low, and a large proportion is discharged with exhaust air, resulting in waste and pollution. The water-based paint can be fully reused by adding a simple recovery device, and the recycling cost is extremely low.
(b) Coating process requirements for waterborne coatings
Water-based paints are different from oil-based paints, and the construction conditions are relatively special. Therefore, at the beginning of this year, we organized industry-related experts to develop a “standard process for water-based coating of steel drumsâ€, which unified the construction methods of water-based paints. Its main contents are as follows:
- The construction environment temperature is 5 to 40 ° C, and the optimum construction temperature is 20 to 26 ° C. The relative temperature is 30% to 80%, and the optimum relative humidity is 40% to 60%.
- Oil, rust, scale, corrosives, welding slag, impurities, etc. on the surface of the steel drum must be removed before spraying. The surface of the steel drum is required to be pre-painted by a suitable surface treatment process.
- The blending of the paint should be carried out in strict accordance with the ratio proposed by the paint manufacturer. Deionized water or distilled water should be used for the preparation of the coating, and the conductivity of the water should not exceed 20 μs/cm. The paint should be thoroughly stirred before use. After mixing, it should be filtered with a 200 mesh filter. The stirring speed should not exceed 200 rpm.
- It is recommended to spray with high pressure airless spraying method. The outlet pressure should be 6~12MPa when high pressure airless spraying. When spraying, the temperature of the barrel should not be lower than 30 °C (two-color spraying is not lower than 70 °C), not higher than 90 °C.
- Before baking, a leveling time of not less than 1 minute must be performed. When baking, it is advisable to adopt a two-stage or three-stage baking process. The first stage baking temperature should not exceed 100 ° C for 3 minutes; the second stage and third stage baking temperature is 150-170 ° C, time is not Less than 15 minutes.
- The temperature and storage temperature of water-based paint should be controlled at 5 ~ 30 °C, should be stored in a cool, ventilated place, avoid direct sunlight, storage period is 6 months.
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