Mechanical properties and damage evolution characteristics of waste tire steel fiber-modified cemented paste backfill

During the process of constructional backfill mining,the cemented paste backfill(CPB)typically exhibits a high degree of brittleness and limited resistance to failure.In this study,the mechanical and damage evolution characteristics of waste tire steel fiber(WTSF)-modified CPB were studied through uniaxial compression tests,acoustic emission(AE)tests,and scanning electron microscopy(SEM).The results showed that the uniaxial compressive strength(UCS)decreased when the WTSF content was 0.5%,1%,and 1.5%.When the WTSF content reached 1%,the UCS of the modified CPB exhibited a minimal decrease(0.37 MPa)compared to that without WTSF.When the WTSF content was 0.5%,1%,and 1.5%,peak strain of the WTSF-modified CPB increased by 18%,31.33%,and 81.33%,while the elastic modulus decreased by 21.31%,26.21%,and 45.42%,respectively.The addition of WTSF enhances the activity of AE events in the modified CPB,resulting in a slower progression of the entire failure process.After the failure,the modified CPB retained a certain level of load-bearing capacity.Generally,the failure of the CPB was dominated by tensile cracks.After the addition of WTSF,a gradual increase in the proportion of tensile cracks was observed upon loading the modified CPB sample to the pore compaction stage.The three-dimensional localization of AE events showed that the WTSF-modified CPB underwent progressive damage during the loading,and the samples still showed good integrity after failure.Additionally,the response relationship between energy evolution and damage development of WTSF-modified CPB during uniaxial compression was analyzed,and the damage constitutive model of CPB samples with different WTSF contents was constructed.This study provides a theoretical basis for the enhancement of CPB modified by adding WTSF,serving as a valuable reference for the design of CPB constructional backfill.

Top slag refining for inclusion composition transform control in tire cord steel

Controlling conditions for inclusion plasticization were calculated by FactSage, and the steel/slag reaction equilibration time was determined by pre-equilibrium experiments. Laboratory experiments with different top slags were carried out in 90 rain, and industrial tests were performed based on the results of calculation and laboratory experiments. Scanning electron microscopy （SEM） and energy-dispersive spectroscopy （EDS） were used to determine the morphology and composition of inclusions in tire cord steel. It is found that the shape of in- clusions can be controlled well, and the composition of inclusions varies in the industrial test as the following transformation route： MnO-A1EOa-SiO2→CaO-AIEOa-SiO2→MnO-A1203-SiO2. Inclusion plasticization can be achieved by controlling the binary basicity of top slag （CaO/SiO2 by mass） around 1.0 and the （A1203） content in top slag below 10wt%. Under these controlling conditions in the industrial test, almost all of inclusions in the wire rods achieve plastic deformation.

Simulation on solidification structure of 72A tire cord steel billet using CAFE method

The solidification microstructure has an important effect on the mechanical properties of castings. Therefore, an FE （Finite Element） - CA （Cellular Automaton） coupling model was developed for the simulation of solidification structure during the continuous casting process of 72A tire cord steel. In the model, the effect of phase transformation （λ→γ→α） during solidification was considered based on a thermodynamic database. The effect of electromagnetic stirring （EMS） was determined by increasing both the thermal conductivity and crystal formation rate in the liquid phase. The results show that the cooling curves and solidification structure calculated by this model agree well with the experimental results. The optimum pouring temperature range for tire cord steel casting was also discussed based on the present model. By comprehensive consideration of billet quality and smooth production, the pouring temperature should be controlled at about 1,495 ℃ under the casting conditions of the local plant in this study.

Effect of Carbon Content on Ti Inclusion Precipitated in Tire Cord Steel

The precipitation of TiN inclusion during solidification of different carbon content of 0.72%, 0.82% and 0.95% in tire cord steel is thermodynamically studied respectively. The results show that the carbon content has obvious effect on TiN inclusion precipitated in tire cord steel of different strength levels. With the carbon content of tire cord steel increasing, the temperature before solidifying reduced gradually and the required activity product of titanium and nitrogen for TiN inclusion precipitation also declined gradually. With the same condition of initial Ti and N content in liquid steel, the size of TiN inclusion precipitated in tire cord steel of higher carbon content is bigger than that of lower carbon content. In order to control the harmful effects on processability of TiN inclusion precipitated in hypereutectoid tire cord steel of the ultra high strength level, the measures of smelting process must be taken to further reduce the titanium and nitrogen content in liquid steel.

Effect of boron on inclusions morphology in tire cord steel

B_2O^3 was added into tire cord steel during refining in carbon tube furnace.The influence of boron which was added in tire cord steel on the deformability of oxide inclusions was studied by metallographic and scanning electron microscope(SEM) observation.The melting points of boron-bearing compound oxide inclusions were calculated by the software of Factsage.The results showed that the most part of inclusions were boron-bearing compound oxide and their deformation properties were obviously improved by adding B_2O_3 in steel.As the boron content was increased from 0.0046%to 0.039%,the proportion of long strip type inclusions changed a little and the number of inclusions decreased.The low-melting point areas of MnO-SiO_2-Al_2O_3 and CaO-SiO_2-Al_2O_3 ternary system were increased due to adding B_2O_3 in steel.Moreover,the areas increased with the increasing of B_2O_3 content in conclusions.Evident effect on low-melting point inclusion occurred when B_2O_3 content went up to 5% in CaO-SiO_2-Al_2O_3 inclusions system and to 10%in MnO-SiO_2-Al_2O_3 inclusions system.

Research on the Solid Solution Behavior of Titanium Inclusion for the High Strength Tire Cord Steel

In order to improve the quality of the cord steel wire rod and achieve the effective control of titanium inclusion, the solid solution behavior of titanium inclusion in tire cord steel during the heating process was discussed in this paper, through the thermodynamic theory analysis, combined with the CLSM experiment. The conclusions are as follows: 1) According to the law of Ostwald repening, the coarsening rate of titanium carbonitride inclusion is very small, the coarsening behavior of titanium carbonitride inclusion cannot be considered in the heating and holding stage. 2) The solid solution behavior of titanium inclusion in the heating process is obviously existed. 3) Through the proper control of rolling temperature, holding time and the subsequent cooling rate, the size and quantity of large particle titanium inclusion in the high strength tire cord steel can be effectively controlled.

Innovative Application of Scrap-Tire Steel Cords in Concrete Mixes

Many researchers have investigated the use of recycled tire products in several traditional civil engineering materials. This research is exploring the use of steel cords, a by-product of the tire recycling process, in concrete mixes. Different concrete specimens were fabricated and tested in uniaxial compression and splitting tensile strength. The steel cords were substituted into the concrete mix in volumetric percentages of various ratios. Results show that mechanical properties of concrete made with steel cords are improved compared with concrete mix made with the traditional scrap-tires recycled material. Also, results show that even though the compressive strength is reduced when using steel cords, this reduction is minimal. When 2% of steel cords are used there is 18% increase in ductility. Moreover, splitting tensile tests show that concrete mixtures with any steel cords content have much greater toughness than control mixture. This mechanical property mix indicates an excellent potential application of modified concrete mix in structures that absorb large amount of energy.

Basic Properties of Pyrolysis Carbon Black of Waste Tyres and Application of Pyrolysis Carbon Black in Transition Layer Rubber of All Steel Radial Tire

The main chemical composition of pyrolysis carbon black of waste tires is C,O,Cu,Zn and so on.The content of ash and fine powder in pyrolysis carbon black is high,and the 300%elongation stress is high.The difference between pyrolysis carbon black and furnace black N326,which is commonly used in rubber,is obvious compared with chemical property.The pyrolysis carbon black was used to replace furnace black N326 in the transition layer of all steel load Radial tire rubber through experimental study.It was found that the compression heat generation and dynamic loss(Tanδ)of the blend rubber before and after aging were obviously reduced,the elongation at break and resilience increased,while the tensile stress and tear strength decreased by 100%and 300%,but the hardness and tensile strength changed little before and after aging.According to the latest raw material price calculation,15 used tire pyrolysis carbon black instead of furnace carbon black N326 used in all steel Radial tire transition layer rubber application,excluding labor costs,electricity and equipment depreciation,a ton of blended rubber saves about$22.86 in production costs.

Utilization of waste vehicle tires in concrete and its effect on the corrosion behavior of reinforcing steels

The mechanical and physical properties of concrete specimens obtained from replacing natural coarse aggregate with waste vehi- cle rubber tires at levels of 2vol%, 5vol%, 7vol%, and 10vol% were studied, and the corrosion behavior of reinforcing steels was investigated in these specimens. Corrosion rates were determined by measuring the galvanic current between steel-reinforced concrete specimens both with and without chloride addition. The change in electrode potential of reinforcing steels in these concrete specimens was measured daily for a period of 60 d in accordance with the testing method in ASTM C876. The results show that the use of waste vehicle tires in concrete instead of coarse aggregate decreases the mechanical strength of the specimens, and increases the corrosion rates of the reinforcing steels embedded in the concretes.

Adhesion Enhancement Mechanism of Plasma-Modified Tire Cord

Tire cord was treated with oxygen glow-discharge plasma in order to enhance the adhesion.The treated surfaces were characterized by scanning electron microscopy(SEM),specific surface area analysis Brunauer-Emmett-Teller(BET),X-ray photoelectron spectroscopy(XPS),contact angle measurement,and the standard H-pull test.Results indicated that the plasma treatment could increase the surface roughness,modify the nature and density of surface functional groups,and greatly improve the surface energy and adhesion of tire cord.After long term storage in ambient air,the enhanced adhesion decreased slightly.

AN INVESTIGATION INTO THERMO MECHANICAL PROPERTIES OF NYLON TIRE CORDS

An experimental research was made to have a grasp of the overall thermo-mechanicalproperties of nylon 6 and nylon 66 tire cords. The strength, fatigue, thermal shrinkage, therm-al aging and dynamic-mechanical properties of both were measured, investigated and corn-pared. So far as their comprehensive performance is concerned, and favoritism to nylon 66cord for tire cord fabrics is perhaps unwarranted. And the effect of twist on the tensile proper-ties and fatigue behavior also have been measured and analyzed.

A STUDY OF PET TIRE CORD TREATED BY LOW TEMPERATURE PLASMA

The process of treating the PET tire cord (210D/3×2) by low temperature nitrogen and airlow temperature plasma and dipping in RFL (resorcinol-formaldehyde-latex) adhesive system wasstudied.The H-pull test value can be improved from about 35 N/cm of untreated sample to 55N/cm of nitrogen plasma treated sample.The photograph of SEM demonstrates that the adhe-sion between nitrogen plasma treated tire cord and rubber has reached the strength of rubber.Airplasma treatment has bad effect on adhesion improvement.The mechanism of plasma treatment on the surface of the PET tire cord and the mechanism ofadhesion improvement are investigated by diffuse reflection infra-red spectrum and XPS (X-rayphotoelectron spectroscopy).From the spectral analysis,it is believed that the contribution to im-provement of the adhesion of the tire cord is the oxidation on the surface.The serious breaking ofthe chemical bonds on surface can cause the adhesion inferior.

Progress of tyre cord steel in Baosteel

With the development of automobile industry,tire is marching toward lighter,energy-saving and safer,and it has been a trend for steel cord to develope in high strength and ultrahigh-strength.In order to reduce fracture of tire cord,steel cord is producted with bloom casting machine by soft reduction to reduce segregation,with clean steel smelt technology to control inclusion.TMCP of wire cord is improved in Baosteel.With technological advancement,the quality of steel cord has been noticeably raised and ultrahigh-strength has developed successfully.The paper introduces the development of steel cord in Baosteel.

Forecast of steel cord demand after the financial crisis

To analyze the production and marketing of China automobile in Year 2009,and also the development of China automobile and steel cord in those 11 years.The single-element regression mathematics model was set up to analyze the steel cord demand and automobile production.It predicted that automobile production would up to 15 170 000,16 690 000 and 18 360 000 respectively from 2010 to 2012,with the confidence as of 95%,the steel cord consumption in those three years will be 1 180 000 - 1 370 000 t, 1 320 000 - 1 520 000 t and 1 470 000 - 1 680 000 t.As to the policy of China stimulation,The role of Chinese tire has converted from the export-oriented to domestic consumer smoothly,so the effect of US special protectionist tariffs is limited in China.

全钢工程机械子午线轮胎胎里露线的原因分析及解决措施

分析全钢工程机械子午线轮胎胎里露线的原因,并提出解决措施。通过采取确保成型机平宽与带束层贴合鼓周长合理、缠绕机挤出胶条尺寸稳定、成型鼓扇形块周长一致、防止垫胶贴合偏歪、内衬层接头压实、合理设定硫化定型压力等措施,有效解决了胎里露线问题。

BFRP筋回收轮胎钢纤维混凝土黏结性能分析

对玄武岩纤维增强复合材料(BFRP)筋在回收轮胎钢纤维(RTSF)混凝土中的黏结性能进行了试验和分析研究.对不同RTSF体积掺量、BFRP筋直径和嵌入长度的试件进行了拉拔试验,研究其对黏结破坏模式、黏结滑移响应和黏结强度的影响,并提出了BFRP筋RTSF混凝土的黏结滑移理论模型.结果表明:BFRP筋RTSF混凝土黏结破坏类型包括拔出破坏、劈裂破坏以及拔出且劈裂破坏;BFRP筋直径对黏结破坏模式无显著影响,而RTSF体积掺量、BFRP筋直径和嵌入长度均对黏结强度有较大影响,且RTSF体积掺量与极限黏结强度呈正相关,BFRP筋直径和嵌入长度对其影响与之相反;当RTSF体积掺量从0增大至1.5%时,其极限黏结强度最大可提高约23.87%.与已有模型相比,所提出的黏结滑移理论模型对BFRP筋RTSF混凝土的黏结滑移曲线具有更高的拟合精度.

1×1钢丝帘线的开发与性能探讨

开发1×1钢丝帘线,并研究其性能。结果表明:采用校直器校直和加捻反扭两种工艺均可以得到符合设计要求的1×1钢丝帘线,校直器校直的钢丝帘线残余扭转更稳定,而加捻反扭的钢丝帘线直线性更好;在材料确定的情况下,1×1钢丝帘线的弯曲刚度和低负荷伸长率主要与直径相关,而与强度关系不大;在1500 MPa试验压力下,1×0.30ST钢丝帘线的亨特疲劳性能比2×0.30ST钢丝帘线更好。

国产溶聚丁苯橡胶在半钢子午线轮胎胎面胶中的应用

研究国产溶聚丁苯橡胶(SSBR)在半钢子午线轮胎胎面胶中的应用。结果表明:与进口SSBR胶料相比,国产SSBR胶料的硫化特性、物理性能和耐臭氧老化性能相当;成品轮胎的高速性能和耐久性能均通过测试,滚动阻力相当,干地和湿地制动性能可满足使用要求,且可降低材料成本。

具有三角胶缓冲与补强胶片的轮胎结构设计

介绍具有三角胶缓冲与补强胶片的轮胎结构设计。第1层胎体帘布采用反包设计,第2层胎体帘布采用正包设计,三角胶内外侧分别贴缓冲胶片和补强胶片,且缓冲胶片和补强胶片采用预复合贴合工艺,有效增强了胎圈部位的强度,提升了轮胎的耐久性能。