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英文原文
CNC flame cutting basic common sense
The basic knowledge of CNC flame gas cutting
(A) the basic working principle of gas cutting and gas cutting process
Heat using a gas flame cutting the workpiece is preheated to at a certain temperature, the discharge speed cutting oxygen stream, so that combustion and gives off heat to achieve cutting method is called torch cutting.
The oxygen cutting process has the following three stages:
1, the beginning of the preheating gas cutting, using a gas flame (oxygen-acetylene flame, oxygen, propane flame) of the workpiece to be cut at the ignition of the metal material is preheated to approximately 1100 to 1150 ° C) (For low carbon steel.
Combustion emit high-speed cutting oxygen flow reached lighted metal intense burning in an oxygen stream.
3, blowing slag metal oxide combustion generated by the oxygen stream to blow off the incision is formed, so that the metal separation, the completion of the cutting process.
(B) gas welding, gas cutting equipment used in the composition of the
Gas welding, gas cutting equipment, oxygen bottles, oxygen regulator, acetylene bottles (acetylene generator), acetylene regulator, the tempering insurance, torch (torch) and rubber tube.
(C) what is good notched
Cutting the middle of the notched surface after the whitening did not burn scar notched without waste side of the phenomenon
(D) gas cutting metal shall comply with the following conditions:
1) the melting point of the metal oxide should be less than the melting point of the metal. Table 1 - 1 are some common melting point of the metal and its oxide.
2) metal with oxygen combustion can release a lot of heat, and the thermal conductivity of the metal itself.
The gas cutting conditions metal iron, low carbon steel, medium carbon steel and low alloy steel and titanium. Other commonly used metals such as cast iron, stainless steel, aluminum and copper, etc., must use special method or melting method of oxyfuel cutting.
8mm sheet, it is not easy to CNC gas cutting.
CNC flame cutting
Gas cutting accuracy is the error between After cutting geometry with its drawing size comparison, cutting the quality of the workpiece is cut off
The surface roughness of the surface, the melting degree of collapse section on the edge of the incision, the incision edge is dross and the uniformity of kerf width.
First, the impact of steel flame cutting quality three basic elements (gas, cutting speed, cutting nozzle height)
1. Gases (oxygen, combustible gas and the flame adjusted)
(1) Oxygen Oxygen is necessary for combustion of the combustible gas, in order to provide the energy required for steel reaches the ignition temperature; addition, oxygen is carried out after the steel is preheated achieve ignition combustion as necessary. Cutting steel with oxygen must have a high purity of more than 99.5%, the general requirements, some advanced countries by industry standards, the oxygen purity of 99.7%. The oxygen purity decreasing by 0.5%, steel plate cutting speed should be reduced by about 10%. If the oxygen purity is reduced by 0.8% to 1%, not only cutting speed decreased by 15% -20%, while the slotted also will be wider, hanging at the bottom of the incision the Residue and clean difficult, significant deterioration of the quality of the cutting section, gas consumption also increases. Obviously, this reduces the production efficiency and cutting quality, the production costs are also significantly increased (see Figure 9-1).
Figure 9-1 under the same oxygen pressure, oxygen purity of cutting time and oxygen consumption.
The use of liquid oxygen cutting, although the one-time investment, but in the long run, its comprehensive economic indicators are much better than imagined.
The stability of the gas pressure on the cutting quality of the workpiece is also essential. The oxygen pressure fluctuations will cut the apparent deterioration of the quality of cross-section. The air pressure is adjusted according to the type of the cutting nozzle, the cutting of the plate thickness. Cutting if the oxygen pressure exceeds a predetermined value, does not improve the cutting speed, but the cutting section decline in the quality of the dross is difficult to be cleared, increasing the processing time and cost of cutting.
Table 9-1 is commonly used in gas welding machine factory production the GK1 series of fast cutting nozzle (ie the Laval nozzle structure cutting nozzle) using the parameter (manufacturers may at any time modify the parameters should be cutting nozzle subject to the attached document, this table is for reference).
(2) flammable gas flame cutting, commonly used flammable gases such as acetylene, gas, natural gas, propane, some foreign manufacturers also use MAPP, namely: methane + ethane + propane.
Generally, the combustion speed, high combustion value of the gas is suitable for sheet metal cutting; low combustion value, the slow combustion of flammable gas is more suitable for cutting slab, especially steel sheet of a thickness of more than 200mm, such as a gas or gas be cut, you will get the desired cut quality, but the cutting speed will be slightly lower.
In comparison, the acetylene is much more expensive than natural gas, owing to resource constraints in the actual production, the general use of acetylene gas, but at the same time cutting the slab require high cutting quality and adequacy of resources, it will consider the use of natural gas.
(3) The flame can be adjusted by adjusting the proportion of the oxygen and acetylene the three cutting flame: neutral flame (ie, normal flame), oxidizing flame, reducing flame, as shown in Figure 9-2.
The normal flame characterized in that no free oxygen in the reduction zone and the activated carbon, there are three distinct regions, the flame core distinctive outline (approximately cylindrical). The flame core component of acetylene and oxygen, and its ends were uniformly round and shiny shell. The housing is made of red hot carbon particles. Flame core temperature up to 1000 ° C. Reducing zone in the flame core, a significant difference with the flame core is its brightness is darker. Reduction zone by the product of incomplete combustion of acetylene - carbon monoxide and hydrogen, the reduction zone temperature up to 3000 ° C or so. Completely Waiyan i.e. the combustion zone is located outside of the reducing zone, it is composed of carbon dioxide and water vapor, nitrogen, its temperature varies between 1200 to 2500 ° C.
Oxidizing flame is generated in the case of excess oxygen, the flame core conical, length shortened significantly, the outline is not clear, the brightness is dim; Similarly, the reduction zone and outer flame has been shortened, the flame was purple blue combustion accompanied by sound, the sound of the size of the pressure of oxygen, oxidizing flame temperature is higher than normal flame. If you are using the oxidizing flame cutting will make the cut quality significantly deteriorated.
Reducing flame is generated in the case of excess acetylene flame core is no obvious silhouette green edge, the flame end of the core, to determine the excess of acetylene in accordance with the green edge; reducing zone is unusually bright, almost The flame core lumped together; Waiyan the yellow. When the excess acetylene is too far, black smoke, which is caused because of the lack of necessary oxygen acetylene flame in combustion.
Preheat the energy of the flame size and cutting speed, cut quality are all very close. With the cut workpiece thickness increases and the cutting speed to accelerate, the energy of the flame also should increase as, but not too strong, particularly when the slab is cut, the the metal combustion heat of reaction generated increases, strengthening the cutting point preheat capabilities, cutting-edge, then, too strong preheating flame will make serious melting collapsed on the edge of the cut edge. Too weak to preheat flame, the steel will not get enough energy to force to reduce the cutting speed, even cutting process is interrupted. So preheating flame strength and cutting speed relationship of mutual restraint. In general, the steel cutting 200mm neutral flame can get a better cut quality. Used in the cutting of steel plates should restore preheat flame cutting, because the reducing flame of the flame length, flame length should be at least a thickness of 1.2 times or more.
(2) cutting speed
The cutting speed of the steel sheet is corresponding with the burning rate of the steel in an oxygen. In the actual production should be based on the performance parameters of the cutting nozzle, gas type and purity, steel plate thickness to adjust the cutting speed. Cutting speed directly affects the stability of the cutting process and the quality of cutting section. If you want to artificially increase the cutting speed to improve production efficiency and slow down the cutting speed to best improve the quality of the cutting section, it is impossible, only make the poor quality of the cutting section. Too fast cutting speed can cause the cutting sections with quality defects such as dents and dross, serious may result in cutting interrupt; too slow cutting speed make the incision on the edge of the melting edge of collapse, the lower edge rounded, cutting cross-section in the second half part of the flush-shaped deep groove pit.
By observing the characteristics of the slag discharged from the incision, adjust to the appropriate cutting speed.
In the normal flame cutting process, cutting oxygen stream relative to the vertical cutting torch slightly at an angle, and its corresponding offset is called drag amount (see Figure 9-3). Speed ??is too low, there is no amount of post-drag, offset the workpiece cut below the mouth of the fire bouquets to the cutting direction. Improve the running speed of the torch, the fire bouquet will be offset in the opposite direction, when the fire bouquet and cutting oxygen flow parallel to the cutting speed. Speed ??is too high, the fire bouquet significantly after partial, as shown in Figure 9-4.
Cutting nozzle and cut the height of the workpiece surface
Steel plate flame cutting process, the cutting nozzle to cut the height of the work surface is one of the main factors in decision notch quality and cutting speed. Different thickness of the plate, using different parameters of the cutting nozzle, adjust the height. In order to obtain high quality cuts, the cutting nozzle to the height of the workpiece surface to be cut in the cutting process must be kept basically the same.
Second, the thermal deformation of the control
Will allow to be cut due to the unevenness of the steel sheet heating and cooling, the material of internal stress the role of the workpiece in the cutting process, different degrees of bending or displacement of - i.e. heat deformation, the specific performance is the deviation of the shape of the twisting and cutting size . Material internal stress can not be balanced and completely eliminated, it can only take some measures to try to reduce the thermal deformation.
Third, the steel surface preparation
The steel from the steel plant through a series of intermediate links to the cutting workshop, during that time, the steel surface will inevitably produce a layer of oxide. Furthermore, the steel sheet is also produced during the rolling process the layer of oxide is attached to the surface of the steel sheet. These oxide has a high melting point, is not easy to burn and melt, warm-up time, reducing the cutting speed; heated at the same time, scale splash, can easily cause congestion, reduce the service life of the cutting nozzle cutting nozzle. Therefore, prior to cutting, it is necessary on the surface of the steel sheet rust pretreatment.
The common method is to shot blasting, rust after painting. Upcoming small iron sand blasting machine sprayed into the surface of the steel plate, rely on the impact of iron ore to steel descaling, then sprayed flame retardant, electrical conductivity and good anti-rust paint.
Rust paint pretreatment before steel cutting has become an indispensable part in the production of metal structures.
Fourth, CNC flame cutting quality defects cause analysis
In the actual production process, often one way or another quality problems, generally there are several defects: edge defects, cutting cross-section defects, dross, cracks, etc.. And quality accidents caused by many reasons, if the oxygen purity to ensure normal, normal operation of equipment, causing flame cutting quality defects is mainly manifested in the following aspects: cutting torch, cutting nozzle, the quality of the steel itself, steel plate.
1. On the cutting edge of quality defects
This is caused due to melting of quality defects.
(1) on the edge of collapse edge
Phenomenon: the edge of the melting too quickly, resulting in a rounded edge collapse.
Reasons: (1) cutting speed is too slow, too preheat flame;
(2) cutting height between the nozzle and the workpiece is too high or too low; cutting nozzle number is too large, excess oxygen in the flame.
(2) teardrop-shaped melting string beans (see Figure 9-9)
Phenomenon: the upper edge of the cut to form a series of teardrop-shaped melt beans.
Reasons: (1) the surface of the steel corrosion or oxide;
(2) cutting height between the mouth and the steel is too small, preheat flame is too strong;
(3) cutting height between the mouth and the steel is too large.
(3) the upper edge of the mat section and presents the the eaves shape (see Figure 9-10)
Phenomena: in the upper edge of the cut forming the eaves-like projecting edge collapse.
Reasons: (1) Preheat the flame is too strong; the ② cut too low an altitude between the mouth and steel;
(3) Cutting speed is too slow; cutting height between the nozzle and the workpiece is too large, the cutting nozzle number is too large, the the preheat flame in oxygen excess.
(4) the upper edge of the cutting section of dross (see Figure 9-11)
Phenomenon: on the edge of the incision depression and dross.
Reasons: (1) cutting height between the nozzle and the workpiece is too large, cutting oxygen pressure is too high; (2) Preheat the flame is too strong.
2. The cutting section rugged flatness
(1) cutting the section below the upper edge, a concave defect (see Figure 9-12)
Phenomenon: the receiving depression, on the edge of the cutting section at the upper edge there are different degrees of melting mat section.
Reasons: (1) cutting oxygen pressure is too high;
(2) cutting height between the nozzle and the workpiece is too large; the cutting nozzle becomes clogged, the wind line disturbed deformation.
(2) slotted be contracted from top to bottom (see Figure 9-13)
Phenomenon: slotted wider at the top.
Reasons: (1) cutting oxygen pressure is too high;
(2) cutting height between the nozzle and the workpiece is too large; the cutting nozzle becomes clogged, the wind line disturbed deformation.
Phenomenon: slotted the narrow width, bell-shaped.
Reasons: (1) the cutting speed is too fast, cutting oxygen pressure is too high;
② cutting nozzle number is too large, too much cutting oxygen flow;
(3) cutting height between the nozzle and the workpiece is too large;
(4) cutting section recess (see Figure 9-15)
Phenomenon: the cutting section, especially the middle part with depression.
Reasons: (1) cutting speed is too fast; (2) to use the cutting nozzle is too small, the cutting pressure is too low, cutting nozzle is clogged or damaged;
(3) cutting oxygen pressure is too high, the wind line blocked deterioration.
(5) cutting section showing a corrugated shape (see Figure 9-16)
Phenomenon: Cutting Section uneven, showing a large corrugated shape.
Reasons: (1) cutting speed is too fast; (2) cutting oxygen pressure is too low, cutting nozzle clogging or damage, deterioration of air line;
(3) using the cutting nozzle number is too large.
(6) the angular deviation of the vertical direction of the incision (see Figure 9-17)
Phenomenon: a vertical incision, a bevel.
Reasons: ① torch and the workpiece surface is not perpendicular to; ② the wind line is not correct.
(7) under the edge of the incision into rounded corners (see Figure 9-18)
Phenomenon: the lower edge of the incision have different degrees of melting, rounded shape.
Reasons: ① cutting nozzle clogging or damage, deterioration of air line; ② cutting speed is too fast, cutting oxygen pressure is too high.
(8) the recess and the lower edge of the lower part of the incision into the rounded corners (see Figure 9-19)
Phenomenon: close to the lower edge of the depression and the lower edge is melted into a fillet.
Cause: The cutting speed is too fast, the cutting nozzle clogging or damage to, deterioration of air line blocked.
3. Roughness defects of the cutting section cutting cross-section of the roughness of the directly affect subsequent step, the processing quality of the cut surface roughness and ahead of the amount of its depth of cut pattern.
(1) excessive drag cutting section (Figure 9-20)
Phenomenon: the cutting section cut pattern offset backwards, at the same time as the size of the offset and varying degrees of depression.
Reasons: (1) cutting speed is too fast; (2) to use the cutting nozzle is too small, too small cutting oxygen flow, cutting oxygen pressure is too low;
(3) cutting height of the nozzle and the workpiece is too large.
(2) in the upper half of the cutting section, a cut Advance amount (see Figure 9-21)
Phenomenon: a cut near the upper edge, the formation of a certain degree of advance amount.
Reasons: (1) cutting torch is not perpendicular to the cutting direction, cutting nozzle clogging or damage; ② the wind line blocked deteriorate;
Phenomenon: the section close to the cutting edge of a cut ahead too much.
Reasons: ① cutting nozzle clogging or damage, the wind line blocked deterioration; ② torch vertical or cutting nozzle, the wind line is not right, tilt.
4. Dross on the cutting section or the lower edge of difficult to remove the dross.
(1) The lower edge of the dross (see Figure 9-23)
Phenomenon: the lower edge of the cutting section to produce a continuous dross.
Reasons: ① cutting speed is too fast or too slow, the cutting nozzle number is too small, cutting oxygen pressure is too low;
(2) preheating flame gas excess steel surface oxide rust or unclean;
(3) cutting height between the nozzle and the workpiece is too large, too preheating flame.
(2) cutting section dross
Phenomenon: the dross on the cutting section, especially in the lower half of the dross.
Cause: The content of alloy composition is too high.
5. Crack
Phenomenon: a visible crack on the cutting section, or pulsation in the cutting section near internal crack, or just cracks can be seen in cross section.
Reasons: the amount of carbon or alloy composition containing too high, the use of warm-up cutting method, the preheating temperature of the workpiece is not enough, the the workpiece cooling time is too fast, the material work hardening
中文譯文
數(shù)控火焰氣割的基本常識
（一） 氣割的基本工作原理及氣割的過程
利用氣體火焰的熱能將工件切割處預(yù)熱到一定溫度后，噴出高速切割氧流，使其燃燒并放出熱量實(shí)現(xiàn)切割的方法，叫氣割。
氧氣切割過程有下列三個(gè)階段：
1、預(yù)熱? 氣割開始時(shí)，利用氣體火焰(氧乙炔焰、氧丙烷焰)將工件待切割處預(yù)熱到該種金屬材料的燃點(diǎn)(對于低 碳鋼約為1100～1150℃)。
2、燃燒? 噴出高速切割氧流，使已達(dá)燃點(diǎn)的金屬在氧流中激烈燃燒。
3、吹渣? 金屬燃燒生成的氧化物被氧流吹掉，形成切口，使金屬分離，完成切割過程。
（二） 氣焊、氣割用設(shè)備的組成
氣焊、氣割用設(shè)備由氧氣瓶、氧氣減壓器、乙炔瓶(乙炔發(fā)生器)、乙炔減壓器、回火保險(xiǎn)器、焊炬(割炬)和橡膠管等組成。
（三）什么樣的割口是好的
切割后的割口面 中間泛白 沒有疤痕 割口不帶廢渣 沒有燒邊現(xiàn)象
（四）可以氣割的金屬應(yīng)符合下述條件：
1）金屬氧化物的熔點(diǎn)應(yīng)低于金屬熔點(diǎn)。是一些常用的金屬及其氧化物的熔點(diǎn)。
2）金屬與氧氣燃燒能放出大量的熱，而且金屬本身的導(dǎo)熱性要低。
符合上述氣割條件的金屬有純鐵、低碳鋼、中碳鋼和低合金鋼以及鈦等。其它常用