CN103207194A - Method for determining content of element W in matrix after long-term operation of T/P92 steel - Google Patents

Abstract

The invention relates to a method for determining the content of the element W in a matrix after long-term operation of T/P92 steel. The method comprises the following steps: observing a to-be-detected sample by using a scanning electron microscope so as to obtain a volume fraction of the sample; acquiring mol fractions ni of main constituent elements in an Laves phase of the T/P92 steel under an operation temperature; calculating proportion of each element in the Laves phase of the T/P92 steel under the operation temperature based on the mol fractions ni; calculating the distribution amount of the element W in the Laves phase of the T/P92 steel after long-term operation based on an obtained proportionality coefficient and the distribution amount of the element W in an M23C6 phase of the T/P92 steel in an equilibrium state; and finally calculating the content of the element W in the matrix after long-term operation. The method provided by the invention has the advantages of a short analysis period, low cost, no need for a large-size sample, easiness and fastness.

Description

A kind of method of measuring matrix W constituent content after the long-time running of T/P92 steel

Technical field

The present invention relates to the assay method of W constituent content in a kind of steel, especially relate to the method for matrix W constituent content after the long-time running of a kind of T/P92 of mensuration steel.

Background technology

The T/P92 steel is to add 1.5-2.0%W at T/P91 base steel plinth, Mo is reduced to 0.5%, a kind of novel 9%Cr martensite heat-resisting steel that adds micro-B and obtain, the alloying improvement makes its creep rupture strength improve about 30% than the T/P91 steel, the high temperature critical component that is widely used in the ultra supercritical unit, as main steam pipe, heavy caliber thick wall pipeline such as collection case etc., and heating surface tubes such as superheater, reheater.

The W element can strengthen the adhesion between the solid solution atom effectively, improves the recrystallization temperature of matrix, makes the strong distortion of lattice and improves diffusion activation energy, so can significantly improve the heat resistance of P92 steel.But, in high temperature long service process, can separate out the intermetallic compound Laves phase of a kind of W of containing in the T/P92 steel, W constituent content in the solid solution is reduced, cause heat resistance to reduce gradually, therefore measure the content of W element in the matrix, can identify and metal supervision provides foundation for the material after the long-time running of T/P92 steel.

Measure at present that alloying element content generally is to obtain by the electrolysis method of isolating in the matrix, ultimate principle is to go out second phase by electrolytic separation, the second phase alloy composition is analyzed, and then calculated alloying element content in the matrix.The precision height of this method, but analytical cycle is long, cost is high, and need the sample of large-size, practical application is severely limited.

Summary of the invention

The present invention mainly is that solution existing in prior technology analytical cycle is long, cost is high, and needs the sample of large-size, the technical matters that practical application is severely limited; The method of matrix W constituent content after a kind of easy, the quick and economic a kind of T/P92 of mensuration steel long-time running is provided.

Above-mentioned technical matters of the present invention is mainly solved by following technical proposals:

A kind of method of measuring matrix W constituent content after the long-time running of T/P92 steel is characterized in that, may further comprise the steps:

Step 1, sampling obtains tested sample (if specimen size thickness is less than 5mm the T/P92 steel after long-time running, the inconvenience of taking, take method for embedding to prepare metallographic specimen), tested sample being placed observation under the scanning electron microscope (SEM), utilize backscattered electron contrast principle identification Laves phase, takes pictures in the visual field of getting more than 5, by the quantitative metallography method Laves is carried out quantitatively obtaining its volume fraction V mutually _f, will in step 4, use;

Step 2 is obtained under running temperature in the T/P92 steel Laves mole fraction n of main component mutually based on thermodynamics (can by Thermo-Calc software calculate) _i

Step 3, by following formula calculate under running temperature T/P92 steel Laves mutually in the ratio of each element: k _i(then be k to the W element _W):

$k_i=\frac{M_i{n}_i}{M_{\mathrm{Fe}}{n}_{\mathrm{Fe}}+M_W{n}_W+M_{\mathrm{cr}}{n}_{\mathrm{cr}}+M_{\mathrm{Mo}}{n}_{\mathrm{Mo}}}$ Formula one;

Wherein, M _Fe, M _W, M _Cr, M _MoBe respectively the atomic weight of Fe, W, Cr, Mo, n _Fe, n _W, n _Cr, n _MoBe respectively the mole fraction value of Fe, W, Cr, Mo element, i represents any one element in the Laves phase composition element;

Step 4, by following formula calculate T/P92 steel Laves after the long-time running mutually in the sendout c of W element _W:

$c_W^{\′}=k_W{V}_f\frac{{\mathrm{\ρ}}_{\mathrm{Laves}}}{{\mathrm{\ρ}}_{P92}}$ Formula two;

Wherein, ρ _P92And ρ _LavesBe respectively T/P92 steel and Laves average density mutually, V _fBe the Laves phase volume fraction that obtains by quantitative metallographic analysis;

Step 5 is obtained T/P92 steel M under equilibrium state based on thermodynamics (can calculate by Thermo-Calc software) ₂₃C ₆The sendout c of mutually middle W element " _WBecause M ₂₃C ₆Before operation, all separate out, so its W sendout remains unchanged in long-time running.

Step 6, calculate T/P92 steel content of W element in the matrix after long-time running by following formula:

Formula three;

In the formula,

Be T/P92 steel operation t content of W element in the matrix after the time, Total amount for W element in the T/P92 steel.

Therefore, the present invention has following advantage: analytical cycle is short, cost is low, does not need the sample of large-size, and method is easy, quick.

Embodiment

Below by embodiment, technical scheme of the present invention is described in further detail.

Embodiment:

Below for adopting a specific embodiment of method of the present invention.

The T/P92 steel of composition such as following table 1 is simulated 650 ℃ of ag(e)ing tests of hot operation, and the time is respectively 500h and 3000h, measures the content through W element in the matrix behind the different aging times.

The chemical constitution (wt.%) of table 1 embodiment P92 steel

Assay method comprises the steps:

Step 1, sampling grinds metallographic sample, corrodes with picric acid hydrochloric acid alcoholic solution then, keeps sample drying and excellent conductive performance is arranged, and preparation SEM observes sample.

Step 2 selects 6 visual fields to take the BSE photo respectively under SEM at random, and comparison film carries out quantitative metallographic analysis, and the volume fraction result who obtains the Laves phase is respectively V _f ^500h=0.2897%, V _f ^3000h=1.186%

Step 3. is calculated the T/P92 steel in 650 ℃ of following Laves mole fraction of main component mutually according to Thermo-Calc software, the results are shown in table 2.

Table 2T/P92 steel is in the mole fraction (%) of 650 ℃ of following Laves phase key components

Element	Cr	Fe	Mo	W
					n i	9.60	56.88	3.98	29.18

Step 4. according to formula 1 calculate 650 ℃ of following T/P92 steel Laves mutually in the ratio of W element, the results are shown in table 3.

Table 3T/P92 steel is in the ratio (wt%) of 650 ℃ of following Laves phase key components

Element	Fe	W	Cr	Mo
					k i	33.72	56.94	5.30	4.04

Step 5. calculates the T/P92 steel after 650 ℃, 500h and 650 ℃, 3000h timeliness according to formula 2, Laves mutually in the sendout of W element be respectively $c_W^{\′500h}=0.2578\%,$ $c_W^{\′3000h}=0.6621\%;$

Step 6. is calculated the T/P92 steel at 650 ℃ of following M according to Thermo-Calc software ₂₃C ₆The sendout c of mutually middle W element " _W=0.2348%;

Step 7. is calculated T/P92 steel content of W element in the matrix after long-time running according to formula 3, the results are shown in table 4.For comparing, provided the electrolysis experimental result of isolating in the table 4 simultaneously.

Table 4T/P92 steel constituent content among the matrix W after 650 ℃ of timeliness

By table 4 as seen, under two kinds of aging time conditions, this method measurement result and electrolysis segregation experimental result are all very approaching, and the difference between them shows that embodiment of the present invention are feasible in 5%.

Specific embodiment described herein only is that the present invention's spirit is illustrated.Those skilled in the art can make various modifications or replenish or adopt similar mode to substitute described specific embodiment, but can't depart from spirit of the present invention or surmount the defined scope of appended claims.

Claims (1)

1. a method of measuring matrix W constituent content after the long-time running of T/P92 steel is characterized in that, may further comprise the steps:

Step 1, sampling obtains tested sample the T/P92 steel after long-time running, tested sample placed under the scanning electron microscope observe, utilize backscattered electron contrast principle identification Laves phase, and take pictures in the visual field of getting more than 5, by the quantitative metallography method Laves is carried out quantitatively obtaining the volume fraction V of tested sample mutually _f

Step 2 is obtained under running temperature in the T/P92 steel Laves mole fraction n of main component mutually based on thermodynamics _i

Step 3 is with the mole fraction n that obtains in the step 2 _iIn conjunction with formula: obtain T/P92 steel Laves under the running temperature mutually in the ratio of each element: k _i:

$k_i=\frac{M_i{n}_i}{M_{\mathrm{Fe}}{n}_{\mathrm{Fe}}+M_W{n}_W+M_{\mathrm{cr}}{n}_{\mathrm{cr}}+M_{\mathrm{Mo}}{n}_{\mathrm{Mo}}}$ Formula one;

Wherein, M _Fe, M _W, M _Cr, M _MoBe respectively the atomic weight of Fe, W, Cr, Mo, n _Fe, n _W, n _Cr, n _MoBe respectively the mole fraction value of Fe, W, Cr, Mo element, i represents any one element in the Laves phase composition element;

Step 4 is with the k that obtains in the step 3 _iIn conjunction with formula: obtain T/P92 steel Laves after the long-time running mutually in the sendout c of W element _W:

$c_W^{\′}=k_W{V}_f\frac{{\mathrm{\ρ}}_{\mathrm{Laves}}}{{\mathrm{\ρ}}_{P92}}$ Formula two;

Wherein, ρ _P92And ρ _LavesBe respectively T/P92 steel and Laves average density mutually, V _fBe the Laves phase volume fraction that obtains by quantitative metallographic analysis, k _WIt is W element in the T/P92 steel under the running temperature

Laves mutually in shared ratio;

Step 5 is obtained T/P92 steel M under equilibrium state based on thermodynamics ₂₃C ₆The sendout c of mutually middle W element " _WBecause M ₂₃C ₆Before operation, all separate out, so its W sendout remains unchanged in long-time running,

Step 6, calculate T/P92 steel content of W element in the matrix after long-time running by following formula:

Formula three;

In the formula,

Be T/P92 steel operation t content of W element in the matrix after the time,

Total amount for W element in the T/P92 steel.