Evaluation of cold resistance of large forgings made of 38хн3мфа-ш improved steel based on «data mining» of industrial control of process and product

A statistical analysis of the results of end-to-end industrial control of large (weight ∼5 t) cylindrical forgings of variable cross-section made of 38ХН3МФА-Ш (Russian name) improved steel with preserved cast structure was performed, using an original algorithm for processing an array of data. As an additional characteristic of cold resistance, a two-parameter criterion ∆ij-ij is proposed, where ∆ij = - characterizes the «steepness» of the impact toughness decrease for forgings’ test standard temperatures: +20 and -50 °C, and ij = (+) / 2 is its absolute level. The relationship between the proposed criterion and the process parameters was established: the chemical composition of steel after ESR, the ingot heating temperature for forging, the temperatures of the beginning of forging and the second tempering. The approach can be useful for ranking forgings by cold resistance.