| The copper is soft. The emission of bullets with copper-rotating band will leadto copper stuck to the rifling, causing rifling pollution, as well as the loss of copperband, by the same time, making the bullets deteriorating its closure. The soft iron isof high hardness, when bullets are launched, the band will be in friction with therifling, which will make the rifling weareven more serious. Against the problemscopper band and soft iron band exist,the subject has come up with the idea of softiron-copper compound band, with the steps of surfacing soft iron and depositionwelding of iron. Due to the characteristics of high hardness and high strength, softiron can improve the rigidity of theband on the whole, avoiding slippage of thecopper band, slowing down the wear of the filing.Using high-frequency induction deposition welding method, investigate theparameters of the welding if brass.The results showed that using of the heatingcurrent of300A,the time for brass to melt completely is moderate, which is about10s, while the thickness of the Pan-iron layer is approximately3μm. Increasing theheating time, the Pan-iron continued to spread to copper, by the same timeproducing new Pan-iron at the interface. The thickness of Pan-iron layer increasesslowly, when the heating time increases to30s, the thickness of Pan-iron layer isabout25μm. Increasing the heating current, the spread of Pan-iron shows noregularity any more, a sharp increase inthickness of the iron pan happens, when theheating current increases to500A, the thickness of the Pan-iron layer has grown to200μm or more.By observing the macro photos of the joint, we have found that the interfaces ofthe four kind of joints are straight, and all belong to brazed joints. Except for thebrass welded joints, the phenomenon of iron spreading can be found in the surfacingcopper layers of the other surfacing joints. It can be found from thephotomicrograph of joints that, a layer of a solid solution layer can be found incopper, aluminum bronze, and silicon bronze welding joints. This layer is caused byiron melted near the surface, which didn’t mix up with the liquid copper,butcondensedby the steel substrate surface after the cooling process.The morphology of Pan-iron in the copper layer was observed, and a spectrumtest was done near the interfacial area. The results show that, the presentation ofPan-iron in copper and aluminum bronze is spherical, petal-like and dendritic, whilethe Pan-iron in silicon bronze is in granular form, not smooth and irregular. ThePan-iron in brass, copper and aluminum bronze is a solid solution of Fe element in the copper alloy, while the Pan-iron in silicon bronze is attached to the siliconparticles, while a copper-rich aggregates therein. The universal law for the solidsolution region in TIG welding joints is that, from soft iron side to copper side, Cuelement of the solution is increasing, but as a result of the copper-rich solid solutionregions contained in silicon bronze welding joints, the distribution of Fe and Cushow no regularity.A hardness test was done to the elastic material layer. The rules of the changeof hardness in copper in those two joints of soft iron-copper and steel-copper are ofthe same, which means the difference in components of soft iron and steel causes noeffect on interface behavior laws. Among them, the hardness trend of copper layerand aluminum bronze layer is more intense, while the trend in brass layer and thesilicon bronze layer is relatively flat, which is resulted from the differentmorphology of Pan-iron in copper layers. A tensile test and a shear test weresubjected to the joints. The results show that, the average tensile strength and shearstrength in copper, silicon bronze, aluminum bronze and brass layers satisfy thepositive correlation with the hardness of the copper layer. Copper, aluminum bronze,silicon bronze and brass have got their own applicability and can be used forsoldering soft iron-steel compound bands, which will show excellent performance. |
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