Analysis Of Heat Treatment Process For 690 Material Used For Shear Cap For Squib Valve

The squib valve is the important and special equipment in PXS of AP1000 nuclear power plant which is used for the first time in PWR power plant. The material of the shear caps used in the squib valve is Inconel 690 alloy, which is a kind of austenite corrosion resistant alloy content 30% chrome. Consider the feature of gunpowder actuate for the squib valve, the mechanical property of 690 alloy used for shear caps of squib valve is defined within a very narrow scope, to match the design and analysis of gunpowder.The heat treatment of the 690 alloy for the heat-transfer tube is solution treatment of vacuum or gas shield + vacuum desensitization heat treatment. Consider the diameter size of the shear caps and the lot weight, if the heat treatment of the shear caps 690 alloy also use the same heat treatment as the heat-transfer tube, i.e. solution treatment of vacuum or gas shield + vacuum desensitization heat treatment, the requirement of equipment for the heat treatment will be very high, the cost of material is high.This article focuses on comparison of two different heat treatment processes, “vacuum solution + vacuum desensitization”(abbreviated as “vacuum heat treatment”) and “air solution treatment + air desensitization heat treatment”(abbreviated as “air heat treatment”) on the 690 alloy for Squib Valve Share Caps. Through comparing the two heat treatment processes’ effects on 690 alloy bar’s metallographic structure, mechanical property and corrosion resisting property, etc. and studying a series of lab tests, there are some important results below:1) Through the control of proper process parameters of air heat treatment, and the proper machine of the surface for the shear cap bar, the air heat treatment can also provide the satisfied mechanical properties.2) During the lab simulation data for 690 alloy via air heat treatment, the proposed machine thickness for the surface of bar is not lower than 0.1mm.3) During the lab simulation data for the chemical composition of 690 alloy, the recommended temperature of solution treatment is 1050℃, the 690 alloy bars can provide the satisfied mechanical properties.The article shows the air heat treatment is practicable for the 690 alloy bars used for the squib valve shear caps and provides the proposal air heat treatment processes.