A Guide to Gas Welding and Cutting Techniques

gas flame

1. Gases that produce gas flames

(1) Oxygen

Oxygen is a gas at normal temperature and pressure, with the molecular formula O2.

Oxygen itself is not combustible, but it can help burn other combustible substances and has a strong combustion-promoting effect.

Oxygen purity has a direct impact on the quality, productivity and oxygen consumption of gas welding and cutting.

The higher the purity of oxygen, the better the quality of gas welding and cutting.

(2) Acetylene

Acetylene is a colorless hydrocarbon compound with a special odor, obtained by the interaction of calcium carbide and water, with molecular formula C2H2.

Acetylene is a combustible gas and the temperature of the flame generated when it is mixed with air is 2350°C, while the temperature of the flame generated when it is mixed with oxygen and burned is 3000-3300°C.

Acetylene is a dangerous gas that is explosive under certain pressure and temperature conditions.

(3) Liquefied Petroleum Gas (LPG)

Liquefied petroleum gas is mainly composed of hydrocarbons such as propane (C3H8), butane (C4H10) and propylene (C3H6).

It exists as a gas under normal pressure, but can be liquefied at a pressure of 0.8-1.5 MPa for storage and transport, hence the name Liquefied Petroleum Gas.

Like acetylene, LPG is explosive when mixed with air or oxygen, but it is much safer than acetylene.

2. Types and properties of gas flames

(1) Oxy-acetylene flame.

The structure and shape of the oxy-acetylene flame:

a) Neutral flame b) Carburizing flame c) Oxidizing flame

1- Center of the flame 2- Internal flame 3- External flame

Type of flame	Mixing ratio of oxygen and acetylene	Maximum flame temperature/℃	Flame characteristics
Neutral flame	1.1-1.2	3050-3150	The oxygen and acetylene are completely burned, without excess oxygen or excess acetylene. The flame core is bright, with clear contours, and the internal flame has a certain degree of reducibility
Carbonization flame	<1.1	2700-3000	Acetylene is surplus, and there are free carbon and hydrogen in the flame, which has a strong reduction effect and also a certain carbon effect. The entire flame of the carbonization flame is longer than that of the neutral flame
Oxide flame	>1.2	3100-3300	There is excess oxygen in the flame, which has strong oxidizing properties. The entire flame is short, and the inner and outer flame layers are unclear

• Oxygen Liquefied Petroleum Gas Flame

The structure of the Oxygen Liquefied Petroleum Gas flame is basically the same as the Oxy-Acetylene flame, and can also be classified into oxidizing flame, carburizing flame and neutral flame.

The center of the flame undergoes partial decomposition reactions, but with fewer decomposition products.

The inner flame is not as bright as that of acetylene and appears slightly bluish, while the outer flame is brighter and longer than the flame of oxy-acetylene.

Due to the higher ignition point of Liquefied Petroleum Gas, it is more difficult to ignite than acetylene and requires a direct flame for ignition.

Gas Welding

1. Principles, characteristics and applications of gas welding.

(1) Principles of Gas Welding.

1 – Gas mixing tube; 2 – Piece; 3 – Welded joint; 4 – Filling wire; 5 – Gas welding flame; 6 – Welding torch.

(2) Characteristics and applications of gas welding

The advantages of gas welding are that it requires simple equipment, is easy to operate, has low cost and strong adaptability. It can be used in places without electricity supply for convenient welding.

The disadvantages of gas welding are that the flame temperature is low, the heating is dispersed, the heat-affected zone is wide, the workpiece is easily deformed and overheated, and the quality of gas welding joints is not so easy to ensure as in the electrode arc. Welding.

Productivity is low and it is difficult to weld thick metals. It is also a challenge to achieve automation.

2. Gas welding materials

(1) Gas welding wire

Table 3-2 Class and Use of Common Steel Welding Wires.

Carbon Structural Steel Welding Wire		Structural Steel Alloy Welding Wire		Stainless Steel Welding Wire
Note	purpose	Note	purpose	Note	Purpose:
H08	Welding of general low carbon steel structures	H10Mn2	Same purpose as HO8Mn	H03Cr21Ni10	Ultra low carbon stainless steel welding. Type 18-8 Stainless Steel Union
		H08Mn2Si
H08A	Welding of important low and medium carbon steels and certain low alloy steel structures	H10Mn2MoA	Welding of common low alloy steel	H06Cr21Ni10	18-8 Type Stainless Steel Welding
H08E	Same purpose as H08A, with good process performance	H10Mn2MoVA	Welding of common low alloy steel	H08Cr21Ni10	18-8 Type Stainless Steel Welding
H0SMn	Welding of important structures made of carbon steel and common low alloy steel, such as boilers, pressure vessels, etc.	HO8CrMoA	Welding of chrome molybdenum steel and other H	O8Cr19Ni10Ti	Welding of high-strength structural steel and heat-resistant alloy steel, etc.
H08MnA	Same purpose as H08Mn, but with good process performance	H18CrMoA	Welded structural steel, such as chrome molybdenum steel, chromium manganese silicon steel, etc.	H12C24Ni13	Welding of high-strength structural steel and heat-resistant alloy steel, etc.
H15A	Welding of medium resistance parts	H30CrMnSiA	Chromium manganese silicon steel welding	H12Cr26Ni21	Welding of high-strength structural steel and heat-resistant alloy steel, etc.
H15Mn	Welding of medium resistance parts	H10CrMoA	Heat Resistant Alloy Steel Welding

Welding Wire Model	Welding Wire Class	name	Main chemical components	Melting point/℃	purpose
SCu1898 （CuSnl）	HS201	Pure Copper Welding Wire	ω(Sn) ≤ 1.0% ω(Si)=0.35% -0.5% ω(Mn)=0.35% -0.5%, the rest is Cu	1083	Gas welding, argon arc welding and pure copper plasma arc welding
SCa6560 （CuSi3Mn）	HS211	Bronze Welding Wire	ω(Si)=2.8%~4.0% ω(Mn) ≤ 1.5%, the rest is cu	958	Gas welding, ammonia arc welding and bronze plasma arc welding
SCu4700 （CuZn40Sn）	HS221	Brass Welding Wire	ω(Cu)=57% -61% ω(Sn)=0.25% -1.0%, the remainder is Zn	886	Gas welding, argon arc welding and plasma arc welding of brass
SCu6800 （CuZn40Ni）	HS222	Brass Welding Wire	ω(Cu)=56% -60% ω(Sn)=0.8% -1.1% ω(Si)=0.05% -0.15% ω(Fe)=0.25% -1.20% ω(Ni)=0.2% -0.8% The rest is Zn	860
SCu6810A （CuZn40SnSi）	HS223	Brass Welding Wire	ω(Cu)=58% -62% ω(Si)=0.1% -0.5% ω(Sn) ≤ 1.0. The rest is Zn	905

Table 3-4: Types, classes, chemical compositions and common applications of aluminum and aluminum alloy welding wires.

Welding Wire Model	Welding Wire Class	name	Main chemical components	Melting point/℃	purpose
SAl1450 （A199.5Ti）	HS301	Pure Aluminum Welding Wire	ω（Al）≥99.5%	660	Gas welding and argon arc welding of pure aluminum
SAl4043 （AIS）	HS311	Aluminum Silicon Alloy Welding Wire	ω(Si)=4.5% -6%, others are Al	580-610	Welding of aluminum alloys other than aluminum and magnesium alloys
SAB103 （AIMnl）	HS321	Aluminum Manganese Alloy Welding Wire	ω(Mn)=1.0% -1.6%, the rest is Al	643-654	Gas welding and ammonia arc welding of aluminum manganese alloy
SAl5556 （AlMg5 MnlTi	HS331	Aluminum Magnesium Alloy Welding Wire	ω(Mg)=4.7%~5.5% ω(Mn)=0.3% -1.0% ω(Ti)=0.05% -0.2 The rest is Al	638-660	Welding of aluminum and magnesium alloys and aluminum, zinc and magnesium alloys

Table 3-5: Types, classes, chemical compositions and applications of cast iron gas welding wires.

Welding wire model and class	Chemical composition/%					purpose
	ω (W)	ω （Mn）	ω (S)	ω (P)	ω (Si)
RZC-I	3.20-3.50	0.6-0.75	≤0.10	0.5-0.75	2.7-3.0	Gray cast iron welding repair
RZC-2	3.5-4.5	0.3-0.8	≤0.1	≤0.05	3.0-3.8
HS401	3.0~4.2	0.3-0.8	≤0.08	≤0.5	2.8-3.6
HS402	3.0-4.2	0.5-0.8	≤0.05	≤0.5	3.0-3.6	Ductile Iron Welding Repair

(2) Gas welding flux

Table 3-6: Classes, performance and applications of commonly used gas welding fluxes.

Welding Flux Grade	name	Basic Performance	Application
CJ101	Stainless Steel and Heat Resistant Steel Gas Welding Flux	It has a melting point of 900℃ and good wetting properties, which can prevent the oxidation of molten metal. Slag is easy to remove after welding.	Used for gas welding of stainless steel and heat-resistant steel
CJ201	Cast Iron Gas Welding Flux	It has a melting point of 650 ℃ and alkaline reaction. It has deliquescence and can effectively remove silicates and oxides generated during gas welding of cast iron. It also has the function of accelerating the fusion of metals.	Used for gas welding of cast iron parts
CJ301	Copper Gas Welding Flux	It is a boron-based salt, prone to deliquescence and with a melting point of about 650 ℃. It has an acidic reaction and can effectively dissolve copper oxide and cuprous oxide.	Used for gas welding of copper and copper alloys
CJ401	Aluminum Gas Welding Flux	The melting point is about 560 ℃, it has an acidic reaction and can effectively destroy the aluminum oxide film. However, due to its strong hygroscopicity, it can cause corrosion of aluminum in air. After welding, the slag must be carefully cleaned.	Used for gas welding of aluminum and aluminum alloys

Gas welding flow grades are represented by CJ followed by three digits, and the coding method is: CJxxx.

3. Gas welding equipment and tools.

The composition of gas welding equipment:

• 1. Oxygen hose
• 2. Welding torch
• 3. Acetylene hose
• 4. Acetylene cylinder
• 5. Acetylene regulator
• 6. Oxygen Regulator
• 7. Oxygen cylinder

1. Oxygen cylinder

• 1. Bottom of the bottle
• 2. Cylinder body
• 3. Bottle ring
• 4. Oxygen cylinder valve
• 5. Bottle cap
• 6. Cylinder head

2. Acetylene Cylinder

• 1. Bottle mouth
• 2. Bottle Cap
• 3. Cylinder valve
• 4. Asbestos
• 5. Cylinder body
• 6. Porous filling material
• 7. Bottom of the bottle

3. Liquefied Petroleum Gas Cylinder (LPG Cylinder)

• 1. Protective shield
• 2. Cylinder valve
• 3. Cylinder body
• 4. Base

4. Pressure regulator

(1) Functions and types of pressure regulators

The function of a pressure regulator is to reduce the high pressure gas in the cylinder to the pressure required for operation and to maintain a stable pressure during operation.

Pressure regulators can be classified into oxygen pressure regulators, acetylene pressure regulators, liquefied petroleum gas pressure regulators, etc. according to their uses.

According to their structures, they can be classified into single-stage regulators and two-stage regulators. According to their operating principles, they can be classified into direct-acting and reverse-acting regulators.

(2) Oxygen regulator

• 1. High pressure gauge
• 2. High pressure chamber
• 3. Low pressure chamber
• 4. Pressure adjustment spring
• 5. Pressure adjustment handle
• 6. Diaphragm
• 7. Passage
• 8. Valve Stem
• 9. Valve stem spring
• 10. Low pressure gauge

(3) Acetylene Regulator

(4) Liquefied Petroleum Gas Regulator

The function of the Liquefied Petroleum Gas Regulator is to reduce the pressure in the gas cylinder to the working pressure and stabilize the outlet pressure to ensure uniform gas supply.

Generally, home use regulators can be slightly modified to be used for general thickness cutting of steel sheets.

Additionally, the Liquefied Petroleum Gas Regulator can also be used directly with a propane regulator.

5. Welding torch

(1) Functions and types of welding torch

The function of a welding torch is to mix fuel gas and oxygen in a certain proportion and spray them at a certain speed for combustion, thus generating a flame with a certain energy, composition and stable shape.

According to the different ways of mixing fuel gas and oxygen, welding torches can be divided into injection-type welding torches (also known as low-pressure welding torches) and equal-pressure welding torches.

(2) Structure and principle of injection type welding torch

• 1. Acetylene valve
• 2. Acetylene conduit
• 3. Oxygen conduit
• 4. Oxygen valve
• 5. Mouthpiece
• 6. Injection tube
• 7. Mixed Gas Conduit
• 8. Pair of welding nozzles

(3) Representation of the Welding Torch Model

The welding torch model is composed of the Pinyin letter “H” followed by the serial number and specification that represents the structural form and mode of operation.

6. Gas hose

The gases from the oxygen cylinder and acetylene cylinder need to be transported to the welding or cutting torch through rubber hoses.

According to the national standard “Rubber hose for gas welding, cutting and similar operations”, the oxygen hose is blue and the acetylene hose is red.

The length of the hose connected to the welding torch should not be less than 5 meters, but if it is too long it will increase the resistance to gas flow.

Generally, a length of 10 to 15 meters is recommended. The rubber hose used for the welding torch must not be contaminated with oil, gas leakage, and changing hoses between different gases is strictly prohibited.

7. Other auxiliary tools

(1) Welding glasses

(2) Ignition Gun

A pistol-style ignition gun is the safest and most convenient way to ignite the welding torch.

In addition, welding tools also include cleaning tools such as wire brushes, hammers, and files; tools for connecting and closing gas passages, such as pliers, wires, hose clamps, wrenches, and cleaning needles for welding nozzles.

4. Gas welding process

1. Joint shape

• a) Lap joint
• b) Butt joint
• c) Corner Joint

Table 3-7 Shape and dimensions of lap joint and butt joint for low carbon steel

Joint form	Plate thickness/mm	Curled and blunt edges/mm	Clearance/mm	Groove angle	Welding wire diameter/mm
Crimp joint	0.5-1.0	1.5-2.0			there is no necessity
Butt joint with I-shaped groove	1.0-5.0		1.0-4.0		2.0-4.0
V-groove butt joint	>5.0	1.5-3.0	2.0-4.0	Left welding method 80°, right welding method 60°	3.0-6.0

2. Gas welding parameters

(1) Type, class and diameter of welding wire

Welding thickness/mm	1-2	2-3	3-5	5-10	10-15
Welding wire diameter/mm	1-2 or without soldering wire	2-3	3-3.2	3.2-4	4-5

(2) Gas welding flux

Gas welding flux selection should be based on the composition and properties of the workpiece. Generally, carbon structural steel does not require gas welding flux for gas welding.

However, stainless steel, heat-resistant steel, cast iron, copper and copper-aluminum alloys and aluminum alloys require the use of gas welding flux for gas welding.

(3) Flame Properties and Efficiency

1) Properties of Flames

2) Flame Efficiency

Table 3-9 Selection of gas welding flames for various metallic materials.

Material type	Type of flame	Material type	Type of flame
Low and medium carbon steel	Neutral flame	Nickel aluminum steel	Neutral flames or slightly more neutral flames in acetylene
Light alloy steel	Neutral flame	Manganese steel	Oxide flame
Purple copper	Neutral flame	Galvanized Iron Sheet	Oxide flame
Aluminum and aluminum alloys	Neutral flame or slightly charred flame	High speed steel	Carbonization flame
Lead, tin	Neutral flame	Hard league	Carbonization flame
Bronze	Neutral flame or light oxidation flame	High carbon steel	Carbonization flame
Stainless steel	Neutral flame or slightly charred flame	Cast iron	Carbonization flame
Brass	Oxide flame	Nickel	Carbonization flame or neutral flame

(4) Nozzle size and welding torch tilt angle

The nozzle is the outlet for the gas mixed with oxy-acetylene. Each welding torch is equipped with a set of nozzles of different diameters. When welding thicker parts, a larger nozzle should be selected.

Table 3-10 Selection of Nozzles for Welding of Different Thickness.

Welding nozzle number	1	two	3	4	5
Welding thickness/mm	<1.5	1~3	2~4	4~7	7~11

(5) Welding direction.

(6) Welding speed.

Impact of gas welding parameters on welding quality and weld bead formation.

Welding speed:

• Very fast, easy to cause solder melting
• Too slow, easy to cause welding overheating

Welding wire diameter:

• Too thin, easy to cause incomplete fusion of the weld seam
• Too thick, easy to overheat the welded parts

Welding nozzle number:

• Large number, high flame efficiency
• Small number, low flame energy rate

Surface condition of base material:

• Surfaces with paint stains or rust can easily produce porosity
• Incomplete cleaning of welds can lead to slag inclusion.

Distance from the end of the welding nozzle to the welding:

• If it is too large, the flame energy rate will decrease, which can easily lead to incomplete fusion of the weld seam
• Too small, easy to cause welding overheating

3. Gas cutoff

1. Principle, characteristics and applications of gas cutting

1. Gas Cutting Principle

Gas cutting is a cutting method that uses the thermal energy of a gas flame to preheat the cutting area of ​​a workpiece to ignition temperature and then sprays a stream of cutting oxygen onto it. high speed, causing it to burn and release heat, thus achieving the cutting process.

• 1 – Cut
• 2 – Cutting Nozzle
• 3 – Oxygen Flow
• 4 – Workpiece
• 5 – Oxide
• 6 – Preheating Flame

2. Features and applications of gas cutting

(1) Advantages of gas cutting:

High cutting efficiency, steel cutting speed is faster than other mechanical cutting methods.

For shapes and cross-sectional thicknesses that are difficult to cut using mechanical methods, oxyfuel flame cutting is more economical.

The investment in gas cutting equipment is lower than that in mechanical cutting equipment, and gas cutting equipment is light in weight and can be used for field operations.

When cutting small arcs, the cutting direction can be changed quickly.

Both manual and mechanical cutting can be performed using gas cutting.

(2) Disadvantages of gas cutting:

Low dimensional cutting precision, with dimensional tolerances lower than those obtained by mechanical methods.

The preheating flame and hot slag discharge present risks of fire, equipment damage, and operator burns.

During cutting, adequate dust control and ventilation devices are required to control the combustion of gases and the oxidation of metals.

Material cutting is limited.

(3) Gas cutting applications

Due to its high efficiency, low cost and simple equipment, gas cutting is widely used to cut steel plates and parts with various complex shapes in various positions. It is widely used in cutting steel plates, cutting weld chamfers and cutting casting risers, with cutting thicknesses up to 300mm or more.

2. Conditions and properties of gas cutting of metals

1. Conditions for gas cutting

(1) The ignition point of the metal in oxygen must be lower than its melting point. This is the most basic condition for the normal oxyfuel cutting process.

(2) The melting point of the metal oxide produced during the oxyfuel cutting process must be lower than the melting point of the metal itself and must have good fluidity so that the oxide can be blown away from the cut in a liquid state.

Table 3-11 Melting points of common metallic materials and their oxides.

Metal materials	Metal melting point/℃	Oxide melting point/℃
pure iron	1535	1300-1500
mild steel	1500	1300~1500
high carbon steel	1300~1400	1300-1500
aluminum	1200	1300~1500
copper	1084	1230-1336
lead	327	2050
aluminum	658	2050
chrome	1550	nineteen ninety
nickel	1450	nineteen ninety
zinc	419	1800

(3) The combustion of metals in the cutting oxygen jet must be an exothermic reaction. This is because the result of an exothermic reaction is the production of a large amount of heat from the combustion of the upper metallic layer, which plays a preheating role for the lower metallic layer.

(4) The thermal conductivity of the metal should not be too high. Otherwise, the heat released by oxidation during the preheating flame and the gas cutting process will be conducted and dissipated, making it impossible to start or stop gas cutting halfway.

2. Gas cutting properties of common metals

(1) Low carbon steel and low alloy steel can meet the requirements so that gas cutting can be carried out smoothly.

(2) Cast iron cannot be cut with oxyfuel cutting.

(3) High chromium steel and chromium-nickel steel will produce high melting point chromium oxide and nickel oxide (about 1990 ℃), making gas cutting difficult.

(4) Copper, aluminum and their alloys have ignition points higher than their melting points and good thermal conductivity, making it difficult to cut the gas.

3. Gas cutting equipment and tools

1. Cutting torch

(1) Function and Classification of Cutting Torch

The function of a cutting torch is to mix fuel gas and oxygen in a certain proportion and manner to form a preheating flame with a certain energy and shape, and to spray cutting oxygen into the center of the preheating flame for cutting at gas.

Cutting torches can be divided into two types: injection type cutting torch and equal pressure cutting torch according to the different mixture forms of fuel gas and oxygen.

According to the different types of fuel gas, they can be divided into acetylene cutting torches, liquefied petroleum gas cutting torches and so on.

(2) Structure and principle of injection type cutting torch

Injection type cutting torch structure.

• 1. Cutting nozzle
• 2. Gas mixing tube
• 3. Injection tube
• 4. Mouthpiece
• 5. Preheating oxygen regulating valve
• 6. Acetylene regulating valve
• 7. Acetylene connector
• 8. Oxygen connector
• 9. Cut-off oxygen regulating valve
• 10. Cutting the oxygen tube.

During gas cutting, first open the preheating oxygen regulating valve and the acetylene regulating valve and light to produce a preheating flame to preheat the workpiece.

When the workpiece is preheated to the ignition point, open the cut-off oxygen regulator valve.

At this time, high-speed cutting oxygen flows through the cutting oxygen tube and is sprayed from the center hole of the cutting nozzle to realize gas cutting.

(3) Representation of the Cutting Torch Model

The cutting torch model is composed of the Chinese Pinyin letter G and a number that represents the structure and mode of operation, as well as specifications.

(3) Cutting torch model representation method

The cutting torch model is composed of the Chinese Pinyin letter G plus a sequence of numbers and specifications that represent the structural form and method of operation.

(4) Liquefied Petroleum Gas Cutting Torch

For liquefied petroleum gas cutting torches, due to the different combustion characteristics between liquefied petroleum gas and acetylene, the injector-type cutting torch used for acetylene cannot be used directly.

It is necessary to modify the cutting torch or use a special cutting nozzle for liquefied petroleum gas.

In addition to self-modification, liquefied petroleum gas cutting torches can also be purchased as specialized equipment.

(5) Equal pressure cutting torch.

• 1- Cutting nozzle
• 2- Nozzle gasket
• 3- Cutting the oxygen hose
• 4- Acetylene gas hose
• 5- Cutting off the oxygen regulator
• 6- Main body
• 7- Oxygen gasket
• 8- Acetylene gasket
• 9- Preheating oxygen regulator
• 10- Preheating the oxygen hose

2. Gas cutting machine

The gas cutting machine is a mechanized equipment that replaces manual gas cutting torches.

(1) Semi-automatic gas cutting machine.

(2) Profile gas cutting machine.

(3) CNC gas cutting machine.

4. Gas cutting process

1. Gas cutting parameters.

Table 3-12: Relationship between steel plate gas cutting thickness, cutting speed and oxygen pressure.

Steel sheet thickness /mm	Gas cutting speed /(min/min)	Oxygen pressure /MPa
4	450-500	0.2
5	400-500	0.3
10	340-450	0.35
15	300-375	0.375
20	260-350	0.4
25	240-270	0.425
30	210-250	0.45
40	180-230	0.45
60	160-200	0.5
80	450-180	0.6

(2) Gas cutting speed

(3) Preheating flame properties and efficiency.

The purpose of the preheating flame is to heat the metal cutting parts and maintain a temperature that can burn in the flow of oxygen, while also causing the oxide film on the surface of the steel to peel off and melt, facilitating the oxygen flow. combine with the iron.

The efficiency of the preheating flame is expressed in terms of the amount of fuel gas consumed per hour and must be selected based on the thickness of the cutting part.

Generally, the thicker the cutting piece, the greater the efficiency of the preheating flame.

(4) Inclination angle of the cutting nozzle and cutting piece.

Relationship between the angle of inclination of the cutting nozzle and the thickness of the cutting piece.

Cutting thickness /mm	<6	6-30	>30
			Start cutting	After cutting	Stop cutting
Tilt angle direction	Tilt back	Vertical	Forward lean	Vertical	Tilt back
Tilt angle	25°-45°	0°	5~10°	0°	5°~10°

(5) Distance between the cutting nozzle and the surface of the cutting piece.

The distance between the cutting nozzle and the surface of the cutting piece should be determined based on the length of the preheating flame and the thickness of the cutting piece, generally between 3 to 5 mm.

This heating condition is ideal and minimizes the possibility of carburization of the cutting surface.

When the thickness of the cutting piece is less than 20mm, the flame can be larger and the distance can be increased accordingly.

When the thickness of the cutting piece is greater than or equal to 20 mm, the flame should be shorter and the distance should be reduced accordingly due to the slower speed of gas cutting.

2. Gas Cutting Quenching (Welding).

(1) The gas transport hose is too long, too narrow or too twisted.

(2) The gas cutting (welding) time is too long or the cutting (welding) nozzle is too close to the workpiece.

(3) The end face of the cutting (welding) nozzle adheres to many scattered molten metal particles.

(4) Solid particles of carbon or other substances adhere to the gas passage inside the gas transport hose or cutting (welding) torch.