This is a very important issue. In traditional lead-acid battery
production, the welding rod alloy does not need to add tin. In addition, some
corrections have been made to some people who say that the welding rod of DZM
battery should be made of the same alloy as the grid.
This is a very important issue. In traditional lead-acid battery
production, the welding rod alloy does not need to add tin. In addition, some
corrections have been made to some people who say that the welding rod of DZM
battery should be made of the same alloy as the grid.
The first thing to explain is the alloy used in lead-acid batteries. The
negative electrode is lead calcium tin aluminum. The positive electrode is made
of lead, antimony and cadmium. Because the melting points of the positive
electrode alloy components are similar, especially the presence of antimony, its
melting point is close to 270°C of the low antimony alloy, which will not affect
welding. But the negative electrode is different, because the melting points of
each element in the quaternary alloy of the negative electrode are: the melting
point of lead is 327°C, the melting point of calcium is 839°C, the melting point
of tin is 231°C, and the melting point of aluminum is 660°C. Explain the lead
base Alloy, so-called lead-based, is a synthetic metal made mainly of lead with
the addition of other small amounts or trace elements. Battery Production
Technology - The Necessity of Adding Tin to Lead-Calcium Battery Welding Rods It
can be seen from these metals that their melting points are very different.
Under the same heating conditions, it is impossible to melt at the same time.
High-melting-point metals oxidize quickly at high temperatures, and an oxide
film forms on their surface when they are close to their melting point. The
melting point of most metal oxides is more than twice that of the original
metal.
It is impossible to melt it again using ordinary welding guns and operating
techniques. Let’s talk about the melting process during welding. The two
relatively high melting point metals contained in the electrode plate do not
actually melt when the alloy as a whole is melted, but are dispersed and
decomposed.
Because as a whole it is called an alloy, but as individual units, calcium
and aluminum still exist. The calcium and aluminum at this time can be called
infusible substances free in the low-melting-point metal melt. Pure lead itself
has very poor stretchability and fluidity. If elements such as antimony and tin
are not added to pure lead, it cannot be cast (battery production has been done
with pure lead in the past, but the grids were die-cast). The welding rod is the
main filler of the bus bar, and the plate ears occupy about 1/3. The function of
the bus bar is to connect the plates of the same polarity in a pole group
together in parallel, and to transmit the power of these plates through the bus
bar. to the external circuit.
The melting point of lead-tin alloy is 183°C. Under the same temperature
conditions, the melting time of lead-tin alloy is more than 1/3 shorter than
that of pure lead. This leads to the following question: eutectic point metal,
the welding rod does not contain high melting point metal. There is no oxidation
problem, but the plates contain high melting point metals.
Oxidation process of the electrode plate lug: When the welding gun flame
first contacts the electrode plate lug, there is a process of melting the
low-melting-point metal and oxidizing the high-melting-point metal. However, it
must be noted that the oxidation rate of aluminum in an oxygen-rich environment
is Extremely fast. Because there is aluminum in this alloy, the purpose is to
prevent the loss of calcium in the molten state.
Therefore, there are requirements for the amount of eutectic point metal.
The purpose is to achieve mutual fusion of the plate lug alloy and the electrode
alloy in a relatively uniform period of time.
It can be understood that as long as the molten electrode alloy can reach
the plate lug at the first time and meet the eutectic point alloy of the
electrode plate lug, there will be no false welding. However, when the welding
technology is immature (poor control of flame, technique, and time), false
welding will still occur. For this reason I think it necessary to impose a
double control on our welding at this stage.
Explain the so-called special alloy for positive and negative electrodes.
This special alloy refers to the alloy used in the positive and negative
electrode grids. It is okay if the positive electrode uses a grid alloy as a
welding rod.
The negative electrode is impossible and cannot be welded at all. When the
alloy ratio was high calcium and low tin, the amount of tin added to the
electrode alloy was 2%. Now the amount of tin added is between 0.8% and 1%. This
amount is less. There is insufficient eutectic point metal in the molten pool
during welding, resulting in uneven welding quality.
In addition, the cadmium in the positive electrode and the calcium in the
negative electrode cannot be mixed together. These two metals simply cannot be
formulated into alloys. The two components together will cause the metal texture
to disperse. In practical applications, if the positive electrode alloy is mixed
If it enters the negative electrode alloy, it will cause the busbar to crack and
have a fatal impact on the quality of the battery.
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