Research on testing method of resin sand high temperature compressive strength

High temperature compressive strength is one of the most important performances of resin sand; its value directly concerns the quality of castings. In order to seek the best testing method of resin sand high temperature compressive strength, a self-developed instrument was used to carry out experiments, and the sample shape and size were designed and studied. The results show that a hollow cylinder sample can reflect the strength difference of different resin sands better than a solid cylinder sample, and its data is stable. The experiments selected Φ20/5×30 mm as the size of the hollow cylinder samples. The high temperature compressive strengths of phenol-formaldehyde resin coated sand, furan resin self-setting sand, and TEA resin sand were each tested. For the resin sand used for cast steel and cast iron, 1,000 oC was selected as the test temperature; for the resin sand used for cast non-ferrous al oy, 800 oC was selected as the test temperature; and for all the resin sand samples, 1 min was selected as the holding time. This testing method can truthfully reflect the high temperature performance of three kinds of resin sand; it is reproducible, and the variation coefficients of test values are under 10%.

Effects of interface adhesive and resin cohesive strength on tensile strength of resin sand based on numerical analysis

A plane-strain unit-cell finite element model was proposed to study the effects of resin/sand interface adhesive and resin cohesive strength on the overall tensile strength of resin sand,as well as the fracture modes.The main micro-scale characteristics of the numerical model were extracted from the micrograph of resin sand specimens by three-dimensional X-ray microscopy(3 D-XRM).The extended finite element method(XFEM)and cohesive behavior method were employed to explicitly describe the resin fracture and sand/resin interface debonding,separately.The corresponding experimental observation of micro-scale failure behavior based on the scanning electron microscopy(SEM)was presented for a comparison.The numerical results show that the initial failure of the model occurs at the sand/resin interface,followed by consequent resin failure.Dependent on the resin cohesive strength,the location of resin failure varies from the central zones to resin neck arc zones.A typical mixed mode fracture is observed,which is consistent with the corresponding micro-scale experimental observation.When the resin cohesive strength ranges between 8 and 12 MPa,the resin cracks occur at the central zone of resin bridges and propagate perpendicularly to the tensile direction until through cracks happen.At a higher range(between 12 and 16 MPa),interface cracks cross with resin cracks,bonding bridges of resin sand are broken.The interface adhesive strength has a more significant effect on the overall tensile strength of resin sand than the resin cohesive strength.The overall tensile strength of resin sand increases first then keeps stable with the increase of the resin cohesive strength.This work attempts to establish a numerical model which accurately describes the complicated mixed mode fracture of resin sand,which is beneficial to understand deeply the fracture mechanism of resin sand.

Influence of resin flow on shrinkage of additive manufacturing coated sand molds

Coated sands are used extensively for additive manufacturing sand molds in the metal casting process, and the packing structure changes caused by the resin flow promote the shrinkage and deformation of the part. During the coated sand heating, the resin on the surface flowing to the contact points of the particles forms the resin neck and causes particles to pack close to each other. In this work, the diameters of the coated ceramsite sand before and after heating were measured based on in-situ experimental observations with image measuring apparatus and blue laser, to obtain the relationship between resin coating thickness and the particle diameter. The particle packing model was established to describe the particles' achievement of a stable state one by one. A re-packing simulation was then performed after reducing the particle diameter according to the resin coating thickness, to obtain the shrinkage ratios at different particle size distributions. It was found that the resin coating thickness increased from 0.8 to 2.3 μm as the particle diameter increased from 107 to 500 μm, for the coated ceramsite sand with the resin content of 2 wt.%; the shrinkage ratio decreased first and then increased as the particle diameter increased. The experimental minimum shrinkage ratio was 3.28%, and the corresponding particle diameter was 300-375 μm, while the minimum shrinkage ratio obtained by simulation was 3.43%, and the corresponding particle diameter was 214-300 μm. After mixing the five groups proportionally, the shrinkage ratios of the simulation and experiment dropped to 2.81% and 3.04%, respectively, indicating the best results.

Development of a new instrument for measurement of high temperature mechanical properties of resin-bonded sand

The mechanical properties of resin-bonded sand mixtures at high temperatures significantly affect the quality of casting. However, the existing instruments for high-temperature performances testing mainly focus on inorganic binder-bonded sands no matter the test items or the atmospheric protection, while the instrumentss specially designed for resin-bonded sand are not yet available. A new instrument for testing the hightemperature performance of resin sand was designed including the confirmation of the testing parameters, loading, measurement and control systems, and the design of the frame shape and heating furnace. This instrument can test the compressive strength, heat tolerance time and restraining load of phenol-formaldehyde resin coated sand, self-hardened furan resin sand, and trimethylamine(TEA)-based resin bonded sand at high temperatures. The developed instrument has a high accuracy offering smaller than 0.3% deviation at a full scale in the measurement of the high temperature compressive strength and the restraining load over the range of 0-6.8 MPa and 0-2,000 N, respectively. The high temperature heat tolerance time range is 0-300 s and its measurement accuracy is ±1 s.

耐高温泡沫树脂低伤害均匀固砂技术

针对常规泡沫树脂体系耐温性较差和辽河油田疏松砂岩稠油油藏化学固砂储层伤害大与有效期短的问题,以环氧树脂、酚醛树脂、疏水纳米SiO_(2)、硅烷偶联剂等为原料制得纳米改性树脂基液,然后加入固化剂、乳化剂、起泡剂、稳泡剂等添加剂制得泡沫树脂固砂体系。评价了该体系的固化温度、固砂强度、渗透性能、耐温性能和非均质多层注入性能;研发了配套的泡沫发生器,形成了耐高温泡沫树脂低伤害均匀固砂技术,并在辽河油田进行了现场应用。结果表明,泡沫树脂固砂体系的最优配方为:20%~30%树脂基液+8%~12%酚醛胺类固化剂+0.3%乳化剂OP-10+0.5%起泡剂有机硅表面活性剂+0.1%固体稳泡剂纳米SiO_(2)+0.1%聚合物稳泡剂聚乙二醇+57%~71%清水。该体系的起泡体积约为发泡前的7倍、半衰期大于20 min,可在35℃以上固化,固化后耐温可达280℃,既具有低温固化的特点,又具有耐高温的特点。在不同温度下固化的泡沫树脂固结岩心的抗压强度达到5 MPa以上,固砂强度高,满足疏松砂岩固砂强度的要求。对用0.25~0.42 mm石英砂制得的固结岩心的固砂渗透率达到4.8μm2,优于常规树脂固砂剂(1.9μm~2)。在非均质多油层中可明显防止高渗透层突进,改善固砂剂注入剖面,实现均匀固砂。现场试验取得良好的防砂效果,验证了该技术可实现均匀固砂和低伤害特性。利用泡沫树脂流体特性实现非均质多油层均匀固砂,达到了提高化学固砂效果和防砂有效期的目的。

铸造混合型旧砂的复合再生工艺研究

对含不同类型树脂芯砂的粘土混合旧砂进行再生试验研究,对比了湿法再生、化学再生和复合再生等对再生砂表面形貌和性能的影响。结果表明:单一再生方法无法同时满足对含泥量、灼减量、酸耗值等要求。“水洗+碱/酸处理+高温焙烧”工艺能充分发挥不同工艺优势,获得理想结果,适宜的工艺参数为在400 r/min的转速下水洗6次,每次5 min,砂水比约为1.7∶1,并在水洗初期和水洗后每100 g旧砂依次加入0.1 mol/L的氢氧化钠溶液4 mL和草酸溶液6 mL,最后将水洗后的砂子在700℃焙烧15 min。再生砂含泥量、酸耗值、灼减量分别达到0.18%,2.61 mL和0.08%,均超过行业标准和企业生产要求。

选区激光烧结技术在复杂流道砂芯中的应用

介绍了选区激光烧结技术生产复杂流道砂芯的整套工艺流程,通过合适的选区激光烧结砂芯结构设计、成形制造工艺及覆膜砂原材料的选择,制造出了结构复杂的整体流道砂芯。原材料采用抗拉强度更高的覆膜宝珠砂、合理的砂芯定位支撑面和砂芯排气通道等措施,更能满足复杂薄壁流道砂芯的实际铸造需求,通过实际生产验证,利用选区激光烧结技术整体制造了复杂流道砂芯,生产的铸件尺寸精度达到CT8级,采用100/200目的覆膜砂原材料,流道表面粗糙度可达Ra 6.9~10μm。

新型改性酚醛树脂的特点和使用性能

本文旨在探讨新型改性酚醛树脂(简称“B树脂”)在铸钢生产领域的特点和使用性能。首先概述了改性酚醛树脂的技术指标和特点,包括其绿色化、高旧砂再生率和低旧砂再生成本等优势。然后研究了如何提高酚醛树脂的耐热性,包括化学和物理改性方法。在此基础上,通过与其他常用砂种的成本比较,展示了改性酚醛树脂砂在清理和模具成本方面的优越性。通过进一步分析改性酚醛树脂砂的使用性能,包括型砂强度和溃散性,发现该树脂不仅能保护金属表面,降低氧化程度,还能提高铸钢件表面质量,有效地减少刺激性气体的产生。综合以上研究结果,得出结论:改性酚醛树脂“B树脂”不含游离甲醛与苯酚,具有无毒性、环保性,在铸钢生产中实现了高度可再生率,降低了废砂排放量。

高韧性砂纹粉末涂料用聚酯树脂的合成研究

为提高砂纹粉末涂料的机械性能,探索了醇酸比、三羟甲基丙烷(TMP)用量、柔性单体种类、合成工艺及增韧助剂等对聚酯树脂的影响,通过漆膜冲击仪、T型弯曲仪、氙灯老化、中性盐雾测试等表征了涂层性能。结果表明,以醇酸比1.13、三羟甲基丙烷用量1.2%、己二酸(ADA)作为柔性单体、先IPA酸解后ADA酸解并二次抽真空的工艺条件,采用增韧剂C可赋予聚酯树脂优异的机械性能,该聚酯树脂还具有较高的玻璃化转变温度、良好耐候性和优异的耐盐雾性能。

水基树脂型化学固砂体系在海上出砂井研究及应用

海上油田具有高孔高渗的储集物性特征,单井日产液量大且因地层埋深浅、欠压实,岩石胶结程度弱,地层中砂粒易被高速流体拖拽进入井筒,造成冲蚀油嘴、停泵,甚至砂埋,严重影响海上油田高效开发。本研究评价一种水基树脂型固砂体系,结果表明:水基树脂化学固砂体系在25℃时、48 h内黏度保持在2~7 mPa·s,充分保证了注入安全性;固结后岩心渗透率保留率为84.6%~91.4%,岩心抗压强度为3.44~6.95 MPa,化学固砂固结后岩心酸化后强度基本不变,满足生产井后期多轮次酸化要求。化学固砂后岩心耐冲刷临界流速为160 mL·min^(-1),满足海上单井大产液量生产特点。该体系应用于海上M1井,作业前日产液量为196.9 m^(3)·d^(-1),日产油23.6 m^(3)·d^(-1)。化学固砂后日产液量为167 m^(3)·d^(-1),日产油量为18.4 m^(3)·d^(-1),井口化验无砂产出,持续稳产。水基树脂型化学固砂体系海上成功应用,对海上出砂井治理具有重要意义。

利用微胶囊包覆技术提高耐碱树脂砂的环境适应性——以大庆油田为例

大庆油田三元复合驱常出现压裂裂缝内支撑剂移动现象,通常采用压裂后尾追树脂砂的工艺来延长压裂有效期,但目前适用于三元复合驱的耐碱树脂砂存在高温储存易胶结的难题。利用微胶囊包覆技术,以耐碱树脂砂为囊芯,以明胶等组分制作囊壁,开展耐碱树脂砂的环境适应性研究。结果表明,有覆膜的耐碱树脂砂有效保存周期在2 a以上,强碱浸泡72 h后抗压强度为3.1 MPa。先期试验3口井,未发现支撑剂运移现象,固砂有效期长达814 d且仍有效,平均单井累计增油4057 t,具有良好的固砂增油效果,在三元复合驱区块具有良好的应用前景。

环氧树脂改性多异氰酸酯微胶囊的制备及其防砂性能

为提高疏松油田的采油率,研发高性能防砂是必须要采取的工艺措施,本论文通过二苯基甲烷二异氰酸酯多聚体(MDIP)与环氧树脂(E-51)反应,制备环氧树脂改性多异氰酸酯(EMP).通过物理化学法中复相乳液法对EMP进行微胶囊化.进行红外、核磁、扫描电镜等结构表征,证明EMP的成功制备.同时EMP微胶囊固砂液平均粒径为0.1359μm和动力学稳定指数(TSI)为0.468,表明该微胶囊的粒径分布均一,且体系稳定.在达到油井粉细砂固结要求的同时最环保和节约成本条件下,得到最佳固砂配方和条件下固结砂柱的抗压强度为6.563 MPa,渗透率为1476 mD,出砂量为6 mg,出砂率为0.006%,同时还具备良好的耐酸、耐盐、耐氧化性,显著提高油井采油率.

数值模拟热物性参数反求技术研究及其在轨道交通铸件中的应用

通过测定不同种类的合金材料、砂型和冒口的铸件实际降温曲线,来优化热物性参数,提高碱酚醛树脂砂仿真精度。首先,基于华铸CAE与参数反求技术,在不同条件下对铸件开展正交试验,建立铸件的降温曲线。其次,对于各类铸件实际测温,并对比与降温曲线的相似度,进行误差分析。最后,根据对比结果选取与实测的降温曲线最接近的模拟曲线,确定热物性参数。正交试验表明,当温度在1000℃~1500℃时,反求之后的实际测温曲线与模拟曲线的相似度大于95%,两者吻合良好。

纳米SiO_(2)/酚醛树脂复合材料裂纹扩展行为分析及力学性能研究

油气井出砂是疏松砂岩油气藏开采面临的主要矛盾。树脂固结人工井壁防治细粉砂效果优良,可实现复杂井况下的无筛管防砂,是目前油田应用最广泛的化学防砂方法,决定其防砂成败的关键是树脂的固结性能。借助扩展有限元(XFEM)对裂纹经过单个粒子、一对粒子、均匀分布的多个粒子进行数值模拟,研究纳米粒子对裂纹扩展路径和损伤耗散能量的影响,发现纳米SiO_(2)对裂纹影响区间为5个纳米粒子直径,纳米SiO_(2)的最佳质量分数为树脂基体的3%。树脂样条的抗冲击强度和树脂防砂体的抗压强度的测定结果表明,纳米SiO_(2)质量分数为3%时,树脂样条抗冲击强度提高39%左右,树脂防砂体抗压强度提高36%左右,显著改善了酚醛树脂的力学性能。

石油压裂支撑剂的研究现状

概述了石英砂支撑剂、陶粒支撑剂和覆膜支撑剂等3类石油压裂支撑剂的优势与不足;介绍了3类支撑剂目前的研究成果;对石油压裂支撑剂的发展提出了相关建议,在支撑剂的不断发展中,需要考虑油井废弃后,支撑剂将对地层环境产生的长久影响,力求井底存留支撑剂对地质环境的影响降到最低。

呋喃树脂砂抗拉强度影响因素研究

利用“8”字试块拉伸实验研究了树脂与固化剂加入量、微粉含量以及含水量对呋喃树脂砂抗拉强度的影响。试验结果表明,随着树脂加入量的增加,试块终止抗拉强度逐渐增大,初始强度先增加后减小;随着固化剂加入量增加,试块的终止抗拉强度先增加后减小。当树脂加入量占砂1%,固化剂占树脂80%时达到峰值。随微粉含量、含水量的增加,试块的抗拉强度逐渐下降,因此建议再生砂微粉含量≤2%,含水量≤0.2%。

超吸水人棉沙障的制备和性能

以丙烯酸(AA)和丙烯酰胺(AM)为单体,过硫酸钾为引发剂,合成高聚物溶液;以胶黏剂GH-710、氢氧化铝作为交联剂,将其整理到织物上。考察了单体配比、丙烯酸中和度、聚合温度、交联剂用量等对织物吸水倍率的影响,并对吸水机理进行探讨。结果表明:水浴温度65℃,丙烯酸20 mL、中和度80%,丙烯酸和丙烯酰胺质量比为0.4∶1,过硫酸钾质量为0.12 g,胶黏剂GH-710、氢氧化铝分别为单体总质量的3%、0.5%,烘干温度80℃时,经超吸水树脂整理后的人棉沙障吸水倍率最好,可达180 g/g。

呋喃树脂砂生产球墨铸铁件的色差问题研究

对自硬呋喃树脂砂生产球墨铸铁件的表面球化衰退引起铸件色差的问题进行研究,并作金相组织分析,根据分析结果采用FQ30pro防渗硫涂料,阻隔或中和型砂中的S进入铸件表层,解决了球墨铸铁件的表层球化不良引起的色差问题。

海绵城市中硅砂覆膜及其粘结剂改性研究

硅砂在海绵城市中应用广泛,硅砂透水砖可以破坏水表面张力,增强自身透水性。本文通过回顾硅砂覆膜的生产工艺及其物理化学原理,介绍了硅砂焙烧和覆膜的作用。其间通过类比铸造用覆膜砂粘结剂改性的原理,总结砂基透水砖用覆膜砂粘结剂常用的改性方法,以期为有效建设海绵城市提供参考。

海绵城市背景下硅砂透水砖性能研究

采用氢化双酚A型环氧树脂改性硅砂透水砖,探究硅砂粒径(35目、50目、70目)与环氧树脂掺量(2%、4%、6%、8%)对硅砂透水砖的强度、透水性能、保水性能、滤水性能以及防滑性能的影响规律。试验结果表明:当硅砂粒径为50目、环氧树脂掺量为4%时,硅砂透水砖的抗压、抗折和防滑性能最好,透水速率为1.5 mL/(min·cm^(2))、保水率为0.068 g/cm^(3),滤水率为90.2%。