H13模块退火组织均匀化热处理工艺试验研究

为改善H13模块退火组织均匀性，进行了高温固溶＋球化退火热处理试验研究，结果表明，该工艺可显著改善H13退火组织均匀性，并提高了H13模块的力学性能。     

H13钢带状偏析演化规律研究

 针对H13钢中普遍存在的带状偏析现象,利用金相显微镜及SEM研究了H13钢不同状态带状偏析的演化规律。研究结果表明,H13钢退火态的带状偏析由枝晶偏析的热变形引起,表现为碳化物的球化程度、颗粒大小及分布的不均匀;退火组织的不均匀性直接影响H13淬火、回火态的组织均匀性,且退火组织中金属元素分布的不均匀及偏析带中存在的一次液析共晶碳化物一直保留到钢的回火状态,影响了H13钢的等向性;良好的退火组织是制造高品质H13热作模具钢的关键因素。     

热作模具钢H13热处理技术研究

高温均质化、超细化处理是优质H13模块生产中的关键热处理技术。高温均质化处理可基本消除钢中的共晶碳化物，显著改善成分偏析；超细化处理可使H13组织得到细化，进一步提高性能均匀性。五钢新流程生产的P级H13(SWPH13)等向性明显改善，冲击韧性、热疲劳抗力显著提高。     

提高热作模具钢H13退火组织均匀性的措施

某特钢厂在高端热作模具钢H13生产过程中，在对其退火组织进行检测时，发现个别批次未能达到北美压铸协会NADCA#207-2003的要求，评级为AS10～AS13不合格级别，金相组织在显微镜下呈现不同程度网状和链状碳化物分布，组织均匀性也较差。较差组织易造成模具在使用过程中早期开裂，同时降低冲击韧性导致使用寿命缩短。为解决组织差问题，分析了退火组织异常的原因，并进行了针对性工艺优化。通过控制电渣冶炼熔速降低铸锭合金偏析，保证夹杂物充分上浮析出，提升铸锭纯净度；优化高温均质化均热段温度和时间，促进偏析元素快速溶解并重新均匀分布，改善带状偏析；超细化热处理工艺细化晶粒尺寸和实现均匀分布，提升晶界结合强度；控制锻造变形方式和终锻温度，对铸态组织进行破碎，实现细化晶粒，提高材料致密性；优化热处理冷却方式，进一步降低二次碳化物析出量及成链状网状概率等一系列措施，退火组织碳化物尺寸、分布和均匀性得到明显改善，合格率达到99%以上。     

热轧H13钢硬度不均匀性的分析

 对H13钢试样进行了退火试验,对退火前后试样进行了硬度测试及扫描电镜和能谱分析。分析了H13钢热轧材硬度不均匀性的形成原因。结果表明,低倍“黑斑”区域硬度平均值为91.43HRB,比正常区域高7.53%;“黑斑”区域主要由“白斑”和“黑色质点”组成,“白斑”化学成分主要是铁,“黑色质点”主要成分为合金碳化物;H13钢试样经退火后,原“黑斑”区域硬度明显降低,从190.2HB下降到168.26HB,退火后“黑色质点”尺寸变小,其碳质量分数大幅度降低,从80%下降到15%;H13钢热轧材硬度不均匀主要是由于钢液凝固过程中成分不均匀所致。     

电渣重熔速度对H13钢组织和冲击性能的影响

利用双极串联电极坯电渣重熔直径φ385mm H13钢锭,研究了快速重熔与慢速重熔对电渣锭的铸态组织、锻造成品的退火组织和冲击性能的影响。结果表明:快速重熔比慢速的电渣锭的二次枝晶间距大,并且一次碳化物等枝晶间显微偏析严重;慢速重熔的锻造成品的退火组织均匀和带状偏析减轻,横向冲击性能明显提高,达到NADCA207-90标准规定的优质H13钢的水平。     

锻造变形方式对H13钢退火组织和力学性能的影响

利用金相显微镜、扫描电镜等对不同锻造变形方式下H13钢的退火组织及力学性能进行了研究。结果表明:与"一镦一拔"工艺相比,采用"三镦三拔"工艺后,H13钢的带状偏析显著减轻;退火态碳化物尺寸更均匀、分布更弥散;调质态力学性能和等向性能显著提高;横向冲击功由6. 34 J增加至9. 06 J,横纵向冲击功比值由0. 84增加至0. 92,符合NADCA#207-2003标准中优质H13钢的性能要求。     

热作模具钢H13连轧材退火工艺研究

为满足用户对加工硬度的特殊需求(硬度≤220HBW),对热作模具钢H13连轧材进行了不同退火温度、保温时间和辊速下的退火试验,以确定最佳的退火工艺,并借助金相显微镜对最佳退火工艺下的H13退火态组织进行分析。结果表明:H13的退火硬度与退火温度、保温时间、辊速有关,退火温度越高、保温时间越长、辊速越慢,试样硬度越低。退火温度为840℃,保温时间为5~6h,辊速5.5m/h为最佳退火工艺,钢材平均硬度可以降到198HB左右,金相组织满足用户标准要求。     

高温扩散-超细化H13模具钢的组织和性能

测试和分析结果表明:非高温扩散-超细化的H13(4Cr5MoSiV1)钢材存在大块状的共晶碳化物,带状偏析严重,钢的横向冲击韧性较差;而经过合理的高温扩散和超细化处理的H13钢材,共晶碳化物基本消失,带状偏析和组织均匀性明显改善,显著提高钢的横向冲击韧性。     

1～2Cr13退火工艺操作与退火硬度的研究

通过对炉外机械化炉及连轧厂车底式退火炉1-2Cr13退火工艺操作及退火硬度的研究,及大量的退火试验工作,解决了攀长钢连轧厂车底式退火炉退火均匀性的问题,通过采取一系列措施来保证1~2Cr13退火硬度满足用户的需求。     

Influence of Thermal Homogenization Treatment on the Structure and Impact Toughness of H13 ESR Steel

 High levels of isotropy and homogeneous structure are very important criterion for high quality H13 hot work steel. In this paper, the cast microstructure of H13 ESR ingot and the influence of high temperature diffusion treatment on the structure and impact toughness have been investigated. The results show that: the dendrite arm spacing gradually becomes wide from the surface to the center of ingot and the interdendritic segregation areas always exist large primary carbides particles; by means of high temperature diffusion treatment of ingot prior to hot forging, the banded segregation is nearly eliminated, the annealed structure is more uniform and the isotropy properties have been improved remarkably.     

Influence of Thermal Homogenization Treatment on Structure and Impact Toughness of H13 ESR Steel

The as-cast microstrueture of H13 ESR ingot and the influence of high temperature diffusion treatment on the structure and impact toughness have been investigated. The results show that the dendrite arm spacing gradually becomes wide from the surface to the center of ingot, and the large primary carbide particles always exist in interdendritic segregation areas; by means of high temperature diffusion treatment of ingot prior to hot forging, the banded segregation is nearly eliminated, the annealed structure is more uniform and the isotropic properties have been improved remarkably.     

热处理工艺对SAE8620H低碳齿轮钢带状组织的影响

试验了由300mm×340mm连铸坯生产的SAE8620H齿轮钢(%:0.19C、0.48Cr、0.48Ni、0.18Mo、0.032Al)φ100mm轧材在热轧、完全退火(930℃1 h炉冷至650℃1 h空冷)以及等温退火(930℃1 h出炉快冷至650℃1 h空冷)3种状态下的的带状组织。结果表明,完全退火后轧材带状级别较热轧态高;因930～650℃快冷抑制先共析铁素体的析出,等温退火轧材带状级别较热轧态低1.0～1.5,显著改善了钢的带状组织。     

C-Curves of Tool Steels for Annealing and Their Application

C curvesoftoolsteelsareusuallyusedforquenching .Theaustenitizingtemperaturemeasuredishigherthanthatofsoften annealingwhichisslightlyaboveAc1,andtheformerissuitedforquenching[1,2 ] .Thekineticcurvesoftoolsteelsarenotusedastheparametersofsoften annealing .TTTdiagrams ,CCTdiagramsandcritical pointsofAmericantoolsteelsH13,S7,S5 ,D2andA6forannealingweremeasuredandinvestigatedbymeansoffull automaticdilatometerinordertomakean nealingtechnologyscientificandobtaineffectivesoftening .Anewsoften ann…     

Mechanism of Annealing Softening of Rolled or Forged Tool Steel

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Mass production of magnetocaloric LaFeMnSiB alloys with hydrogenation

LaFe_(11.39)Mn_(0.35)Si_(1.26)B_(0.1)Hxalloys were prepared by hydrogenation.Samples were annealed at 1343Kfor30-90 hto form the NaZn13 phase.La-rich andα-Fe secondary phases were also detected.Saturated hydrogenation at 553 Kand 0.15 MPa of H_2 pressure for 5hwas employed to improve the Curie temperature of the alloys to 279 K.The maximum magnetic entropy change,relative cooling power,and adiabatic temperature change of LaFe_(11.39)Mn_(0.35)Si_(1.26)B_(0.1)H_x annealed at 1343 Kfor 90hafter hydrogen absorption are 6.38J/(kg·K)(magnetic changesμ0ΔH =1.65T),100.1J/kg(μ0ΔH =1.65T),and 2.2 K(μ0ΔH =1.48T),respectively.Although the maximum magnetic entropy change of the LaFe_(11.39)Mn_(0.35)Si_(1.26)B_(0.1)H_x alloys is lower than those of similar alloys with high purity raw materials,the relative cooling power is nearly the same.The effect of impurities of the raw materials used was also discussed.It is assumed that the impurity of 0.2wt.% Al is responsible for the reduced entropy change of the resulted alloys.The LaFe_(11.39)Mn_(0.35)Si_(1.26)B_(0.1)H_x alloys prepared by this method could be a low cost alternative material for room temperature magnetic cooling applications.     

Microstructure and variable emittance property of annealed La-Sr-Mn-O films

The La-Sr-Mn-O films were deposited on Si(100) substrates by DC magnetron sputtering and followed by air annealing at 973 K for 1 h.The microstructure and temperature dependence of total hemispherical emittance ( H) of the annealed La-Sr-Mn-O films prepared at various processing parameters were investigated.The results indicated the films deposited at lower sputtering pressure and lower O2/(O2+Ar) volume proportion (RO) were present in rhombohedral perovskite structure and the length of Mn-O bond was shorter.The metal-insulator transition temperature (TMI) was higher.All of the annealed films showed the unique feature of variable emittance based on metal-insulator transition.The films showed low emittance at low temperature but high emittance at high temperature.Moreover,the H significantly changed in the vicinity of TMI.The variability of total hemispherical emittance (Δε) and the temperature range with obvious emittance change could be adjusted by changing the processing parameters.The Δεcould be 0.45 andΔε/ε355 ( 355 is the εH at 355K) exceeded 50% for the annealed La-Sr-Mn-O films.Therefore,the annealed La-Sr-Mn-O films showed much potential for thermal control applications as smart thermochro-mic variable emittance materials.     

Giant Magneto-Impedance Effect in Amorphous and Current Annealed Fe_(73.5)Cu_1Nb_3Si_( 13.5)B_9 Wire

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