偏析

　　鋼中化學(xué)成分與雜質(zhì)漫衍的不勻稱征象，稱為偏析。普通將高于平衡成分者，稱為正偏析，低于平衡成分者，稱為負(fù)偏析。尚有宏觀偏析，如區(qū)域偏析與微觀偏析，如枝晶偏析，晶間偏析之分。

　　大鍛件中的偏析與鋼錠偏析親切相關(guān)，而鋼錠偏析程度又與鋼種、錠型、冶煉質(zhì)量及澆注條件等有關(guān)。合金元素、雜質(zhì)含量、鋼中氣體均加劇偏析的開(kāi)展。鋼錠愈大，澆注溫度愈高，澆注速率愈快，偏析程度愈緊張。

　?。?）區(qū)域偏析  屬于宏觀偏析，是由鋼液在凝集歷程中選定結(jié)晶，溶解度變更和比重迥異惹起的。

　　對(duì)策是：

　　1）低落鋼中硫、磷等偏析元素和善體的含量，如接納爐外精煉，真空碳脫氧（VCD）處理及錠底吹氬工藝。

　　 2）接納多爐合澆、冒口補(bǔ)澆、振動(dòng)澆注及發(fā)燒絕熱冒口，加強(qiáng)冒口補(bǔ)縮才氣等措施。

　　3）嚴(yán)酷控制注溫與注速，接納短粗錠型，改善結(jié)晶條件。

　　 （2）枝晶偏析  屬于微觀偏析。樹(shù)枝狀結(jié)晶與晶間微區(qū)成分的不勻稱性，大概惹起構(gòu)造性能的不勻稱漫衍。接納掃描電鏡（SEM）、波譜儀（WDS）、能譜儀（EDS）進(jìn)行微區(qū)調(diào)查和成分說(shuō)明能夠檢出并闡明緣故，普通經(jīng)歷高溫分散加熱，鍛壓合理變形與勻稱化熱處理能夠消除或減輕其不良影響。

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Segregation

The uneven sign of chemical composition and impurity diffusion in steel is called segregation. Ordinary will be higher than the balance component, called positive segregation, lower than the balance component, called negative segregation. There are still macro segregation, such as regional segregation and microsegregation, such as dendrite segregation, intergranular segregation.

Segregation in large forgings is closely related to segregation of steel ingots, and the degree of segregation of steel ingots is related to steel grade, ingot type, smelting quality and casting conditions. Alloying elements, impurity content, and gas in steel all exacerbate the development of segregation. The larger the ingot, the higher the pouring temperature, the faster the casting rate, and the more segregation.

(1) Regional segregation It is a macrosegregation, which is caused by the selection of crystals in the agglomeration process of molten steel, the change in solubility and the difference in specific gravity.

The countermeasures are:

1) The content of segregation elements and good bodies such as sulfur and phosphorus in low steel, such as refining outside the furnace, vacuum carbon deoxidation (VCD) treatment and ingot bottom blowing argon.

2) Accept multi-furnace pouring, riser refilling, vibrating pouring and heat-insulating riser, and strengthen measures such as feeding and refining.

3) Strictly control the temperature injection and injection speed, accept short and thick ingot type, and improve crystallization conditions.

(2) Dendritic segregation belongs to microsegregation. The unevenness of dendritic crystals and the intergranular micro-area components probably cause the uneven distribution of structural properties. Acceptance of scanning electron microscopy (SEM), spectrometer (WDS), energy spectrometer (EDS) for micro-area investigation and composition description can detect and clarify the reason, ordinary experience high temperature dispersion heating, forging reasonable deformation and uniform heat treatment can eliminate or reduce Its adverse effects.