Feeding of high-nickel alloy castings

Feeding of the nickel-based alloys CZ-100, M-35-1, and CW-12MW, as well as of the austenitic stainless steel CN-7M, is investigated, using a combination of casting experiments and simulation. Casting trials are performed at five foundries, to produce a total of 55 plates of varying lengths and radiographic soundness levels. In order to develop the property databases necessary to simulate the casting of these alloys, temperature data are recorded for each alloy during the casting trials. These measured data are used in conjunction with material property simulation to develop the necessary property data for each alloy, including the solidification path. These property data are used to simulate the casting trials. Good agreement between the simulation results and the radiographic testing (RT) results for the castings is obtained. A quantitative relation between the measured ASTM X-ray levels and the predicted minimum Niyama criterion value is established for all but the CZ-100 alloy, which does not appear to suffer from shrinkage defects. A large number of additional simulations are used to develop general feeding distance (FD) rules. The new rules are shown to provide accurate FDs for the casting trial plates. The FDs of the high-nickel alloys (except CZ-100) are found to be at least 25 pct shorter than those for typical low-alloy steels.     

Pipe production from continuous-cast high-alloy steel blanks

Experiments are conducted on pipe production from continuous-cast billet made of TP 304L and TP 316L corrosion-resistant steel from various suppliers. A wide range of pipe is industrially produced by hot pressing and cold and hot rolling. Assessment of pipe quality shows compliance with the relevant standards.     

Working surface of components made from high-alloy corrosion-resistant steel

The internal (working) surfaces of pipes and other components made from corrosion-resistant austenitic steel are investigated. The influence of the production parameters, the metal structure, and the operating conditions on the surface of critical components is established.     

Inclusion characteristics of stainless steel castings

The characteristics of non-metallic inclusions in 347 stainless steel samples taken during a net-shape casting process after different holding times and melting temperatures were investigated using electrolytic extraction and polished cross-sections. The inclusions can be classified into three groups: oxides, composite inclusions and sulphides. Within the first two groups the inclusions were subdivided based on their morphology into the following categories: spherical, irregular and clusters. As the temperature decreased, sulphide and NbC precipitated within the steel melt as well as on the surface of existing oxides. The number density and area fraction of inclusions as well as the total oxygen contents increased with higher melt temperatures and longer holding times. The results obtained from thermodynamic calculations carried out using the FactSage? commercial software agreed well with the experimental observations. In addition, it has been concluded that turbulent collisions are the dominant mode for the growth of inclusion clusters.     

Improvement of top casting of high-alloy steel into a mold

The problems related to improving the process of top casting of complexly alloyed and high-alloy steels and alloys are considered. To increase the ingot surface quality and the ingot-to-product yield, a new method of top casting of steels and alloys is proposed. In this method, a floating shield made of a light refractory material is placed in a mold and protects the mold surface against metal splashes.     

2.3t铸锭高合金冷作模具钢轧制开坯工艺实践

阐述了高合金莱氏体冷作模具钢2.3t铸锭轧制开坯的工艺开发过程。通过热模试验机实测Cr12MoV在高温状态的抗拉强度和断面收缩率,分析确定了2.3t铸锭高合金莱氏体冷作模具钢脆性铸态组织轧制的温度区域。采取了控制轧制温度、控制变形量等方法,制定了相应的初轧加热工艺制度和初轧机压下规程及轧制方法,确认初轧具备2.3t铸锭Cr12MoV、X210CrW12轧制生产的可行性,实现规模化轧制生产,提高了生产效能,较大幅度地降低了生产成本,且突破高合金莱氏体冷作模具钢惟有小于等于1.2t铸锭组织生产的传统模式。     

Production and quality investigation of 20GML steel castings for pipeline fittings

The technology of OAO Izhorskie Zavody and OOO OMZ Liteinoe Proizvodstvo of OMZ Corporation for the production of 20GML steel castings is described. Quality analysis of cast pipeline parts is performed.     

高分辨率单道扫描型电感耦合等离子体原子发射光谱法测定高合金钢中铝

在测定基体复杂的高合金钢中铝含量时,采用Al 308.215 nm或Al 394.401 nm作为分析谱线,无需使用复杂前处理方法及干扰因子校正模式,使用高分辨率单道扫描型电感耦合等离子体原子发射光谱仪(ICP-AES)对铬、镍质量分数小于20%,铜、锰、钨、钴质量分数小于5%,钼质量分数小于4%的高合金钢中微量铝进行测定。并与普通分辨率全谱电感耦合等离子体原子发射光谱仪测定高合金钢中铝的方法在光谱干扰方面的情况进行了比对。结果表明:方法中铝的测定下限为0.002%(质量分数);校准曲线采用基体匹配法消除基体效应的影响,线性相关系数达0.999 9以上。按照实验方法测定高合金钢样品中铝含量,结果的相对标准偏差(RSD,n=9)不大于6.2%;标准样品中铝的测定结果与认定值相符。     

Microscopic modeling of fundamental phase transformations in continuous castings of steel

A model has been developed to describe the microscopic behavior of phase transformation of carbon steels in the range of cooling rate occurring in continuous casting. In the liquid-to solidphase transformation, this model simulates the phenomena of dendrite nucleation and growth during solidification. Both δ- and γ-dendrites are involved. The nucleation and growth model has been established on the basis of published experimental data and previous work. Also, a model of the peritectic transformation of carbon steels has been included. In the solid-to solidphase transformation, the model considers the δ→ γ, γ→ α, and γ→ α + Fe₃C phase transformations. The δ→ γ and γ→ α phase transformations have been modeled by using the Johnson-Mehl equation, also known as the Avrami equation. For the pearlite transformation, a nucleation law, as well as the growth kinetics, has been established. Good agreement has been found between the prediction of the model and the experimental data.     

Influence of small additions of antimony on the texture and magnetic properties of isotropic high-alloy electrical-engineering steel

The influence of small additions of antinomy (0.004–0.015% Sb) on the texture and magnetic properties of isotropic electrical-engineering steel with ∼3% Si and no more than 0.006% C is studied. The texturing of the final steel is improved, with faster development of favorable orientations (hk0) and a smaller proportion of orientations “220”〈uvw〉. Steel modified with antimony is characterized by smaller magnetic losses (P _1.5/50 ≤ 2.7 W/kg), without loss of magnetic induction: B ₂₅₀₀ = 1.550–1.556 T. The asymmetry is acceptable: ΔP _1.5/50 = 9–11%; ΔB ₂₅₀₀ = 0.07–0.08 T.     

Influence of recrystallizing annealing on the properties of high-alloy isotropic steel with ultralow magnetic losses

A technology is developed for the production of highly alloyed (with up to 3% Si) isotropic electrical steel characterized by ultralow magnetic losses (P_1.5/50 ≤ 2.70 W/kg for strip of rated thickness 0.50 mm). The structure, texture, and magnetic and mechanical properties of vacuum-treated (<0.005% C) cold-rolled strip consisting of high-silicon steel (alloyed with >1% Al and >0.015% Sb) is investigated as a function of the heating rate and also the temperature and holding time in recrystallizing annealing. By refining the boundary conditions in the recrystallizing annealing of cold-rolled isotropic electrical steel, optimal grain size is obtained, and the pole densities of cubic orientations in the texture are increased. That reduces the magnetic losses.     

Effect of soft reduction process on segregation of a 400 mm thick high-alloy steel slab

During the solidification of high-alloy steel (0.4C-1.5Mn-2Cr-0.35Mo-1.5Ni),the high temperature gradient of solidified shell as well as the columnar crystal de...     

Behavior of oxygen in the ladle treatment of 08X18H10T high-alloy steel

The actual activity of oxygen in liquid metal is determined by means of sensors during the ladle treatment of 08X18H10T high-alloy steel. The activity of the components of the metallic and oxide solutions is calculated by means of models of a pseudosubregular solution for the liquid metal and a pseudoregular solution for the oxide slag. The corresponding energy parameters were determined in previous research. A formula is derived for the activity of oxygen in equilibrium with the components of Fe-Cr-Ni-Mn-Si-C-Al-Ti liquid steel, eight-component FeO-MnO-CaO-MgO-SiO₂-CrO_1.5-AlO_1.5-TiO₂ slag, and the gas phase. It is found that the metal-slag-gas system at the end of reduction is considerably closer to equilibrium than at the end of oxidation. The development of the reduction process is studied in terms of the difference in chemical potentials of the actual and equilibrium oxygen.     

Influence of peritectic transformation on the hardening,structure, and properties of steel castings

The influence of peritectic transformation on the deposition of solid phase over the cross section of pearlitic steel ingots with 0.2–0.4% C is studied. To prevent structural and chemical microheterogeneity, measures ensuring dense and uniform metal over the casting cross section are proposed.     

轻压下对GCr15轴承钢大方坯内部质量的影响

轴承钢棒材中心致密性和碳化物缺陷与大方坯铸态内部质量控制水平密切相关。以GCr15 轴承钢为研究对象,建立了大方坯连铸过程二维纵向凝固传热模型,结合现场测温试验验证了凝固模型的准确性。基于凝固末端轻压下补偿当地凝固收缩、控制中心缩孔的理论,通过对大方坯凝固进程的准确预测,揭示出其糊状区内合理的轻压下范围。其中,浇铸试验条件下对应铸坯中心固相率为0.30~0.75的合理压下区间为16.4~22.5 m。生产试验表明,轻压下对铸坯凝固组织转变与形貌影响不大,但可明显消除中心缩孔,中心疏松也可由1.5级以上稳定降至0.5~1.5级,满足轧制要求; 合理的轻压下位置和适度的轻压下量可明显改善轴承钢大方坯中心缩孔和中心疏松程度,提高轧材探伤合格率。同时也发现,压下位置与压下量分配不合理或不稳定可能诱发铸坯内裂纹,从而不利于轧材质量的稳定性和一致性。当前生产条件下,稳定拉速并在3~6号压下辊合理分配压下量可达到有效改善内部质量的目的。