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    T12A钢锉刀热处理工艺是什么样的?

    2018-10-25 08:50:17 无锡盛发地坪科技有限公司 阅读

    锉刀是一种多刃的切削工具,主要用于锉削硬度在18~58HRC范围内的金属材料,工作中常受到弯曲变形和冲击,因此要求锉刀在保证高耐磨性的同时还应具有一定的韧性。我国的锉刀有相当数量进入国际市场,由于质量不甚优良,其价格仅为国际名牌——美国双刀牌锉刀的1/8~1/5。尽管两者所用材料化学成分相近,但失效形式完全不同。双刀牌锉刀主要为正常磨损失效,国产锉刀则主要为断齿崩刃等非正常失效,寿命差距很大。为提高国产锉刀质量,首先对进口高寿命锉刀进行分析解剖,进而针对性地提出整改措施。
    File is a multi-edged cutting tool, mainly used for filing hardness in the range of 18 ~ 58HRC metal materials, work is often subject to bending deformation and impact, so the requirements of the file in order to ensure high wear resistance at the same time should have a certain degree of toughness. A considerable number of Chinese filings have entered the international market. Because of their poor quality, their prices are only one-eighth to one-fifth of those of the international famous brand, the American double-blade file. Although the chemical composition of the two materials is similar, their failure modes are completely different. The double-blade file is mainly normal wear failure, while the domestic file is mainly abnormal failure, such as broken teeth and broken edges, and the life gap is very big. In order to improve the quality of domestic file, firstly, the imported high-life file is analyzed and dissected, and then the rectification measures are put forward.
    1)双刀牌锉刀的质量分析。
    1) quality analysis of double tool file.
    ①化学成分。由表3-8可知,双刀锉刀与国产锉刀的化学成分相近,所用材料相当于国产T12A,不过微量元素有些差异。
    (1) chemical constituents. As can be seen from Table 3-8, the chemical composition of the double-blade file is similar to that of the domestic file, and the material used is equivalent to that of the domestic T12A, but there are some differences in trace elements.
    表3-8 锉刀用钢化学成分(质量分数) (%)
    Table 3-8 chemical composition (mass fraction) of file steel (%)
    锉刀用钢化学成分(质量分数)
    Chemical composition (mass fraction) of steel for file
    ②锉削试验。用8in细扁锉作试验,双刀牌锉刀的锉削达到一定次数后,锉削曲线呈平缓状,表明该锉刀持久性好,使用寿命长,在达到50万次时锉齿表面仍保持良好的锋利的状态。相反,国产锉刀锉削一般在达到30万次以后,断齿崩刃的现象就大量出现,不能继续使用。
    Filing test. The experiment with 8-minute thin flat file shows that the curve of the double-blade file is smooth after cutting for a certain number of times. It shows that the file has good durability and long service life, and the surface of the file teeth remains in a sharp state when it reaches 500,000 times. On the contrary, after 300,000 times of domestic filing, a large number of broken teeth and broken edges appear and can not be continued to use.
    ③组织形态及断口形貌。在双刀牌锉刀的显微组织中发现,碳化颗粒大小不均,相当数量的大颗粒碳化物均匀分布在组织中,且碳化物颗粒棱角钝化。在透射电镜下观察,基体组织为隐晶马氏体,其中有大量的板条马氏体。国产锉刀的显微组织是片状马氏体和弥散的碳化物小颗粒。
    (3) histomorphology and fracture morphology. In the microstructure of the double-blade file, it was found that the size of carbide particles was uneven, a considerable number of large particles of carbide were uniformly distributed in the microstructure, and the edges and corners of carbide particles were passivated. Under transmission electron microscope, the matrix structure is cryptocrystalline martensite, and there are many lath martensite. The microstructure of domestic files is lamellar martensite and dispersed carbide particles.
    ④质量分析。双刀牌锉刀和国产锉刀用材的化学成分相近,仅仅是组织结构的差异,即碳化物形状与基体组织的形态不同。双刀牌锉刀所获得的这种特殊组织结构,正是其质量好的主要原因。T12A钢是过共析高碳钢,脆性较大。常规的热处理都是以获得细小弥散的碳化物为目标,改善其韧性以得到强韧化效果。然而对这种特殊工作条件下工作的工件,耐磨性是第一位的,要得到良好的锉削性能,在组织中保持一定数量的大颗粒碳化物是很有效的方法。只是这样势必会使本来就很脆的材料的韧性进一步下降。因此,还必须通过热处理来获得韧性极好的板条马氏体并将碳化物颗粒的棱角钝化。
    (4) quality analysis. The chemical composition of the double-blade file is similar to that of the domestic file, but the difference of the structure is only the difference of the carbide shape and the matrix structure. The special structure of the double knives file is the main reason for its good quality. T12A steel is hypereutectoid high carbon steel with high brittleness. Conventional heat treatment aims to obtain fine dispersed carbides and improve their toughness in order to obtain strength and toughness. However, the abrasion resistance of the workpiece under this special working condition is the first. To obtain good filing performance, it is an effective method to keep a certain amount of large particles of carbide in the structure. Only in this way will the toughness of the material which is already fragile become lower. Therefore, the lath martensite with excellent toughness must be obtained by heat treatment and the edges and corners of carbide particles must be passivated.
    由上述分析可知,如果采用某种特殊的热处理方法,获得与双刀牌锉刀相近似的显微组织结构,必将使国产锉刀的使用寿命大大提高。
    It can be seen from the above analysis that if a special heat treatment method is adopted to obtain the microstructure similar to that of the double-blade file, the service life of the domestic file will be greatly improved.
    2)锉刀热处理工艺。
    2) file heat treatment process.
    ①预处理工艺。为了达到上述强韧化的效果,采用了如图3-5所示的两段等温球化退火工艺,改变了锉刀的原始组织状态。首先把钢加热至比Accm(820℃)稍高的840~850℃的高温,适当保温,使组织中只保留为数不多的碳化物颗粒,且奥氏体组织不均匀。然后进入第一阶段——球化退火阶段,在Ac1( 730℃)以上的等温阶段较短,不均匀奥氏体中未溶碳化物和高浓度碳偏聚区都将成为大颗粒碳化物萌生长大的核心。同时在周边组织中碳浓度降低,为淬火后得到板条马氏体做好组织准备。当进入第二阶段球化退火时,即在Ac1以下等温,碳化物进一步扩散、析出、聚集球化,使得大颗粒碳化物进一步球化长大,并新生许多弥散分布的小颗粒碳化物。这样就形成了一定数量的大颗粒碳化物及大量低碳的基体组织。这种先期的组织为最终热处理创造了良好的组织条件。
    (1) pretreatment process. In order to achieve the above strengthening and toughening effect, the two-stage isothermal spheroidizing annealing process as shown in Fig. 3-5 was adopted to change the original microstructure of the file. Firstly, the steel was heated to 840 ~ 850 C higher than that of Accm (820 C), so that only a few carbide particles were retained in the microstructure and the austenite structure was inhomogeneous. Then the first stage, spheroidizing annealing stage, is shorter than the isothermal stage above Ac1 (730 C). Undissolved carbide and high concentration carbon segregation zone in inhomogeneous austenite will become the core of large carbide sprouting and growth. At the same time, the carbon concentration in the surrounding tissues is reduced, so as to prepare the lath martensite after quenching. When entering the second stage of spheroidizing annealing, i.e. below Ac1, the carbide further diffuses, precipitates, aggregates and spheroidizes, resulting in further spheroidizing and growth of large particles of carbide, and the formation of many small particles of dispersed carbide. This resulted in the formation of a large number of large granular carbides and a large number of low carbon matrix structures. This pre organization creates a good organizational condition for final heat treatment.
    T12A钢两段球化退火工艺
    Two stage spheroidizing annealing process of T12A steel
    图3-5 T12A钢两段球化退火工艺
    Fig. 3-5 two stage spheroidizing annealing process for T12A steel
    ②最终热处理工艺。采用快速加热短时保温的热处理工艺。由于加热温度较低,保温时间短,碳化物颗粒大小不均,溶解速度不同,故得到成分极不均匀的奥氏体和一定数量的碳化物。淬火后组织结构与美国双刀牌锉刀相近,为一定数量的板条马氏体和较多的隐晶马氏体,碳化物大小不均,且棱角钝化。
    (2) the final heat treatment process. Heat treatment process with quick heating and short time insulation is adopted. Because the heating temperature is low, holding time is short, carbide particle size is uneven, dissolution rate is different, so a very uneven composition of austenite and a certain number of carbides. The microstructure after quenching is similar to that of American double-blade file. It is lath martensite and more cryptocrystalline martensite. The size of carbide is uneven and the edges and corners are passivated.
    国产T12A钢锉刀按上述工艺处理后,断口形貌与双刀牌锉刀相似,出现了大量的浅口韧窝和撕裂棱,而传统工艺处理的锉刀断口形貌基本为准解理和沿晶型。锉削试验都能达到50万次以上,达到双刀牌锉刀水平,失效形式为正常磨损失效,基本消除断齿、崩刃等非正常失效现象。
    The fracture morphology of T12A steel file made in China is similar to that of double-blade file. A large number of shallow dimples and tearing edges appear. However, the fracture morphology of T12A steel file treated by traditional process is quasi-cleavage and intergranular. Filing test can reach more than 500,000 times, reaching the level of double-blade file, the failure form is normal wear failure, basically eliminating abnormal failure such as tooth breakage, edge breakage and so on. 


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