【正文】 , where special carbides begin to develop, is there a deviation from the linear relationship. Of course, these processes affect the boundary zones first, where conditions are favorable for the formation of carbide phase due to the geometric imperfection of the crystal structure. It can be assumed that the Tso peak is due to a change in the condition of the boundaries. This assumption is confirmed by the results of electron microscopic analysis: The condition of the matrix (dislocation density, size of fragments), causing an increase in the strength of the material [8, 9], remains unchanged up to Ttemper = 600 176。 for 10 h the overall character of the dislocation arrays and the fragmentation of the crystals are retained. The average size of the laths (width and length)and the average size of the colonies remain unchanged. The only noticeable change is the precipitation of finely dispersed carbide phases. The size of the particles is 150200 A and the average density ~1015cm2. They are precipitated on dislocations and evently distributed through the bulk of the martensite laths. Larger precipitates with the shape of needles (platelets) ~250 A in diameter and ~2 10 176。 on five samples 3 mm in diameter. Figure 1 shows the variation of the mechanical properties of heat 1 with the tempering temperature. The mechanical properties of this heat are almost constant after tempering at 100600 176。該峰的高度和回火溫度也相應(yīng)增加時，幾乎線性釩濃度從 0提高到 ％，但他們是在 ％的磷濃度限制 下表現(xiàn)出來的 。 在二次硬化溫度 時， 很可能 最大程度的 削弱 碳化物與基體或與 沉淀、 連貫的最大密度 的邊界， .。這也證實了結(jié)構(gòu)進行檢查和對回火溫度與屈服強度的變化。 脆化可能是由于 體積 和邊界的影響。隨著他們有更大的圓形沉淀 ? 2?103 A位于邊界的十字路口。這些沉淀在混亂通過板條馬氏體 空間 分布。 淬火后的結(jié)構(gòu)由 帶有位錯的 板條馬氏 體 組成 。當釩濃度變化從 0到 ％的高峰上升％ 60 176。如同淬火條件對 峰值 相比增加了 100 ℃ 。 拉伸強度 通過 5個直徑 為 3毫米 的 樣品確定的為 20176。 釩 被 添加到在一個重達 16公斤 的 鑄塊 中 ， 它被鍛造、 軋制 成 10毫米厚的 金屬板 。 在這項工作的關(guān)注 是 淬火鉻鉬合金，以防止在釩和磷的含量 RTB的鋼回火脆化。 脆 性是從 Tso 和 Ttemper變 化中來 確定 ， Ttemper是淬火鋼 的 回火溫度 ， Tso是韌 脆轉(zhuǎn)變溫度，它具有 最完整的脆化特征。 更改影響 回火 鋼的穩(wěn)定的情況下釩濃度 ，因為不含 釩 的 鋼的強度 會 下 降 至 約 500 176。在 730 ℃ 后的 Tso鍛煉價值 與熱 27（ 110至 130 176。 在 回火 期間的 鋼的力學(xué)性能改變顯然取決于精細結(jié)構(gòu)的變化。木板條的平均大?。▽挾群烷L度） 它 的平均規(guī)模保持不變。單元格的平均規(guī)模為 ? 。 因此，氫脆回火過程中鉻鉬釩鋼，作為對 Tso與 Ttemper出現(xiàn)明顯的高峰表現(xiàn)，從我們的實驗結(jié)果?？梢栽O(shè)想， Tso峰 值 是由于在邊界條件的變化。 這 原種影響的理 可以概括介紹如下 ， 隨回火溫度 的增加 滲碳 體 開始凝聚，在 250350℃開始沉淀 。 15Kh3MFA類型的鋼都容易脆化，在給定的回火溫度 下 達到高峰。 (1 h). Samples were prepared from the plates after quenching and after tempering at 100760 176。. As pared with the quenched condition the increase of Tso at the peak is 100 176。. Comparing heats 1 and 3, 6, differing in their metallurgical prehistory but similar in vanadium content (~%), one can see that the increase of Tso in the region of the peak is almost the same as for the quenched condition. In amounts of and %, phosphorus has no effect on Tso after the heat treatments tested. The changes in the mechanical properties of the steel during tempering evidently depend on changes in fine structure. Figure 3 shows the microstructure of heat in the quenched condition, after tempering at 600 176。 the quantity of Fe3C carbide gradually decreases and the quantity of M7C3 increases. The concentration of strong carbideforming elements in the residues increases: Cr, Mo, and V. This process is particularly well developed at 500600 176。, especially MC3 [8]. Precipitating evenly throughout the volume on disloca tions, lowangle boundaries of martensite laths, and highangle boundaries of colonies of laths, they strengthen the matrix and weaken (embrittle) the boundaries. It is probable that the boundaries are weakened most with the maximum density of carbides coherent with the matrix or with their precipitation, ., at secondary hardening temperatures. Such elements as vanadium, promoting refi