首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
There are a number of methods of joining metal articles together, depending on the type of metal and the strength of the joint w
There are a number of methods of joining metal articles together, depending on the type of metal and the strength of the joint w
admin
2013-09-23
69
问题
There are a number of methods of joining metal articles together, depending on the type of metal and the strength of the joint which is required. Soldering gives a satisfactory joint for light articles of steel, copper or brass, but the strength of a soldered joint is rather less than a joint which is brazed, riveted or welded. These methods of joining metal are normally adopted for strong permanent joints.
The simplest method of welding two pieces of metal together is known as pressure welding. The ends of metal are heated to a white heat—for iron, the welding temperature should be about 1 , 300℃—in a flame. At this temperature the metal becomes plastic. The ends are then pressed or hammered together, and the joint is smoothed off. Care must be taken to ensure that the surfaces are thoroughly clean first, for dirt will weaken the weld. Moreover, the heating of iron or steel to a high temperature causes oxidation, and a film of oxide is formed on the heated surfaces. For this reason, a flux is applied to the heated metal. At welding heat, the flux melts, and the oxide particles are dissolved in it together with any other impurities which may be present. The metal surfaces are pressed together, and the flux is squeezed out from the centre of the weld. A number of different types of weld may be used, but for fairly thick bars of metal, a vee-shaped weld should be employed. It is rather stronger than the ordinary butt weld.
The heat for fusion welding is generated in several ways, depending on the sort of metal which is being welded and on its shape. An extremely hot flame can be produced from an oxyacetylene torch. For certain welds an electric arc is used. In this method, an electric current is passed across two electrodes, and the metal surfaces are places between them. The electrodes are sometimes made of carbon, but more frequently they are metallic. The work itself constitutes one of them and the other is an insulated filler rod. An arc is struck between the two, and the heat which is generated melts the metal at. the weld. A different method is usually employed for welding sheets or plates of metal together. This is known as spot welding. Two sheets or plates are placed together with a slight overlap, and a current is passed between the electrodes. At welding temperature, a strong pressure is applied to the metal sheets. The oxide film, and any impurities which are trapped between the sheets, are squeezed out, and the weld is made.
The word "flux" in Paragraph 2 means______.
选项
A、a situation in which things are changing a lot
B、flowing out
C、substance mixed with metal to promote fusion
D、continuous succession of changes
答案
C
解析
语义题。根据上下文中的“For this reason,a flux is applied to the heated metal.At welding heat,the flux melts,and the oxide panicles…and the flux is squeezedout from the centre of the weld.”可知,flux有助于焊接表面氧化物的熔解,可以推测出该物质可加速金属的融化和熔合,所以[C]是正确答案。
转载请注明原文地址:https://kaotiyun.com/show/nHLK777K
0
专业英语四级
相关试题推荐
RhodeIslandwasthe【C1】______ofAmericantennis:whentheUnitedStatesNationalChampionships(nowtheUnitedStatesOpen)w
RhodeIslandwasthe【C1】______ofAmericantennis:whentheUnitedStatesNationalChampionships(nowtheUnitedStatesOpen)w
RhodeIslandwasthe【C1】______ofAmericantennis:whentheUnitedStatesNationalChampionships(nowtheUnitedStatesOpen)w
Acommonassumptionabouttheprivatesectorofeducationisthatitcatersonlytotheelite.【C1】______recentresearchpoints
Acommonassumptionabouttheprivatesectorofeducationisthatitcatersonlytotheelite.【C1】______recentresearchpoints
Acommonassumptionabouttheprivatesectorofeducationisthatitcatersonlytotheelite.【C1】______recentresearchpoints
Theboysandgirls______togetherroundthecampfiretellingstoriesandsingingsongs.
Noonecankeepundetachedbywitnessingsuchaformidabletrainwreckwithanunknownnumberof______.
Altogetherhowmanypeoplewereinjuredduringtheviolence?
随机试题
美式期权是指在规定的合约到期日方可行权的期权。()
中共中央领导真正认识到马克思主义中国化这个问题重要性的会议是【】
改革开放以来,中国出现的社会新阶层是()。
建设工程项目实施CM承包模式时,代理型合同由()的计价方式签订。
已知甲乙两个方案投资收益率的期望值分别为10%和12%,两个方案都存在投资风险,在比较甲乙两方案风险大小时应使用的指标是()。
阅读下面的学生作文,回答问题。案例:不同的角度。不同的结果①世界本是五颜六色的,从不同的角度看问题,用不同的态度分析事物,我们看到的结果是大不一样的。②就像一个圆,从不同的角度去看它,意义是不
设f"(x)≤0(x≥0),P(x,y)为曲线L:y=f(x)上任一点,过点P的切线交y轴于点Q,且S△OPQ=x3e-x,又曲线过点(1,).(Ⅰ)求f(x);(Ⅱ)求y=f(x)在[0,+∞)上的最小值和最大值,并求曲线y=f(x)在(0,+∞)的
在一行上写多条语句时,应使用的分隔符是( )。
(1)Bythe1840sNewYorkwastheleadingcommercialcityoftheUnitedStates.IthadlongsinceoutpacedPhiladelphiaasthel
A、Theconditionsarenotyetclear.B、Theconditionsareadequate.C、Theconditionsarethesameasthespeakerisusedto.D、Th
最新回复
(
0
)