JC/T 497-2013 Building Materials Industry Kiln Use Direct Bonded Magnesium-Chrome Bricks
2023-12-06
Direct-bonded magnesia-chrome bricks for building material industrial kilns
1 Scope
This standard specifies the terminology and definitions, classification, shape and size, technical requirements, test methods, inspection rules, packaging, marking, transportation, storage and quality certificates of direct-bonded magnesia-chrome bricks for building material industrial kilns. This standard applies to direct-bonded magnesia-chrome bricks used in cement kilns and glass kilns.
2 Normative references
The following documents are indispensable for the application of this document. For dated references, only the dated version applies to this document. , Only the dated version applies to this document.
For undated references, the latest version ( including all amendments ) applies to this document.
GB/T 2992.1 General refractory brick shapes and sizes Part 1 Part : General bricks
GB/T 2997 Dense shaped refractory products Test methods for bulk density, apparent porosity and true porosity
GB/T 3002 Refractory materials Test method for high temperature flexural strength
GB/T 5070 Chemical analysis methods for chromium-containing refractory materials
GB/T 5072 Refractory materials Test method for compressive strength at room temperature
GB/T 7320 Test method for thermal expansion of refractory products
GB/T 7321 Preparation method for shaped refractory product samples
GB/T 10326 Inspection methods for dimensions, appearance and section of shaped refractory products
GB/T 16546 Packaging, marking, transportation and storage of shaped refractory products
GB/T 17912 Shapes and sizes of refractory bricks for rotary kilns
GB/T 18930 Terminology of refractory materials
GB/T 21114 Refractory materials X-ray fluorescence spectrometry chemical analysis cast glass片法
YB/T 370 Test method for load softening temperature of refractory products (non-differential-heating method)
YB/T 376.1 Test method for thermal shock resistance of refractory products (water quenching method)
YB/T 376.2 Test method for thermal shock resistance of refractory products (air quenching method)
3 Terms and definitions
Defined in GB/T 18930 and the following terms and definitions apply to this document.
Direct bonded magnesia-chrome bricks
Refers to products made from high-purity magnesia and chrome ore as main raw materials, fired at a temperature above 1700°C, and whose refractory grains are mostly in direct contact.
4 Classification, shape and size
4.1 Products are divided into direct-bonded magnesia bricks for cement kilns and direct-bonded magnesia-chrome bricks for glass kilns according to their use. Direct-bonded magnesia-chrome bricks for cement kilns are divided into low-chromium type and medium-chromium type according to their Cr 2 O 3 content, and direct-bonded magnesia-chrome bricks for glass kilns are high-chromium type (DMC-12).
4.2 Products are divided into straight bricks and cylindrical bricks according to their shape. The shape and size of straight bricks shall conform to the provisions of GB/T 2992.1. The shape and size of simple bricks and other special shapes shall be agreed upon by both the supplier and the demander.
4.3 The shape and size of direct-bonded magnesia bricks for cement kilns shall conform to the provisions of GB/T 2992.1 and GB/T 17912. Special requirements shall be agreed upon by both the supplier and the demander.
5 Technical requirements
5.1 The physicochemical properties of direct-bonded magnesia-chrome bricks shall conform to the provisions of Table 1 and Table 2.
Table 1 Physicochemical properties of direct-bonded magnesia-chrome bricks for cement kilns | |||||
Item | Index | ||||
Medium chromium type | Low chromium type | ||||
Chemical composition | MgO/% | μ 0 | ≥73 | ≥80 | |
Cr 2 O 3,/% | μ 0 | 7~10 | 2~5 | ||
SiO 2/% | μ 0 | ≤1.8 | |||
σ | 0.2 | ||||
Physical properties | Apparent porosity/% | μ 0 | ≤18 | ||
σ | 1.0 | ||||
Compressive strength at room temperature/MPa | μ 0 | ≥50 | ≥55 | ||
σ | 10 | ||||
X min | 40 | 45 | |||
Load softening temperature T 0.6/ ℃ | μ 0 | ≥1650 | ≥1600 | ||
σ | 10 | ||||
Thermal shock resistance/times | 1100℃, water cooling | μ 0 | ≥5 | ||
X min | ≥4 | ||||
950℃, air quenching | μ 0 | ≥30 | |||
X min | ≥25 | ||||
Thermal expansion rate/% | Provide measured data | ||||
The temperature of the thermal expansion rate can be agreed upon by both the supplier and the demander. | |||||
Table 2 Physico-chemical indicators of directly bonded magnesia-chromium bricks for glass kilns | |||
Item | Index | ||
DMC-12 | |||
Chemical composition | MgO/% | μ 0 | ≥70 |
Cr 2 O 3,/% | μ 0 | ≥12 | |
σ | 1.0 | ||
SiO 2/% | μ 0 | ≤2.0 | |
σ | 0.2 | ||
Physical properties | Bulk density/(g/cm) |
| ≥3.0 |
Apparent porosity/% | μ 0 | ≤18 | |
σ | 1.0 | ||
Compressive strength at room temperature/MPa | μ 0 | ≥45 | |
σ | 10 | ||
X min | 35 | ||
Load softening temperature T 0.6 /℃ | μ 0 | ≥1650 | |
σ | 10 | ||
Thermal shock resistance/times 1100℃, water cooling | μ 0 | ≥5 | |
X min | ≥4 | ||
Thermal expansion rate/% | Provide measured data | ||
High temperature bending strength/MPa 1260℃x0.5 h | Provide measured data | ||
The temperature of the thermal expansion rate can be agreed upon by both the supplier and the demander. | |||
5.2 The dimensional tolerance and appearance of the bricks shall conform to the provisions of Table 3.
Table 3 Dimensional tolerance and appearance quality of bricks Unit: mm | ||
Item | Index | |
Dimensional tolerance | Size ≤230 | ±1.0 |
Size >230 | ±1.5 | |
Size of wedge brick | Allowable deviation | ±1.0 |
Wedge difference | 1.0 | |
Distortion | ≤0.5% | |
Chipped corner | ≤10 allowed, 10 | |
Chipped edge | ≤25 allowed, 25 | |
Crack length | Width <0.1 | Allowed |
Width 0.1~0.25 | ≤40 | |
Width >0.25 | Not allowed | |
Section | Width ≤0.5 | ≤0.5 |
Melt hole | Diameter | ≤6 |
Note 1: The appearance quality and dimensional deviation of special-shaped products shall be agreed upon by both the supplier and the demander. Note 2: Simple bricks are packaged in grades according to the height difference, which is agreed upon by both the supplier and the demander. | ||
6 Test methods
6.1 Sampling
According to GB/T 7321.
6.2 MgO, Cr 2 O 3 、SiO 2 Inspection
According to GB/T 5070 or GB/T 21114. GB/T 5070 is the arbitration method for testing bulk density and apparent porosity.
6.3 According to GB/T 2997.
6.4 Inspection of compressive strength at room temperature
According to GB/T 5072.
6.5 Inspection of load softening temperature
According to YB/T 370.
6.6 Inspection of thermal shock resistance
According to YB/T 376.1 or YBT 376.2. YB/T 376.1 is the arbitration method.
6.7 Inspection of thermal expansion rate
According to GB/T 7320.
6.8 Inspection of dimensional deviation and appearance quality shall be carried out according to GB/T 10326.
6.9 The inspection of high temperature bending strength shall be carried out according to GB/T 3002.
7 Inspection rules
7.1 Inspection classification
Inspection is classified into factory inspection and type inspection.
7.1.1 Factory inspection
Factory inspection shall be carried out when the product leaves the factory. The factory inspection items include appearance quality, dimensional deviation, chemical composition, bulk density, room temperature compressive strength and apparent porosity.
7.1.2 Type inspection
Type inspection items include all items specified in Chapter 5 Technical Requirements. Type inspection shall be carried out under the following circumstances:
a) When there is a significant change in the production process or raw materials;
b) At least twice a year during normal production;
c) When production is resumed after being suspended for more than six months;
d) When the factory inspection results differ significantly from the previous type inspection results.
7.2 Batching
Products are batched according to the same production conditions and the same grade, and each batch shall not exceed 300t.
7.3 Sampling
7.3.1 Sampling for appearance and size inspection
This standard provides appearance and dimension sampling inspection plans based on the acceptable quality limit (AQL), as shown in Table 4. Unless otherwise specified, appearance inspection is conducted according to the AQL = 4.0 sampling plan, and dimension inspection is conducted according to the AQL = 6.5 sampling plan. If stricter requirements are imposed on appearance and dimensions, AQL = 1.5 can be selected for appearance and AQL = 4.0 for dimensions, but this needs to be specified in a bilateral agreement.
Samples for appearance and dimension inspection should generally be randomly selected at once from the finished product stacks delivered by the manufacturer. For ease of sampling, the products delivered by the manufacturer should be neatly stacked in order of brick type and production time, leaving a passage for sampling operations. Before sampling, the number of units (N) in the delivered brick type sub-batch should be counted, and then samples should be drawn according to the sample size (n) specified in Table 3. When the sampling numbers for appearance and dimensions are the same, the total number of samples = appearance sampling number n = dimension sampling number n. The appearance and dimensions of the sampled products are inspected separately, and quality judgment is made according to the corresponding acceptance number Ac. When the sampling numbers n for appearance and dimensions are different, the total number of samples should be drawn at once according to the larger n, and the appearance and dimensions of the sampled products are all inspected, and then quality judgment is made according to the corresponding acceptance number Ac.
Table 4 Sampling Plan for Dimension and Appearance Inspection | |||
Acceptable Quality Limit (AQL)% | Batch Size N (pieces) | Sample Size n (pieces) | Acceptance Number Ac |
1.5 | ≤31 | N | Reject Non-Conforming Products |
32~1200 | 32 | 1 | |
1201~3200 | 50 | 2 | |
3201~10000 | 80 | 3 | |
>10000 | 125 | 5 | |
4.0 | ≤12 | N | Reject Non-Conforming Products |
13~280 | 13 | 1 | |
281~500 | 20 | 2 | |
501~1200 | 32 | 3 | |
1201~3200 | 50 | 5 | |
3201~10000 | 80 | 7 | |
>10000 | 125 | 10 | |
6.5 | ≤7 | N | Reject Non-Conforming Products |
8~150 | 8 | 1 | |
151~280 | 13 | 2 | |
281~500 | 20 | 3 | |
501~1200 | 32 | 5 | |
1201~3200 | 50 | 7 | |
3201~10000 | 80 | 10 | |
>10000 | 125 | 14 | |
7.3.2 Sampling for Physico-Chemical Property Inspection
Samples should be randomly selected from the finished product stacks. In special cases, they can also be randomly selected during the production process (e.g., when the products are taken out of the kiln) after mutual agreement. Samples must not have appearance defects that affect the physico-chemical properties.
7.4 Judgment Rules
7.4.1 Judgment of Appearance Quality and Dimensional Deviation
After the samples are drawn, the appearance and dimensional quality of each sample should be judged as "qualified" or "unqualified" according to the product quality standard requirements. After all samples are tested, the number (y) of cumulative unqualified samples for appearance and dimensions is counted separately, and compared with the acceptance number Ac specified in Table 3. If y ≤ Ac, the sub-batch of products is judged as qualified; if y > Ac, the sub-batch of products is judged as unqualified. For sub-batches that fail appearance or dimension inspection, if unqualified products can be removed from the batch through inspection, the manufacturer is allowed to re-deliver after inspection, and re-inspection is conducted. If the quality of the unqualified sub-batch cannot be improved through inspection, the batch of products is rejected.
7.4.2 Judgment of Physico-Chemical Properties
The acceptance sampling inspection items for the physico-chemical properties of shaped refractory products include MgO content, Cr 2 O 3 content, SiO 2 content, bulk density, apparent porosity, compressive strength, load softening temperature, and thermal shock stability. Among them, the judgment of MgO content, Cr 2 O 3 content, SiO 2 content, and load softening temperature can be made according to Tables 5 and 6 (the sample sizes in the two tables are different, either can be selected). The judgment of bulk density, apparent porosity, compressive strength, and thermal shock stability is made according to Table 6. The single value of room temperature compressive strength is not allowed to be lower than X min where σ is the standard deviation in Tables 1 and 2, and S is the standard deviation of 9 samples after retesting when a non-conforming item is detected. The above indicators meet the requirements of Table 5 or Table 6 are judged as qualified.
Table 5 Qualified/Unqualified Judgment of Single Quality Characteristic with Batch Mean as Quality Indicator (n=3) | ||||
Quality Requirements | First Test: 1 Sample | Cumulative Test of 2 Tests: 3 Samples | ||
Test Results | Judgment | Test Results | Judgment | |
Low Value Not Applicable | x i ≥μ 0 | Qualified | - | - |
x i <μ 0 | Continue Inspection | Average of x ≥μ 0 | Qualified | |
Average of x <μ 0 | Unqualified | |||
High Value Not Applicable | x i ≤μ 0 | Qualified | - | - |
x i >μ 0 | Continue Inspection | Average of x ≤μ 0 | Qualified | |
Average of x >μ 0 | Unqualified | |||
Table 6 Qualified/Unqualified Judgment of Single Quality Characteristic with Batch Mean as Quality Indicator (n=9) | ||||
Quality Requirements | First Test: 3 Samples | Cumulative Test of 2 Tests: 9 Samples | ||
Test Results | Judgment | Test Results | Judgment | |
Low Value Not Applicable | Average of x ≥μ 0 | Qualified | - | - |
Average of x <μ 0 -1.5σ | Unqualified | - | - | |
μ 0 -1.5σ ≤ Average of x < μ 0 | Continue Inspection | Average of x ≥μ 0-0.62S | Qualified | |
Average of x <μ 0-0.62S | Unqualified | |||
High Value Not Applicable | Average of x ≤μ 0 | Qualified | - | - |
Average of x >μ 0 +1.5σ | Unqualified | - | - | |
μ 0 < Average of x ≤ μ 0 +1.5σ | Continue Inspection | Average of x ≥μ 0 +0.62S | Qualified | |
Average of x >μ 0 +0.62S | Unqualified | |||
7.5 Comprehensive Judgment
If all the physico-chemical properties and appearance quality, and dimensional deviations to be inspected in the inspection batch are qualified, then the batch of products is qualified; otherwise, it is unqualified.
Packaging, marking, transportation, storage and quality certificate
8.1 Packaging
Bricks should be packaged with moisture-proof measures.
8.2 Marking, transportation and storage
According to GB/T 16546.
8.3 Quality Certificate
Bricks should be accompanied by a quality certificate upon leaving the factory. The quality certificate should include: supplier's name or factory mark, customer's name, production date, shelf life, contract number, product name, standard number, grade, brick number, batch number and corresponding physical and chemical test results.
Direct bonded magnesium-chrome bricks for furnaces in the building materials industry
1 Range
This standard specifies the terms and definitions, classification, shape and size, technical requirements, test methods, inspection rules, packaging, marking, transportation, storage and quality certificates of directly bonded magnesia chrome bricks for industrial kilns of building materials. This standard applies to directly bonded magnesium-chrome bricks for cement and glass kilns.
2 Normative reference documents
The following documents are essential for the application of this document. For dated references, the date-only version applies to this document.
For undated references, the latest version (including all amendment orders) applies to this document.
GB/T 2992.1 Shape and dimensions of general purpose firebricks – Part 1: general purpose bricks
Test method for bulk density, apparent porosity and true porosity of GB/T 2997 compact shaped refractory products
GB/T 3002 refractories high temperature bending strength test method
GB/T 5070 chromium containing refractory chemical analysis method
GB/T 5072 refractories – normal temperature compressive strength test method
Test method for thermal expansion of GB/T 7320 refractory products
GB/T 7321 shaped refractory product sample preparation method
GB/T 10326 shaped refractory products size, appearance and section inspection method
GB/T 16546 shaped refractory products packaging, marking, transportation and storage
GB/T 17912 refractory brick for rotary kiln shape and size
GB/T 18930 refractory terminology
GB/T 21114 refractories X-ray fluorescence spectrochemical analysis cast glass sheet method
Test method for Load softening temperature of YB/T 370 refractory products (non-differential warming method)
YB/T 376.1 Test method for thermal shock Resistance of Refractory products (water quench method)
YB/T 376.2 Test method for Thermal shock Resistance of Refractory products (Air quench cooling method)
3 Terms and definitions
GB/T 18930 and the following terms and definitions apply to this document.
Direct bonded Magnesia-Chrome bricks
Refers to high purity magnesia and chromium concentrate as the main raw materials, fired at temperatures above 1700C, the direct contact between the grain of the refractory products.
4 Classification, shape and size
Products are divided into cement kiln direct bonded magnesia brick and glass close direct bonded magnesia chrome brick, cement kiln direct bonded magnesia chrome brick is divided into low road type and medium chromium type two grades according to Cr2O3 content, glass kiln direct bonded magnesia chrome brick is high road type grade (DMC-12).
Products are divided into straight bricks and cylindrical bricks according to their appearance, and the shape and size of straight bricks shall comply with the provisions of GB/T 2992.1. The requirements for simple bricks and other special shapes and dimensions shall be agreed upon by both parties.
The shape and size of the direct bonded magnesite bricks for cement kilns shall comply with the provisions of GB/T 2992.1 and GB/T 17912, and the special requirements shall be agreed by the supply and demand parties.
5 Technical Requirements
The physical and chemical properties of directly bonded magnesium-chrome bricks shall comply with the provisions of Table 1 and Table 2.
Table 1 Physical and chemical properties of directly bonded magnesium-chrome bricks for cement kilns | |||||
Index | Item | ||||
Medium chrome type | Low chromium type | ||||
Chemical composition | MgO/% | μ 0 | ≥73 | ≥80 | |
Cr 2 O 3,/% | μ 0 | 7~10 | 2~5 | ||
SiO 2/% | μ 0 | ≤1.8 | |||
σ | 0.2 | ||||
Physical property | Apparent porosity/% | μ 0 | ≤18 | ||
σ | 1.0 | ||||
Compressive strength at room temperature/MPa | μ 0 | ≥50 | ≥55 | ||
σ | 10 | ||||
X min | 40 | 45 | |||
Softening temperature under loadT 0.6/ ℃ | μ 0 | ≥1650 | ≥1600 | ||
σ | 10 | ||||
Thermal shock stability/time | 1100℃, water-cooled | μ 0 | ≥5 | ||
X min | ≥4 | ||||
950℃, the air is cold | μ 0 | ≥30 | |||
X min | ≥25 | ||||
Thermal expansion rate /% | Provide measured data | ||||
The temperature of the thermal expansion rate can be agreed upon by the supply and demand parties. | |||||
Table 2 Physicochemical indexes of directly bonded magnesia-chromium bricks for glass kilns | |||
Index | Item | ||
DMC-12 | |||
Chemical composition | MgO/% | μ 0 | ≥70 |
Cr 2 O 3,/% | μ 0 | ≥12 | |
σ | 1.0 | ||
SiO 2/% | μ 0 | ≤2.0 | |
σ | 0.2 | ||
Physical property | Bulk density/(g/cm) |
| ≥3.0 |
Apparent porosity/% | μ 0 | ≤18 | |
σ | 1.0 | ||
Compressive strength at room temperature/MPa | μ 0 | ≥45 | |
σ | 10 | ||
X min | 35 | ||
Softening temperature under loadT 0.6/ ℃ | μ 0 | ≥1650 | |
σ | 10 | ||
Thermal shock stability / 1100℃, water-cooled | μ 0 | ≥5 | |
X min | ≥4 | ||
Thermal expansion rate /% | Provide measured data | ||
High temperature bending strength /MPa1260℃ x0.5h | Provide measured data | ||
The temperature of the thermal expansion rate can be agreed by both sides of the supply arrow. | |||
The permissible size deviation and appearance of the brick shall comply with the provisions of Table 3.
Table 3 The permissible size deviation of bricks and their apparent mass are measured in millimeters | ||
Index | Item | |
Allowable deviation of dimension | Dimension≤230 | ±1.0 |
Dimension>230 | ±1.5 | |
Wedge brick size head size | Allowable deviation | ±1.0 |
Wedge difference | 1.0 | |
Tortuosity | ≤0.5% | |
Missing corner | If the value is less than or equal to 10, 10 | |
Wane | ≤25 is allowed; 25 | |
Crack length | Breadth<0.1 | Permit |
Breadth 0.1~0.25 | ≤40 | |
Breadth>0.25 | Not allowed | |
Section | Breadth≤0.5 | ≤0.5 |
Molten cavern | Diameter | ≤6 |
Note 1: The appearance quality and size deviation of special shape products shall be agreed by the supply and demand parties. Note 2: The simple brick is packaged according to the height difference agreed by the supply and demand parties. | ||
6 Test methods
6.1 Sample Preparation
According to GB/T 7321.
6.2 Inspection of MgO, Cr2O3 and SiO2
According to GB/T 5070 or GB/T 21114. Wherein, GB/T 5070 is the test of volume density and apparent porosity by arbitration method.
6.3 According to GB/T 2997
6.4 Test of compressive strength at room temperature
According to GB/T 5072.
6.5 Test of softening temperature under load
According to YB/T 370.
6.6 Test of thermal shock resistance
According to YB/T 376.1 or YBT 376.2. Where YB/T 376.1 is arbitration law.
6.7 Test of thermal expansion rate
According to GB/T 7320.
6.8 The inspection of dimension deviation and appearance quality shall be carried out according to GB/T 10326.
6.9 The test of high temperature bending strength shall be carried out according to GB/T 3002.
7 Inspection Rules
7.1 Inspection Classification
The inspection is divided into factory inspection and type inspection according to the type.
7.1.1 Factory inspection
The product shall be inspected before leaving the factory. Factory inspection items include appearance quality, dimensional deviation, chemical composition, bulk density, pressure strength at room temperature and apparent porosity.
7.1.2 Type inspection
Type inspection items include all items specified in Chapter 5 Technical requirements. Type inspection is performed in the following cases:
a) When there is a major change in the production process or raw materials;
b) During normal production, at least twice a year;
c) Stop production for more than half a year and resume production;
d) When there is a big difference between the factory inspection result and the last type inspection result.
7.2 Batch Group
Products according to the same production conditions of the same brand batch, each batch should not exceed 300t.
7.3 Sampling
7.3.1 Sampling for appearance and dimension inspection
The sampling inspection scheme of appearance and dimension given in this standard is formulated according to the acceptable quality limit AQL, see Table 4. If there is no special provision, the appearance inspection shall be carried out according to AQL=4.0, and the size inspection shall be carried out according to AQL=6.5 sampling scheme. If there are strict requirements on appearance and size, AQL=1.5 can be selected for appearance, and AQL=4.0 can be selected for size sampling scheme, but it needs to be indicated in the agreement between the two parties.
Samples for dimensional inspection should normally be randomly selected at one time in the finished product stacks delivered by the manufacturer. In order to facilitate sampling, the products delivered by the manufacturer should be neatly placed according to the brick type and production time order, and the sampling operation channel should be left. Before sampling, the number of units of product (N) in the brick sublot delivered shall be counted and samples shall be taken according to the sample size (n) specified in Table 3. When the sampling numbers specified by the appearance and size are consistent, the total number of samples = the appearance sampling number n= the size sampling number n, the appearance and size of the samples taken are respectively inspected, and the quality is determined according to the corresponding receiving number Ac. When the appearance and size of the specified sampling number n is different, the total number of samples should be taken by n large number once, the appearance and size of the samples taken are all inspected, and then the quality is determined according to the corresponding receiving number Ac.
Table 4 Sampling scheme for dimensional and visual inspection | |||
Receive quality limit AQL% | Batch N block | Sample size n blocks | Reception number Ac block |
1.5 | ≤31 | N | Eliminate nonconforming products |
32~1200 | 32 | 1 | |
1201~3200 | 50 | 2 | |
3201~10000 | 80 | 3 | |
>10000 | 125 | 5 | |
4.0 | ≤12 | N | Eliminate nonconforming products |
13~280 | 13 | 1 | |
281~500 | 20 | 2 | |
501~1200 | 32 | 3 | |
1201~3200 | 50 | 5 | |
3201~10000 | 80 | 7 | |
>10000 | 125 | 10 | |
6.5 | ≤7 | N | Eliminate nonconforming products |
8~150 | 8 | 1 | |
151~280 | 13 | 2 | |
281~500 | 20 | 3 | |
501~1200 | 32 | 5 | |
1201~3200 | 50 | 7 | |
3201~10000 | 80 | 10 | |
>10000 | 125 | 14 | |
7.3.2 Sampling for physical and chemical properties inspection
Samples should be randomly drawn on the finished stack. In special cases, it can also be randomly extracted during the production process (such as when the product is out of the kiln) by consensus of the two parties. The sample shall not have appearance defects that affect the physical and chemical quality characteristics.
7.4 Decision Rules
7.4.1 Determination of appearance quality and size deviation
After sample extraction, the appearance and dimensional quality of each sample should be determined as “qualified” or “unqualified” according to the requirements of the product quality standard. After all samples are tested, the number of accumulated nonconforming samples (y) of appearance and size is counted separately and compared with the number of acceptances Ac specified in Table 3. If y≤Ac, the sub-batch product is qualified; if y>Ac, the sub-batch product is unqualified. The appearance or size inspection of the unqualified batch, if passed, can be removed from the batch of unqualified products, allowing the manufacturer to re-deliver after the inspection, again for acceptance. If the unqualified batch does not pass the inspection to improve the quality, the batch will be rejected.
7.4.2 Determination of physical and chemical properties
The acceptance sampling inspection items of physical and chemical quality characteristics of shaped refractory products include MgO content, Cr2O3 content, SiO2 content, bulk density, apparent porosity, compressive strength, load softening temperature and thermal shock stability. The determination of MgO content, Cr2O3 content, SiO2 content and load softening temperature can be carried out according to Table 5 and Table 6 (the sample size of the two tables is different, you can choose one of them). The determination of bulk density, apparent porosity, and thermal shock stability can be carried out according to Table 6. The single value of compressive strength at room temperature is not allowed to be lower than Xmin, where σ is the standard deviation in Table 1 and Table 2. S is the standard deviation of the 9 samples after testing when there are nonconforming items. If the above indexes meet the requirements of Table 5 or Table 6, they are judged to be qualified.
Table 5 Pass/Fail determination of a single quality feature with batch average as quality index (n=3) | ||||
Quality requirement | Test 1 sample for the first time | Three samples were tested twice | ||
Test result | Determine | Test result | Determine | |
Low-value discomfort | x i ≥μ 0 | Up to standard | - | - |
x i <μ 0 | Further inspection | Mean of x≥μ 0 | Up to standard | |
Mean of x<μ 0 | Below standard | |||
High value discomfort | x i ≤μ 0 | Up to standard | - |
|
x i >μ 0 | Further inspection | Mean of x≤μ 0 | Up to standard | |
Mean of x>μ 0 | Below standard | |||
Table 6 Pass/Fail determination of a single quality feature with lot average as quality index (n=9) | ||||
Quality requirement | Test 3 samples for the first time | A total of 9 samples were tested twice | ||
Test result | Determine | Test result | Determine | |
Low-value discomfort | Mean of x≥μ 0 | Up to standard | - | - |
Mean of x<μ 0 -1.5σ | Below standard | - | 一 | |
μ 0 -1.5σ≤Mean of x<μ 0 | Further inspection | Mean of x≥μ 0-0.62S | Up to standard | |
Mean of x<μ 0-0.62S | Below standard | |||
High value discomfort | Mean of x≤μ 0 | Up to standard | - |
|
Mean of x>μ 0 +1.5σ | Below standard | - |
| |
μ 0 | Further inspection | Mean of x≥μ 0 +0.62S | Up to standard | |
Mean of x>μ 0 +0.62S | Below standard | |||
7.5 Comprehensive Judgment
If all the physical and chemical properties, appearance quality and dimensional deviation of the inspection batch to be accepted are qualified, the batch of products is qualified, otherwise it is unqualified.
8 Packing, marking, transportation, storage and quality certificate
8.1 Packaging
Bricks should be packed with moisture-proof measures.
8.2 Marking, transportation and storage
Proceed as GB/T 16546.
8.3 Quality Certificate
The quality certificate shall include: supplier name or factory standard, demander name, production date, shelf life, contract number, product name, standard number, brand number, brick number, batch number and corresponding physical and chemical inspection results.
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