Kontrol kualitas tempa nosel

Kontrol kualitas tempa nosel

Artikel ini memberikan ringkasan dan analisis singkat tentang masalah kualitas yang muncul selama proses pembuatan tempa pengambilalihan dari perspektif pengawasan peralatan, terutama analisis inklusi peleburan material dan non-logam, termasuk pemahaman standar, interpretasi proses produksi dan elemen manufaktur, pengenalan proses dan teknologi baru dalam negeri, dan pembelajaran ulang fondasi profesional ilmu material, Dimaksudkan untuk meningkatkan kontrol kualitas manufaktur penempaan nosel.

1. Pendahuluan

Tempa pipa biasanya menanggung berbagai beban mekanis dan dapat menahan suhu tinggi dan tekanan tinggi, sehingga persyaratan untuk tempa juga sangat ketat. Kualitas dari pembuatan tempa secara langsung memengaruhi kualitas dan masa pakai peralatan pemrosesan berikutnya, dan pentingnya hal ini sudah jelas. Mereka mengambil penempaan nosel yang terbuat dari bahan 16MND5 sebagai contoh untuk diskusi.

2. Pengenalan Manufaktur

2.1 Bahan, proses, dan titik kontrol kualitas untuk menyambung tempa

Proses pembuatan tempa nosel terutama mencakup peleburan bahan, pengecoran, penempaan, perlakuan panas, permesinandll. Peleburan baja harus dilakukan di dalam tungku listrik, dengan penambahan Al untuk deoksidasi dan degassing vakum. Poin kontrol kualitas manufaktur penempaan terutama mencakup tinjauan awal, analisis peleburan material, perlakuan panas kinerja, uji kinerja pemotongan, inspeksi properti mekanis, NDT (inspeksi ultrasonik, inspeksi partikel magnetik, inspeksi penetran cair), dll. Status pengiriman tempa pipa penghubung adalah pendinginan dan tempering pra-pengelasan.

2.2 Standar dan spesifikasi penerimaan untuk tempa nosel

Standar penerimaan dan spesifikasi untuk tempa pengambilalihan meliputi garis besar produksi, rencana kualitas, dokumen kontrak, spesifikasi teknis, gambar, prosedur inspeksi, dan standar produksi dan inspeksi yang ditentukan dalam gambar desain.

3. Kontrol kualitas pengawasan atas tempa pengambilalihan

3.1 Dasar kontrol kualitas pengawasan

Dasar utama untuk pengawasan kontrol kualitas meliputi garis besar produksi, rencana kualitas, dokumen kontrak, spesifikasi teknis, gambar, prosedur inspeksi, proses produksi, prosedur operasi, dokumen jaminan kualitas, dokumen manajemen pengawasan, peraturan manajemen ketidaksesuaian (NCR), dll.; Selama proses produksi, dokumen standar yang sesuai harus diikuti dengan ketat.

3.2 Pengenalan dan analisis proses manufaktur utama untuk tempa nosel (pengecoran, penempaan, perlakuan panas, pemesinan)

• (1) Peleburan material: Proses dasarnya adalah pembuatan dan persiapan baja → peleburan tungku listrik → penyulingan tungku penyulingan (penghilangan fosfor, penghilangan belerang, deoksidasi aluminium, dll.) → pengecoran tungku ganda hingga tundish mati dan diberi perlakuan vakum → pengecoran vakum. Proses peleburan meliputi beberapa analisis peleburan dan penyesuaian komposisi kimia;
• (2) Penempaan: mesin press hidrolik yang umum digunakan untuk penempaan gratis;
• (3) Perlakuan panas kinerja: dilakukan dalam tungku gas industri dan tungku listrik, termasuk proses normalisasi, pendinginan, dan tempering;
• (4) Pemesinan: Di area pemrosesan khusus, peralatan pemrosesan khusus, personel khusus, dan posisi khusus digunakan untuk pemrosesan;
• (5) Inspeksi kinerja mekanis: biasanya dilengkapi dengan instrumen dan peralatan inspeksi dan pengujian khusus;
• (6) Pengujian tidak rusak: Lakukan item demi item sesuai dengan persyaratan desain.
• Disebutkan bahwa upaya pengawasan dan pengendalian harus diperkuat pada simpul-simpul proses utama (pengecoran, penempaan, perlakuan panas) dalam pembuatan tempa, terutama dalam memantau sumber material, pemotongan kepala dan bagian bawah batang baja, dll.

3.3 Analisis Material

The bahan penempaan nosel harus memiliki dua poin utama: kemampuan las dan pengerasan, sifat mekanik yang sangat baik, kekuatan luluh suhu kamar, kekuatan tarik patah akhir, plastisitas, ketangguhan, ketahanan terhadap korosi, dan kerapuhan dingin. Kinerja penempaan nosel terutama bergantung pada sifat material dan proses pengecoran, penempaan, dan perlakuan panas. Performa material adalah fondasi, terutama ditentukan oleh komposisi kimianya (lihat Tabel 1 dan 2). Karena persyaratan performa pengelasannya, kandungan karbonnya tidak boleh melebihi 0,20%. Sifat mekanik dan pengerasan baja jenis ini terutama bergantung pada penambahan sejumlah kecil elemen paduan seperti Mn, Si, Ni, dan Mo untuk meningkatkannya. Mn adalah elemen dasar untuk penguatan, dengan fungsi deoksidasi dan desulfurisasi. Kandungannya umumnya di bawah 1.6%, dan kandungan yang berlebihan akan secara signifikan mengurangi plastisitas, ketangguhan, dan kinerja pengelasan baja. Ni dan Mo dapat menghaluskan butiran dan meningkatkan dispersi, sedangkan Si dan Al memiliki fungsi antioksidan dan deoksigenasi obat penenang. Perlu ditekankan bahwa dengan berbagai ukuran dan ketebalan tempa, pengerasan menjadi sangat penting, karena secara langsung memengaruhi sifat mekanis tempa nosel dan juga menjadi fokus analisis kualitas. Pada saat yang sama, juga harus ditunjukkan bahwa S, P, N, H, dan O adalah elemen berbahaya, dan indikator jumlah totalnya Σ (S + P + N + H + O) adalah indikator utama untuk mengukur kemurnian baja cair. Setelah tahun 2000, Σ (S + P + N + H + O) ≤ 50 × 10-6 adalah tujuan yang dikejar oleh manufaktur penempaan China. Dehidrogenasi, deoksigenasi, dan pemurnian unsur S dan P selalu menjadi tugas penting dalam peleburan logam, dan kandungannya juga merupakan salah satu indikator utama untuk menentukan kualitas bahan. Dalam produksi tempa, sifat mekanik tempa sering kali ditingkatkan dengan menyesuaikan komposisi kimiawi material.

• (1) Karbon ekuivalen Ceq = C + Si/24 + Mn/6 + Ni/40 + Cr/5 + Mo/4 + V/14 = 0,55 - 0,65
• (2) Pengelasan koefisien sensitivitas retak ulang △ G = 3.3Mo + Cr + 8.1V-2 ≤ -0.1.

Setara karbon adalah indeks referensi penting untuk mengevaluasi kemampuan las baja.
Semakin tinggi ekuivalen karbon, semakin besar kecenderungan retak dan semakin buruk kemampuan las baja.
Tabel.1 Persyaratan komposisi kimia untuk tempa baja paduan Mn Ni Mo yang digunakan untuk nozel (dengan deoksigenasi yang dibunuh Al dan degassing vakum)

Elemen	Analisis sendok (%)	Analisis Produk (%)
Karbon	<0.20	<0.22
Mangan	1.15-1.55	1.15-1.60
Fosfor	<0.012	<0.012
Belerang	<0.012	<0.012
Silikon	0.10-0.30	0.10-0.30
Nikel	0.50-0.80	0.50-0.80
Kromium	<0.25	<0.25
Molibdenum	0.45-0.55	0.43 〜0.57
Vanadium	<0.01	<0.01
Tembaga	<0.20	<0.20
Aluminium	Lebih baik <0,04	<0.04
Bor	<0.03	<0.03

Table.2 Manufacturing Outline of Materials for Pipe Forgings (16MND5) Chemical Composition

Grade 16MND5
Elemen	Analisis sendok (%)	Analisis Produk (%)
C	<0.20	<0.22
Mn	1.15-1.55	1.15-1.60
P	<0.008	<0.008
S	<0.005	<0.005
Si	0.10-0.30	0.10-0.30
Ni	0.50-0.80	0.50-0.80
Cr	<0.15	<0.15
Mo	0.45-0.55	0.43-0.57
V	<0.01	<0.01
Cu	<0.08	<0.08
Al	<0.04	<0.04
Co	<0.03	<0.03
As	0.01	0.01
Zn	0.01	0.01
Sn	0.002	0.002
B	0.0003	0.0003
H	1.5 ppm	0.8 ppm
O,N	provide data	provide data

3.4 Pengawasan Pengendalian Proses Kualitas

The supervision work is carried out by standard specifications, manufacturing outline, quality plan, contract documents, technical specifications, drawings, inspection procedures, manufacturing processes, operating procedures, supervision management documents, nonconformance (NCR) management regulations, etc., mainly including witness and inspection of W and H points. These inspections are strictly carried out one by one from personnel, machinery, materials, methods, and the environment.

• (1) The inspection of “personnel” mainly refers to the qualification inspection of special operation personnel, non-destructive testing personnel, physical and chemical analysis, mechanical performance testing personnel, and visual inspection personnel. For example, personnel engaged in nondestructive testing of pressure vessels should obtain corresponding qualifications, and operators for physical and chemical analysis and mechanical performance testing must also have a technical qualification certificate of intermediate level or above for physical and chemical inspection personnel to be allowed to operate.
• (2) The inspection of “machines” mainly refers to the review of processing equipment, performance testing machines, hydraulic testing pumps, non-destructive testing instruments, etc., to examine the compatibility, compliance, and effectiveness of the equipment. The equipment and process equipment must be compatible with the tasks they undertake. It must comply with the provisions of corresponding standards, such as room temperature tensile testing machines, high-temperature tensile testing machines, UT inspection instruments, etc., and be fully equipped, in normal, good condition, and within the calibration period. The manufacturing unit must establish management regulations for using and maintaining equipment and process equipment, a job responsibility system, establish equipment archives, and conduct regular inspections.
• (3) ‘Material’ mainly refers to the raw materials of forgings. Raw materials are the foundation and guarantee for taking over forgings. The supervision and inspection of raw materials are carried out through physical identification inspection, and on the other hand, through the review of melting analysis reports, chemical analysis reports, and completion data of materials for judgment and control.
• (4) The “law” mainly inspects equipment related manufacturing processes, management procedures, inspection procedures, acceptance standards, etc. Review the compliance and effectiveness of manufacturing processes, procedures, inspection procedures, and acceptance standards, such as whether the cut test material after taking over the forging tempering meets the drawings, whether the sampling method meets the specification requirements, and for example, during the commencement inspection, review the manufacturing outline, quality plan, drawings, inspection procedures, manufacturing processes, enterprise qualifications, personnel qualifications, production and manufacturing capabilities, etc.; Whether the technical documents inspected on site are controlled and effective.
• (5) Environmental inspections are also necessary. The environment is an important factor affecting the quality of forgings. It is not only a requirement for safe and civilized production but also meets functional and technical requirements. For example, in material smelting, the basic process is steel preparation → electric furnace smelting → refining furnace refining (phosphorus removal, sulfur removal, etc.) → double furnace combined casting to tundish vacuum treatment → vacuum casting. The pre-treatment of the steel ladle, refining furnace, and tundish is very strict, and it is necessary to prevent secondary oxidation and protect the tundish from casting. Part of the non-metallic inclusions in the nozzle forging is self-generated, while the other part is external inclusions that enter the steel ingot. Moreover, the harm of external inclusions to the steel ingot is extremely great, indicating that the quality of the environment directly affects the quality of the nozzle forging. For example, mechanical performance testing requires an environment that is warm in winter and cool in summer to ensure that the state of the testing instruments meets the requirements. For example, ultrasonic testing, liquid penetrant testing, and magnetic particle testing (PT, MT, UT testing) all require the measurement of the surface temperature of the workpiece, as these tests have limitations on temperature conditions. The testing temperature for PT is required to be within 10 ℃ -50 ℃; We use multiple methods to coordinate this.
• (6) The witnessing of points W and H should ensure 100% attendance, and individual R points can also be witnessed according to point W, such as visual inspection and dimensional inspection of forgings.
• (7) Patrol inspection is an important means and process for ensuring quality control in manufacturing supervision. It connects and fills the gaps and deficiencies between witness points. Many problems are discovered during inspection, such as damage and failure of production drawings, incorrect identification of workpieces, expiration of testing equipment and measuring tools, isolation of scrapped products, and subsequent processing of non-conforming products.

3.5 Pengawasan Pengendalian Dokumen Kualitas

Supervision quality document control mainly includes inspection reports, completion reports, quality plan reviews, inspection procedures, NCR reviews, production processes, process drawings reviews, and a large amount of work during the review process involves familiarizing oneself with standards, inspection procedures, acceptance standards, etc.
Taking the acceptance criteria as an example, it is now explained that:
Acceptance standard values for Mn Ni Mo alloy steel forgings used for nozzles:
(1) The specified values for mechanical properties are listed in Table 3.
(2) After final machining, liquid penetrant inspection (PT) must be performed on the surface to be welded. Inspect according to the design-specified inspection standards.
Recording conditions and inspection criteria: Any defect with a size equal to or greater than 1mm should be recorded.
Any defect showing the following indications shall be deemed as unqualified:

• 1) Linear display;
• 2) Nonlinear display with dimensions exceeding 3mm;
• 3) Three or more displays arranged in rows with a spacing of less than 3mm;
• 4) On a rectangular area of 100cm2, there are 5 or more dense traces. The long side of the rectangle is at most 20cm and is located in the area with the most severe trace assessment.

(3) Volume inspection
Internal defect inspection adopts ultrasonic inspection (UT). The inspection time must be carried out after the final machining of the parts, and the parts that cannot be inspected after forming should be inspected as early as possible. The implementation method of ultrasonic inspection shall comply with the regulations.
Table.3 Required values of mechanical properties

Test items	Test temperature ° C	Performance	Specified value
			Circumferential (Horizontal) (3)	Axial (longitudinal) (3)
Ketegangan	Room temperature	R0.002	>400MPa
		Rm	550/670MPa
		A%(5D)	>20
	350	R0.002t	>300MPa
		Rm	>497MPa
KV impulse	0	Minimum average	56J	72J
		Individual minimum value (1) ⑵	40J	56J
	-20	Minimum average	40J	56J
		Individual minimum value (1) ⑵	28J	40J
	20	Individual minimum value	72J	88J
(1) Acceptance is only allowed when at most one result in each group of three samples is lower than the specified average value.
(2) If neither the forging program nor the test results can accurately indicate the horizontal indication, samples should be taken at the same depth and tested in both horizontal and vertical directions to obtain accurate individual minimum values.
(3) Sampling depth circumferential: 40X80mm; Axial direction: 80X160mm.

The characteristic parameters of the probe are usually as follows:
Direct beam inspection: According to different structures, the probe frequency is 4MHz or 2MHz.
Oblique beam inspection: According to different structures, the probe frequency is 2MHz or 1MHz, and the reflection angle is 45 °.
(4) Magnetic particle inspection
Any defect with a size equal to or greater than 1mm should be recorded.
All defects that present the following magnetic marks must be marked with their location, removed, or repaired:

• 1) Linear magnetic traces;
• 2) Nonlinear magnetic traces with dimensions exceeding 3mm;
• 3) Three or more magnetic traces arranged in rows with a spacing of less than 3mm; Or magnetic traces with a spacing of 3-6mm and a distribution length greater than 15mm. If the distance between two magnetic traces is less than twice the length of the smaller one, then these two magnetic traces are considered as one magnetic trace. The total length of this magnetic trace should be the sum of the lengths of two magnetic traces plus the distance between these two magnetic traces.

3.6 Koordinasi pengawasan dan pekerjaan komunikasi informasi

Coordination and information communication are the basic abilities that equipment supervision personnel must possess, achieving clear responsibilities, timely communication of major events, and no omission in general communication.

3.7 Masalah kualitas umum dan tindakan pengendalian

There is a significant amount of non-metallic slag inclusion in the material of the nozzle forging, mainly composed of Si₂O₃. The focus issue is that the mechanical properties of the forging are not qualified, non-destructive testing is not qualified, and the cutting tool does not meet the requirements. Through holding a special meeting to analyze the causes of quality problems and improvement measures, after discussion and analysis, it was found that the exposed slag is mainly aluminum oxide, which is mainly caused by the production process of steelmaking. The steelmaking production process has always adopted mature methods, processes, technologies, and materials, without any abnormalities, but some shortcomings were found:

• (1) The casting temperature control is unstable, and the range of casting temperature control is generally very narrow. High temperature casting can ensure that the inclusions have enough time to grow and float during the solidification of the steel ingot. Still, it seriously increases the inclusion in the steel due to erosion of refractory materials, suction during casting, and secondary oxidation. Low temperature casting is not conducive to the inclusion of floating. Unstable casting temperature control, on the one hand, generates too much aluminum oxide, and on the other hand, it shortens the inclusion floating time.
• (2) The casting speed is relatively low, and the casting speed of steel ingots is around 5t per minute. A low casting speed is equivalent to reducing the casting temperature, which shortens the floating time of inclusions during the solidification process of molten steel, thereby increasing the content of inclusions in the steel ingot.
• (3) The excessive oxidation and secondary oxidation of molten steel are severe. When the crude refining molten steel C ≤ 0.05%, the oxygen content in the steel is very high, which poses certain difficulties for refining deoxygenation; on the one hand, increasing the use of deoxidizers may increase the oxide content in the steel. During casting, the injection flow is prolonged, the exposure time of molten steel is long, and secondary oxidation is severe.
• (4) The tundish process is short, and the pouring is started early. In the past, ordinary 60t tundish was used for casting steel ingots. In recent years, a new type of 100t tundish has been widely used for casting in production, which can allow sufficient time for inclusions to gather and grow up and is conducive to the accumulation of inclusions in the mold, which greatly improves the purity of molten steel and improves product quality to a certain extent; Although the problematic steel ingots were cast using a new type of 100t tundish, the molten steel in the tundish was opened for casting when it rose by 3/4 of the height. The process of molten steel in the tundish was short, and the sedation time needed to be longer, failing to achieve the goal of fully floating inclusions.
• (5) The casting sequence needs to be revised, and the sequence of steel ingots with problems is from small ladle to large ladle. The small amount of steel water and heat storage in a small ladle is not conducive to steel sedation and does not achieve the goal of fully floating inclusions.
• (6) Due to increased production tasks, frequent personnel changes, and insufficient experience of new employees, process control is flexible, such as unstable casting temperature control and low casting speed.
• (7) The amount of deoxidizer (Al) added needs to be revised.

Improvement measures:

• (1) Control the amount and timing of aluminum addition and control its oxidation
• (2) Using a 100t tundish for casting and strictly requiring the cleaning standards and masonry quality of the tundish, increasing the process and increasing the floating time of inclusions.
• (3) Control the casting temperature and speed, requiring a casting speed greater than 5.5t/min, and increase the floating time of inclusions in the mold;
• (4) Promote the application of long nozzle protection casting to avoid secondary oxidation of molten steel and reduce the entry of external inclusions.
• (5) When the rising height of the molten steel in the tundish is above 1500mm, the pouring should be started to appropriately prolong the cooling time of the molten steel in the tundish, achieving the goal of fully floating the inclusions;
• (6) Change the casting sequence by pouring the steel ingots together, first casting the large refining package (5 #, 6 #) and then casting the small refining package (7 #).
• (7) Control the carbon content of rough refining molten steel to prevent excessive oxidation and require a C content greater than 0.05%.

In response to the above issues, a special meeting will be held to analyze and discuss and formulate improvement measures. The correctness of the improvement measures will be verified through future production practices. Here are some suggestions:
Firstly, universal quality issues should be given great attention, and specialized research should be conducted. It is necessary to establish a research group for non-metallic inclusions in steelmaking and make great efforts to solve them, especially to reduce adverse human behavior. The problem of non-metallic inclusions in taking over forgings can be solved; after all, there have been successful experiences and precedents in the past; Secondly, one should be good at innovation. As experts have said, in the production of clean steel, Al₂O₃ should be eliminated as much as possible before the molten steel enters the crystallizer; Thirdly, writing articles on the tundish, such as using a long nozzle between the refining ladle and the tundish to reduce the total amount of N, adding protective casting (using an immersion nozzle) between the tundish and the crystallizer to prevent secondary oxidation, and adding Mg Ca based coating alkaline lining in the tundish to absorb inclusions effectively.

4. Kesimpulan

While maintaining traditional and mature methods, processes, and technologies, manufacturing plants must also strengthen and improve in many aspects, such as technology, processes, production, quality assurance, equipment updates, quality innovation, and talent cultivation. Our supervision personnel also face many new problems and challenges, such as familiarity and implementation of response standards and procedures, supervision and execution, implementation of supervision concepts, and performance of supervision functions, all of which require our down-to-earth efforts and dedication. We need to clarify the following:

• (1) While adhering to the principle of conscientiously doing a good job at witness points, we should strengthen inspection and inspection work and ensure that quality tracking is closely followed and implemented item by item.
• (2) We should focus on coordinating with various departments of the manufacturing plant, timely grasp the equipment manufacturing status, identify critical paths in the equipment manufacturing process, track the progress of critical paths and nodes, identify and avoid risks as soon as possible, and ensure the smooth progress of the project.
• (3) Details determine success or failure. Only by looking at the smallest details can we timely detect and stop illegal operations, and at the same time, timely and targeted supervision of manufacturing plants to improve the management level and innovation ability, ensuring the quality of equipment manufacturing.
• (4) Equipment supervision is a big classroom, where there will be rewards if there is effort and gains if there is hard work.

Penulis Jia Lin