High-temperature-resistant silicon molybdenum ferrite nodular cast iron for steam turbine and preparation technology therefor

Abstract

The invention discloses high-temperature-resistant silicon molybdenum ferrite nodular cast iron for a steam turbine and a preparation technology therefor. The nodular cast iron comprises components: 3.0-3.5% of C, 2.8-3.2% of Si, less than 0.2% of Mn, less than 0.040% of P, less than 0.015% of S, 0.5-0.8% of Mo, less than 0.010% of Re, 0.040-0.055% of Mg, and 0.004-0.007% of Sb, the balance being iron and residual elements. The preparation technology comprises furnace charge matching; intermediate frequency induction furnace fusing; spheroidizing and addition of first inoculation ferrosilicon; control of contents of elements; pouring into a pulling runner box for secondary inoculation; casting moulding. The obtained nodular cast iron has good combination properties and a low cost, the nodularity reaches more than 80% of the nodularity prescribed by GB / T9441-2009 nodular cast iron metallographic examination, the ferrite amount is more than 90%, and normal temperature and high temperature mechanical properties meet production requirements.

Description

technical field [0001] The invention relates to a metal material and a preparation process thereof, in particular to a nodular cast iron and a preparation process thereof. Background technique [0002] Due to its good casting performance and low production cost, ductile iron has been widely used in the field of equipment engineering, such as steam turbine cylinders, bearing housings, etc. Nowadays, high power, high parameters, high reliability, high thermal efficiency and clean environmental protection have become the development direction of steam turbine technology. The application of the steam turbine reheating technology makes the reheating temperature of the unit reach 625°C, the pressure is 35MPa, and the operating temperature of the outer cylinder reaches 350-450°C, which has a significant impact on the strength, creep characteristics, oxidation resistance, and fatigue resistance of the material. more stringent requirements. The service temperature of ordinary ducti...

AI Technical Summary

Problems solved by technology

[0011] The silicon content in this material is high, which can easily cause brittle castings and increase the risk of casting production; at the same time, aging stress relief annealing treatment is required to prolong the production cycle and increase production costs.

Images