Grain Boundary Precipitate Appearing in the Weld Heat Affected Zone of Boron Treated High Tensile Strength Steel (Report No.1)
Precipitation Characteristics of Boron Constituent
1965 Volume 34 Issue 1 Pages 38-45
Details
1965 Volume 34 Issue 1 Pages 38-45
The precipitation characteristics of boron constituent appearing in the weld heat affected zone of boron treated T-1 type high tensile strength steel has been investigated. Following results are obtained:
1. The precipitatation of boron constituent is extremely little when the steel contains 0.002% of B but predominant in the steel containing 0.005% of B.
2. In the steel containing 0.002% of B, the precipitation characteristics of boron constituent varies with the cooling rate of heat affected zone. When the cooling condition of heat affected zone is such that the cooling time from 800°C to 500°C is 28.5 sec., there is no precipitation of boron constituent. When the choling time from 800°C to 500°C is more than 51.5 sec., slight precipitation of boron constituent has been observed. In case of the steel containing 0.005% of B, the precipitate has been observed in all the cooling conditions ranging from 10 sec. to 163.5 sec. in cooling time from 800°C to 500°C.
3. The precipitation characteristics of boron constituent can be deduced from the isothermal precipitation diagram by superimposing the cooling curve of heat affected zone on the diagram. And, the isothermal precipitation curve of boron constituent moves to the left as the austenitizing temperature is higher. It also moves to the left if the steel has more tendency to reveal the boron constituent in its heat affected zone.
4. The precipitation characteristics of boron constituent at different cooling condition can be more easily known by the observation of precipitate on the side of Jominy specimen, because each point at various distance from quenched end of this specimen represents various different cooling condition.
