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Defects Caused by Medium Manganese Anti-wear Ductile Iron Castings and Analysis and Prevention

来源: 编辑 浏览次数:1360 Release date: 2019-06-06 Source: Edit Views: 1360
般缺陷外,还有碳化物量过高或连续网状分布、索氏体量和奥氏体量过高等。 In the production of middle manganese anti-wear nodular cast iron parts, in addition to the common defects of gray cast iron and nodular cast iron parts , there are also excessive levels of carbides or continuous network distribution, soxite and austenite. The amount is too high. Si/Mn 比的选择问题,有时还有造型制芯、熔炼浇注、配砂质量、落砂清理等许多生产工序的问题,因此必须具体分析,以便采取相应的合理措施加以解决。 In general, the reasons for these defects are not only the selection of the Si / Mn ratio in the chemical composition , but also the problems of many production processes such as core molding, smelting and pouring, sand distribution quality, and falling sand cleaning. Take appropriate reasonable measures to solve it.

( 包括球化处理方面 的)外,属于中锰抗磨球墨铸铁件特有的一些缺陷及其原因分析与防止方法可参见如下。 In the production of medium manganese anti-wear nodular cast iron parts, in addition to the common general ( including nodularization ), some defects unique to medium manganese anti-wear nodular cast iron parts and their causes analysis and prevention methods can be found below.

Carbide excessive or continuous network distribution

: Features :

脆性大、冲击韧度 α k 4.0J/cm 2 1. High brittleness, impact toughness α k 4.0J / cm 2

试片断口齐平,颜色灰白,或者白而发亮 2. The test piece is flush, the color is gray, or white and shiny                               

三角试片白口过大 3. Triangular test piece is too white

: Cause analysis :

低或 Mn 是过高 1.Si/Mn is low or Mn is too high

冷却速度过快,或打箱太早 2. The cooling speed is too fast, or the boxing is too early

残留量 )>0.1% 或球化剂加入最过多 3.ω (RE + Mg residual amount )> 0.1%

孕育剂加入量不够或效果不佳 4. Insufficient amount of inoculant or poor effect

碳化物的质量分数 >40% 5.Carbide mass fraction > 40%

: Prevention method :

进行护前快速分析,正确控制 Si Mn 含量 1. Perform fast analysis before protection to control Si and Mn content correctly

控制球化剂加入量,在保证球化的前提下,尽量减少球化剂加入量 2. Control the amount of spheroidizing agent, and minimize the amount of spheroidizing agent under the premise of ensuring spheroidization

球化剂加入量过多时,应及时补加原铁液。 3. When the amount of nodulizer is too much, the original molten iron should be added in time. 10%-15% ,原铁液可使白口宽度减少 1-2mm Generally add 10% -15% , the original molten iron can reduce the white mouth width by 1-2mm

减少 RE+Mg 残留量中的 RE 量,使 RE 4. Reduce the amount of RE in the RE + Mg residue to make RE

适当增加 Si量 Si/Mn 5. Properly increase the amount of Si or Si / Mn ratio

加强孕育,增加一次孕育量和进行二次孕育或瞬时孕育 6. Strengthen the pregnancy, increase the amount of one pregnancy and carry out the second or instant pregnancy

炉前补加质量分数 0.2%~0.3% FeSi75 可降低三角试片白口宽度 1-2mm 7.Adding FeSi75 with a mass fraction of 0.2% ~ 0.3% before the furnace can reduce the white mouth width of the triangle test piece by 1-2mm

减少冷却速度,提高金属型顶热温度,采用隔热涂料 8. Reduce the cooling rate, increase the top temperature of the metal mold, and use thermal insulation coating

 

Excessive amount of sorbite or austenite

: Features :

冲击韧度 α k 和硬度 HRC 1. Low impact toughness α k and hardness HRC

脆性增加,抗磨性能不好 2. Increased brittleness and poor abrasion resistance

试片断口呈深灰色,敲击声发哑 3. The mouth of the test piece is dark gray, and the percussion sound is dumb.

: Cause analysis :

800~500冷却过程中冷却速度太低。 1. The cooling rate is too low during the 800 ~ 500cooling process. φ>40% Austenite is easy to be transformed into sorbite, tobite, and the amount of sorbite is φ> 40%

过大, Si 量过高,共析转变温度区扩大,有利于形成索氏体 2.Si/Mn is too large, the amount of Si is too high, and the eutectoid transformation temperature zone is enlarged, which is beneficial to the formation of sorbite

量过高,或者 Si/Mn 太小,共析温度低下,奥氏体量过多( φ 50% 3. The Mn content is too high, or the Si / Mn is too small, the eutectic temperature is low, and the amount of austenite is too large ( φ > 50% )

: Prevention method :

控制冷却速度, ω Si 3.4%~4.5% ω Mn 5.5%~6.5% 时,在 750~500范围内。 1. Control the cooling rate, ω Si 3.4% ~ 4.5% , ω Mn 5.5% ~ 6.5% , in the range of 750 ~ 500. >20/min ,控翻在 18~36/min 为宜。 The cooling rate should be > 20/ min , and it is better to control the temperature at 18 ~ 36/ min ./min 易产生索氏体。 <18/ min is easy to produce sorbite./min 易形成奥氏体 > 36/ min easy to form austenite

根据铸件壁厚、铸型工艺等影响冷却速度的因素,选择合适的 Si/Mn 控制奥氏体转变成索氏体的数量。 2. According to the casting wall thickness, casting process and other factors that affect the cooling rate, select the appropriate Si / Mn to control the amount of austenite to solute. Si/Mn 0.6 时即 Si Mn 高,奥氏体量增多, Si/Mn 0.75 时。 Generally, when Si / Mn < 0.6 , Si is low and Mn is high, and the amount of austenite increases, and when Si / Mn > 0.75 . Si Mn 低,索氏体量增高,在冷却速度一定条件下, Si/Mn 是控制奥氏体和索氏体 t 的重要手段 That is, Si is high, Mn is low, and the amount of solute is increased. Under a certain cooling rate, Si / Mn is an important means for controlling austenite and solute.

Stomata, slag inclusion, shrinkage

: Features :

铸件产生皮下气孔 1. Casting produces subcutaneous pores

铸件内部有集中或分散气孔 2.There are concentrated or dispersed pores in the casting

冒口下或周围出现集中或分散性气孔或缩孔且深浅不一 3. Concentrated or dispersive pores or shrinkage pores appear under and around the riser and vary in depth

铸件内或热节处产生密集蜂窝状气孔 4.Dense honeycomb pores are produced in the casting or at the hot junction

: Cause analysis :

出温度低于 1400浇注温度过低 1. Out temperature is lower than 1400 ℃. Pouring temperature is too low.

球化反应不充分,搅拌扒渣不够 2. Insufficient spheroidization reaction and insufficient slag stirring

渣气孔层取样分析结果 ( 质量分数 ) 如下 :C4.98% Mn4.67% P0.088% S0.128% RExOy:0.663% Mg0.203% 3. Slag gas pore layer sampling analysis results ( mass fraction ) are as follows : C4.98% , Mn4.67% , P0.088% , S0.128% , RExOy: 0.663% , Mg0.203% .

: 渣气孔主要是稀土镁的氧化物和石墨,当铁液温度低或浇注温度过低,此类夹渣不易排出 Analysis shows that the slag pores are mainly rare earth magnesium oxides and graphite. When the temperature of the molten iron is low or the pouring temperature is too low, such slag inclusions are not easy to discharge

: Prevention method :

提高出铁温度,出铁槽中铁液温度应 >14501. Increase the tapping temperature. The temperature of the molten iron in the tapping tank should be > 1450 ℃.

采用半封闭式浇注系统直浇道断面:横浇道断面:溢流口:内浇道 =1.2:2:1=1.4 2.Semi -closed pouring system adopts direct runner section: cross runner section: overflow port: inner runner = 1.2: 2: 1 = 1.4 . > 溢流口有利于缓流。 Sprue > overflow port is good for slow flow. < 横浇道有利于撇渣。 Overflow port < horizontal runner is favorable for skimming. Inner gate overflow opening facilitates exhaust

炉前球化处理后,加人冰晶石( NaAlF 2 ) 3. After the spheroidizing treatment in front of the furnace, add cryolite ( NaAlF 2 ) . MgS 化合成低溶点易凝聚的MgF 2Na 2 SNaO 等化合物,从溶渣中排出。 It is easy to chemically synthesize MgF 2 , Na 2 S , NaO and other compounds with low melting point and easily agglomerate with MgS , and is discharged from the molten residue. After adding cryolite, it should be allowed to stand, which is conducive to the above reaction to fully proceed

金属型需预热至 200~300时浇注,刷涂料要及时烤干。 4. The metal type should be poured when it is preheated to 200 ~ 300, and the paint should be baked in time. <4%( 质量分教 ) Moisture of molding sand should be <4% when molding wet sand ( quality education )

厚大铸件浇注应采用一快、二慢、三冲。 5. For thick and large castings, one fast, two slow and three punches should be used. Small and medium pieces use one fast and two slow pouring methods


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