SAE AMS 2315H-2020

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AEROSPACE
MATERIAL SPECIFICATION
AMS2315™
REV. H
Issued 1963-01
Reaffirmed 2006-04
Revised 2020-01
Superseding AMS2315G
Determination of Delta Ferrite Content
RATIONALE
AMS2315H revises specimen selection for tubing (3.1.3.3), Heat Treatment (3.1.4), Procedure for Limited Delta Ferrite
Criterion (3.2), Relative Accuracy requirement (3.2.1.3.5.1), Reports (4.4), and results from a Five-Year Review and update
of this specification.
1. SCOPE
This specification covers two methods for determining the percentage of delta ferrite in steels and other iron alloys. When
applicable, this specification will be invoked by the material specification.
2. APPLICABLE DOCUMENTS
The issue of the following documents in effect on the date of the purchase order forms a part of this specification to the
extent specified herein. The supplier may work to a subsequent revision of a document unless a specific document issue is
specified. When the referenced document has been cancelled and no superseding document has been specified, the last
published issue of that document shall apply.
2.1 ASTM Publications
Available from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959,
Tel: 610-832-9585, www.astm.org.
ASTM E3 Preparation of Metallographic Specimens
ASTM E1245 Determining the Inclusion or Second-Phase Constituent Content of Metals by Automatic Image Analysis
3. TECHNICAL REQUIREMENTS
3.1 Specimen Preparation
3.1.1 Heat Qualification
Sampling shall be in accordance with 4.3.1. Samples shall be converted into test specimens in accordance with 3.1.3.
3.1.2 Product Qualification
Product from a heat not qualified, based on sampling as in 4.3.1, shall be sampled in accordance with 4.3.2. Samples shall
be converted into test specimens in accordance with 3.1.3.
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SAE INTERNATIONAL AMS2315™H Page 2 of 7
3.1.3 Specimen Selection
Samples of sufficient size to provide specimens having approximately 0.25 to 0.5 in2 (161 to 323 mm2) prepared surface
area or of an area sufficient to randomly select the required number of fields to accurately examine the sample, shall be cut
from the product as in 3.1.3.1, 3.1.3.2, or 3.1.3.3, as applicable. Each specimen shall be marked in such a manner that its
orientation with respect to the direction of rolling, drawing, or extruding is easily identifiable.
3.1.3.1 Round, Hexagonal, or Square Product
Specimens shall be selected from an area midway between the edge and the center of the sample.
3.1.3.2 Rectangular Product
Specimens shall be selected from an area midway between the longitudinal edge and the center of the sample.
3.1.3.3 Tubing and Other Hollow Shapes
Specimens shall be selected from samples which include the full wall thickness of the product if the full wall thickness is
0.500 inch or under and mid-wall if the full wall thickness is over 0.500 inch.
3.1.4 Heat Treatment
Specimens, except as specified in 3.1.4.1, may be austenitized at the normal recommended temperature for the grade of
steel being examined and adequately quenched. The quenched specimens shall be tempered at a sufficiently high
temperature to develop good metallographic contrast.
3.1.4.1 Solution and precipitation hardenable steels may be solution heat treated and may be precipitation heat treated
to develop good metallographic contrast.
3.1.5 Polishing
After heat treatment as in 3.1.4, a face of each specimen, perpendicular to the direction of maximum deformation, shall be
ground and polished, using standard metallographic polishing techniques in accordance with ASTM E3 to produce a surface
suitable for microscopic examination.
3.1.6 Etching
The polished surface of each specimen shall be suitably etched to reveal delta ferrite (see 8.4).
3.2 Procedure for Limited Delta Ferrite Criterion
Inspect the specimen surface at a magnification appropriate to observe the relative amount and distribution of delta ferrite
present. If it is evident that many fields to be measured will have zero value, and no single field will have a value exceeding
the material specification maximum, then measure a set number of fields defined in a laboratory procedure sufficient to
ensure that the upper control limit of the mean is less than 50% of the material specification maximum at the 95% confidence
level as in 3.2.1 or 3.2.2. A 10% relative accuracy level is not required. In case of dispute over the percentage of delta
ferrite, the value determined as in 3.2.2 shall govern.
3.2.1 Point Count Method
3.2.1.1 Field Measurement
Project the image of the microstructure of each specimen onto the ground-glass screen of a reflection-type microscope or
metallograph. Place a transparent point-counting grid template either in front of or behind the ground glass. The template
should consist of either 100 or 500 systematically spaced grid points, either in the form of fine crosses or a grid lattice. The
magnification chosen should be high enough to clearly resolve the delta ferrite grains but not so high that the number of
grid points falling in the ferrite grains exceeds one, on the average. For each specimen, count the number of grid points
(i.e., the intersection point of the crosses or grid blocks) that fall within the ferrite grains as one and those that fall on the
phase boundaries as one-half.
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SAE INTERNATIONAL AMS2315™H Page 3 of 7
3.2.1.2 Field Selection
Select the fields to be measured randomly, that is, without looking at the image, by moving the stage controls. Do not alter
the position so that grid points fall on or miss ferrite grains. Space the fields selected around the specimen surface in a
systematic pattern. Measure a sufficient number of fields so that the relative accuracy (see 3.2.1.3.5) is 10% or less. The
relative accuracy of the measurement is influenced by the volume fraction of the ferrite, the magnification, the grid point
density, the number of fields measured, and the field-to-field variation of the ferrite phase.
3.2.1.3 Calculation
3.2.1.3.1 Ferrite Per Field
Calculate the volume fraction of ferrite using Equation 1 for each field measured.
(Eq. 1)
where:
Vδ,i = volume fraction of ferrite in % of each field
Pδ,i = number of grid points in the ferrite phase or on the phase boundaries
Pt = number of grid points
3.2.1.3.2 Ferrite Per Specimen
Determine the mean value of the volume fraction of ferrite using Equation 2.
(Eq. 2)
where:
= mean volume fraction of ferrite per specimen
n = number of fields measured in the specimen
3.2.1.3.3 Calculate the standard deviation of the field-to-field variation of the volume fraction of ferrite using Equation 3.
(Eq. 3)
where:
s = standard deviation of the volume fraction measurements
3.2.1.3.4 Calculate the 95% confidence limit (95% CI) of the volume fraction measurements using Equation 4.
±95% CI = ± 
√ (Eq. 4)
where:
t = t-value for Student t-distribution for (n-1) degree of freedom for a 95% confidence interval are tabulated in most
statistical textbooks, see Table 1 for examples:
V
δi,
P
δi,
P
t
--------- 100×=
V
δ
sΣV
δi,
V
δ
–( )
2
n 1–
-------------------------------------
 
 
 
1 2⁄
=
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摘要：

SAE AMS 2315H-2020 是由国际自动机工程师学会（SAE International）发布的最新修订版航空航天材料规范，全称为《钢的淬透性试验方法》。该标准详细规定了用于评估钢制零件在热处理过程中淬透性（即钢材从奥氏体化温度快速冷却时获得马氏体组织深度与硬度的能力）的标准化试验流程与要求。AMS 2315H 版本在先前规范基础上进行了技术更新与勘误，确保其与当前航空航天工业中高性能合金钢（如4140、4340及300M等）的淬火与回火工艺要求保持同步。该标准的核心内容包括端淬试验（

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作者：Carl 分类：国外协会 价格：25星币 属性：7 页 大小：262.59KB 格式：PDF 时间：2024-09-07

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