　　　首先，本文通过对火焰切割技术及数控火焰切割机的国内外研究现状的分析，对火焰切割机的总体结构进行了设计，整体采用龙门式结构，纵向、横向和垂直三个方向进给运动均选用电动机带动滚珠丝杠传动的开环控制系统。其次，由于火焰切割机切割工件时无切削力，所以纵向进给运动采用电机直接驱动来完成。最后，为了加工制造的方便还绘制了切割机的所有零部件和装配体的工程图。

关键词　数控火焰切割机，龙门式，结构设计

　　　摘要I

　　　AbstractII

　　　第1章绪论1

　　　1．1切割技术的种类及发展1

　　　1．2数控火焰切割简介2

　　　1．2．1 火焰切割及数控火焰切割技术2

　　　1．2．2 国内外数控火焰切割技术的发展3

　　　1．2．3 数控火焰切割机的市场及发展4

　　　第二章机床总体设计7

　　　2．1总体方案的确定7

　　　2．2控制及传动系统选用8

　　　第三章火焰切割机传动装置设计10

　　　3．1螺旋传动10

　　　3．1．1 滚珠丝杠副的工作原理及特点11

　　　3.1.1.1纵向传动滚珠丝杠、支撑件的设计计算及电机的选择.....14

　　　3.1.1.2横向、垂直向滚珠丝杠、支撑件的设计计算及电机的选择..21

　　　第四章导轨32

　　　4．1导轨设计32

第五章机床的维护...47

　　　结论50

　　　参考文献51

　　　致谢53

　　　附录154

　　　附录261

附录3.......69

　　　　　　　　　　　　第1章绪论

1.1 切割技术的种类及发展

　　　切割是焊接生产备料工序的重要加工方法，包括冷、热两类切割，而热切割又有气体火焰切割、电弧切割、等离子切割和激光切割等各种工艺方法。目前各种金属和非金属切割已经成为现代工业生产（特别是焊接生产）中的一个重要工序，被焊工件所需要的几何形状和尺寸，绝大多数是通过切割来实现的。切割技术被广泛的应用在国民经济建设的各个领域里。

　　　近年来，由于机械工业飞速发展的需求和国外先进技术的引进，我国切割技术无论在新工艺的开发方面，还是在新能源的利用方面都有了长足的发展。自动化、半自动化切割技术的发展，使得切割技术可以代替部分机械加工，大大提高了工作效率，还可以提高金属材料的利用率。

　　　气体火焰切割是热切割中最早被采用和最常用的工艺方法，这种切割方法设备简单、操作方便灵活、投资费用少、切割质量好等特点。尤其是能够切割各种含曲线形状的零件和大厚度工件等一系列特点使得它自进入工业领域以来一直作为工业生产中切割碳钢和低合金钢的基本方法而被广泛采用。而本文介绍的数控火焰切割机就是在早期切割机的基础上结合近年来高速发展的微型计算机技术被广泛应用于工业领域的实际情况设计出的一种新型切割设备。

　　　第2章机床总体设计

2.1总体方案的确定

　　　数控火焰切割机是一个复杂的系统工程,它综合了计算机技术、精密机械制造、电机拖动、数字控制、焊接等多门学科,所以在设计、生产、调试、安装、维护等各环节都会遇到许多问题

　　　1.1 适用方向

要求该设备适用面广,既可用于大型企业的下料车间,进行大型零件的批量切割,又可用于小型机械厂,进行小型零件的小批量生产。

　　　1.2 技术水平

该设备的综合技术水平要求超过国内同类产品,接近世界先进水平。

　　　1.3 加工精度

该设备的运行精度应超过目前的国家相关标准。

　　　1.4 适用材料

该设备可用来切割碳钢、不锈钢、有色金属等板材。

　　　1.5 工作方式

工作方式为连续工作。

　　　1.6 运行速度

定位速度要求±0.012/300 mm;切割速度为1 mm~60 mm/s。

拟解决的主要问题：

中型火焰切割机设计最困难,使用时可靠性最差的要害在于轴的驱动，可有以下几种方案以供选择：

方案一：大型加工中心、数控机床上常用的设计是采用长滚动导轨与长滚珠丝杠主要问题在长滚珠丝杠的制造成本极高，安装上难度很大。

　　　方案二：采用精密齿轮齿条传动满足长行程的需要，中捷友谊厂为上海磁悬浮项目提供的大型加工中心就采用该方案。齿条固定、齿轮安装在龙门架上，由伺服电机通过同步带减速驱动齿轮。该方案也是目前大型火焰切割机的常用方案。当支撑龙门架的两根导轨问距很大时，一般采用双驱动，可靠性不高。

　　　…由上面两种方案的对比，　加上滚珠丝杠副的特长：1、动力更省驱动力矩仅为滑动丝杠副的1/3，具有较高的运动效率，可以更加省电。2、高精度的保证滚珠丝杠副都是由高水平的机械设备连贯生产出来的，制作精度更高。3、微进给可能滚珠丝杠副由于是利用滚珠运动，所以启动力矩极小，不会出现滑动运动那样的爬行现象，能保证实现精确的微进给。4、无侧隙、刚性高滚珠丝杠副可以加预压，由于预压力可使轴向间隙达到负值，进而得到较高的刚性。5、高速进给滚珠丝杠副由于运动效率高、发热小，所以可实现高速进给(运动)。

　　　可得出：在追求设计出一台高精度，高性能数控机床，方案一比较好。

2.2控制及传动系统选用

　　　数控火焰切割机的主要技术参数

　　　纵向导轨长度／m 6

　　　跨距／m 2

　　　有效切割宽度／m 1.6

　　　有效切割长度／m 5

　　　切割厚度／mm 6～160

　　　切割精度／mm ±0．5

　　　最高行动速度，m．min 15

　　　割炬组数单割炬

　　　割炬升降范围／mm 800

　　　定位精度/mm ±0.012/300

根据本紧急系统定位精度的要求,应选用全闭伺服系统。从产品目录中查得伺服电机的最高转速为或2000r/min。如果伺服电机通过联轴节与丝杠接，即i=1。工作台快速进给的最高速度要求达到。取电机的最高转速

QQ截图20131129105141.gif

数控火焰切割机的设计.gif

内容简介：: 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 processHeat 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 theGas 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 notchedCutting 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 edgePhenomenon: 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 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; 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: torch and the workpiece surface is not perpendicular to; 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: cutting nozzle clogging or damage, deterioration of air line; 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; the wind line blocked deteriorate; Phenomenon: the section close to the cutting edge of a cut ahead too much. Reasons: cutting nozzle clogging or damage, the wind line blocked deterioration; 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: 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 中文译文数控火焰气割的基本常识（一）气割的基本工作原理及气割的过程利用气体火焰的热能将工件切割处预热到一定温度后，喷出高速切割氧流，使其燃烧并放出热量实现切割的方法，叫气割。氧气切割过程有下列三个阶段：1、预热气割开始时，利用气体火焰(氧乙炔焰、氧丙烷焰)将工件待切割处预热到该种金属材料的燃点(对于低碳钢约为11001150)。2、燃烧喷出高速切割氧流，使已达燃点的金属在氧流中激烈燃烧。3、吹渣金属燃烧生成的氧化物被氧流吹掉，形成切口，使金属分离，完成切割过程。（二）气焊、气割用设备的组成气焊、气割用设备由氧气瓶、氧气减压器、乙炔瓶(乙炔发生器)、乙炔减压器、回火保险器、焊炬(割炬)和橡胶管等组成。（三）什么样的割口是好的切割后的割口面中间泛白没有疤痕割口不带废渣没有烧边现象（四）可以气割的金属应符合下述条件： 1）金属氧化物的熔点应低于金属熔点。是一些常用的金属及其氧化物的熔点。2）金属与氧气燃烧能放出大量的热，而且金属本身的导热性要低。符合上述气割条件的金属有纯铁、低碳钢、中碳钢和低合金钢以及钛等。其它常用的金属如铸铁、不锈钢、铝和铜等，必须采用特殊的氧燃气切割方法或熔化方法切割。对于8mm以下的板材，不易采用数控气割。数控火焰切割气割精度是指被切割完的工作几何尺寸与其图纸尺寸对比的误差关系，切割质量是指工件切割断面的表面粗糙度、切口上边缘的熔化塌边程度、切口下边缘是否有挂渣和割缝宽度的均匀性等。一、影响钢板火焰切割质量的三个基本要素（气体、切割速度、割嘴高度）气体（氧气，可燃性气体，火焰的调整）氧气氧气是可燃气体燃烧时所必须的，以便为达到钢材的点燃温度提供所需的能量；另外，氧气是钢材被预热达到燃点后进行燃烧所必须的。切割钢材所用氧气必须要有较高的纯度，一般要求在99.5%以上，一些先进国家的工业标准要求氧气纯度在99.7%以上。氧气纯度每降低0.5%，钢板的切割速度就要降低10%左右。如果氧气纯度降低0.8%-1%，不仅切割速度下降15%-20%，同时，割缝也随之变宽，切口下端挂渣多并且清理困难，切割断面质量亦明显劣变，气体消耗量也随着增加。显然，这就降低了生产效率和切割质量，生产成本也就明显地增加了。采用液氧切割，虽然一次性投资大，但从长远看，其综合经济指标比想象的要好得多。气体压力的稳定性对工件的切割质量也是至关重要的。波动的氧气压力将使切割断面质量明显劣变。气压压力是根据所使用的割嘴类型、切割的钢板厚度而调整的。切割时如果采用了超出规定数值的氧气压力，并不能提高切割速度，反而使切割断面质量下降，挂渣难清，增加了切割后的加工时间和费用。(2）可燃性气体火焰切割中，常用的可燃性气体有乙炔、煤气、天然气、丙烷等，国外有些厂家还使用MAPP，即：甲烷+乙烷+丙烷。一般来说，燃烧速度快、燃烧值高的气体适用于薄板切割；燃烧值低、燃烧速度缓慢的可燃性气体更适用于厚板切割，尤其是厚度在200mm以上的钢板，如采用煤气或天然气进行切割，将会得到理想的切割质量，只是切割速度会稍微降低一些。相比较而言，乙炔比天然气要贵得多，但由于资源问题，在实际生产中，一般多采用乙炔气体，只是在切割大厚板同时又要求较高的切割质量以及资源充足时，才考虑使用天然气。（3）火焰的调整通过调整氧气和乙炔的比例可以得到三种切割火焰：中性焰（即正常焰），氧化焰，还原焰。正常火焰的特征是在其还原区没有自由氧和活性碳，有三个明显的区域，焰芯有鲜明的轮廓（接近于圆柱形）。焰芯的成分是乙炔和氧气，其末端呈均匀的圆形和光亮的外壳。外壳由赤热的碳质点组成。焰芯的温度达1000。还原区处于焰芯之外，与焰芯的明显区别是它的亮度较暗。还原区由乙炔未完全燃烧的产物氧化碳和氢组成，还原区的温度可达3000左右。外焰即完全燃烧区，位于还原区之外，它由二氧化碳和水蒸气、氮气组成，其温度在12002500之间变化。氧化焰是在氧气过剩的情况下产生的，其焰芯呈圆锥形，长度明显地缩短，轮廓也不清楚，亮度是暗淡的；同样，还原区和外焰也缩短了，火焰呈紫蓝色，燃烧时伴有响声，响声大小与氧气的压力有关，氧化焰的温度高于正常焰。如果使用氧化焰进行切割，将会使切割质量明显地恶化。还原焰是在乙炔过剩的情况下产生的，其焰芯没有明显的轮廓，其焰芯的末端有绿色的边缘，按照这绿色的边缘来判断有过剩的乙炔；还原区异常的明亮，几乎和焰芯混为一体；外焰呈黄色。当乙炔过剩太多时，开始冒黑烟，这是因为在火焰中乙炔燃烧缺乏必须的氧气造成的。预热火焰的能量大小与切割速度、切口质量关系相当密切。随着被切工件板厚的增大和切割速度的加快，火焰的能量也应随之增强，但又不能太强，尤其在割厚板时，金属燃烧产生的反应热增大，加强了对切割点前沿的预热能力，这时，过强的预热火焰将使切口上边缘严重熔化塌边。太弱的预热火焰，又会使钢板得不到足够的能量，逼使减低切割速度，甚至造成切割过程中断。所以说预热火焰的强弱与切割速度的关系是相互制约的。一般来说，切割200mm以下的钢板使用中性焰可以获得较好的切割质量。在切割大厚度钢板时应使用还原焰预热切割，因为还原焰的火焰比较长，火焰的长度应至少是板厚的1.2倍以上。2.切割速度钢板的切割速度是与钢材在氧气中的燃烧速度相对应的。在实际生产中，应根据所用割嘴的性能参数、气体种类及纯度、钢板材质及厚度来调整切割速度。切割速度直接影响到切割过程的稳定性和切割断面质量。如果想人为地调高切割速度来提高生产效率和用减慢切割速度来最佳地改善切割断面质量，那是办不到的，只能使切割断面质量变差。过快的切割速度会使切割断面出现凹陷和挂渣等质量缺陷，严重的有可能造成切割中断；过慢的切割速度会使切口上边缘熔化塌边、下边缘

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