Topic: Making a coat hanger. Technological features of the manufacture of clothes hangers by welding

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1. History and development prospects of welding

Welding is the process of obtaining permanent joints by establishing interatomic bonds between the parts to be joined during heating and plastic deformation.

Arc welding. The source of heating during welding is an electric arc, the open of which belongs to the Russian professor of the former St. Petersburg Medical-Surgical Academy Vasily Vladimirovich Petrov. He was the first in the world literature to describe an electric arc, its properties, in particular, its melting of the electrode metal.

For a long time, the Petrov arc was not used in any country in the world due to the lack of practically suitable sources of electric current.

It has been used for metal parts since 1881. Preserved in the archive of our compatriot N.N. Bernados' descriptions, drawings and figures indicate that essentially all types of manual and automatic arc welding, which are used today, are proposed by him. In a number of countries of the world N.N. Bernados was issued the relevant documents for inventions in carbon arc welding.

Nikolai Gavrilovich Slavyanov developed equipment and technology for arc welding of metals with steel electrodes, organized an electric welding shop at the Perm plant, used machines of his own design and published several scientific papers on welding. The first patent for arc welding was issued to N.G. Slavyanov, originally in France in 1890, later in other countries of the world including Russia.

The principles developed by Nikolai Nikolaevich are used in many modern arc welding methods. The inventor has developed a number of designs of welding machines, methods of arc welding with different electrodes, arc cutting, underwater welding and cutting, welding on a vertical surface, original methods of spot and seam resistance electric welding.

2. Purpose and device of the structure

The hanger is designed to accommodate outerwear, it is installed in classrooms, libraries, offices, conference rooms, etc. It consists of two legs of the base of the lower longitudinal lintel, two upper lintels of large and small hooks and a detail of the pattern.

The uprights, bases and the lower lintel are made of a square tube with a cross section of 25x25, the upper lintel is made of a rod with a diameter of 14 mm, the hanger hooks are made of a rod with a diameter of 10 mm, the details of the patterns are made of wheels with a diameter of 76 mm.

3. Steel grade and its chemical composition

For the manufacture of clothes hangers, steel made from steel grade Vst3sp is used. This steel of group "B" is supplied with a guaranteed chemical composition and mechanical properties. Low-carbon steel, grade 3, deoxidizing semi-calm. Steel grade Vst3sp is supplied, according to GOST 380-88 it is smelted only by open-hearth and oxygen-converter methods.

According to standardized indicators, rolled steel with a thickness of 4 mm and more is divided into delivery categories, for group "B" the permissible deviations in the chemical composition are as follows:

Carbon - 0.3%,

Manganese - 0.03-0.04%,

Silicon - 0.025-0.3%,

Phosphorus - 0.005%,

Sulfur - 0.005%.

Steel has a high purity from metal inclusions. Fluctuations in carbon content within the grade should be no more than 0.07%.

Table 1. Metallic inclusions

4. Selection of assembly and welding equipment \

I assemble and weld the clothes hanger on the welding table using clamping and fixing devices (vise, clamps). I mark out the blanks using universal tools: a metal ruler, coal, scribe. For straightening and bending parts, I use a bench hammer, bench vice. I cut square pipes with an angle grinder. I clean metal from rust with a metal brush. I remove splashes and slag with a slag hammer or chisel.

For electrode welding, I choose the "Builder-300 R" welding inverter.

Specifications.

Rated welding current at air temperature from minus 25 to + 40C ?:

With a duty cycle of 60%, A 300,

With a duty cycle of 100%, A 250.

The limits of regulation of the welding current, A 30-320.

Open circuit voltage, V 85 ± 5 Supply voltage 3 phrases (without neutral), V 300-450.

Power supply frequency, Hz 50-60.

Rated power consumed from the network, kVN 12.

Protection degree according to GOST 14254-80 IP23.

Climatic modification according to GOST 15150-69 X3.

Efficiency,%, not less than 92.

Overall dimensions (LxWxH), mm:

Without fencing 480x200x360,

With a fence 550x255x390.

Weight, kg:

Without fencing - 17,

With a guardrail 18.6.

Average service life, years 7.

I weld some elements of the hanger using gas welding. For gas welding I use a medium-power gas torch GZ-03.

Table 3. Specifications of the universal welding torch

Hoses are used to supply gases from cylinders to the burner. I use type III hoses for oxygen, type I for acetylene. I choose hoses with one fabric layer, inner diameter 9 mm.

For the gas station, I choose an oxygen and acetylene cylinder.

Oxygen cylinders.

Oxygen cylinders have a steel, one-piece, cylindrical body. The height of the cylinder is 1370 mm, diameter 219 mm, wall thickness 7 mm, capacity 40 dm / 3, weight without gas 67 kg. The cylinders are designed for a working pressure of 15 MPA (150 kgf / cm / 2); test pressure is 22.5 MPa (225 kgf / cm / 2). In a full cylinder, the volume of oxygen corresponding to atmospheric pressure and a temperature of 20 degrees is 6 m / 3.

Acetylene cylinders.

Acetylene cylinders differ from oxygen cylinders in their body and valves, but have the same dimensions, with a capacity of 40 dm / 3, weight without gas 83 kg, acetylene operating pressure 1.9 MPA (19 kgf / cm / 2), maximum pressure 3, 0 MPA (30 kgf / cm / 2). The acetylene cylinder is filled with a porous mass of activated charcoal, which is impregnated with acetone at the rate of 225 ... .30 kg. 1 dm3 / 3 cylinder capacity. The color of the balloon is white, the inscription is red.

Gas reducers are used to reduce the pressure of the gas coming from the cylinder and automatically maintain the specified operating pressure, as well as regulate the pressure and protect the cylinder from flame backfire. The oxygen reducer is connected to the cylinder with a union nut, and the acetylene reducer with a clamp.

Table 4. Technical data of the gearbox

5. Selection of welding consumables

The clothes hanger is made of low-carbon steel, so I use standard welding consumables for welding, UONII 13/45 electrodes.

E46A - type of electrode;

UONII - 13 / 45- electrode brands;

3.0 - electrode diameter, mm

U - for welding carbon and low-alloy steels;

D - with a thick coating;

2 - workmanship group;

E43 2 (5) - a group of indices characterizing the deposited metal;

B - electrodes are designed for welding in all spatial positions;

O - for direct current welding of reverse polarity.

For gas-welded seams, I perform welding wire SV-08A. low-carbon wire with low sulfur and phosphorus content and high toughness and ductility.

Table 5. Chemical composition of the welding wire

For gas welding, I use acetylene as a combustible gas. Gaseous acetylene (C2H2) is a colorless gas with a specific garlic odor due to the presence of impurities of hydrogen phosphide, hydrogen sulfide and others. Acetylene is lighter than air; at atmospheric pressure and temperature 20C? its density is 1.09 kg / m. cub.

Acetylene dissolves well in liquids, especially acetone, making it safer.

Table 6. Characteristics and properties of acetylene

I use oxygen to keep the acetylene burning.

Gaseous oxygen (colorless, odorless and tasteless, slightly heavier than air. It does not belong to combustible gases, but actively supports combustion. Gaseous technical oxygen according to GOST 5583-78 is produced in three grades with varying degrees of purity percent 1 grade - 99.7% ; 2nd grade - 99.5%; 3rd grade - 99.2%.

6. Selecting the welding mode

The main indicators of the welding mode are: diameter of the electrode or welding wire, welding current, arc voltage and welding speed.

Additional indicators of the welding mode: the type and polarity of the current, the type and brand of the coated electrode, the angle of inclination of the electrode, the temperature of the preheating of the metal.

The choice of the arc welding mode often comes down to determining the diameter of the electrode and the welding current. The welding speed and arc voltage are set by the welder himself, depending on the type (type) of the welded joint, steel and electrode grade, the position of the seam in space, and so on.

The diameter of the electrode is selected depending on the thickness of the metal to be welded, the type of welded joint, the type of seam, and others. The current is selected depending on the diameter of the electrode. To select the current, you can use the dependence:? = Kd, where k = 35 / 60A / mm; d- electrode diameter, mm. A relatively low welding current leads to an unstable arc burning, non-penetration, increased spattering of the electrode material and the K factor is influenced by the composition of the electrode coating: for gas-forming coatings.

Tack welding is performed with electrodes with a diameter of 3 mm.

Table 7. For gas welding, I choose the nozzle of the torch No. 3

Table 8. Consumption of acetylene when welding carbon steels

welding plastic deformation torch

Table 9. Determination of the angle of inclination of the mouthpiece

Filler wire diameter:

I use a normal flame for welding.

Power - M = 300-390 dm / 3 / h.

Consumption of filler material.

P = Kg xS / 2 (kg)

P = 12 x3 / 16 = 12x1.6 = 19.2 kg.

7. Technology of assembly and welding of the structure

First, I assemble the stand and the bases, check the 90C angle between them? and I grab the joint of the tacks butt length 5 mm, tack width 3-4 mm. Do I turn the knot at 180C? and I make the same potholder on the other side. I clean the slag from the tacks and check the seams, on both sides the butt joint, the seam width is 8 mm, on the other two sides the T-leg joint is 4 mm, I also weld the base to the other stand. After that, using gas welding, I weld decorative parts. After that, I put the racks vertically and grab the lower and two upper jumpers to them. Using a tape measure, I check the diagonals, if the geometrical dimensions correspond, after stripping the slag, I weld the seams, on the lower jumper there are T-and butt joints, on the two upper ones - T-joints. I grab and weld the T-joint hooks to the upper jumpers, the seam is a double-sided leg of the seam 4mm. After welding the hangers, I remove slag and metal spatter, then I inspect the product to make sure there are no defects.

8. Defects of welded joints and their correction

Defects in welded joints reduce the strength of welded structures and, under unfavorable conditions, can lead to the destruction of individual seams or the entire structure.

In welding production, defects of the following types are distinguished: preparation and assembly of products for welding; seam shape; external and internal.

Distinguish between admissible defects, for which norms in size and quantity are established, and not admissible defects subject to mandatory correction. External defects include: a crack in the welded joint; microcrack of the welded joint (crack detected with a magnification of more than 50 times); shrinkage cavity of the weld (deepening in the seam); a hole in the welded joint (deepening on the surface of the reverse side of the welded joint in an incompletely melted base metal; concavity of the root (depression on the surface of the reverse side of a one-sided weld seam); weld fistula (blind depression of the weld seam); damage to the weld (superficial, chain of pores) ; metal spatter; surface oxidation of the welding joint (scale, film of oxides and or tarnishing colors); undercutting the fusion zone (longitudinal depression along the fusion line of the weld with the base metal); sagging on the welded joint; excess weld reinforcement; excess penetration; non-smooth mating weld seam; displacement of welded edges (mismatch of welded edges in height due to poor-quality welding of the welded joint) Undercuts, surface pores of small depth, concavity of the seam and understating the dimensions of the weld seam section are heated by 10 mm if the pore diameter does not exceed 1 mm (at least 25 mm with a pore diameter of 2 mm).

The craters of the seams are welded; when welding non-hardenable steels, they can be brought out to the side from the axis of the seam at a distance of 20 mm. Burns and burns in the seams are rare, they need to be cleaned and welded. Metal spatter is removed mechanically. The influx is difficult to determine by superficial examination, it is distinguished by metallographic examination. The fistula is cleared, and the place of the defect is welded.

9. Product quality control

I check the manufactured structure by external examination and measurements. In this control, the quality of products is determined with unarmed gas (it is allowed to use a magnifying glass). Using a tool (templates, probes and meters). All raw materials and equipment, welded beams, assemblies and finished welded products themselves, regardless of their purpose, are subject to control.

I check the assembled unit or products.

· Compliance with the geometric and basic dimensions of the worker, drawing, compliance with tolerances.

· Gaps between parts, no displacement of the welded edges, the amount of overlap in the joint.

· Cleanliness of metal in the welding area, absence of rust, oil and other contaminants.

Control of the welding process and finished welded joints.

· The order of making seams in accordance with the approved technological process.

· Cleaning of previous seam layers before applying the next seam layer.

· Modes of welding.

On the basis of the stage of manufacturing welded products, control is distinguished: input, technological herd. In terms of duration, everyday, periodic, volatile, peroperative prophylactic.

By location: stationary: at workplaces, By performers: by controllers, workers with self-control. By volume cohesive: selective.

10. Labor protection

Safety precautions during welding.

Persons who are at least 18 years old are allowed to work on welding after passing the technical minimum according to safety rules.

The organization of each workplace must ensure the safe execution of the robot. The workplace should be equipped with various kinds of fences, protective and safety devices and adapted.

To create a safe environment for robot welders, it is necessary to take into account, in addition to the general provisions of industrial safety, the particularities of performing various welding works. Such features are possible electric shock, poisoning with harmful gases and vapors, burns by welding arc radiation and molten metal, damage from explosion of cylinders with compressed and liquefied gases.

The electric welding arc emits bright visible light rays and invisible ultraviolet and infrared rays. Light beams have a blinding effect. Ultraviolet rays cause eye diseases, and with prolonged exposure lead to skin burns.

To protect the eyes and skin of the face, shields, masks or helmets are used, light filters are inserted into the viewing holes, which detain and absorb the rays. To protect welders' hands from burns and splashes of molten metal, it is necessary to use protective gloves, and put on a special tarpaulin on the body. Clothes. During the welding process, a significant amount of aerosol is released, which leads to poisoning of the body. The highest concentration of dust and harmful gases in the cloud of smoke rising from the welding area, therefore the welder must ensure that the flow does not fall behind the shield. To remove harmful dust gases from the welding zone, a local ventilation device, an exhaust and general volumetric supply - exhaust is required. In winter, supply ventilation must supply heated air into the room. In case of poisoning, the victim must be taken out into the fresh air, freed from tight clothes and allowed to rest until the doctor arrives, and if necessary, artificial respiration should be applied

Electrical safety.

During electric welding, the passages between single-station welding power sources for fusion welding, cutting, surfacing must have a width of at least 0.8 m, between multi-station sources - at least 1.5 m, the distance from single- and multi-station welding power sources to the wall must be at least 0.5 m. The welding current regulator can be located next to or above the welding transformer. It is forbidden to install a welding transformer above the current regulator. It is forbidden to carry out electric welding works during rain and snowfall in the absence of sheds over the electric welding equipment and the workplace. When electric welding works in industrial premises, the welders' workplaces must be separated from adjacent workplaces and walkways by fireproof screens (screens, shields) with a height of at least 1.8 m. carpet. During electric welding work, the welder and his assistants must use personal protective equipment: a protective helmet made of current non-conductive materials, which should be conveniently combined with a shield that serves to protect the face and eyes: safety glasses with colorless glass to protect the eyes from fragments and hot slag when cleaning welding seams with a hammer or chisel; mittens with gaiters or gloves, special clothing made of spark-resistant materials with low electrical conductivity, leather boots.

Fire safety.

The causes of a fire during welding can be sparks and drops of molten metal and slag, careless handling of the torch flame in the presence of combustible materials near the welder's workplace. To prevent fires, the following fire-prevention measures must be observed: do not store flammable or flammable materials near the welding site, as well as carry out welding work in rooms contaminated with oiled rags, paper, wood waste; It is forbidden to use clothes and gloves with traces of oils, fats, gasoline, kerosene and other flammable liquids; it is impossible to carry out welding and cutting of structures freshly painted with oil paints until they are completely dry; It is forbidden to weld devices under electrical voltage and vessels under pressure. You need to constantly have fire-fighting equipment - fire extinguishers, boxes with sand, shovels, buckets, fire hoses and monitor their good condition, as well as keep the fire alarm in good working order; after the end of welding work, it is necessary to turn off the welding machine, and also make sure that there are no burning or smoldering objects.

Literature

1 GOST 5266-80. Manual arc welding. Welded connections.

2 GOST 9466-75. Electrodes for welding carbon and low alloy steels.

3 GOST 380-94-carbon steel of ordinary quality.

4 Chernyshev G.G. Welding business: "welding and cutting metals" Textbook for primary vocational education. Second edition, Publishing eraser "Academy", 2004 - 496s.

5 Vinogradov VS "Electric arc welding" textbook for primary vocational education. 4 Items Erased. M. Publishing Center "Academy" 2010. - 320s.

6 Maslov BT "Production of welded structures" a textbook for students of institutions of secondary vocational education. Erased. M. Publishing Center "Academy" 2007. - 288p.

7 Svechnikov V.V "Defects of welded joints" textbook. Erased. M. Publishing Center "Academy" 2008 - 64p.

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