Effect of Pressure on Second Dendrite Arm Spacing and Columnar to Equiaxed Transition of 30Cr15Mo1N Ingot,Steel Research International

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Effect of Pressure on Second Dendrite Arm Spacing and Columnar to Equiaxed Transition of 30Cr15Mo1N Ingot
Steel Research International ( IF 1.9 ) Pub Date : 2021-06-30 , DOI: 10.1002/srin.202100197
Zhi-Yu He ₁ , Hua-Bing Li _{1,

2} , Zhuo-Wen Ni ₁ , Hong-Chun Zhu ₁ , Zhou-Hua Jiang _{1,

2} , Hao Feng ₁ , Dong-Sheng Mao ₁

Affiliation

In order to clarify the effects of pressure on the second dendrite arm spacing (SDAS) and columnar to equiaxed transition (CET) of 30Cr15Mo1N ingot, changes in solidification parameters, cooling rate and columnar dendrite tip growth rate with pressure have been investigated. A formula is proposed to obtain the quantitative correlation between pressure (≤ 2 MPa) and interfacial heat transfer coefficient:

h_{i} = (28.01 P^{2} + 299.28 P + 1129.10) t^{- 0.24}

. And then, A formula is proposed to calculate SDAS with cooling rate:

λ_{2} = 21.48 \times R^{- 0.77}

, which is applicable for low pressure (≤2 MPa) and low cooling rate (0.4–1.4 K · s⁻¹). There are tiny changes in solidification mode and equilibrium partition coefficient with increasing pressure from 0.5 to 2 MPa. Therefore, increasing pressure refines SDAS mainly by enlarging cooling rate. Pressurization can increase columnar dendrite tip growth rate by enhancing undercooling, and inhibit nucleation and growth of equiaxed dendrite by decreasing constitutional undercooling. It results that the distance between the center of ingot and CET position decreased with increasing pressure from 0.5 to 2 MPa. And a formula is proposed to calculate columnar dendrite tip growth rate with undercooling:

V = 1.33 \times 10^{- 5} Δ T^{2} + 2.71 \times 10^{- 7} Δ T^{3}

, which is suitable for low pressure (≤2 MPa).

中文翻译：

压力对30Cr15Mo1N铸锭二次枝晶间距和柱状向等轴转变的影响

为了阐明压力对 30Cr15Mo1N 铸锭第二枝晶臂间距 (SDAS) 和柱状向等轴转变 (CET) 的影响，研究了凝固参数、冷却速率和柱状枝晶尖端生长速率随压力的变化。提出了一个公式来获得压力（≤ 2 MPa）和界面传热系数之间的定量关系：

H_{一世} = (28.01 磷^{2} + 299.28 磷 + 1129.10) 吨^{- 0.24}

. 然后，提出一个公式来计算带有冷却速率的 SDAS：

λ_{2} = 21.48 \times {电阻}^{- 0.77}

，适用于低压（≤2 MPa）和低冷却速度（0.4-1.4 K · s ^-1）。随着压力从 0.5 增加到 2 MPa，凝固方式和平衡分配系数有微小的变化。因此，增加压力主要通过增大冷却速度来细化 SDAS。加压可以通过增强过冷度来增加柱状枝晶尖端的生长速度，并通过降低结构过冷度来抑制等轴枝晶的形核和生长。结果表明，随着压力从 0.5 增加到 2 MPa，铸锭中心与 CET 位置之间的距离减小。并提出了计算柱状枝晶尖端生长速率的公式：