Ferritic stainless steel and steel sheet for heat pipes, and heat pipe and high-temperature exhaust heat recovery system

Abstract

Provided is a ferritic stainless steel for heat pipes of high-temperature exhaust heat recovery systems, which comprises, in terms of % by mass, from 16 to 32% of Cr, at most 0.03% of C, at most 0.03% of N, at most 3% of Si, at most 2% of Mn, at most 0.008% of S, from 0 to 0.3% of Al, and at least one of at most 0.7% of Nb, at most 0.3% of Ti, at most 0.5% of Zr and at most 1% of V, and optionally at least one of at most 3% of Mo, at most 3% of W, at most 3% of Cu, at most 0.1% of Y, at most 0.1% of REM (rare earth metal) and at most 0.01% of Ca, with a balance of Fe and inevitable impurities, and which satisfies at least the following formula (1), formula (2) and formula (5):

Cr+3(Mo+Cu)≧20  (1)

Cr+3(Si+Mn+Al−Ti)≧20  (2)

0.037{(C+N)/(V+Ti+0.5Nb+0.5Zr)}+0.001≦0.01  (5).

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to stainless steel and steel sheets for use for heat pipes for heat exchange that harness the latent heat of evaporation of water, as well as to the heat pipe thereof and a high-temperature exhaust heat recovery system comprising it.[0003]2. Background Art[0004]Recently, a high-temperature exhaust heat recovery system is being put into practical use for the purpose of recovering the heat of engine exhaust gas to be discharged at high temperatures in vehicle driving and recycling it as an energy source for vehicles for the purpose of enhancing fuel efficiency in vehicles. In general, a heat exchanger is applied to recovery of exhaust heat, which is for heat exchange between exhaust heat and cooling water or any other heat medium; and as a method of realizing efficient heat exchange, a heat exchanger with a heat-transferring means that may be referred to as a heat pipe is being specifically n...

AI Technical Summary

Benefits of technology

[0021]According to the invention, the increase in the inner pressure of a stainless steel-made heat pipe, which is caused by hydrogen generation in the heat pipe and is problematic therein, can be significantly relieved

Problems solved by technology

However, a heat pipe formed of stainless steel may have a large quantity of hydrogen generated inside it in the early stage of driving.

In addition, the hydrogen generation inside the heat pipe is a risk factor of lowering the heat transfer efficiency to cooling water and is additionally a risk factor of impar

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