New repair method for steel drums

In the production process of steel drums, it is inevitable that there will be leakage of the weld seam and the “big circle” (that is, the bottom of the barrel, the top of the barrel, and the mechanical crimping of the barrel). However, with the further development of the market economy, the ISO9000:2000 standard will refer to the first place in the management principle of the standard Big Eight with the customer as the focus of attention. Satisfying customer requirements has become the goal of steel drum companies, otherwise the company's production and operation will be in crisis.

Recently, I visited several barrel factories. Everyone complained about the increasingly high quality requirements of the customers. They said that customer requirements are too high, steel drums can have a few welding files, and national standards allow welding.疤 疤 , , , , , , , , , 。 。 In fact, I have encountered these problems every day at work. At present, many customers require that the appearance of steel drums is dazzling, and there are no problems such as welding lacquer, paint dripping, peeling of paint, and pits on the surface of steel drums. Even if the welding seam is repaired with an argon arc welder (the welding bead is very small, it is almost invisible after grinding), but it is difficult to realize the “zero defects” in the barrel products. This is mainly because Limited by the level of industry management. Currently, the steel drum industry cannot meet the requirements of zero-defective production conditions in terms of personnel quality, equipment status, and the management level of the company. Therefore, we have been looking for a method that does not affect the appearance of steel drums and prevent them from leaking. Bonding is currently used by several steel drum companies.

The leakage of steel drums is mostly at the bottom of the barrel, the top of the barrel and the mechanical crimping of the barrel; followed by seam welding at the barrel. A very small part is the leakage caused by the defects of the steel plate material itself such as sand holes, interlayers, and the like. Adhesive substructure and non-structural bonding. The important feature of structural bonding is that the joints are required to withstand mechanical loads for a long time; non-structural bonding refers to non-mechanical bearing bonding such as sealing, encapsulation, positioning, and repair. Therefore, the bonding of steel drums is a non-structural bonding of metal. Here we discuss the bonding process and methods of steel drums:

First, steel drum repair adhesive bonding options

To choose a reasonable and appropriate adhesive, we must first understand the properties and characteristics of the adhesive. In general, the adhesives we use to bond steel drums are synthetic adhesives. Synthetic adhesives can be classified into chemical reaction type and physical coagulation type, or classified into thermosetting and thermoplastic based on their state at different temperatures. Once cured, the former will not dissolve or melt, forming a cross-linked network structure; while the latter will soften with increasing temperature, when the temperature is higher than a characteristic temperature of a material (such as crystallization temperature or Glass transition temperature), they can viscously flow, and once the temperature decreases, they will re-solidify. Thermosetting adhesives are generally chemically reactive, whereas thermoplastic or thermosetting adhesives are generally chemically reactive. Thermoplastic or hot melt adhesives are generally physically setting.

Thermoset adhesives have higher strength and stiffness, and less tendency to creep. Thermoplastic adhesives have greater plasticity and toughness, and have better fatigue properties.

According to the characteristics of the adhesive and the environment in which the steel drum is used, we usually use the epoxy glue referred to as epoxy glue as the repair adhesive for the steel drum.

Epoxy adhesive has high bonding strength, good workmanship, easy preparation and use, small volume shrinkage after curing, stable product size, wide operating temperature range, and no toxicity to human body. Epoxy adhesives of various grades and various properties are not only available on the market, but also can be self-formulated or modified according to the needs of the adhesive, so the epoxy adhesive is called "all-purpose adhesive."

Second, surface treatment before steel drum repair

Before welding, the most important point different from welding is that the surface of the drum to be bonded has a certain degree of roughness and cleanliness. It also requires that the surface of the drum to be bonded has a certain chemical or physical reactivity. In order to ensure the bonding quality of steel drums. Therefore, before the bonding, the drum surface cleaning and surface activation must be performed. These are collectively referred to as pretreatment of the drum surface.

The common process methods for steel drum surface treatment are as follows:

Solvent, alkaline or ultrasonic bath degreasing

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Machining, grinding, lighting, sandblasting

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Chemical etching and anodizing

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Coated primer treatment

In the drum surface treatment process, the following points should be considered:

1. The condition of the surface of the steel drum is contaminated, including the thickness of the pollution layer, the tightness of the pollution layer, and the type and nature of surface contamination. For example, the surface of a steel drum is painted, electroplated, or mineral or vegetable oil.

2, the use of adhesive structure performance requirements, such as the short-term requirements are not leaking, that emergency treatment requires long-term no leakage, the leakage of steel barrels all use this method to deal with the requirements of the new steel drum level.

3. The economics and necessity of the materials used. That is, the type of the surface of the barrel to be bonded (paint buckets, electroplating buckets, galvanized buckets, or cold-rolled white buckets), the type of adhesive, the performance requirements, and the surface treatment process should be the best among the four. Eclectic point.

In general, the following methods are commonly used for steel drum surface treatment:

Degreasing liquid: trichloroethylene or gasoline

Treatment solution: Orthophosphoric acid (85%): Ethanol=1:2 (weight ratio)

Treatment methods: 1, solvent degreasing

2, in the coarse abrasive cloth

3. Soak in a 60°C treatment solution for 10 minutes. Then use a nylon brush to brush the surface to remove the contamination, then rinse with distilled water and dry at 120°C in air for 1 hour.

This method is most effective for surface treatment of steel drums that are not painted.

Third, the steel drum repair process

The general contents and procedures of the drum repair bonding process are as follows:

Surface treatment of steel drum leaks

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Apply adhesive on the treated drum surface

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Cure

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test

Drum leaks are generally hand-bonded. Hand-bonding should master the following points:

1, according to the type and nature of the adhesive to choose the right coating tools such as hair brush, spray gun or injection needle. The coating should be uniform and free of bubbles. The thickness of the film should be within 0.2~0.5mm.

2. After the glue is applied, the open time should be controlled within the allowable melon opening time of the adhesive. At the same time, the open film should be prevented from absorbing dust or contaminated. This requires that the amount of each adhesive should be appropriate, otherwise, it can not be used, and it can not be used after the reaction.

3, the correct choice of curing parameters

The curing process of the adhesive is a chemical melon process and it is important to choose the correct curing process parameters. The theoretical basis for controlling the chemical reaction adhesive curing process is the chemical reaction kinetics, and its basic parameters are reaction time, reaction temperature, opening time and the like. The effect is as follows:

1 reaction time

When the temperature of a chemical reaction is constant, the concentration ratio of the components of the reactants in the system will change with the extension of the reaction time. At the beginning of the reaction, the concentration of the components of the reactants is the highest, and the reactivity of the system is the highest, so the reaction rate is fastest. As the reaction time increases, the reaction rate decreases exponentially; in the final stage of the reaction, the reaction rate is very slow, and at this time, the cohesive strength of the adhesive has been basically established. Therefore, it is generally believed that when the reaction reaches about 90%, Curing is complete.

2 reaction temperature

Temperature is the most sensitive parameter affecting the speed of chemical reaction. In summary, the reaction temperature increases about 10 times for each increase in reaction temperature, and the reaction temperature also affects the structure and properties of the reaction product (such as the degree of cross-linking, Cohesive strength and adhesion strength, etc.).

Many adhesives have a wide range of reaction temperature adjustment, so the predetermined mechanical properties can be achieved by adjusting the temperature parameters of the curing reaction.

3 Opening hours

The opening time is the duration of the mixing of the components in the adhesive until the mixture can no longer be used, that is, the maximum time allowed for the adhesive to be parked in the air. The length of the opening time depends on the curing reaction rate of the adhesive system. In general, the faster the curing reaction of the adhesive, the shorter the opening time. In practical work, the open time can be determined by measuring the gelation time of the adhesive, and the open time can also be roughly determined by constantly stirring the adhesive and judging the degree of curing by experience. In order to ensure the performance of the adhesive, in principle, it is best to use it now and how much it is used.

IV. Quality inspection after steel drum repair

The mechanical properties of steel drums after repair and bonding must be tested, inspected and analyzed in accordance with national standards or relevant international standards. The basic test content of the structural bonding is the tensile strength, peel strength, impact strength, tensile strength, and non-uniform tear strength of a single-sided lap bonded sample. The most important of these is the tensile shear strength test.

The national standard GB 7124-86 makes detailed provisions on the test of tensile shear strength of bonded joints of metal and metal on one side. This standard can be used to test the strength of steel drums after adhesive repair.