Binary alloy design method for marine stress corrosion-resistant high-strength low-alloy (hsla) stress corrosion-resistant steel

Abstract

A binary alloy design method for a marine high-strength low-alloy (HSLA) stress corrosion-resistant steel is provided. The binary alloy design method permits synergistic inhibition of anodic dissolution and hydrogen embrittlement by binary alloying to prepare the marine HSLA stress corrosion-resistant steel, the marine HSLA stress corrosion-resistant steel has an increase of more than 50% in stress corrosion resistance in a simulated SO2 polluted marine atmospheric environment. Microalloying of one element is carried out to improve properties of a rust layer on a surface of a HSLA steel in a marine environment and reduce a electrochemical activity in a local microenvironment to inhibit the anodic dissolution. Microalloying of another element is carried out to reduce a cathodic hydrogen evolution, to increase a hydrogen trap density and to decrease a multiplicative hydrogen diffusion channel density as well as enhance a hydrogen resistance of a structure to inhibit the hydrogen embrittlement.

What is claimed is: 
     
         1 . A binary alloy design method for a marine high-strength low-alloy (HSLA) stress corrosion-resistant steel, wherein a synergistic inhibition of an anodic dissolution and a hydrogen embrittlement is achieved by a binary alloying to prepare a 690 MPa marine HSLA stress corrosion-resistant steel, wherein the 690 MPa marine HSLA stress corrosion-resistant steel has an increase of more than 50% in a stress corrosion resistance in a simulated SO 2  polluted marine atmospheric environment. 
     
     
         2 . The binary alloy design method according to  claim 1 , wherein a first one of two alloying elements used in the binary alloying is one or more alloying elements for an alleviating enrichment of Cl −  in a rust layer and thus an induced acidification in a marine environment while reducing an electrochemical activity of a matrix in an acidic Cl − -containing environment, while a second one of the two alloying elements is one or more alloying elements for inhibiting a cathodic hydrogen evolution in the marine environment, forming irreversible hydrogen traps and improving a microstructure. 
     
     
         3 . The binary alloy design method according to  claim 2 , wherein the cathodic hydrogen evolution in the marine environment is inhibited by reducing an electric current density for an hydrogen evolution; the irreversible hydrogen traps are formed by increasing a hydrogen trap density in the marine HSLA stress corrosion-resistant steel; and the microstructure is improved by enhancing a hydrogen resistance at special interfaces. 
     
     
         4 . The binary alloy design method according to  claim 1 , wherein an alloying element for inhibiting the anodic dissolution is selected from the group consisting of P, Sb, Co, Cr, Ni, Cu, Mo, Re, Zr, Ca, Mg, and dispersive oxides of P, Sb, Co, Cr, Ni, Cu, Mo, Re, Zr, Ca, and Mg, and the alloying element for inhibiting the anodic dissolution is abbreviated as anti-corrosion element for short; and an alloying element for inhibiting the hydrogen embrittlement is selected from the group consisting of Nb, V, Ti, Zr, Re, Mo and W, and the alloying element for inhibiting the hydrogen embrittlement is abbreviated as anti-damage element for short. 
     
     
         5 . The binary alloy design method according to  claim 1 , wherein the marine HSLA stress corrosion-resistant steel is composed of following chemical elements in a mass percentage: C: 0.04%-0.08%, Si: 0.2%-0.3%, Mn: 1.45%-1.65%, P≤0.015%, S≤0.005%, Cr: 0.4%-0.5%, Cu: 0.25%-0.35%, Ni: 0.75%-0.85%, Ti: 0.005%-0.015%, Nb: 0.03%-0.06%, Sb: 0.05%-0.1%, and a balance of Fe. 
     
     
         6 . The binary alloy design method according to  claim 1 , wherein the marine HSLA stress corrosion-resistant steel is prepared specifically by the following steps:
 smelting and casting chemical components into a billet steel, heating the billet steel to an austenitizing temperature ranging from 1180 to 1220° C., holding the austenitizing temperature for 1.5-2.5 hours to homogenize the billet steel for a hot rolling;   controlling an initial rolling temperature within a range of 980-1020° C., carrying out a multi-pass rolling until a target steel plate thickness is obtained, and controlling a finishing rolling temperature within a range of 860-900° C.; after rolling, cooling in a laminar water flow zone at a cooling rate controlled within a range of 25-30° C./s to ensure the billet steel is at a temperature ranging from 420 to 440° C. when taken out of water; and   air-cooling to a room temperature to obtain a finished marine HSLA stress corrosion-resistant steel.   
     
     
         7 . The binary alloy design method according to  claim 6 , wherein a slow strain rate tensile test is conducted on the finished marine HSLA stress corrosion-resistant steel under following conditions: an SO 2  polluted marine atmospheric environment simulated by using 3.5 wt % NaCl+0.05 M NaHSO 3  with 100% humidity; an experimental temperature of the room temperature;
 and a slow strain tension rate of 0.5*10 −6  to 1.5*10 −6  S −1 .   
     
     
         8 . The binary alloy design method according to  claim 6 , wherein a loss of an elongation percentage and a loss of a section shrinkage percentage of the finished marine HSLA stress corrosion-resistant steel are calculated to evaluate a stress corrosion sensitivity of the finished marine HSLA stress corrosion-resistant steel in the simulated SO 2  polluted marine atmospheric environment. 
     
     
         9 . The binary alloy design method according to  claim 8 , wherein the loss of the elongation percentage of the finished marine HSLA stress corrosion-resistant steel is 11.05%-15.21%, while the loss of the section shrinkage percentage of the finished marine HSLA stress corrosion-resistant steel is 12.1%-14.33%, with a maximum decrease of approximate 60% in the stress corrosion sensitivity compared with a traditional HSLA stress corrosion-resistant steel. 
     
     
         10 . The binary alloy design method according to  claim 2 , wherein an alloying element for inhibiting the anodic dissolution is selected from the group consisting of P, Sb, Co, Cr, Ni, Cu, Mo, Re, Ca, Mg, and dispersive oxides of P, Sb, Co, Cr, Ni, Cu, Mo, Re, Zr, Ca, and Mg, and the alloying element for inhibiting the anodic dissolution is abbreviated as anti-corrosion element for short; and an alloying element for inhibiting the hydrogen embrittlement is selected from the group consisting of Nb, V, Ti, Zr, Re, Mo and W, and the alloying element for inhibiting the hydrogen embrittlement is abbreviated as anti-damage element for short. 
     
     
         11 . The binary alloy design method according to  claim 3 , wherein an alloying element for inhibiting the anodic dissolution is selected from the group consisting of P, Sb, Co, Cr, Ni, Cu, Mo, Re, Zr, Ca, Mg, and dispersive oxides of P, Sb, Co, Cr, Ni, Cu, Mo, Re, Zr, Ca, and Mg, and the alloying element for inhibiting the anodic dissolution is abbreviated as anti-corrosion element for short; and an alloying element for inhibiting the hydrogen embrittlement is selected from the group consisting of Nb, V, Ti, Zr, Re, Mo and W, and the alloying element for inhibiting the hydrogen embrittlement is abbreviated as anti-damage element for short.