First, the required raw materials for the preparation of cable sheath lead

(A) addition of Cu in order to avoid a serious impact on the Cu ₂ Sb generated between the metal cable sheath extrudability lead compound, the method using copper is added directly to the lead melt. The copper content of the sheathed lead product is in good agreement with the amount of production at the time of production. Under normal conditions, the error between the two is less than 5%.

Now the cable factory has gradually increased the copper content of the sheath lead, tending to 0.06%. This brings certain difficulties to the production. On the one hand, the time of the melting process is prolonged; on the other hand, due to the increase of the copper content, it is easy to be melted from the melt, so that the copper content in the lead liquid is decreased, especially in the presence of In the case of Sb. But trying to avoid the effects of some unfavorable factors, it is completely feasible to increase the Cu content. The melting of copper in lead liquid does not mean that copper and lead have been alloyed. The process of alloying must be given.

(Ii) a melting point of Sb is antimony added 630.5 ℃, specific gravity of 6.684. In the case of burning, it is easy to oxidize to produce white sulphur dioxide. The affinity of hydrazine for oxygen is greater than the affinity of lead for oxygen. Therefore, hydrazine is easily burned during the formulation process. However, helium has a higher solubility in liquid lead and a faster dissolution rate. The broken crucible is placed in the stirred lead liquid, and is quickly vortexed by the inhalation flow, and no longer floats out of the liquid surface. It takes only a few minutes from addition to dissolution, but the agitation must be sufficient. It will take a while after the ruthenium is completely dissolved, otherwise a separate 锑 phase can still be seen in the metallographic photograph.

The loss of bismuth is large, and the degree of loss (also called burning loss) is related to the temperature of lead liquid, the stirring intensity and time, the amount of lead oxide remaining on the surface of lead liquid, and the burning rate can reach l0%~l8%. The effect of temperature on the utilization of helium. In order to reduce the burning loss, the lower temperature and stirring intensity and shorter mixing time should be adopted on the premise of meeting the production process requirements. This has practical implications for reducing production costs. Calculated by the finished product containing Sb of 0.55%, if the utilization rate of bismuth is increased from 85% to 90%, the cost per ton of sheathed lead can be reduced by nearly 3 yuan.

(III) Addition of tin In the Pb-Sn-Sb alloy, tin is added. Tin has a melting point of 231.9 ° C and a specific gravity of 7.29. The problem to be aware of when fitting tin is similar to that of fitting. The rate at which it is oxidized and damaged is greatly affected by the operating temperature and the stirring strength. Since tin is easily reacted with PbO to form PbO•SnO ₂ , the amount of lead oxide remaining on the lead liquid surface directly affects the utilization of tin. The effect of operating temperature on the utilization of tin. Since the burning loss of tin increases sharply with the increase of the operating temperature, in order to reduce the burning loss, it should be controlled at the lowest possible temperature. The control is in the range of 400 to 4l0 °C. If the temperature is too low, it will increase the difficulty of the operation of the ingot casting machine. The flash burrs and surface slag inclusions of the sheathed lead ingots are obviously increased, the pouring holes are also easily blocked, and the labor intensity of the workers is greatly increased. Excessive agitation can reduce the tin content of the alloy, so the agitation intensity and time should be controlled during operation. In addition, in the ingot casting, the reflux flow of the lead liquid should be minimized and the duration of the casting process should be shortened as much as possible. Under the condition that the stirring strength is constant, the influence of the stirring time on the amount of Sn in the alloy is tested. As the stirring time is extended, the amount of Sn contained in the alloy is lowered.

When the liquid alloy was placed in a calm and heat-insulated state, the amount of Sn contained changed little after several hours. It can be seen that the burning of tin is related to the contact of fresh liquid with air.

2. Metallographic structure of Pb-Sb-Cu alloy

The Pb-Sb-Cu sheathed lead alloy should be a lead-based metal solid solution from the controlled chemical composition range and the Pb-Sb-Cu ternary phase. The as-cast microstructure of the sheathed lead ingot is unbalanced, and dendritic segregation is inevitable. This segregation will disappear after annealing. Since the sheathed lead ingot is remelted before being used to make the cable sheath, the solution temperature generally reaches 380 to 400 ° C, and the as-cast structure is inevitably destroyed. Therefore, the state of the as-cast structure should not be used as a basis for judging the quality of the sheathed lead ingot.

However, cable manufacturers from the practice of sheath lead extrusion processing, it is believed that the presence of acicular Cu ₂ Sb in the sheath lead is very harmful, which will seriously affect the extrusion properties of the alloy. Therefore, some manufacturers require that there should be no needle-like Cu ₂ Sb in the sheath lead when ordering. The diameter of the agglomerated Cu ₂ Sb should not exceed 1 mm on the X250 gold photograph, that is, the diameter of the pellet should not exceed 4× ^10—3 mm. Whether the quantitative criteria for this requirement are reasonable is another matter, but reflects the practical experience of cable manufacturers from one aspect.

If a Pb-Sb-Cu alloy is produced by first adding a Sb-Cu master alloy and then adding lead, there must be a large amount of Cu ₂ Sb in the alloy, wherein the needle-like Cu ₂ Sb accounts for a considerable proportion. This alloy cannot be used in the production of continuous extruders. This point was confirmed by the cable factory.

The method of directly incorporating copper and ruthenium can greatly reduce the formation of Cu ₂ Sb, but it is impossible to produce Cu ₂ Sb. At 1l% Sb and 0.075% Cu, there is a eutectic point of lead, antimony and deuterated copper, and the eutectic temperature is only 248 °C. If the alloy melt composition is a point containing Sb>11% and containing Cu>0.075%, the Cu ₂ Sb phase first appears in the cooling process, followed by the eutectic of Cu ₂ Sb and Sb, and finally Pb, Sb and Cu ₂ Sb ternary eutectic, in which a part of Cu ₂ Sb forms a needle-like structure. Therefore, as long as the process conditions are strictly controlled, the formation of acicular Cu ₂ Sb can be avoided.

       The activation method of the Slep Furnace is a method of activating the steam and flue gas alternately. The SLEP Furnace is mainly composed of the furnace body, the regenerator, the water seal, the feeder and the chimney.

     It is suitable for the production of various kinds of granular carbon, the process conditions are stable, the quality of the product is uniform, the adsorption performance is good, the production of various advanced activated charcoal, big production capacity , the mechanical automation can be realized, the fuel is not needed, long furnace life  and so on. So it is widely used in the production of international granular activated carbon.