Optimizing the production of steel with reduction by aluminum,in casting and rolling systems

Data on the metallurgical defects in pipe show that they may be due to nonmetallic oxide inclusions. Analysis of the formation of oxide inclusions from smelting to the continuous casting of steel shows that, in order to reduce the incidence of such defects, additional measures must be taken in the smelting and ladle treatment of the steel. Such measures reduce the content of oxide inclusions in the steel by half. The benefits of this approach are confirmed by the reduced rejection rate of the pipe on account of defects associated with the presence of nonmetallic inclusions.     

Removing oxide and sulfide inclusions from molten steel by filtration

On the basis of thermodynamic calculations indicating that rare-earth sulfide inclusions may form in molten nonalloyed structural steel, the influence of filtration on the content of sulfur, oxygen, and nonmetallic inclusions in the steel is investigated. It is found that filtration removes the oxide phase and oxygen from 30Л steel. There is no change in the content of sulfide inclusions and sulfur. Filtration of steel preliminarily treated with 0.05–0.30% rare-earth metals removes 10–60% of the sulfur. Metallographic data show that the content of both oxide and sulfide inclusions is reduced here. Gray impressions of filter templates show that the sulfur-bearing phase is removed by an adhesive mechanism: this phase adheres to the filter surface, forming continuous borders around it.     

Eliminating corrosive nonmetallic inclusions from pipe steel

Measures to optimize the production of corrosion-resistant steel have been introduced at OAO Severskii Trubnyi Zavod. They ensure that the steel’s content of corrosive nonmetallic inclusions of the first and second type is no more than 2 mm^?2. The measures were developed on the basis of research on the morphology and composition of nonmetallic inclusions and their formation and also current concepts regarding the formation and removal of corrosive nonmetallic inclusions.     

Evolution of MnS inclusions in Ti-bearing X80 pipeline steel

Studies show that manganese sulfide(MnS)inclusions in pipeline steel affect the lateral performance of steel in its rolling deformation,as well as the hydrogen-induced cracking and sulfide stress corrosion cracking resistance performance.To inhibit the precipitation of MnS and its effect on pipeline steel,a quenching experiment and a diffusion couple experiment,which investigated the evolution of MnS inclusions in Ti-bearing X80 pipeline steel,were conducted.The experimental results show that the transformation of the MnS inclusions during solidification is as follows:MnS→titanium sulfide(TiS)→Ti_4C_2S_2.The transition temperatures of MnS to TiS and TiS to Ti_4C_2S_2 are 1 673 and 1 273 K,respectively,and the overall size of the sulfide decreased as well.Thermodynamic calculation results confirm that the transition temperatures of MnS to TiS and TiS to Ti_4C_2S_2 are 1 623 and 1 203 K,respectively.When the sulfur content in the X80 pipeline steel is 0.001 5%,all the sulfur in the steel can be converted into Ti_4C_2S_2 with a titanium content of more than 0.02%.     

Production of continuous-cast pipe blank without large nonmetallic inclusions

The quality of metal in continuous-cast pipe blanks is investigated, for different steel-production technologies. The presence of large nonmetallic inclusions is largely due to disruptions in the continuouscasting technology. Other significant factors are nonoptimal modification of the nonmetallic inclusions and problems in ladle treatment. Measures ensuring acceptable content of nonmetallic inclusions are developed and tested.     

Q345B热轧带钢冷弯开裂成因分析

针对热连轧厂生产的Q345B冷弯型钢用钢带在生产矩形管过程中出现的焊缝开裂、热影响区压扁开裂和弯曲弧开裂问题,通过对Q345B带钢成分、组织、夹杂物、气体、硫偏析等检验、分析以及对焊接工艺研究,得出焊接工艺不合理是造成焊缝开裂和热影响区压扁开裂的主要原因;原料中夹杂物多、带钢中存在的孔洞(或微裂纹)是造成弯曲弧开裂的主要原因。通过改进焊接工艺、减少钢中硫含量和提高钙处理效果等提高了矩形管合格率。     

管线钢硫化物钙处理技术分析

在对管线钢中硫化物的作用进行综合分析的基础上,结合莱钢的生产实践,利用冶金热力学原理,分析计算了管线钢硫化物的钙处理工艺条件,并对管线钢中的夹杂物进行了检测分析。结果表明,莱钢生产管线钢时,大部分炉次精炼终点氧质量分数高于理论计算钙处理所需的目标氧质量分数3.42×10-6,钢中钙质量分数未达到理论计算钙硫平衡时所需的量,硫化物夹杂物变性并不完全,钢中存在MnS、MnS CaS复合夹杂物。     

Inclusions in commercial low and medium carbon ferromanganese

The microstructures of commercial low and medium carbon ferromanganese have been studied by optical microscopy and electron microprobe techniques. Element analysis and mapping have been performed on impurities in the matrix and nonmetallic inclusions present. The results show that the most common nonmetallic inclusion is managanese oxide, followed by complex compounds of managanese oxide, silicon oxide, and manganese sulfide. The different inclusions have been assessed according to the SS 111116 method. It follows that over 85 pct of the present nonmetallic inclusions are manganese oxides and that the amount of manganese oxide inclusions is inversely proportional to the carbon content in standard refined ferromanganese.     

Corrosive Damage Close to Nonmetallic Inclusions in Bearing Steels

The development of corrosive damage in bearing steels close to nonmetallic inclusions is analyzed. The influence of the chemical and mineralogical composition of the inclusions on their activity in corrosive media is studied.     

Technology for out-of-furnace treatment of steel with the use of a new deoxidizer

A technology has been proposed for obtaining rolled plates with the use of calcium carbide instead of vacuum degassing. The technology makes it possible to obtain steel that is equivalent to vacuum-degassed steel with respect to the composition and quantity of nonmetallic inclusions and the quality of the finished plates. It is shown that the use of calcium carbide reduces the content of nonmetallic inclusions by a factor of roughly 1.5 compared to use of the standard technology without vacuum degassing. The percentage of hot-rolled plates rejected for defects detected in ultrasonic tests is also decreased.     

钙处理对钢中非金属夹杂物变性效果分析

从VD钙处理前后非金属夹杂物的组成及尺寸的变化、钢中氧化物与硫化物夹杂变性效果的角度,对某钢厂管线钢的钙处理效果进行了研究.结果发现:经过VD钙处理后,钢水中的非金属夹杂物的尺寸进一步降低,夹杂物的类型也有所变化,脆性Al2O3夹杂与沿晶界分布的有害的MnS夹杂都得到不同程度的变性,但钢中的氧化物及硫化物夹杂均没有达到完全变性的要求.     

Mastering the Production of Rolled Products and Tubes of Steel 20-KSKh Guaranteed to Be Free of Corrosion-Active Nonmetallic Inclusions

Results obtained from comprehensive corrosion tests have established that in addition to limiting the content of corrosion-active nonmetallic inclusions in steel to make it resistant to corrosion, it is also desirable to restrict the steel's contents of sulfur, manganese, and silicon. The new specifications for steels 20-KS (corrosion-resistant) and 20-KSKh (corrosion- and cold-resistant) were therefore developed based on steel 20sp, which is distinguished by its relatively low contents of manganese and silicon. These steels also have a limited sulfur content, and they are microalloyed with niobium or vanadium to obtain a fine-grained structure. All the other indices of the steels meet the requirements of SNiP. Mastering the production of welded tubes made of steel 20-KSKh is an important step toward the goal of improving the durability of oil-field tubing in Western Siberia. Such tubes are the first type of tubular metal product that has been guaranteed to be clean with respect to corrosion-active nonmetallic inclusions, and guarantees of this kind are a prerequisite to ensuring that pipelines have satisfactory corrosion resistance and last for their normal service life. __________ Translated from Metallurg, No. 6, 43–48, June, 2005.     

Effect of the conditions of REM microalloying of steel on the corrosion activity of nonmetallic inclusions

Experimental heats of low-alloy steel are performed under various conditions of rare-earth metal microalloying and aluminum and calcium deoxidation. Electron-probe microanalysis of nonmetallic inclusions and a metallographic investigation of a metal are used to show that, when interacting with water, nonmetallic cerium oxide inclusions do not form hydrates and, correspondingly, are not aggressive. When aluminum, calcium, and cerium additions are sequentially introduced into a melt, a continuous cerium oxide shell forms on calcium aluminates, protects corrosive nonmetallic inclusions against interaction with water, and weakens local metal corrosion.     

管线管氢致开裂试样检测及分析

对管线管氢致开裂(HIC)试验后试样进行超声波探伤和金相分析。结果表明:HIC试验后未发现氢致裂纹缺陷,但超声波探伤可检测到大型B类夹杂物及表面氢鼓泡。本试验所取试样较大B类夹杂物出现在管体壁厚中心与外壁之间,可以大致推断较大B类夹杂位于原始铸坯1/2半径到表层细晶区之间,其成因与铸坯芯部成分偏析无关。氢鼓泡中有大颗粒状氧化镁及硫化钙夹杂,其余区域为铝酸钙夹杂,故夹杂物是形成氢鼓泡的诱因之一。     

Influence of sulfide inclusion on ductility and fracture behavior of resulfurized HY-80 steel

The influence of sulfide inclusions on the ductile fracture process of experimental HY-80 steels having graded sulfur levels from 50 to 500 ppm and heat-treated to different strength levels was studied with respect to mechanical properties, namely, tensile ductility and Charpy impact en-ergy. Sulfide inclusions are found to have deleterious effect on both axisymmetric ductility and Charpy impact properties, whereas the plane strain ductility was found to be less sensitive to sulfide inclusions. The effect of interaction between the inclusion and the matrix and the as-sociated stress strain distribution at the void nucleating sites, which control the fracture process by microvoid coalescence, were discussed in the light of various models to suggest a micro-mechanism of fracture. Other toughness parameters obtained from instrumented impact tests were evaluated and discussed as a function of sulfur content.     

Effect of a secondary metallurgy technology on the types of forming nonmetallic inclusions and the corrosion resistance of steel

The effect of a secondary metallurgy technology on the metal quality during the production of lowcarbon corrosion-resistant steels is estimated. The content of a modifier introduced is found to principally influence the types of inclusions and, via them, the corrosion resistance of parts from the metal subjected to deep refining from sulfur and nonmetallic inclusions.     

Production of corrosion-resistant 09ГСФ steel

New production technology for low-alloy 09ГСФ steel for rolled sheet resistant to hydrogen-sulfide corrosion is described. The quantity of modifier introduced determines the impurity content of the metal after deep refining to remove sulfur and nonmetallic inclusions, the types of inclusions formed, and hence the resistance of the metal to corrosion cracking. Row inclusions formed in the sheet after nonoptimal ladle treatment of the steel are mainly responsible for the impairment of corrosion resistance.     

Increasing the quality of forged ingots via thermal shielding of ingot molds

Thermal shielding of the top one-third of the ingot mold intended for 58-t ingots by a cap-thermos is tested. An increase in the ingot solidification time weakens the development of defects revealed by ultrasonic inspection in the near-sinkhead zone; favors the removal of large nonmetallic inclusions in the axial part of the ingot; weakens the sulfur, carbon, and phosphorus segregation; and excludes the rejection of roll billets in these defects.     

Effect of liquid–solid pouring on the as-cast structure and the distribution of nonmetallic inclusions in a 24.2-t steel 38KhN3MFA ingot

The primary dendrite structure and the distribution of nonmetallic inclusions in large-scale 24.2-t forging ingots of 38KhN3MFA steel cast by a standard technology and with the inoculation of a metallic stream are studied. The dendrite parameter in the inoculated ingot is found to be significantly smaller than that in the usual ingot. Therefore, the solidification process in the inoculated ingot should be faster than that in the usual ingot. This is confirmed by a more homogeneous dendrite structure of the inoculated ingot. The estimation of contamination with nonmetallic inclusions shows that nonmetallic inclusions in the ingots under comparison are of the same type, and among them are oxides, sulfides and oxysulfides. The study of the distribution of nonmetallic inclusions shows that the ingots to be compared are mainly contaminated with oxysulfide nonmetallic inclusions, and the contents of oxide and sulfide nonmetallic inclusions are minimal. The experimental ingot has lower total contamination with nonmetallic inclusions than that of the reference ingot. In this case, the inoculators having formed from a metallic melt stream do not favor an increase in the contamination of steel with nonmetallic (among them are oxide) inclusions. The study of the structure of large metal volumes shows that the inoculation of the stream is accompanied by an increase in the number of metallic droplets, which transform into solid particles in flight and increase the solidification rate when reach a solidifying ingot. This process suppresses the development of segregation phenomena in the cast metal and decreases the chemical and physical heterogeneities.     

Interaction of metal matrix with nonmetallic inclusions in rail steel

The stress at the boundary between nonmetallic oxide inclusions and the matrix may be calculated, for different loads, by simulation of the system consisting of the matrix and inclusions. On that basis, the nonmetallic inclusions may be ranked in terms of the risk of contact-fatigue defects. The phase composition and geometry of the nonmetallic inclusions in rail steel are determined by the reduction of the rail steel and are extremely important for high rail performance.