Elimination of cracks in stainless steel casings via 3D printed sand molds with an internal topology structure

The important supporting component in a gas turbine is the casing,which has the characteristics of large size,complex structure,and thin wall.In the context of existing 3DP sand casting processes,casting crack defects are prone to occur.This leads to an increase in the scrap rate of casings,causing significant resource wastage.Additionally,the presence of cracks poses a significant safety hazard after the casings are put into service.The generation of different types of crack defects in stainless steel casings is closely related to casting stress and the high-temperature concession of the sand mold.Therefore,the types and causes of cracks in stainless steel casing products,based on their structural characteristics,were systematically analyzed.Various sand molds with different internal topology designs were printed using the 3DP technology to investigate the impact of sand mold structures on high-temperature concession.The optimal sand mold structure was used to cast casings,and the crack suppression effect was verified by analyzing its eddy current testing results.The experimental results indicate that the skeleton structure has an excellent effect on suppressing cracks in the casing.This research holds important theoretical and engineering significance in improving the quality of casing castings and reducing production costs.

Insulation effect of air cavity in sand mold using 3D printing technology

The insulation effect of the air cavity surrounding the riser in a 3D printed sand mold was studied. The influence of the air cavity on heat flux was theoretically analyzed. The results demonstrated that the heat flux of the air cavity in the 3D printed sand mold was significantly less than that of resin-bonded sand. The insulation effect of the air cavity in sand molds for a cylinder casting and a stress-frame casting were simulated using software COMSOL. The results illustrated that the air cavity could be used to insulate the riser and it was more suitable for a lower melting point metal casting. An air cavity with 10-15 mm width and 5-10 mm away from the riser can significantly prolong the solidification of the riser by over 10%. Meanwhile, the sand mold for the stressframe was made by 3D printing technology and poured with aluminum alloy A356 melt. The experiment results showed that the presence of the air cavity led to a 12.5% increase of the solidification time of its riser.

砂型3D打印材料在岩体物理模型试验中的应用研究及展望

无法获得内部结构高度一致的岩体试样以及预制缺陷制作困难一直是岩石室内物理试验中面临的关键问题。3D打印技术作为近年来快速发展的先进制造技术,可以作为有效方法实现对复杂结构的制备,目前已经有众多研究学者将其应用于岩石室内物理试验中。为了寻求最接近于天然岩石细微观结构特征以及脆性特征的3D打印类岩石模型,相关学者采用了砂型材料对类岩石模型进行打印以达到代替天然岩石进行试验的目的,相关研究成果证实砂型3D打印材料具有与天然岩石材料相似的脆性特征、表面粗糙度特征、细微观结构特征、裂纹扩展规律等,为砂型3D打印类岩石模型开展岩石室内物理试验奠定了基础。基于此,根据近年来国内外相关研究以及本课题组近六年的研究成果,对基于砂型3D打印材料的岩体模型在岩石室内试验中的研究成果进行了总结分析,指出了现有研究存在的问题和局限性,并对未来砂型3D打印材料应用于岩石室内物理试验中的前景进行了展望。

水基涂料涂覆工艺对3D打印砂型表面质量影响的研究

以涂料波美度、单次浸涂时间、浸涂次数等工艺参数为影响因素,设计了水基涂料浸涂正交试验,研究了以上因素对3D打印砂型表面粗糙度、涂料层厚度以及涂料层厚度均匀度的影响,得到水基涂料浸涂最佳工艺。采用该工艺,涂层表面粗糙度可以达到Ra3.2~Ra6.3,涂层厚度0.3~0.35 mm,且涂层均匀度好。实际验证铸件表面粗糙度可以达到Ra6.3。

基于砂型3D打印技术的壳体低压铸造工艺开发与验证

壳体型腔复杂且壁薄,采用传统工艺不仅造型困难,而且从模具设计到整体铸造工艺开发与验证,所用周期长、效率低,生产成本高。基于砂型3D打印技术快速制样优势,本文对壳体浇注系统采用随形设计方案,实现了型腔、叶片一体化结构成形制造,结合数值仿真计算分析,对浇注工艺进行设计优化,开展了浇注试制与铸件实物检测。结果表明,选用3D打印砂型整体成形工艺可实现复杂结构壳体的短周期、低成本与高精密制造,实现工艺样件的快速制造。

Coating process of multi-material composite sand mold 3D printing

Sand mold 3 D printing technology is an advanced manufacturing technology which has great flexible manufacturing ability. A multi-material composite sand mold can control the temperature field of metallic parts during the pouring process, while the current sand mold 3 D printing technology can only fabricate a single material sand mold. The casting temperature field can not be adjusted by using single sand mold material with isotropous heat exchange ability during the pouring process. In this work, a kind of novel coating device was designed. Multi-material composite sand molds could be manufactured using the coating device according to the casting process demands of the final parts. The influences of curing agent content, coating velocity and scraper shape on compactness and surface roughness of the sand layer(silica sand and zircon sand) were studied. The shapes and sizes of transition intervals of two kinds of sand granules were also tested. The results show that, with the increase of the added volume of curing agent, the compactness of sand layer reduces and the surface roughness value rises. With the increase of the velocity of the coating device, the compactness of sand layer reduces and the surface roughness value rises similarly. In addition, the scraper with a dip angle of 72 degrees could increase the compactness value of the sand layer. The criteria of quality parmeters of the coating procedure are obtained. That is, the surface roughness(δ) of sand layer should be equal to or lesser than half of main size of the sand particles(Dm). The parameter H of the coating device which is the distance between the base of hopper and the surface of sand layer impacts the size of transition zone. The width of the transition zone is in direct proportion to the parameter H, qualitatively. Through the optimization of the coating device, high quality of multi-material sand layers can be obtained. This will provide a solution in manufacturing the multi-material composite sand mold.

基于3D打印技术的颗粒球度与砂土物理性质关系研究

【目的】砂土作为一种颗粒材料,形状是影响其堆积状态及剪切特性的重要因素,为探究颗粒整体轮廓(球度)对颗粒物理性质的影响。【方法】利用球谐函数随机生成3种复杂形状颗粒和球颗粒模型,通过3D打印技术打印颗粒模型。对4种打印颗粒进行相对密度试验以及直剪试验,分析不同形状颗粒的堆积状态、力学性能。【结果】分析三维颗粒形状指标,发现复杂颗粒的形状差异主要体现整体轮廓方面(球度最大相差0.718,圆度最大相差0.032)。随着球度的增加,颗粒的最大孔隙比从1.843减小到0.803,最小孔隙比从1.121减小到0.603,极限孔隙比差值从0.722减小到0.200,且在相同相对密实度的条件下更容易达到密实的堆积状态;在相对密实度为0.5的条件下,随着颗粒球度从0.241增大到1,试样峰值抗剪强度逐渐减小,内摩擦角从44.6°减小至33.4°,并且内摩擦角和球度存在线性递减关系。【结论】将球谐函数生成不规则颗粒模型的方法与3D打印技术结合可以得到更加贴近真实情况的复杂形状颗粒。基于试验数据得出了复杂颗粒形状指标球度与剪切特性指标的关系式,为实际工程强度设计和数值模拟计算工作中考虑球度影响时提供理论依据。

3D打印砂芯密度提升的方法

介绍了3D打印砂芯密度提升的试验方法:采用双箱铸造砂芯3D打印设备,按照不同参数打印φ40 mm的抗压试块,并对试块的密度进行检测对比分析。试验结果表明:(1)打印层厚与密度呈反比关系,层厚越高密度越低,打印层厚应参考原砂目数的大小设定;(2)打印过程中在铺砂器上引入增加振动频率或适当增加刮砂板角度能够有效地提高砂芯密度;(3)通过适当增大下砂口与叠型槽的间隙或降低铺砂器速度来增加下砂量,可提高砂芯的密度;(4)将打印参数设定为层厚0.38 mm,振动频率3500~4000 r/min,下砂口间隙5 mm,叠型槽间隙5 mm,可使砂芯密度性能达到最高。

风积沙3D打印砂浆力学及收缩性能试验研究

研究了养护方式及不同风积沙掺量对3D打印砂浆力学性能及收缩性能的影响,并进行了现场打印试验。结果表明:现场养护(覆膜、洒水)有利于3D打印砂浆抗折强度的发展,而试验室养护(恒温水浴)有利于3D打印砂浆抗压强度的发展;随着风积沙取代率的增加,3D打印砂浆各龄期的抗压强度先增加后降低,当风积沙取代率为60%时,28 d抗压强度达到峰值;现场养护条件下,3D打印砂浆的体积变化表现为收缩;试验室养护条件下,3D打印砂浆表现为微膨胀;现场养护条件下,水泥水化生成较多AFt穿插在胶凝体系中,充当骨架作用,提高了3D打印砂浆的抗折强度;试验室养护条件下,水泥水化生成较多较致密的C-S-H、Al(OH)3等水化产物,提高了3D打印砂浆的抗压强度;现场打印试验也进一步证实了掺风积沙3D打印砂浆具有优异的性能。

Effect of gel time of 3D sand printing binder system on quality of sand mold/core

Two important factors affecting the performance of sand mold/core generated by 3D printing(3DP)are strength and dimensional accuracy,which are not only closely related to the reactivity of furan resin and the phase transition of silica sand,but also the curing agent system of furan resin.This paper studies the influence of gel time on the strength and dimensional accuracy of a 3DP sand mold/core,taking the furan resin system as an example and using a sand specimen generated by a 3DP inkjet molding machine.The experiment demonstrates that the gel time of 3 to 6 min for the sand mixture suits 3DP core-making most under the experimental condition.However,it should be noted that under the same resin condition,the strength of a no-bake sand mold/core is higher than that of a 3DP sand mold/core.The dimensional accuracy of the sand mold/core does not change significantly when the gel time is less than 15 min.Improving the activity of binder and developing ultra-strong acid with low corrosion shall be an effective way to improve the quality of the mold/core by 3D printing.

砂型3D打印技术在航空发动机领域的研究与应用

随着航空工业的快速发展,行业对航空发动机的性能和制造效率提出了更高要求。传统的砂型铸造方法已难以满足现代航空发动机复杂结构的制造需求。砂型3D打印技术作为一种新兴的快速成型技术,以其高效、灵活、精确的特点,为航空发动机的设计和制造带来了革命性的变革。本文综述了砂型3D打印技术的原理、优势及其在航空发动机领域的应用现状;分析了目前砂型3D打印技术在航空发动机领域应用存在的问题,并提出了相应的解决措施;通过应用案例分析,强调了砂型3D打印技术在提高航空发动机生产效率和质量方面的重要性。最后,对砂型3D打印技术在航空发动机行业领域的未来发展趋势进行了展望。

Sand-bed defect recognition for 3D sand printing based on deep residual network

The 3D sand printing(3DSP),by binder jetting technology for rapid casting,has a pivotal role in promoting the development of the traditional casting industry as a result of producing high-quality and economical sand molds.This work presents an approach for monitoring and analyzing powder sand-bed images to serve as a real-time control system in a 3DSP machine.A deep residual network(ResNet)is used to classify the defects occurring during the powder spreading stage of the process.Firstly,a pre-trained network was applied as the initial parameter;then it was fine-tuned on the labelled defective sample dataset to accomplish the task,which defines the sand-bed defects induced in the 3DSP processing.Furthermore,the recognition and positioning of sand-bed defects were readily achieved by dividing the sand-bed images into blocks.Experiments show that the fine-tuned network has a 98.7%classification accuracy on the validation dataset of sand-bed defects and 95.4%recognition accuracy for the sand-bed images.

3D立体格栅–砂界面剪切性状试验研究

为探究土工格栅–砂界面的剪切律、强度律和体变律,基于3 D打印技术制作的土工格栅,通过改进的应变控制式直剪仪进行了不同横肋数量的土工格栅与不同干湿类型的标准砂间的界面剪切试验。结果表明:法向应力越大,剪切应力弱化现象越明显,界面抗剪强度及其指标与横肋数量成正比例关系;3 D立体格栅–湿砂界面粘聚力随着横肋数量的增多而减小。3 D立体格栅–干砂界面抗剪强度及其指标比3 D立体格栅–湿砂界面大,剪胀特性更明显。干砂和湿砂均表现出剪胀的体变行为,且横肋数量越多,剪胀特性越明显。研究成果可为探究3 D土工格栅在实际工程中的应用提供参考。

基于砂型3D打印技术的薄壁筒形件铸造成形技术

近年来,砂型3D打印技术取得了重大进展,利用有机粘结剂和树脂结合自硬化技术制作砂型已成熟,可运用于铸造行业,这解决了传统铸造方法普遍存在的生产效率低、工艺设计复杂等问题。采用差压铸造能够生产出性能优异的高质量铸件,当与3D打印技术结合时,能够快速获得复杂、精密的铸造成形零件。本文将3D砂型精密打印技术与差压铸造成形技术结合,采用ZAlSi7MgA铸造铝合金材质,试制了具有复杂内腔结构的薄壁筒形结构件。结果表明:产品附铸试样性能远优于国标要求,其中抗拉强度平均值达到348 MPa,提升18%,断后伸长率平均值为5.5%,提升83%,产品内部质量达到Ⅰ类铸件水平;经尺寸扫描分析,产品内腔单侧尺寸公差范围为-0.0976~+0.1089 mm,满足±0.3 mm的设计指标,实现了薄壁复杂筒形结构件的差压精密铸造成形。

浅谈3D打印结合传统自硬砂在铸造生产中的应用

主要论述了砂型3D打印结合邦尼树脂自硬砂在铸造生产中的应用,介绍了锦州捷通将砂型3D打印和传统自硬砂造型进行有机结合生产铸件的过程。生产实践证明:砂型3D打印工艺与传统自硬砂造型生产的有机结合,可以充分发挥新旧生产技术的优点,缩短铸件产品交货周期,在保证铸件质量的前提下可以降低铸件造型生产的整体综合成本,提高了生产效率,实现柔性研制+生产。为砂型3D打印生产大型铸件提供了新的思路。

壳体铸件3D打印技术的应用

壳体由于其复杂的形状,一直采用传统砂型铸造工艺生产,铸件毛坯在其底部往往存在缺陷,其缺陷产生的主要原因是铸件浇注系统设计的局限性。通过3D打印技术的引进与应用,解决了浇注系统的局限性,通过软件模拟浇注过程,模拟可能出现缺陷的位置,提高铸件的成品率。

砂型3D打印材料对类软岩力学特性影响规律及机理

煤矿巷道围岩普遍岩性软弱、节理裂隙发育,软岩力学是煤矿巷道围岩控制的基础。由于软岩在力学与结构等方面的特殊性,物理试验中存在试样难以符合现场裂隙特征、离散性强等问题,严重制约软岩力学或裂隙岩体力学试验研究。3D打印技术因其数字建模、精度高等技术优势,突破了浇筑法在制作复杂裂隙试样上的局限,被广泛应用于岩石力学试验研究,但采用该技术打印成型的试件受打印材料和参数的影响规律还需深入研究。基于砂型3D打印技术,通过力学试验、声发射监测、电镜扫描等手段,研究不同类型砂粉和不同黏结剂饱和度对类软岩试样的力学特性的影响规律及机理。结果表明:不同类型砂粉由于其颗粒形状、粒径、排列形态等因素,对成型试样的力学特性、破坏模式等影响显著;黏结剂饱和度与试样强度呈正相关关系,相同砂粉类型前提下,改变黏结剂饱和度能将试样强度提高5倍,同时声发射事件信号与能量也随黏结剂饱和度的增大而增大。研究结果揭示了砂型3D打印技术用于软岩物理模拟上的适用性,为精确、科学地还原具体工程条件的软弱煤岩力学特性提供重要依据。

基于砂型3D打印泵体的铸造工艺研究

以泵体为研究对象,就数值模拟和砂型3D打印技术在砂型铸造中的应用进行了研究,利用Anycasting软件比较了泵体铸件侧注式、顶注式和底注式浇注方案,并确定侧注式浇注系统为最佳选择。采用3D打印技术对泵体砂型进行了制作,采用砂型铸造工艺制备出了合格铸件。结果表明,数值模拟结合砂型3D打印技术在铸造中的应用,可有效缩短零件开发周期,降低生产成本,大大提高了生产效率。

蜗壳的3D打印砂型铸造成形模拟及工艺研究

蜗壳铸件复杂,使用传统砂铸方法难以成形,蜗壳顶部存在补缩不足的铸造缺陷。为此提出3D打印的组芯方案。利用Solidworks软件对蜗壳进行三维数字化建模,结合ProCAST模拟分析,对蜗壳铸件工艺方案进行优化,然后利用3D打印设备打印出砂芯,经X射线探伤验证,得到无缺陷的铸件。分析认为,原六角星底注式浇注的设计方案存在冒口较小,保温效果差的缺陷,导致顶部区域补缩不足,最终蜗壳铸件顶部具有明显缺陷。优化方式为改为顶注式浇注,浇口杯和冒口一体设计,使得顶部区域保温效果好,补缩足够,同时减轻了砂芯重量,加强了铸件尺寸精度和强度。通过结合3D打印和传统砂型铸造成型技术,有效简化了铸造操作过程,降低了生产难度,提高了成品精度和强度,符合企业砂铸的经济效益。研究成果有助于推动涡轮增压器蜗壳铸件工艺的研究。

3D打印铁尾矿砂混凝土的力学和冻融循环耐久性研究

研究铁尾矿砂掺量(0%、15%、30%、45%),加载方向(X、Y、Z),养护龄期(3 d、14 d、28 d)对3D打印铁尾矿砂混凝土的抗压强度、劈裂抗拉强度和抗弯强度的影响。结果表明:随着铁尾矿砂掺量的增加,3D打印铁尾矿砂混凝土在X、Y、Z方向上的抗压强度均下降,当铁尾矿砂掺量为45%时,3D打印混凝土在X、Y方向上的劈裂抗拉强度较普通混凝土分别降低了17.4%、17.6%,3D打印混凝土在X、Y、Z方向上的抗弯强度较普通混凝土分别提高了25.0%、31.0%和42.4%;3D打印铁尾矿砂混凝土较3D打印普通混凝土在X、Y、Z方向上的抗压强度分别降低了11.1%、19.0%和3.3%,3D打印铁尾矿砂混凝土和3D打印普通混凝土在X方向上的劈裂抗拉强度最高,在Z方向上的抗弯强度最高;掺加铁尾矿砂有利于3D打印混凝土后期力学性能的提升;经历冻融循环100次后,3D打印铁尾矿砂混凝土在Z方向的抗压强度损失率较高,在Y方向上的抗弯强度损失率较高。