ASTM A333 Frequently used name: killed carbon steel
Standard Specification for Seamless and Welded Steel Pipe for Low-Temperature Service
This specification covers wall seamless and welded carbon and alloy steel pipe intended for use at low temperatures. The pipe shall be made by the seamless or welding process with the addition of no filler metal in the welding operation. All seamless and welded pipes shall be treated to control their microstructure. Tensile tests, impact tests, hydrostatic tests, and nondestructive electric tests shall be made in accordance to specified requirements.
1.1 This specification covers nominal (average) wall seamless and welded carbon and alloy steel pipe intended for use at low temperatures. Several grades of ferritic steel are included as listed in Table 1. Some product sizes may not be available under this specification because heavier wall thicknesses have an adverse affect on low-temperature impact properties.
1.2 Supplementary Requirement S1 of an optional nature is provided. This shall apply only when specified by the purchaser.
1.3 The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the specification. The inch-pound units shall apply unless the "M" designation of this specification is specified in the order.
Note 1: The dimensionless designator NPS (nominal pipe size) has been substituted in this standard for such traditional terms as "nominal diameter", "size", and "nominal size".
2. Referenced Documents
A370 Test Methods and Definitions for Mechanical Testing of Steel Products
A671 Specification for Electric-Fusion-Welded Steel Pipe for Atmospheric and Lower Temperatures
A999/A999M Specification for General Requirements for Alloy and Stainless Steel Pipe
E23 Test Methods for Notched Bar Impact Testing of Metallic Materials
Other ASTM Standards defined on this website
What is killed carbon steel?
Steel that has been completely deoxidized by the addition of an agent such as silicon or alumimium, before casting, so that there is practically no evolution of gas during solidification. Killed steels are characterized by a high degree of chemical homogeneity and freedom from porosity.
We say the steel is "killed" because it will quietly solidify in the mould, with no gas bubbling out. As a result, killed steel is dense in structure, uniform in composition, and not so segregative as other types of steels.
During the steel making process, oxygen may become dissolved in the liquid metal. During solidification, the dissolved oxygen can combine with carbon to form carbon monoxide bubbles. The carbon is added to the steel as an alloying element.
The carbon monoxide bubbles are often trapped in the casting and can act as initiation points for failure.
How Killed Steels are Produced and Their Advantages
Formation of the carbon monoxide bubbles can be eliminated through the addition of deoxidising agents such as aluminium, ferrosilicon and manganese. In the case of aluminium, the dissolved oxygen reacts with it to form aluminium oxide (Alumina, Al2O3). The formation of alumina not only prevents the formation of bubbles or porosity, but the tiny particles or inclusions also pin grain boundaries during heat treatment processes, preventing grain growth.
Completely deoxidised steel are known as "killed steels".
They have a more uniform analysis and are relatively free from ageing.
For a given carbon and manganese content, killed steels are usually harder then rimmed steels.
The disadvantage of using killed steels is they often display deep pipe shrinkage.
Steels that are typically killed and are generally killed include:
- Steels with carbon contents greater then 0.25%
- All forging grades of steel
- Structural steels with carbon content between 0.15 to 0.25%
- Some special steel in the lower carbon ranges
Source from TC Steel Tube Group 2009-06-22 12:31:29 Author: Josen Dong