Influence of Microstructure and Crystallographic Texture on the Surface Brightness of Industrially Produced Tinplated Steels

Abstract

Three distinct layers are present in commercially produced tinplated steels: the top tin layer, the middle Fe-Sn alloy layer, and the bottom steel substrate. The brightness of these steels is inversely proportional to the roughness of the top layer. Substrate steels with recrystallized structure, sharper texture, and cleaner matrix result in flatter Fe-Sn interlayer and subsequently smoother top Sn layer. This in turn gives brighter surface finish.

Appendix A

Time of reaction: 16 seconds

1 lb/bb = 22.4 g/m²

Atomic weight of Sn: 118.7

Atomic weight of Fe: 55.8

Density of FeSn₂: 8.55 g/cc

• 1. Calculation of Sn in the form of FeSn₂ formed on steel substrate after 16 seconds[28]:

  • On (100) surface = 0.25 lb/bb = 2.8 g/m²

  • On (110) surface = 0.13 lb/bb = 1.456 g/m²

  • On (111) surface = 0.17 lb/bb = 1.904 g/m²

• 2. Calculation of FeSn₂ formed on steel substrate after 16 seconds:

In FeSn₂, 2Sn atoms attached with one Fe atom.

Therefore, (2 × 118.7) g of Sn is present in (2 × 118.7 + 55.8) g FeSn₂

$$ \begin{aligned} 2 3 7. 4 {\text{ g of Sn }} & \equiv { 293}. 2 {\text{ g FeSn}}_{ 2} \\ {\text{So}},{ 2}. 8 {\text{ g of Sn }} & \equiv { 3}. 4 5 8 {\text{ g FeSn}}_{ 2} \\ {\text{So}},{ 1}. 4 5 6 {\text{ g of Sn }} & \equiv { 1}. 7 9 8 {\text{ g FeSn}}_{ 2} \\ {\text{So}},{ 1}. 90 4 {\text{ g of Sn }} & \equiv { 2}. 3 5 1 {\text{ g FeSn}}_{ 2} \\ \end{aligned}. $$

Therefore, after 16 seconds

• (100) oriented grains of the samples would have 3.458 g/m² or 3.458 × 10⁻⁴g/cm² of FeSn₂

• (110) oriented grains of the samples would have 1.798 g/m² or 1.798 × 10⁻⁴g/ cm² of FeSn₂

• (111) oriented grains of the samples would have 2.351 g/m² or 2.351 × 10⁻⁴g/ cm² of FeSn₂

• 3. Calculation of FeSn₂ layer height on (100), (110), and (111) oriented grains

Assuming in the present case, the height of FeSn₂ layer on (100), (110), and (111) are h₁₀₀, h₁₁₀, and h₁₁₁, respectively.

For (100) oriented grains for every 1 cm² area:

The volume of FeSn₂ would be h₁₀₀ *1 cm² = h₁₀₀ cm². The weight of this FeSn₂ as calculated is 3.458 × 10⁻⁴ g.

Now, the density of FeSn₂ is 8.55 g/cm³²⁹.

Therefore, 3.458 × 10⁻⁴ g of FeSn₂ ≡ 0.404 × 10⁻⁴ cm³ of FeSn₂.

$$ \begin{aligned} {\text{So}}, \, h_{ 100} {\text{cm}}^{ 2} & = \, 0. 40 4 { } \times { 1}0^{ - 4} {\text{cm}}^{ 3} \\ h_{ 100} & = \, 0. 40 4 { } \times { 1}0^{ - 4} {\text{cm }} = 0.404 \, \mu {\text{m}} \\ \end{aligned}. $$

Similarly, h₁₁₀ and h₁₁₁ are calculated as =0.210 µm and 0.275 µ, respectively.