Atmospheric Corrosion Monitoring of Field-exposed Q235B and T91 Steels in Zhoushan Offshore Environment Using Electrochemical Probes

This work aimed to in-situ monitor the atmospheric corrosion of steels exposed to Zhoushan offshore environment by using electrochemical noise（EN） technique. A portable EN monitoring system was established and two electrochemical probes（named as Q235 B and T91） were designed. Experimental results indicated that the noise resistance of T91 steel was higher than that of Q235 B steel, revealing that the corrosion resistance of T91 was higher than that of Q235 B. A 60-day monitoring result indicated that the noise resistance was well correlated with the weight loss data. Wavelet analyses results of EN data indicated that Q235 B underwent uniform corrosion and T91 suffered from localized corrosion, which was further confirmed by the surface observation. It is concluded that EN can be used as a new method to identify the corrosion form and corrosion resistance in atmospheric conditions.

Effect of Rare Earth (Niobium) on Costed and Hot-Rolled Microstructure and Properties of Heavy Rail Steels

A compared investigation was made on the microstructure and mechanical properties of continuous casting square blanks of BNbRE and U71Mn heavy rail steels having eutectoid composition. The variation of solidified structure of the square blanks was demonstrated by measuring hardness. The observation to the structure and inclusions in the head, waist and base of the hot-rolled rails of the test steels were carried out with optical microscope and SEM. It is found that the casting blanks of both tested steels compose of three areas with constant hardness and three hardness varying areas, and there is considerable P-eutectic structure in the blank of the U71Mn steel. The distribution of the inclusions in the UT1Mn steel rail is mainly oxides in both rail head and rail base, and is mainly MnS in the waist of the rail. There has strong effect of the addition of rare earth elements on them. The discussion on these results was made.

Internal Friction and Profile of Property and Structure of PD_3 and PD_3RE Rail Steels

The profile of both hardness and microstructure of continuous casting blanks and rails of PD3 heavy rail steel and PD3RE steel containing small amount of rare earth （RE） added from tundish were studied. It is found that the addition of RE makes the fluctuation of the hardness value decrease, and inhibits effectively and/or even removes lower hardness value（zone） in the centric area of the blank with a cross section of 280 mm × 380 mm, and that the surface layer in the rail head of PD3RE steel is obviously hardened and the reason causing this hardening is due to the thinning of the pearlite structure. The metallographic observation shows that there exists a Fe-P（C） eutectic structure in the blank center of the PD3 steel containing only 0. 016% P, while the addition of RE can fully inhibit this structure.

Prevention of halfway cracks in continuous cast A36 steel slabs containing boron

The formation of halfway cracks in continuous cast A36 steel slabs containing 17 ppm boron was studied by investigating the zero ductility temperature(ZDT), zero strength temperature(ZST), solidification characteristics, and strain distribution in the steels. Results show that the formation of halfway cracks in A36-B slab is attributed to the increase in both the internal crack susceptibility(ZDT and ZST) of the steel and the external tensile strain at the solidification front. The ZST of both steels with(A36-B) and without(A36) boron addition is nearly the same, but the ZDT of A36-B steel is found 50 oC lower due to a considerable increase of boron content at the final stage of solidification. The decrease of ZDT enlarges the solidification cracking susceptibility zone and results in the A36-B steel being more prone to cracking. In addition, during the unbending segments, a large tensile strain, resulting from the unbending process and the misalignment deviation of supporting rolls, occurs in the upper part of the solidified shell, which is another reason causing halfway cracks in A36-B slab. By decreasing the P and S content to be less than 50 ppm and 150 ppm, respectively, controlling B content in the range of 10 to 15 ppm, increasing the secondary cooling specific water ratio from 0.76 to 0.85 L·kg-1, and restricting roll alignment deviation to less than plus or minus 0.3 mm, halfway cracks in the boron containing slab are almost eliminated.

Enhancing the Stability of Passive Film on 304 SS by Chemical Modification in Alkaline Phosphate–Molybdate Solutions

The purpose of this work was to enhance the corrosion resistance of the passive fi lm on 304 stainless steel(SS)by chemical modifi cation in alkaline phosphate–molybdate solutions.The 304 SS was passivated in both phosphate and phosphate–molybdate mixed solutions to investigate the eff ect of molybdate on its corrosion resistance.The experimental results indicated that the passive fi lm showed better corrosion resistance in Cl?-containing solutions after modifi cation in phosphate–molybdate solutions than in phosphate-only solutions.Energy-dispersive spectroscopy analyses revealed that the passive fi lm formed in phosphate–molybdate solutions contained Mo and P after modifi cation,which is the reason for the enhanced corrosion resistance.

Properties of Fe-20Cr-4Al-Y Alloys

1. Introduction Light rare earth addition can remarkablyenhance the service life of Fe-Cr-Al alloyfor electrical heating element, but itscontent in the alloy must be controlledbelow the level of 0.1 wt-%. When thecontent exceeds that, the performance

Electrochemical measurements used for assessment of corrosion and protection of metallic materials in the field:A critical review

Corrosion degradation is detrimental to metal structures as it shortens their lifetime and leads to huge economic losses and unexpected disasters.Therefore,the detection and monitoring of corrosion degradation is of great importance.Herein,we briefly review the state-of-the-art electrochemical methods,instrumentation(based on virtual instrumentation),and advanced sensor/probes that are used in the field for the assessment of corrosion damage.Typical corrosion monitoring results,some of which have been obtained at Tianjin University in the past 30 years,for metallic materials and organic coating/metal systems in atmospheric,marine,and soil conditions in the field are presented.Detection methods,data analysis,and theoretical and mathematical models regarding each corrosion system are discussed,and the challenges,problems and possible solutions for each case are suggested.Lastly,future developments,such as wireless,intelligent,and automatic electrochemical measurement,that will augment the present electrochemical methods of evaluating corrosion degradation are summarized.

Multi-boiler System Optimization in Integrated Steelworks Based on Decomposition and Coordination Method

As for the existing problems of boilers in integrated steelworks, the multi-boiler system could be quantitatively optimized with the decomposition and coordination method. Then, case studies were carried out based on the data of an integrated steelworks. Two groups of actual production records were contrastively analyzed, and the calculation results from the optimized program of these two groups indicated that for groups 1 and 2, the costs fall by 5.06% and 3.79%and the fuel consumptions decrease by 2.72% and 1.45%, respectively, compared with the actual data. To analyze the cost and fuel consumption change under the same condition of total load demand, assigned fuel consumption and water temperature, five sets of data were selected for further analysis. It was shown that the total cost and fuel consumption of the optimized program could fall by 3.5% and 1.6% respectively, compared with the actual production records. The optimal allocation significantly contributed to energy conservation and cost reduction. The effects of the system energy conservation cannot be realized by single equipment energy conservation. They were complementary to each other, and should be put on the same stage.