Cyfansoddiad cemegol yw'r mynegai mwyaf sylfaenol o belenni dur a thywod dur, a fydd yn pennu microstrwythur pelenni dur a thywod dur ac effaith triniaeth wres ddilynol. Mae carbon (C) yn pennu caledwch ac ansawdd yr ergyd dur, a dylai'r cynnwys fod yn gymedrol. Os yw'r carbon yn uchel, nid yw'r caledwch yn ddigon i gyflawni'r effaith ddyledus. Os yw'r carbon yn uchel, mae'r caledwch yn rhy fawr, ac mae'r ergyd dur yn hawdd i'w dorri. Gall Silicon (Si) wella'n sylweddol y terfyn elastig, pwynt cynnyrch a chryfder tynnol dur, gall manganîs (Mn) wella cryfder a chaledwch pelenni dur, gwella perfformiad gweithio thermol dur, a gall manganîs hefyd leihau niwed sylffwr , gwella ymwrthedd gwisgo pelenni dur. Mae sylffwr (S) a ffosfforws (P) yn elfennau niweidiol, sy'n hawdd brau'r ergyd dur ac yn arwain at rwyg cynamserol, a dylent fod mor isel â phosibl (<0.05% is the best). Chemical composition is the most basic index of steel pellets and steel sand, which will determine the microstructure of steel pellets and steel sand and the effect of subsequent heat treatment. Carbon (C) determines the hardness and quality of the steel shot, and the content should be moderate. If the carbon is high, the hardness is not enough to achieve the due effect. If the carbon is high, the hardness is too large, and the steel shot is easy to be broken. Silicon (Si) can significantly improve the elastic limit, yield point and tensile strength of steel, manganese (Mn) can improve the strength and hardness of steel pellets, improve the thermal working performance of steel, and manganese can also reduce the harm of sulfur, improve the wear resistance of steel pellets. Sulfur (S) and phosphorus (P) are harmful elements, which are easy to brittle the steel shot and lead to premature rupture, and should be as low as possible (<0.05% is the best).
