PSI - Issue 22

Li Yan-hua et al. / Procedia Structural Integrity 22 (2019) 118–124 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Aging sensitivity coefficients based on yield strength according to Equation 1: C T =( R p0. 2S -R p0. 2 )/ R p0. 2 ×100% Aging sensitivity coefficients based on yield ratio according to Equation 2: C Y /T =(R S -R) /R×100% (2) In the equation, C T and C Y /T denotes aging sensitivity coefficients based on yield strength and aging sensitivity coefficients based on yield ratio. Rp 0. 2 and R the average yield strength and yield ratio before strain aging, Rp 0. 2S and R S denote the average yield strength and yield ratio after strain aging. The data before and after artificial strain aging is introduced in the equation (1) and (2) to compute the aging sensitivity coefficients based on yield strength and aging sensitivity coefficients based on yield ratio of X90 pipeline steel manufactured by different manufacturers respectively, which are listed in Table 6 and Table 7. Table 6. Aging sensitivity coefficients based on yield strength and aging sensitivity coefficients based on yield ratio after 200 ℃ , 5min artificial strain aging Sample information Sample A Sample B Sample C Aging sensitivity coefficients based on yield strength 0.09 0.02 0.12 Aging sensitivity coefficients based on yield ratio 0.07 0.03 0.10 (1)

Table 7. Aging sensitivity coefficients based on yield strength and aging sensitivity coefficients based on yield ratio after 250 ℃ , 1h artificial strain aging Sample information Sample A Sample B Sample C Aging sensitivity coefficients based on yield strength 0.09 0.01 0.14

The comparison of aging sensitivity coefficients based on yield strength and aging sensitivity coefficients based on yield ratio of X90 pipeline steel manufactured by different manufacturers after 200 ℃ , 5min artificial strain aging is shown in Figure 1.

Fig. 1. The comparison of aging sensitivity coefficients based on yield strength and aging sensitivity coefficients based on yield ratio of X90 pipeline steel manufactured by different manufacturers after 200 ℃ , 5min artificial strain aging

The causes of pipeline aging phenomenon is attributed to the segregation of interstitial solid solute C, N near