Preface
With the development of production, welding technology and Welding Electrode more widely, at the same time, with the emergence of a variety of unsafe and unhealthy factors serious threat to welders and other production personnel safety and health.

The main hazards are as follows:

1, the process of welding and cutting work needs to flammable gases, pressure vessels and motor electrical contact;

2, the welding process will produce toxic gases, harmful dust, arc radiation, noise and radiation and so on.

Risk factors mentioned above, under certain conditions may cause an explosion, fire, burns, poisoning, electric ophthalmia and skin diseases such as occupational diseases. Addition, it may endanger the equipment, plant and around the safety of personnel, to the state and enterprises should not have losses. Many major and serious accidents was due to welding and cutting operations caused by illegal workers. This article discusses the wider application of the daily gas welding(Gas Shielded Welding Wire), arc welding characteristics, hazards and safe operation.

Gas welding
1, characteristics and hazards

Welding with simple equipment, easy, flexible, practical and so on.

Thus, in the manufacture and maintenance of the industrial sector more widely applied. However, this process takes advantage of combustible gases (such as: C2H2, LPG and H2, etc.), combustion gases (O2) and high pressure gas cylinders (such as: oxygen cylinders, acetylene bottles.) If the welding equipment and safety devices malfunction, or operator operating in violation of safe operation, and are likely to cause an explosion and fire and other accidents.

2, the use of safety requirements

1), industrial acetylene often contain phosphine (PH3), hydrogen sulfide (H2S) and other impurities, these impurities is not only easy to cause an explosion, and welding, in which the sulfur and phosphorus can be transferred to the weld metal in the weld change the mechanical properties, cold brittleness, thermal cracking tend to increase, the weld quality is difficult to guarantee. Therefore, by volume, requires the content of acetylene in the PH3 not exceed 0.2%; H2S content should be less than 0.1%.

2), gas cylinders in the storage and use, to avoid sun exposure, away from open flames and heat radiation.

3), the welding process, gas discharge rate should not be too fast, the gas flows through the valve to avoid static electricity spark.

4), acetylene bottles should be placed vertical stand, lying strictly prohibited place.

5), gas cylinders should be based on national "Gas Cylinder Safety Supervision Regulation," called for periodic technical inspections, extended use is strictly prohibited.

6), the operator should receive safety training certificates.

7), welding torch must be checked before use, including fire smoke case, hose connections and fittings, air leaks, the gas is the clean channel so only after checking the normal operation of the ignition. Use, to prevent tempering, tempering should immediately close the case of acetylene valve, while closing the oxygen valve.

SMAW
1, characteristics and hazards

SMAW is the most widely used industrial production welding method, the important reason is that the arc can effectively and easily convert the electrical energy needed to heat the welding process and mechanical energy. At the same time by hand manipulation of SMAW welding electrodes, can be all-position welding; welding equipment, portable, flexible transportation for all kinds of metal materials, various thickness, various structural forms of welding.
However, there will be less because of its specificity of insecurity:

1), arc arc core temperature of up to 6000 ~ 8000 ℃, welding rods, welding parts and coating at high temperature, the occurrence of evaporation, condensation and gas, resulting in a lot of smoke and dust;

2), arc strong ambient radiation in the arc, will produce ozone, nitrogen oxides and other toxic gases;

3), splash, welding line pipe welding failure or explosion-proof measures for fuel containers properly, will cause an explosion and fire accidents.

4), welding equipment, no-load voltage is higher than the safety of the human body can withstand voltage, high incidence of electric shock.
2, the use of safety requirements

1), welding machine must have a separate dedicated power switch, prohibit more than one welding machine share a power switch;

2), welding machine to prevent the collision, moisture or excessive vibration;

3), welding machine should be well exposed live parts of the protective device, the shell should be grounded not charged, non-overload;

4), welding cable jacket integrity, good insulation, you should use the whole conductor;

5), electrode holder must have good insulation, heat capacity, heat of the welding clamp is strictly prohibited under water immediately after cooling;

6), welding operations, the place should have ventilation and dust removal facilities, flammable, explosive material ignition sources away from the job should be not less than 10m;

7), good welding operations should wear labor protection products, to strengthen their protection, to ensure its own security.

In summary, the potential danger of the welding process, for staff engaged in the job requirements should be strictly and must be appropriate, specialized security technology theoretical study and practical training to improve the safety of such operations technology quality, and after passing an examination to obtain operating permits security technology behind the quasi-independent operations; the same time, through training so that they understand the welding characteristics of the basic principles of soldering and welding techniques, safe use of tools; strictly enforce safety rules and protective measures are implemented to ensure safety production, to avoid accidents.

keywords: welding electrode material

CO2 gas welding as an important welding method, welding electrodes in China has been widely used. For a long time, the operator in the concept of CO2 gas shielded welding operation there is a certain movement and operation of the error, resulting in their use of CO2 gas welding in the production process there is a big limitation. In this paper, this phenomenon, the welding wire  CO2 gas shielded welding methods, for example, by presenting the correct operation of the operating philosophy and dealt with the application action to guide the operator in a scientific and systematic training to improve their skills. Meanwhile, the paper can be used as a solid wire CO2 gas shielded welding operations materials for the majority of welding skills in vocational and technical schools teaching teachers teaching reference.

CO2 gas shielded solid wire welding operation training procedure is divided into 4 parts according to the course:

(1) CO2 gas shielded welding operation of the basic concept;

(2) solid CO2 gas shielded welding wire welding operation deposition level training;

(3) solid wire CO2 gas welding T-joint weld the position of the training;

(4) solid wire CO2 gas welding T-joint welding of the position of the training.

1 CO2 gas shielded welding basic concept of operation

1.1 hand gun

Commonly used welding with CO2 gas shielded welding wire features constant, once the adjustment of welding parameters, the ratio of completion, the operator extended the length of welding wire when the change will directly affect the stability of welding arc burns. Therefore, the operator hand-held welding torch during the welding operation directly affects the quality of stability. CO2 gas shielded welding torch as a larger size (and compared to SMAW welding guns), heavier weight gun (torch threw in silk hose), so you want out of a high quality CO2 welding gas arc welding seam, we need about hands to make stable and harmonious combination with the action to complete (the great, flat welding parameters during welding of the case can also be done using a single hand operation).

Typically, the operator right hand gun grip, left thumb, index finger is holding the gun for goose neck bracket Department. Welding, torch, led by the left hand along the welding direction (vertical) movement, twist your right hand around the wrist to control the welding torch along the seam width direction (lateral) side to side. Figure 1.

1.2 left mainly to the welding method

Under normal conditions, CO2 gas shielded arc welding torch right hand when the operator, from right to left direction welding, welding torch nozzle and the direction was obtuse (> 90 °) is called left-welding method; from left to right direction of welding, torch nozzle acute angle with the welding direction (<90 °) is called the right to the welding method. Figure 2.

CO2 gas shielded welding operations, welding method using the left to the operator with a clear line of sight, weld welding method to smooth over the right, the law should be left mainly to the welding operation.

1.3 before welding two parameters need to adjust

CO2 gas shielded arc welding before you choose adjust the welding current and arc voltage are two parameters, and the reasonable ratio, otherwise it will greatly affect the quality of welding. Welding current and arc voltage ratio of empirical formula:

Formula 1 welding current <300A Time: welding arc voltage = current × 0.04 +16 ± 1.5

Equation 2 when the welding current ≥ 300A: arc welding current and voltage = × 0.04 +20 ± 2.0

Note: Formula 1 ± 1.5 which is fine-tuning of the arc voltage value, the smaller the selection of parameters -1.5; large parameter selection +1.5. Equation 2 were ± 2.0 is also fine-tuning of the arc voltage value, the smaller the selection of parameters -2.0; large parameter selection +2.0.

CO2 gas shielded welding doing, we should first select the value of welding current, welding current in determining the match after the arc voltage regulation.

In addition, in accordance with the empirical formula of choice, after adjusting the welding parameters welding of the actual test. First, the welding current and arc voltage verify the appropriateness of match, and then test the suitability of the welding current selection, or should be adjusted in time and re-adjust the arc voltage match.

Usually, CO2 gas shielded arc welding current choice is based on the thickness of steel, weld thickness, wire diameter, welding space to choose the location and other factors. Beginners because there is no operating experience, tend to select the welding current relatively headache. If the original operating over beginners arc welding rod, then we can combine the existing current selection SMAW experiences CO2 gas shielded welding current choice. For example, the commonly used diameter of 1.2mm solid wire for CO2 gas shielded welding thin pieces or pieces in the thickness of the welding can be based on the use of SMAW welding electrode diameter of 3.2mm of choice to choose the experience of welding current. Table 1.

2 solid CO2 gas shielded welding wire welding operation level training deposited

Practice methods: the thickness of the horizontal plates, the use of CO2 gas shielded welding solid wires for welding line and the horizontal swing practice purposes: â‘  hand gun grip; â‘¡ maintain an appropriate length of wire out; â‘¢ torch to maintain the correct angle; â‘£ welding parameter selection and matching.

Workpiece size: 6 ~ 12mm thick steel plates

Wire Size: ER50-6 Solid φ1.2mm

Welding current: 100 ~ 120A

Arc voltage: 18 ~ 19V

Operating essentials:

Practitioners are preset welding current and arc voltage, you can straight line on the flat and horizontal welding swing deposited heap. Arc before, the operator upper body tilted to the left, head to the left deflection. Holding the gun should be held high while the right hand wrist elbow under the pressure, the left rear of the tiger's mouth light prop gun. Upon completion of this series of action, the operator of the gun nozzle and the workpiece to ensure vertical or near vertical angle. Figure 3.

After arc ignition, the operator's line of sight from one side of the welding arc was 45 ° ~ 70 ° angle of view arc and weld pool, while in the welding process and always maintain an appropriate length of wire out (usually out of φ1.2mm Wire length 15 ~ 20mm). Maintaining a good gun right out of the angle and length of wire after careful observation of the operator out of the end of the melting wire situation, calmly listened to short circuiting transfer welding arc explosion, can be the basis of the information to determine both the initial pre-welding current and arc voltage ratio is appropriate, and make further fine-tuning and matching.

Deposited during the welding beginner level practice, it often has not completed action on a good rush to prepare the body for welding, the process can not be "to maintain proper torch angle and a good extended length of wire," then the operation of his follow-up clear reception in difficult to wire melting and arc sound correct information in these two areas, but can not determine the ratio of the parameters and fine-tuning.

Judgments during the parameter adjustment of the ratio, the need for line reactors on Welding and swing reactors during the trial of two deposited weld welding.

Deposited weld line reactor. Deposited during the welding line reactor, the operator after the right-hand Qingwo arc welding torch ignited no lateral grip swinging, only the left hand action through the welding torch to lead the direction of the straight line welding. At this point, if the ratio of arc voltage is too small would lead to "ligation wire," that is out of time to melt on the tip of the wire tie to the weld pool, resulting in the welding circuit is not short-circuit the normal, long wire and blown fever phenomenon; arc voltage ratio over the General Assembly a "back burn", that is out of the tip of the wire to the weld pool has not been sent down to the edge to melt back up the formation of large particles in the melt volume drops fell in the pool . A "ligation wire" and "back burning" are too large because the parameter matching error caused by the arc at this time to stop immediately and quickly adjust the parameters of a substantial re-trial welding. Exclude the "ligation wire" and "back burning" phenomenon basic to a more stable arc burning, you can fine-tune the welding parameters. Fine-tuning, the operator of the torch at the proper angle to maintain good and wire extending the length of the wire were observed under the premise of the melting end of the situation out, listen to the voice of the arc. If the shape of the ends of wire melting sharper, more crisp sound than the arc tip, indicating that the ratio is slightly lower arc voltage; and wire melting than the sleek shape of the ends of the arc of the sound muffled, then the ratio is slightly higher arc voltage .

Deposited in a straight line reactor test welding welding welding parameters will be carried out immediately after the appropriate ratio of deposited weld swing reactor to further validate the test welding parameters and the ratio of the appropriate selection.

Swing heap on Welding. Deposited weld swing reactor, the operator, after the arc ignition torch through Qingwo right hand grips the wrist for about twist to complete the lateral swinging of the torch, while the left hand moves to the welding torch to lead the direction of welding. Horizontal swing torch, the wire extending the length of constant rate of change to occur, then the welding current and arc voltage to be with the changes. If you previously selected and the appropriate ratio of welding parameters, then this change will continue to remain stable welding arc burn, or the operator based on the actual situation and then make further fine-tuning until the arc to stabilize.

Important Tip: Before welding parameter tuning, be sure to carefully check the welding of the first and second line connection is solid, otherwise the stability of welding arc will have a very big impact, or even result in welding parameters can not be optional.

3 solid wire CO2 gas welding T-joint weld the position of the training

Practice methods: flat plates welded T-joint position, CO2 gas shielded welding solid wires for welding straight and oblique triangle swing.

Exercise Objective: â‘  hand gun grip; â‘¡ constant rate of change to keep the length of wire out; â‘¢ to maintain the correct angle of the horizontal and vertical welding torch; â‘£ welding parameter selection and matching.

Workpiece size: 8 ~ 12mm thick steel plates

Wire Size: ER50-6 Solid φ1.2mm

Welding current: 140 ~ 160A

Arc voltage: 20 ~ 22V

Operating essentials:

Flat plates welded T-joint position CO2 gas shielded welding solid wire welding, the general left-welding method. Welding according to the different thickness of plates using two kinds of straight and oblique triangle swing arc methods of welding operation. Thin plates, the general requirements for single-angle weld foot height using the following line in the 6mm welding; plates thick, the general requirements for single-angle weld foot height at 6 ~ 10mm serrated swing method using the oblique welding .

Straight line method of transportation arc welding torch horizontal and vertical angles shown in Figure 4.

T-joint weld plates welded flat bottom bit uneven heat, horizontal plate side of the weld is much lower than the temperature of the vertical plate side. The same time, CO2 gas shielded solid core filaments enveloped the small size of the welding arc welding, heat highly concentrated, liquid welding pool in the hot metal poor mobility, and rapid cooling characteristics, if the torch angle to horizontal 45 °, arc aligned on both sides the angle between the plates, then welded seam prone to skew out of, or even create a horizontal plate side of the lack of fusion defects. Figure 5.

Angle in Figure 4 and arc welding torch welding position, and its purpose is to make the arc heat is evenly distributed up and down both sides of the fillet weld, to prevent deflection and lack of fusion weld.

When asked to single welding foot height size is large, triangular with diagonal swing arc methods of welding operation. This method of extending the length of welding wire constant rate of change to occur. Specific trajectory and arc welding torch angle changes horizontally as shown in Figure 6.

Welding, the arc running oblique triangular track, arc up and down both sides of the run to the edge of the weld to be staying, in the horizontal plate side of the pause time longer, shorter side of the vertical board. Extended length of wire run to the plates in the arc angle at the longest, running to weld the upper edge of the shortest.

Important Tip: Before operation oblique triangle swing arc methods of welding, general welding of single fillet weld 10mm foot height control in the following more reasonable, or else there will be skewed and undercut weld defects.

4 CO2 gas welding T-joint welding of the position of the training

Practice methods: panel-joint welding of T-spaces, the use of CO2 gas shielded welding solid wires for welding swing back and forth triangle.

Exercise Objective: â‘  hand gun grip; â‘¡ constant rate of change to keep the length of wire out; â‘¢ to maintain the correct angle of the horizontal and vertical welding torch; â‘£ welding parameter selection and matching.

Workpiece size: 8 ~ 12mm thick steel plates

Wire Size: ER50-6 Solid φ1.2mm

Welding current: 120 ~ 140A

Arc voltage: 19 ~ 20V

Operating essentials:

Plates T-joint welding of CO2 gas shielded welding bits of solid core wire welding, arc Methods transported back and forth swing triangle.

Transported back and forth arc of the triangle swing arc angle of the trajectory and vertical welding torch shown in Figure 7.

T-joints in sheet metal welding of position welding, arc welding rod used by the jagged and the crescent-shaped arc trajectory transportation, even with the "middle slightly faster, both sides of the pause," the operating principle, often also due to weld central pool of molten iron caused by high temperature to fall, prominent on both sides of the central folder weld groove defect.

CO2 gas shielded welding wire extending the length of the direct effect on the welding current and arc voltage. Out of shorter length, welding current and arc voltage corresponding larger; extend the length of variable length, welding current and arc voltage corresponding smaller.

Plates T-CO2 gas shielded arc welding of joint operation by reciprocating the triangle method of welding arc, the arc angle plates run to extend the length of wire at the longest, running to the extended length of fillet weld on both sides of the shortest (Figure 7b shown), so by changing the length of wire to bring out different parts of the weld parameters are changed, the heat can do arc welding on both sides as much as possible to spread, coupled with the "middle slightly faster, both sides of the pause "The operating principle, which can effectively prevent hot metal to fall, prominent on both sides of the central folder weld groove, undercut the production of other undesirable phenomena.

Important Tip: Before triangle swing back and forth arc methods of welding operation, the arc running back and forth up the triangular spacing should be appropriate to pay attention to maintaining the continuity of the weld pool, or prone to weld wave of touch.

5 Conclusion

5.1 CO2 gas welding method of welding as an important operation in the concept and operation of the welding operation there is a certain misunderstanding on the action, resulting in the production of CO2 gas welding applications, there is a big limitation.

5.2 In this paper this phenomenon to solid wire CO2 gas shielded welding methods, for example, by asking the right operating philosophy, dealt with the application of the operation of action, to guide the beginner to science, training operation of the system to improve operator skills.
 

keywords: CO2 Gas-Shielded Flux Cored Welding Wire