机械制造专业英语Lesson9(A)翻译
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GAS TUNGSTEN-ARC WELDING(GTAW)
GTAW was the first new arc-welding progress,following stick electrode by about
25years.The Linde Company,a division of Carbide,developed the progress for welding
magnesium,but it proved to be more versatile.The trade name given it by the Linde
Company was Heliarc,since helium was used as a shielding gas.The popular term
used for the welding progress is TIG,short for tungsten inert gas.
TIG welding consists of a nonconsumable，torch-held tungsten electrode and a
workpiece as shown in Fig.9-4.If filler metal is required,a welding rod is fed into the
weld zone and melted with the base metal.
钨极氩弧焊是第一个新的弧焊加工方法，跟随了电焊条大学25年之久。Linde公司是Carbide公司的一个分部，发展了焊接镁的加工方法，但是它被证明是万能的。自从氦被用作保护气体，Linde公司给了它的贸易名称是氦弧。用作描述焊接过程的流行术语叫TIG.
TIG焊接包括了一个非自耗的，持续点燃的钨焊条和一个如表9—4所示的工件。如果需要焊料，一根焊条会被填充到焊接的地区和基底金属熔在一起。
All three welding currents may be used:dcsp,dcrp,and ac.In general,dcsp
provides deep penetration and faster welding on thicker workpieces but is not used on
aluminum and magnesium.Dcrp provides a wide weld pool with shallow penetration
and so is ideal for thin workpieces.Current range is limited due to electrode
over-heating.AC produces the combined characteristics of dcsp and dcrp for high
electrode capacity and excellent oxide cleaning action.
三种焊接电流可能被用到：直流正接，直流反接和交流电。大体上，直流正接可以更深地渗透并且更快地焊接厚的工件，但是不用在金属铝和镁上。直流反接提供一个具有很浅渗透的宽焊池，因此对于薄的工件是很理想的。由于电焊条过度加热，电流是有限制的。交流电综合利用了直流正接和直流反接的高度焊接能力和优秀的氧化物清洁功能的特性。
WELD Characteristics and Gas Choice.Argon provides the most stable arc
and most efficient cleaning action.Helium is hotter than pure argon and so provides
deeper penetration at higher welding speeds.Argon and hydrogen mixtures help
prevent weld bead discoloration.
焊接特性和气体选择。氩提供了最稳定的弧和最高效的清洁功能。氦比纯净的氩更热，所以在更高的焊接速度中提供更深的渗透。氩和氢混合帮助防止焊缝变色。
TIG Electrode.Tungsten is used as the nonconsumable electrode because it has
the highest melting temperature of all metals.It is also a strong emitter of
electrons,which help ionize the arc path and thus generate a stable mercially
pure tungsten may be used as the electrode,but tungsten electrodes alloyed with thoria
and zirconia are used to stabilize the arc and provide easier starting.
The tungsten electrode end may be pointed or completely hemispherical,like a
bulb.The pointed end is ideal for welding in restricted locations.The hemispherical
end profile electrode will handle the greatest current density because less of the
electrode is in contact with the arc.Thoriated and zirconiated tungsten electrodes hold
their shaped ends better than pure tungsten over a large temperature range. TIG电焊条。钨被用作非自耗的焊条，因为它在所有金属中拥有最高的熔点。它也是一个很强的电子发射体，能够帮助电离弧的路径并因此形成一个稳定的弧状物。市售纯净的钨可能用作焊条，但是掺杂氧化钍或者氧化锆的钨焊条被用作稳定的弧状物和提供更容易的开端。
钨焊条的末端可能是尖的或者完全是半球形的，像一个电珠。尖末端焊接受限制的地方是非常理想的。半球状末端剖面焊条将承受最大电流密度，因为很少焊条与弧状物接触。在一个大的温度范围内，加入氧化钍的钨焊条和加入氧化锆的钨焊条比纯净钨焊条更好地保持它们的成形末端。
Advantages and Limitations.GTAW can used to make top-quality welds in
almost all metals and alloy,including high-temperature alloys,many hard-facing
alloys,titanium,zirconium,gold and silver.Almost no weld cleanup is required since no
flux is used.There is very little weld spatter since the weld metal is not carried across
the arc.Welding can be done in all positions.The progress is particularly well suited
for welding thin materials where a high-quality finish is desired.
The main disadvantage of GTAW is that it is relatively slow and for that reason
is not well suited to welding heavier metals.
优点和局限性，在几乎所有金属和合金，包括高温合金，许多表面硬化合金，钛，锆，金和银中，钨极氩弧焊可以用来制作顶级品质的焊接。自从不用助焊剂以来几乎不用清洁工作，自从焊接金属不从弧中取出以来很少有焊接喷溅。焊接可以在任何位置。这个过程是特别适合焊接那些需要高质量完成的薄材料。
钨极氩弧焊的主要缺点是它相当地慢，正因为这个原因它不能很好适应焊接重金属。
