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70Si3MnA梯型弹簧钢是用于制造火炮上的各种螺旋弹簧,72—76年这个产品存在着严重的热缠裂口缺陷——指梯型材在电加热缠簧时,在螺旋簧的外径大面棱角上或心部出现的裂口,裂口外观形状多呈长方形或近似三角形,裂口以单个或群集存在。未腐蚀裂口微观特征是裂口的周围及底部没有夹杂物,并无脱碳现象,纵断面多呈U型,其底部较园钝深0.5—3％。经过大量试验研究及生产实践,本文叙述了热缠裂口缺陷与缠簧工艺参数无关,纯属钢材内在质量问题,并与钢材表面质量、钢中气体,夹杂及脱碳无关。热缠裂口缺陷的实质,是钢锭开坯加热温度高,造成严重过热和局部过烧(对硅锰弹簧钢局部过热一过烧轧制后,不易产生龟裂而产生鳞片,在随后产材时,虽经再变形局部但并不能完全消除,用一般常规方法检验,不易发现),破坏了钢的内部完整性,降低了金属晶粒间的结合力,当钢的基体强度小于缠簧时所受的拉应力,又因簧的外表面受拉应力最大,故产生裂口。严格控制钢锭最高加热温度≤1200℃,钢坯终轧温度870—950℃,收集入坑温度550～650℃,坯料加热温度1030—1070℃,终轧温度≥800℃,就能完全消除热缠裂口缺陷的产生。
70Si3MnA ladder spring steel is used to manufacture various helical springs on artillery, 72-76 years, this product has a serious thermal entanglement defect - refers to the ladder section in the electric winding coil spring, the outer diameter of the spiral spring large Rims or heart on the emergence of the rift, rift appearance mostly rectangle shape or approximate triangle, the rift in a single or cluster exists. The microscopic feature of the unetched rips is that there is no inclusions around the bottom of the rips and there is no decarburization. The longitudinal section is mostly U-shaped with the bottom blunt than the garden by 0.5-3%. After a great deal of experimental research and production practice, this article describes the hot-ripping hole defect has nothing to do with the technical parameters of the coil spring, pure steel intrinsic quality problems, and the steel surface quality, steel gas, inclusions and decarburization has nothing to do. Hot entrapment defect is the essence of the billet billet heating temperature is high, causing severe overheating and local over-burning (on the silicon-manganese spring steel overheating over a rolling after rolling, easy to produce cracks and scales, in the subsequent production of materials , Though the reformation of the local but not completely eliminated, using the conventional method of inspection, not easy to find), undermining the internal integrity of the steel, reducing the binding force between the metal grains, when the steel matrix strength is less than when the winding By the tensile stress, but also because of the spring outer surface of the tensile stress maximum, it creates a gap. Strictly control the ingot heating temperature ≤ 1200 ℃, the final billet rolling temperature 870-950 ℃, collecting pit temperature 550 ~ 650 ℃, billet heating temperature 1030-1070 ℃, finishing rolling temperature ≥ 800 ℃, can completely eliminate hot-slit Defect production.